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Ever since the computer and the critical data it holds came into headlines, so did the malicious programs, attacks and the threat landscape. We have thousands of cases of malware infection, zombies and trojans taking over networks in fast pace. The amount of data that passes through any switch, router, Firewall is enormous. There is ‘gigabits of traffic’ flowing every second through perimeter and internal networking devices. To protect this vast amount of data, we have deployed host as well as network level controls and software. Every security measure we deploy makes it one step harder for the attackers to gain access to the internal resources. There are devices that check for malware patterns, do heuristic scans, and find patters that resemble a black listed file or a cyber-threat. This technology is termed as Deep Packet Inspection (DPI) for it inspects the payload as well as the protocol details of every packet against the set of signatures to match. But, with the constant evolution of attack vectors it’s now a crazy fire-fighting exercise to match every type and strain of malware or every style and patterns of an attack. Moreover the detection capability bridge between malicious and benign software is shrinking rapidly.
Can we have something that can help is narrow down the spread of a malicious file. If we miss the perimeter checks, can we still deal with the spread of the malware? Yes! To some extent by using traffic anomaly detection together with other host based solutions. So, what is Traffic Anomaly? Straight answer is – anything which is not expected in day-today traffic; something that creates an anomaly and raises an alarm. It can be huge amount of requests, response, particular TCP flag, DNS queries, anything. Here I will discuss TCP anomaly with an in-house detection script as well as the DNS anomalies. This is not a full and fool proof measure of detection, but surely can complement your existing security solutions.
TCP Protocol – Deep Dive
TCP of Transmission Control Protocol and is often referred when dealing with high level protocols such as HTTP, FTP etc. A high level analysis of TCP header is shown in Figure 1. The key fields in scope of this article are ‘Port’, ‘Address’ (Source/Destination) and very importantly the ‘FLAGS’. These fields will help identify if there is an anomaly occurring in network traffic without digging deep into the packet payload and patterns. We know how address and port are connected to call it a socket, but how can we devise a simple yet effective measure on the basis of flags. Even though there are 9 flags of 1 bit each, still let’s take a brief overview of 4 most often used flag types,
- SYN
It is derived from the word ‘Synchronize’. Ideally in the start of the connection the first packet sent from each side (client and server) should have this flag enabled.
- ACK
It is derived from the word ‘Acknowledge’. It means that the received packet has been acknowledged.
- FIN
This flag indicated that the host will not accept any more packets and is requesting a termination of connection.
- RST
It forcibly RESETS the connection. When this flag is enabled, the host doesn’t wait for response and is terminating the connection right away. It’s more offensive way to terminate connection.
Figure 1 (Source: Wikipedia)
Now, after having a brief idea on the flags, let’s see how the connection is established. It’s a typical three way handshake as shown in TCP state diagram in Figure 2. So, one thing is clear that if a host is trying to connect to another host, it will initiate a SYN. Similarly, if a host has to refuse a connection it will send an RST, or if it has to accept it then an ACK. Now, can we leverage this knowledge to check if there is an anomaly in the network? Let us assume a host in the network is infected with a malware and it is trying to spread in an internal network. We can expect a lot of packets being generated by the infected machine and lots of drop connection received. This is the key to the checks we will deploy via an in house python script. For ease of explanation let us say we have an infected host HOST-A and various other hosts on the LAN such as HOST-B, HOST-C …
Case-1
So, if malware at HOST-A has the capability to spread in the LAN like a worm, then it will surely try to initiate the connections with HOST-B/C. Therefore we can expect HOST-B and HOST-C receiving SYN flags from HOST-A. Now, if these are end user systems, it points to an anomaly as why would a user on HOST-A attempts to connect to a user HOST-B (if not a business requirement). So, if we have the tool running on HOST-B that can check the SYN packet count, we can then use it as a counter to validate the SYN packets per IP against a threshold value. It can also trigger on a port scan from HOST-A to HOST-B with the sudden hike in SYN packets.
Case-2
On the other hand if the HOST-A receives many packets with RST flags enabled, it means that the target machines denied the initiation of TCP connections. We can infer as if the HOST-A receives too many RST flags, there is a probability that the machine HOST-A is trying to scan the nearby systems with SYN flag set.
So, too many SYN received means the SENDER is infected (Figure 3), and too many RST received means the RECIPIENT is infected (Figure 4).
Figure 2 – TCP State (Source: Wikipedia)
Figure 3 – SYN Packets
Figure 4 – RST Packets
Now, let us go through the python script to understand what it can do, and how to make it work. This is working draft of the script, and may need a revamp, or beautification but logics and working is fine. The python script uses scapy to do the packet analyses and counters to take care of the packet count for each flag. Here is an output screenshot for the script (Figure 5 and Figure 6).
Figure 5 – Flags Counter
Figure 6 – Tool Summary
Tool Working
The script is coded in python and is using the network packet analysis library (scapy) to count, and print the required fields of the packets. Here are the steps with brief understanding,
- Importing required libraries.
import logging
logging.getLogger(“scapy.runtime”).setLevel(logging.ERROR)
from scapy.all import *
from math import *
import sys, os
import ConfigParser
import string
from termcolor import colored, cprint
- Configuration Parameters from “flags.ini” file (Figure 7). This file has to be manually configured with IP address, and the threshold SYN and RST values.
# Configuration Parameters
config = ConfigParser.ConfigParser()
config.read(“flags.ini”)
SYNVAL=config.get(“flag”, “SYN”)
RACVAL=config.get(“flag”, “RAC”)
IPMON=config.get(“target”, “IP”)
RACVAL = string.atoi(RACVAL)
SYNVAL = string.atoi(SYNVAL)
Figure 7 – Flags INI file
- Then, there is a class for packets and flags in the respective packets.
# Counter Class for packets & flags
class COUNTER:
def __init__(self):
self.S = 0
self.A = 0
self.R = 0
self.F = 0
self.SA = 0
self.RA = 0
self.FA = 0
self.T = 0
def countit(S=0, A=0, R=0, F=0, SA=0, RA=0, FA=0, T=0):
c.T = c.T + 1
if S:
c.S = c.S + 1
elif A:
c.A = c.A + 1
elif R:
c.R = c.R + 1
elif F:
c.F = c.F + 1
elif SA:
c.SA = c.SA + 1
elif RA:
c.RA = c.RA + 1
elif FA:
c.FA = c.FA + 1
print colored(“| %10d | %10d | %10d | %10d | %10d | %10d | %10d |” %(c.S,c.A,c.R,c.F,c.SA,c.RA,c.FA),’white’),”\r”,
def findFLAG(p):
IPSRC = p.sprintf(“%IP.src%”)
IPDST = p.sprintf(“%IP.dst%”)
if IPDST == IPMON:
countit(T=1),
FLAG = p.sprintf(“%TCP.flags%”)
if FLAG == “S”:
countit(S=1),
saveout= sys.stdout
fsock = open(‘logs/SYN.log’, ‘a+’)
sys.stdout = fsock
print p.sprintf(“\nSource = %IP.src%:%TCP.sport%\nDestination = %IP.dst%:%TCP.dport%\n%TCP.payload%”)
sys.stdout = saveout
fsock.close()
if FLAG == “A”:
countit(A=1),
if FLAG == “R”:
countit(R=1),
if FLAG == “F”:
countit(F=1),
if FLAG == “SA”:
countit(SA=1),
if FLAG == “RA”:
countit(RA=1),
saveout= sys.stdout
fsock = open(‘logs/RAC.log’, ‘a+’)
sys.stdout = fsock
print p.sprintf(“\nSource = %IP.src%:%TCP.sport%\nDestination = %IP.dst%:%TCP.dport%\n%TCP.payload%”)
sys.stdout = saveout
fsock.close()
if FLAG == “FA”:
countit(FA=1),
c = COUNTER()
sniff(filter=”tcp”, prn=findFLAG, store=0)
- After these packet flags are calculated, and reach a threshold limit, then a log file is generated (Figure 8)
Figure 8 – SYN log file
With this brief overview, following are the changes in next versions,
- Parse the log file to get the most ‘active’ IP address.
- If on a Linux host, with a strict rule the tool can release the DHCP lease.
- P2P model to let the scripts interact with each other on different hosts and isolate the malicious IP address as a network of analysis. This will make the anomaly detection a holistic approach.
DNS Anomaly
In continuation to TCP anomaly detection based on the TCP flags, the DNS anomaly detection can also be embedded into the script. The infected system not only detects the hosts in the network for infection, but also tries to connect to their control centers in external zones. Such infected hosts scan the internal networks for open ports to spread, and contact the external servers by initiating the DNS queries to the malicious domains. A popular and well known technique used by worms controlling domains is the fast-flux. This enables the writers to have a pre-configured domain generating algorithm, and book the domains accordingly. A worm initiates a huge number of DNS queries and this constitutes the anomaly in the network. But, it can result in false positive so the tools need to be heuristic, intuitive as well as able to interact with different tools running on separate hosts.
On the other hand, there are times when worms/ or malicious programs generate DNS packets that violate the format of a valid DNS header. This can be detected at the network level as well as in a well formatted host based script that has the capability to parse the packets and decode DNS traffic for validations. Once we have the anomalies detected, we can look into the action items for the source IP addresses.
TCP sessions vs. DNS queries – There is a close relation between the DNS query and the successive TCP session. In an ideal scenario there should be a ‘threshold’ time of session after a successful DNS query. But, it can be termed as an anomaly if there are lot more DNS queries than number of long-term TCP sessions. Here is a short list of pointers to a DNS traffic anomaly,
- Sudden hike in DNS queries from a singular IP address.
- Sudden drop in successful DNS queries. Drop in resolved queries.
- Increase in the number of DNS queries vs. successful TCP sessions.
- A jump in the recursive queries.
Overall, the next step is to develop and code these ideas into the tool, and have a single standalone tool capable of parsing traffic and detecting different anomalies – TCP and/or DNS at the host level. It can then take the required actions on the basic of configuration. | https://resources.infosecinstitute.com/traffic-anomaly-detection/ | CC-MAIN-2018-39 | refinedweb | 1,949 | 64.91 |
On Sun, 2009-06-14 at 10:21 +0200, Marco wrote:> > Mmm...MEM_MAJOR and RAMDISK_MAJOR have the same value and pramfs works> in memory. We could simply use /dev/null (there was an error in the> submitted kconfig description, my intention was to use /dev/mem). In> that case I can use UNNAMED_MAJOR. PRAMFS root option is not enabled> if it's already enabled the NFS one. What do you think?Why use a major number at all? See how we handle mtd and ubi devices inprepare_namespace() -- can't you do something similar?-- David Woodhouse Open Source Technology CentreDavid.Woodhouse@intel.com Intel Corporation | https://lkml.org/lkml/2009/6/14/35 | CC-MAIN-2014-10 | refinedweb | 104 | 62.14 |
There are two React hooks,
useEffect and
useLayoutEffect, that appear to work pretty much the same.
The way you call them even looks the same.
useEffect(() => { // do side effects return () => /* cleanup */ }, [dependency, array]); useLayoutEffect(() => { // do side effects return () => /* cleanup */ }, [dependency, array]);
But they’re not quite the same. Read on for what makes them different and when to use each. (tl;dr: most of the time you want plain old
useEffect)
The Difference Between useEffect and useLayoutEffect
It’s all in the timing.
useEffect runs asynchronously and after a render is painted to the screen.
So that looks like:
- You cause a render somehow (change state, or the parent re-renders)
- React renders your component (calls it)
- The screen is visually updated
- THEN
useEffectruns
useLayoutEffect, on the other hand, runs synchronously after a render but before the screen is updated. That goes:
- You cause a render somehow (change state, or the parent re-renders)
- React renders your component (calls it)
useLayoutEffectruns, and React waits for it to finish.
- The screen is visually updated
99% of the time, useEffect
Most of the time your effect will be synchronizing some bit of state or props with something that doesn’t need to happen IMMEDIATELY or that doesn’t affect the page visually.
Like if you’re fetching data, that’s not going to result in an immediate change.
Or if you’re setting up an event handler.
Or if you’re resetting some state when a modal dialog appears or disappears.
Most of the time,
useEffect is the way to go.
When to useLayoutEffect
The right time to
useLayoutEffect instead? You’ll know it when you see it. Literally ;)
If your component is flickering when state is updated – as in, it renders in a partially-ready state first and then immediately re-renders in its final state – that’s a good clue that it’s time to swap in
useLayoutEffect.
Here’s a (contrived) example so you can see what I mean.
When you click the page*, the state changes immediately (
value resets to 0), which re-renders the component, and then the effect runs – which sets the value to some random number, and re-renders again.
The result is that two renders happen in quick succession.
import React, { useState, useLayoutEffect } from 'react'; import ReactDOM from 'react-dom'; const BlinkyRender = () => { const [value, setValue] = useState(0); useLayoutEffect(() => { if (value === 0) { setValue(10 + Math.random() * 200); } }, [value]); console.log('render', value); return ( <div onClick={() => setValue(0)}> value: {value} </div> ); }; ReactDOM.render( <BlinkyRender />, document.querySelector('#root') );
* In general, putting
onClick handlers on
divs is bad for accessibility (use buttons instead!), but this is a throwaway demo. Just wanted to mention it!
Try the useLayoutEffect version and then try the version with useEffect.
Notice how the version with
useLayoutEffect only updates visually once even though the component rendered twice. The
useEffect version, on the other hand, visually renders twice, so you see a flicker where the value is briefly
0.
Should I useEffect or useLayoutEffect?
Most of the time,
useEffect is the right choice. If your code is causing flickering, switch to
useLayoutEffect and see if that helps.
Because
useLayoutEffect is synchronous a.k.a. blocking a.k.a. the app won’t visually update until your effect finishes running… it could cause performance issues if you have slow code in your effect. Coupled with the fact that most effects don’t need the world to pause while they run,. | https://daveceddia.com/useeffect-vs-uselayouteffect/ | CC-MAIN-2019-51 | refinedweb | 574 | 55.84 |
PEP 255 -- Simple Generators
Contents
- Abstract
- Motivation
- Specification: Yield
- Specification: Return
- Specification: Generators and Exception Propagation
- Specification: Try/Except/Finally
- Example
- Q & A
- Why not a new keyword instead of reusing def?
- Why a new keyword for yield? Why not a builtin function instead?
- Then why not some other special syntax without a new keyword?
- Why allow return at all? Why not force termination to be spelled raise StopIteration?
- Then why not allow an expression on return too?
- BDFL Pronouncements
- Reference Implementation
- Footnotes and References
Abstract
This PEP introduces the concept of generators to Python, as well as a new statement used in conjunction with them, the yield statement.
Motivation
When a producer function has a hard enough job that it requires maintaining state between values produced, most programming languages offer no pleasant and efficient solution beyond adding a callback function to the producer's argument list, to be called with each value produced.
For example, tokenize.py in the standard library takes this approach: the caller must pass a tokeneater function to tokenize(), called whenever tokenize() finds the next token. This allows tokenize to be coded in a natural way, but programs calling tokenize are typically convoluted by the need to remember between callbacks which token(s) were seen last. The tokeneater function in tabnanny.py is a good example of that, maintaining a state machine in global variables, to remember across callbacks what it has already seen and what it hopes to see next. This was difficult to get working correctly, and is still difficult for people to understand. Unfortunately, that's typical of this approach.
An alternative would have been for tokenize to produce an entire parse of the Python program at once, in a large list. Then tokenize clients could be written in a natural way, using local variables and local control flow (such as loops and nested if statements) to keep track of their state. But this isn't practical: programs can be very large, so no a priori bound can be placed on the memory needed to materialize the whole parse; and some tokenize clients only want to see whether something specific appears early in the program (e.g., a future statement, or, as is done in IDLE, just the first indented statement), and then parsing the whole program first is a severe waste of time.
Another alternative would be to make tokenize an iterator [1], delivering the next token whenever its .next() method is invoked. This is pleasant for the caller in the same way a large list of results would be, but without the memory and "what if I want to get out early?" drawbacks. However, this shifts the burden on tokenize to remember its state between .next() invocations, and the reader need only glance at tokenize.tokenize_loop() to realize what a horrid chore that would be. Or picture a recursive algorithm for producing the nodes of a general tree structure: to cast that into an iterator framework requires removing the recursion manually and maintaining the state of the traversal by hand.
A fourth option is to run the producer and consumer in separate threads. This allows both to maintain their states in natural ways, and so is pleasant for both. Indeed, Demo/threads/Generator.py in the Python source distribution provides a usable synchronized-communication class for doing that in a general way. This doesn't work on platforms without threads, though, and is very slow on platforms that do (compared to what is achievable without threads).
A final option is to use the Stackless [2] [3] variant implementation of Python instead, which supports lightweight coroutines. This has much the same programmatic benefits as the thread option, but is much more efficient. However, Stackless is a controversial rethinking of the Python core, and it may not be possible for Jython to implement the same semantics. This PEP isn't the place to debate that, so suffice it to say here that generators provide a useful subset of Stackless functionality in a way that fits easily into the current CPython implementation, and is believed to be relatively straightforward for other Python implementations.
That exhausts the current alternatives. Some other high-level languages provide pleasant solutions, notably iterators in Sather [4], which were inspired by iterators in CLU; and generators in Icon [5], a novel language where every expression is a generator. There are differences among these, but the basic idea is the same: provide a kind of function that can return an intermediate result ("the next value") to its caller, but maintaining the function's local state so that the function can be resumed again right where it left off. A very simple example:
def fib(): a, b = 0, 1 while 1: yield b a, b = b, a+b
When fib() is first invoked, it sets a to 0 and b to 1, then yields b back to its caller. The caller sees 1. When fib is resumed, from its point of view the yield statement is really the same as, say, a print statement: fib continues after the yield with all local state intact. a and b then become 1 and 1, and fib loops back to the yield, yielding 1 to its invoker. And so on. From fib's point of view it's just delivering a sequence of results, as if via callback. But from its caller's point of view, the fib invocation is an iterable object that can be resumed at will. As in the thread approach, this allows both sides to be coded in the most natural ways; but unlike the thread approach, this can be done efficiently and on all platforms. Indeed, resuming a generator should be no more expensive than a function call.
The same kind of approach applies to many producer/consumer functions. For example, tokenize.py could yield the next token instead of invoking a callback function with it as argument, and tokenize clients could iterate over the tokens in a natural way: a Python generator is a kind of Python iterator [1], but of an especially powerful kind.
Specification: Yield
A new statement is introduced:
yield_stmt: "yield" expression_list
yield is a new keyword, so a future statement [8] is needed to phase this in: in the initial release, a module desiring to use generators must include the line:
from __future__ import generators
near the top (see PEP 236 [8]) for details). Modules using the identifier yield without a future statement will trigger warnings. In the following release, yield will be a language keyword and the future statement will no longer be needed.
The yield statement may only be used inside functions. A function that contains a yield statement is called a generator function. A generator function is an ordinary function object in all respects, but has the new CO_GENERATOR flag set in the code object's co_flags member.
When a generator function is called, the actual arguments are bound to function-local formal argument names in the usual way, but no code in the body of the function is executed. Instead a generator-iterator object is returned; this conforms to the iterator protocol [6], so in particular can be used in for-loops in a natural way. Note that when the intent is clear from context, the unqualified name "generator" may be used to refer either to a generator-function or a generator-iterator.
Each time the .next() method of a generator-iterator is invoked, the code in the body of the generator-function is executed until a yield or return statement (see below) is encountered, or until the end of the body is reached.
If a yield statement is encountered, the state of the function.
Restriction: A yield statement is not allowed in the try clause of a try/finally construct. The difficulty is that there's no guarantee the generator will ever be resumed, hence no guarantee that the finally block will ever get executed; that's too much a violation of finally's purpose to bear.
Restriction: A generator cannot be resumed while it is actively running:
>>> def g(): ... i = me.next() ... yield i >>> me = g() >>> me.next() Traceback (most recent call last): ... File "<string>", line 2, in g ValueError: generator already executing
Specification: Return
A generator function can also contain return statements of the form:
return
Note that an expression_list is not allowed on return statements in the body of a generator (although, of course, they may appear in the bodies of non-generator functions nested within the generator).
When a return statement is encountered, control proceeds as in any function return, executing the appropriate finally clauses (if any exist). Then a StopIteration exception is raised, signalling that the iterator is exhausted. A StopIteration exception is also raised if control flows off the end of the generator without an explicit return.
Note that return means "I'm done, and have nothing interesting to return", for both generator functions and non-generator functions.
Note that return isn't always equivalent to raising StopIteration: the difference lies in how enclosing try/except constructs are treated. For example,:
>>> def f1(): ... try: ... return ... except: ... yield 1 >>> print list(f1()) []
because, as in any function, return simply exits, but:
>>> def f2(): ... try: ... raise StopIteration ... except: ... yield 42 >>> print list(f2()) [42]
because StopIteration is captured by a bare except, as is any exception.
Specification: Generators and Exception Propagation
If an unhandled exception-- including, but not limited to, StopIteration --is raised by, or passes through, a generator function, then the exception is passed on to the caller in the usual way, and subsequent attempts to resume the generator function raise StopIteration. In other words, an unhandled exception terminates a generator's useful life.
Example (not idiomatic but to illustrate the point):
>>> def f(): ... return 1/0 >>> def g(): ... yield f() # the zero division exception propagates ... yield 42 # and we'll never get here >>> k = g() >>> k.next() Traceback (most recent call last): File "<stdin>", line 1, in ? File "<stdin>", line 2, in g File "<stdin>", line 2, in f ZeroDivisionError: integer division or modulo by zero >>> k.next() # and the generator cannot be resumed Traceback (most recent call last): File "<stdin>", line 1, in ? StopIteration >>>
Specification: Try/Except/Finally
As noted earlier, yield is not allowed in the try clause of a try/finally construct. A consequence is that generators should allocate critical resources with great care. There is no restriction on yield otherwise appearing in finally clauses, except clauses, or in the try clause of a try/except construct:
>>> def f(): ... try: ... yield 1 ... try: ... yield 2 ... 1/0 ... yield 3 # never get here ... except ZeroDivisionError: ... yield 4 ... yield 5 ... raise ... except: ... yield 6 ... yield 7 # the "raise" above stops this ... except: ... yield 8 ... yield 9 ... try: ... x = 12 ... finally: ... yield 10 ... yield 11 >>> print list(f()) [1, 2, 4, 5, 8, 9, 10, 11] >>>
Example
# A binary tree class. class Tree: def __init__(self, label, left=None, right=None): self.label = label self.left = left self.right = right def __repr__(self, level=0, indent=" "): s = level*indent + `self.label` if self.left: s = s + "\n" + self.left.__repr__(level+1, indent) if self.right: s = s + "\n" + self.right.__repr__(level+1, indent) return s def __iter__(self): return inorder(self) # Create a Tree from a list. def tree(list): n = len(list) if n == 0: return [] i = n / 2 return Tree(list[i], tree(list[:i]), tree(list[i+1:])) # A recursive generator that generates Tree labels in in-order. def inorder(t): if t: for x in inorder(t.left): yield x yield t.label for x in inorder(t.right): yield x # Show it off: create a tree. t = tree("ABCDEFGHIJKLMNOPQRSTUVWXYZ") # Print the nodes of the tree in in-order. for x in t: print x, print # A non-recursive generator. def inorder(node): stack = [] while node: while node.left: stack.append(node) node = node.left yield node.label while not node.right: try: node = stack.pop() except IndexError: return yield node.label node = node.right # Exercise the non-recursive generator. for x in t: print x, print
Both output blocks display:
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Q & A
Why not a new keyword instead of reusing def?
See BDFL Pronouncements section below.
Why a new keyword for yield? Why not a builtin function instead?
Control flow is much better expressed via keyword in Python, and yield is a control construct. It's also believed that efficient implementation in Jython requires that the compiler be able to determine potential suspension points at compile-time, and a new keyword makes that easy. The CPython reference implementation also exploits it heavily, to detect which functions are generator-functions (although a new keyword in place of def would solve that for CPython -- but people asking the "why a new keyword?" question don't want any new keyword).
Then why not some other special syntax without a new keyword?
For example, one of these instead of yield 3:
return 3 and continue return and continue 3 return generating 3 continue return 3 return >> , 3 from generator return 3 return >> 3 return << 3 >> 3 << 3 * 3
Did I miss one <wink>? Out of hundreds of messages, I counted three suggesting such an alternative, and extracted the above from them. It would be nice not to need a new keyword, but nicer to make yield very clear -- I don't want to have to deduce that a yield is occurring from making sense of a previously senseless sequence of keywords or operators. Still, if this attracts enough interest, proponents should settle on a single consensus suggestion, and Guido will Pronounce on it.
Why allow return at all? Why not force termination to be spelled raise StopIteration?
The mechanics of StopIteration are low-level details, much like the mechanics of IndexError in Python 2.1: the implementation needs to do something well-defined under the covers, and Python exposes these mechanisms for advanced users. That's not an argument for forcing everyone to work at that level, though. return means "I'm done" in any kind of function, and that's easy to explain and to use. Note that return isn't always equivalent to raise StopIteration in try/except construct, either (see the "Specification: Return" section).
Then why not allow an expression on return too?
Perhaps we will someday. In Icon, return expr means both "I'm done", and "but I have one final useful value to return too, and this is it". At the start, and in the absence of compelling uses for return expr, it's simply cleaner to use yield exclusively for delivering values.
BDFL Pronouncements
Issue
Introduce another new keyword (say, gen or generator) in place of def, or otherwise alter the syntax, to distinguish generator-functions from non-generator functions.
Con
In practice (how you think about them), generators are functions, but with the twist that they're resumable. The mechanics of how they're set up is a comparatively minor technical issue, and introducing a new keyword would unhelpfully overemphasize the mechanics of how generators get started (a vital but tiny part of a generator's life).
Pro
In reality (how you think about them), generator-functions are actually factory functions that produce generator-iterators as if by magic. In this respect they're radically different from non-generator functions, acting more like a constructor than a function, so reusing def is at best confusing. A yield statement buried in the body is not enough warning that the semantics are so different.
BDFL
def it stays. ... already made) is "FUD". If this had been part of the language from day one, I very much doubt it would have made Andrew Kuchling's "Python Warts" page.
Reference Implementation
The current implementation, in a preliminary state (no docs, but well tested and solid), is part of Python's CVS development tree [9]. Using this requires that you build Python from source.
This was derived from an earlier patch by Neil Schemenauer [7]. | https://www.python.org/dev/peps/pep-0255/ | CC-MAIN-2018-43 | refinedweb | 2,693 | 54.32 |
Representation of an email address. More...
#include "config.h"
#include <stdbool.h>
#include <stdio.h>
#include <string.h>
#include "mutt/mutt.h"
#include "address.h"
#include "idna2.h"
Go to the source code of this file.
Representation of an email address.c.
Extract a comment (parenthesised string)
Definition at line 78 of file address.c.
Extract a quoted string.
Definition at line 120 of file address.c.
Find the next word, skipping quoted and parenthesised text.
Definition at line 151 of file address.c.
Extract part of an email address (and a comment)
This will be called twice to parse an email address, first for the mailbox name, then for the domain name. Each part can also have a comment in
(). The comment can be at the start or end of the mailbox or domain.
Examples:
The first call will return "john.doe" with optional comment, "comment". The second call will return "example.com" with optional comment, "comment".
Definition at line 198 of file address.c.
Extract an email address.
Definition at line 243 of file address.c.
Parse an email addresses.
Definition at line 283 of file address.c.
Parse an email address.
Definition at line 339 of file address.c.
Parse an email address and add an Address to a list.
Definition at line 364 of file address.c.
Free the result with mutt_addr_free()
Definition at line 385 of file address.c.
Create and populate a new Address.
Definition at line 398 of file address.c.
Remove an Address from a list.
Definition at line 413 of file address.c.
Definition at line 440 of file address.c.
Parse a list of email addresses.
Definition at line 458 of file address.c.
Parse a list of email addresses.
Simple email addresses (without any personal name or grouping) can be separated by whitespace or commas.
Definition at line 607 of file address.c.
Expand local names in an Address list using a hostname.
Any addresses containing a bare name will be expanded using the hostname. e.g. "john", "example.com" -> 'john@.nosp@m.exam.nosp@m.ple.c.nosp@m.om'. This function has no effect if host is NULL or the empty string.
Definition at line 641 of file address.c.
Copy a string and wrap it in quotes if it contains special characters.
This function copies the string in the "value" parameter in the buffer pointed to by "buf" parameter. If the input string contains any of the characters specified in the "specials" parameters, the output string is wrapped in double quoted. Additionally, any backslashes or quotes inside the input string are backslash-escaped.
Definition at line 672 of file address.c.
Copy the real address.
Definition at line 707 of file address.c.
Copy a list of addresses into another list.
Definition at line 728 of file address.c.
Is this a valid Message ID?
Incomplete. Only used to thwart the APOP MD5 attack
Definition at line 755 of file address.c.
Compare two Address lists for equality.
Definition at line 803 of file address.c.
Count the number of Addresses with valid recipients.
An Address has a recipient if the mailbox is set and is not a group
Definition at line 835 of file address.c.
Compare two e-mail addresses.
Definition at line 855 of file address.c.
Definition at line 872 of file address.c.
Does the Address have IDN components.
Definition at line 891 of file address.c.
Does the Address have NO IDN components.
Definition at line 903 of file address.c.
Split a mailbox name into user and domain.
Definition at line 920 of file address.c.
Mark an Address as having IDN components.
Definition at line 942 of file address.c.
Mark an Address as having NO IDN components.
Definition at line 958 of file address.c.
Convert an Address for display purposes.
Definition at line 977 of file address.c.
Write a single Address to a buffer.
If 'display' is set, then it doesn't matter if the transformation isn't reversible.
Definition at line 1016 of file address.c.
Write an Address to a buffer.
If 'display' is set, then it doesn't matter if the transformation isn't reversible.
bufis nul terminated!
Definition at line 1138 of file address.c.
Convert an Address to Punycode.
Definition at line 1188 of file address.c.
Convert an Address list to Punycode.
Definition at line 1217 of file address.c.
Convert an Address from Punycode.
Definition at line 1262 of file address.c.
Convert an Address list from Punycode.
Definition at line 1299 of file address.c.
Remove duplicate addresses.
Given a list of addresses, return a list of unique addresses
Definition at line 1319 of file address.c.
Remove cross-references.
Remove addresses from "b" which are contained in "a"
Definition at line 1355 of file address.c.
Unlink and free all Address in an AddressList.
Definition at line 1382 of file address.c.
Append an Address to an AddressList.
Definition at line 1402 of file address.c.
Prepend an Address to an AddressList.
Definition at line 1413 of file address.c.
An out-of-band error code.
Many of the Address functions set this variable on error. Its values are defined in AddressError. Text for the errors can be looked up using AddressErrors.
Definition at line 57 of file address.c.
Messages for the error codes in AddressError.
These must defined in the same order as enum AddressError.
Definition at line 64 of file address.c. | https://neomutt.org/code/address_2address_8c.html | CC-MAIN-2020-05 | refinedweb | 919 | 63.46 |
Walkthrough: Debugging a Project (C++)
In this step, you modify the program to fix the problem that was discovered when testing the project.
To fix a program that has a bug
To see what occurs when a Cardgame object is destroyed, view the destructor for the Cardgame class.
If you are using Visual C++ Express 2010 with Basic Settings, choose Tools, Settings, Expert Settings.
On the menu bar, choose View, Class View or click the Class View tab in the Solution Explorer window to see a representation of the class and its members. In the Class View window, expand the Game project tree and then choose the Cardgame class. The area underneath shows the class members and methods.
Open the shortcut menu for the ~Cardgame(void) destructor and then choose Go To Definition.
To decrease the totalParticipants value when a card game terminates, type the following code between the opening and closing braces of the Cardgame::~Cardgame destructor:
The Cardgame.cpp file should resemble this after your changes:
#include "Cardgame.h" #include <iostream> using namespace std;.
On the menu bar, choose Debug, Start Debugging or choose the F5 key to run the program in Debug mode. The program pauses at the first breakpoint.
On the menu bar, choose Debug, Step Over or choose the F10 key to step through the program.
Note that after each Cardgame constructor executes, the value of totalParticipants increases. When the PlayGames function returns, as each Cardgame instance goes out of scope and the destructor is called, totalParticipants decreases.
Just before the return statement is executed, totalParticipants equals 0. Continue stepping through the program until it exits, or on the menu bar, choose Debug, Continue, or choose the F5 key to allow the program to continue to run until it exits. | https://msdn.microsoft.com/en-us/library/bb384844(v=vs.100).aspx | CC-MAIN-2017-09 | refinedweb | 295 | 62.58 |
.
Thanks for making free education website.
[int add(int x, int y)
{
return x + y;
}
int main()
{
int a ;
a = 0;
int b;
b = 0;
std::cout << "You are walking down an old hallway." << std::endl;
std::cout << "You come to the end of the hall. " << std::endl;
std::cout << " There are two doors." << std::endl; // this is the introduction of the customised story
std::cout << "Door 0 " << std::endl;
std::cout << "And Door 1" << std::endl;
std::cout << "Which way will you go?";
std::cin >> a;
std::cout << add(a, b);
if (b = 0)
{
std::cout << "You go left. and there is more hallway" << std::endl;
std::cout << "after a few twists and turns you come to three doors." << std::endl;
std::cout << "Door 2" << std::endl;
std::cout << "Door 3" << std::endl;
std::cout << "Door 4" << std::endl;
std::cout << "Which way this time?";
std::cin >> a;
std::cout << add(a, b);
}
if (b=1)
{
std::cout << "You go through the door." << std::endl;
std::cout << "You hear a rumble behind you." << std::endl;
std::cout << "The door dissappeared and was replaced by a wall!" << std::endl;
std::cout << "You are trapped in a box!" << std::endl;
std::cout << "The roof slowly closes in on you!" << std::endl;
std::cout << "You feel as your ribs give way" << std::endl;
std::cout << "You died (Ending 1)";
}
std::cin.clear();
std::cin.ignore(32767, '\n');
std::cin.get();
return 0;
} ]
umm i tried this and it only gives you the door one route help!
You need to use operator== for comparison, not operator= (which is assignment).
ok thank you
Great job, just a few things I think you missed.
isn’t this best practice: return (x > y) ? y : x;
And
shouln’t ErrorCode be a class?
Fixed both issues. Thanks for pointing those out.
hi Alex
i have a question
let's say i want to direct the user input based on the contents he write
like this
[/code]
int input;
string input;// i know i can't name the same name for more than one
it's only for demonstration
if (input != integer )
cin >> input;
else
getline(cin, s_input);
[/code]
how to tell C++ i mean numbers or a string as a class or a group ?
There's no easy way to do this -- C++ doesn't support variable with variable types. The best you can do is read in a string, then determine whether the user actually entered a numeric value, and convert it to an integer.
how bad
thank you Alex
ok so i want to do a thing where enter either (Y/N) into x then if (x==Y)
goto this
if (x==N)
goto that
else;
invalid response
but it sees Y and N as variables not as values any help would be appreciated :)
In this case, 'Y' or 'N' needs to be put in single quotes so the compiler will treat them as literal characters instead of variables.
#include "stdafx.h"
#include <iostream>
using namespace std;
int main()
{
int y;
int x;
cout << " what year were u born in ? " << endl;
cin >> x;
cout << " Your age is " << 2016 - x << endl;
cout << "what number month were u born in ? " << endl;
cin >> y;
if (y == 1)
{
cout << " You were born in January " << endl;
}
if (y == 2)
{
cout << "You were born in February " << endl;
}
if (y == 3)
{
cout << "You were born in March" << endl;
}
if (y == 4)
{
cout << "You were born in April" << endl;
}
if (y == 5)
{
cout << "You were born in May" << endl;
}
if (y == 6)
{
cout << "You were born in June" << endl;
}
if (y == 7)
{
cout << "You were born in July" << endl;
}
if (y == 8)
{
cout << "You were born in August" << endl;
}
if (y == 9)
{
cout << "You were born in September" << endl;
}
if (y == 10)
{
cout << "You were born in October" << endl;
}
if (y == 11)
{
cout << "You were born in November" << endl;
}
if (y == 12)
{
cout << "You were born in December" << endl;
}
std::cin.clear(); // reset any error flags
std::cin.ignore(32767, '\n'); // ignore any characters in the input buffer until we find an enter character
std::cin.get(); // get one more char from the user
return 0;
}
What did i do wrong?
Line 12: inclusive should be exclusive
Line 14: is greater than should be is greater than or equal to
Hello!
Please, who knows C++ well, tell me, if if statements works like this:
string x;
cin >> string;
if (x==hello || x==hi || x==1) {}
My compiler does an error but how could I compare string variables like this? Or maybe Im not allowed to use "||" statement twice?
Help me please, I liked C++ when I just saw this website but I still have some troubles.
String literals have to be in double quotes:
thank you
In your first two "Nesting If Statements" examples, wouldn't the line:
std::cout << x << "is greater than 20\n";
also be printed if x is equal to 20? And similarly for x=10 in the third example? In that case, the printout isn't strictly correct.
Without context, between can be used inclusively or exclusively. I meant it in the inclusive sense here. I've updated the lesson to explicitly note the inclusiveness.
0 is not negative. Also it works with the sqrt() why not include it? Was it not allowed in earlier versions of C++?
I'm not sure what you mean. The code includes 0.0 in the set of valid input:
Anyone want a challenge? Here try this ! It will flex your mental logic muscles.
The program should hide the number the program selects and the user has 10 tries to guess the number from 0-1000. The program should tell you after each guess if you need to pick a high or lower number.
Now the hard part! Your program should keep track of your low and high guess. However as the user guesses more guesses the high and low best guesses should adjust according to the users guesses.
eg. lets say the program picks 300 and the user guesses 500 out of a range of 0-1000 the program will reply back "...lower"
However the program now has to keep track of your best or closest high and low guesses.
Sounds easy? You try it!
disclosure: I don't have the answer as I am at the time banging my head on the keyboard lol
It isn't even the whole code. -_-
Hi there Alex,
I just always wanted to spot something missed that we learned from you that was inconsistent && that no one else has mentioned yet so here is mine.
In the example where you are instructing that you can use if statements with logical operators starting with the and (&&) operator, and the or (||) operator, your code reads:
else if (x > 0 || y > 0)
std::cout << "One of the numbers is evenn";
but wouldn't it actually be:
else if (x > 0 || y > 0)
std::cout << "At least one of the numbers is evenn";
since the logical OR operator evaluating to true means that one or both statements (assuming there are only two) are true?
Also, thank you so much for taking the time to construct this material. You tutorials are by far the best I have came acrost o the internet thus far, you make the material so easy to understand and it's obvious that you very carfuly considered your structure and the proper order to learn the material, it all just works so well. Thnak You so much!
Your logic around how logical OR works is correct -- however, what you're missing here is that this is an else if statement, and else if only executes if the original if isn't true. So consider:
The first if statement checks if both numbers are positive. If so, the rest of the if else chain never executes. So if we reach the else if statement, it must be true that both numbers are not positive! Given that there are only two numbers in this case, and we know both aren't positive, if either one is positive then it means only one is positive. So we can definitively say only one is positive in this case.
hi ALEX .i followed you tutorials and i learned so much about C++ from you (So thanks about this). from this point on i start coding your examples in my own way whit method's which i learned from you . this is your example :
and this is my code :
i'm grateful if you correct my mistakes or tell any suggestion.
Hello there,
Just to clear up the thing that has been bothering me all this time
Is the following
equivalent to this
or this
Or is there any other difference that i am not aware of?
Thanks in advance
None of the above are identical.
In the top example, the two statements are independent (the execution of the first one doesn't impact the execution of the second one).
In the middle example, the two statements are conditional. The second statement will only execute if its expression is true AND the first statement didn't execute.
The the bottom example, the two statements are conditional. The second statement will only execute if its expression is true AND the first statement did execute.
how to understand the logic behind any c++ program. can anyone help me out with the loops!
can you help me with my homework. Create a program that will input a number and will display the number is odd or an even number. SAMPLE OUTPUT: Enter a number: 5
That is odd number. please I've been doing my homework for 8 hours and still having a hard time. I will gladly appreciate if you will help me thanks and God bless you.
I won't solve your homework for you, but I will tell you that an easy way to tell whether a number is even or odd is to use the modulus operator (%). I cover the modulus operator in lesson 3.2 -- Arithmetic operators.
in section "Common uses for if statements", second example.
add
Updated, thanks!
The same is needed for the example just below "Chaining if statements".
What happened to our Todd? :D
You are our new Todd. :) Fixed!
I can never be half as sharp as Todd is, but I'll try. LOL :'D
can anyone help me
i want to know how to do dry run
Don't go out when it's raining?
"Dry run" is an expression from bricklaying. You lay out the bricks for a row without mortar to see how they fit (a dry run). If you need to cut a brick in half, it's better to know in advance so you can put the half-brick near the middle. Otherwise you don't find out that one of the bricks needs to be cut until you're near the end. Having the cut brick near the end is weaker and looks funny.
I know, that's two snarky replies with nothing you can use, but at least this one's interesting.
Note my comment. This program only prints something if user inputs a value greater than 10. But user was never asked to do so. If user inputs a value less than 10, program prints nothing and user can't figure out why it doesn't work.
Yes, correct. This is something you wouldn't want to do in a real program, but the point of the program is to show how use of parenthesis disambiguates a dangling else case.
You'll note in the next example we add an else case to the outer if statement.
Dear Alex,
It seems you are updating the whole tutorial. That's nice and thanx for that. I would like to make a little suggestion.
If you could add a little note mentioning which parts were updated with the updated date that would be very much helpful for us.
Thanx
-Kanchana
I am doing that moving forward. You can already see a few of the previous lessons have been updated with a date.
I'm trying to write a code that that takes a no. from the user another no. from the user in the same line & any one of these operators (+ - * / %) beside the second no.& gives the result as output. How do I do this? Note: the user must be able to do this 5 times in a go.
1) Since the user has to be able to do this 5 times, use a loop to allow the user to do this more than once. The loop can call a function.
2) The function should ask the user for input, and then use an if statement (or switch statement) on the operator to give the result.
This question is pretty similar to a question I asked in the chapter 2 comprehensive quiz, just with a loop so it executes more than one time.
"Without the block, the else statement would attach to the nearest unmatched if statement..."
Hey (not sure if you still check comments), but shouldn't the indentation of your 'else' statement(?) indicate which 'if' it belongs to? I understand the use of parentheses to aid in readability, but is that also the case for indentation in this regard?
In C++, indentation is for readability only. It does not have any effect on the program.
hello everyone
i have a problem .it compiles even but never prints either of the code.just prints "press any key to continue".why so?
#include
#include // for sqrt()
void PrintSqrt(double dValue)
{
using namespace std;
if (dValue >= 0.0)
cout << "The square root of " << dValue << " is " << sqrt(dValue) << endl;
else
cout << "Error: " << dValue << " is negative" << endl;
}
int main()
{
return 0;
}
You created a function, but never called on it in your main() so nothing is being executed.
Ex:
#include
int main()
{
double myValue = 2.0;
PrintSqrt(myValue);
return 0;
}
Hi. I didn´t understand this example in chapter 6.7
if (pnPtr)
cout << "pnPtr is pointing to an integer.";
else
cout << "pnPtr is a null pointer.";
I don´t know what´s the condition for the if statement.
Thanks in advance.
"if (pnPtr) ..." is the same thing as "if (pnPtr != 0) ..." due to the way boolean values evaluate.
This probably is a little easier to understand if you're not used to the shortcut syntax:
post c++11 it is recommended to use the keyword 'nullptr' to check if a pointer is null.
How do you check if a char variable equals a certain character?
where c is your char variable, and 'a' is the character you're testing for.
Is it possible for you to set more than one required parameter for the 'if' statement to pass? Such as - to see what attack a player chose and if they have the ability to use it?
Yes it is, though your example is bad, as it can be done with a single if parameter.
but here's an example -
bool something (bool a, bool b)
{ if ( a == true && b == false )
{ do something();
return true;
}
}
where is my bug in my code:
another thing i can't do:
can i press my choose 1 or 2 without press enter key?
remove the ; after
and both if statements should be
I think that learn from this way of explanation is very directly, whithout hesitating...
I read books for C++, but I spend time more than ussual, because no colours , no tabels,and no
orders of information like in your wwww. Maybe the books must be in electron formats for faster
learning and training, with colours and pictures..
THANK YOU...
MANY GOOD JOBS...
Hi, i am a bit confused.
If nValue is negative, and the function returns ERROR_NEGATIVE_NUMBER. How do you know its an error?
Because ERROR_NEGATIVE_NUMBER could = 3 right?
So when calling this function, if you wanted to make sure there was no error you
would do sometihng like
if (!DoCalculation(9)) {
}
sorry, I accidntly posted before I was finnished writing. What I was saying is Wouldn't the error codes be the same as correct output?
So how would know if the output was an error or an answer?
or are error code usually more obscure, like ERROR_NEGATIVE_NUMBER = E-0f96
just going off the previous lesson about enums.
Hope this makes sence, sorry I might be way off!
Actually you're pretty accurate, the example is rather ambiguous on this point, but it wasn't meant to be usable code. ERROR_NEGATIVE_NUMBER would have to be a value that would not normally be returned by DoCalculation. For example, since DoCalculation does not accept negative numbers, it most likely doesn't return negative numbers, therefore in that case ERROR_NEGATIVE_NUMBER could be -1.
I've updated the example to make it more comprehensive.
Returning an enum error code works if:
* The error code is the only return value (e.g. the function would have otherwise returned void).
* The error codes are defined to be numbers that the function can't normally return (e.g. the error codes are all negative numbers, and the function would otherwise return only positive numbers).
Hi, great website btw!
However, whenever i try to use a char variable in an if statement (e.g :
if(a = "Hello")
cout << "Hello there";
it does not compile correctly.
can anyone help? if so please email me on fight.the.purple@hotmail.co.uk or leave a comment
many thanks
First off, = is for assignment, not comparison. You would normally use == to do comparisons, except == doesn't work on string literals (which is anything inside double quotes). Probably the best way is to declare your a variable as a std::string instead of a char. Then it will work as you expect.
Hey alex just a quick clarification. when a compiler implicitly makes a block if none is declared it will only do so for the first single line statement ? in the example below it will create a block for "return ERROR_NEGATIVE_NUMBER;" and will not include "return ERROR_SUCCESS;" ? thanks.
ErrorCode doSomething(int value)
{
// if value is a negative number
if (value < 0)
// early return an error code
return ERROR_NEGATIVE_NUMBER;
// Do whatever here
return ERROR_SUCCESS;
}
Hey wouldn't it be a blast if you could add a chat section to your website :D ? where we all can collaborate and help each other out with minor questions. for those who are online. i am really new to C++ and i have a ton of questions that would have been considered spamming and could bloat your database.
Yes, only for the first statement.
The chat section is an interesting idea. Let me explore that further.
Name (required)
Website | https://www.learncpp.com/cpp-tutorial/52-if-statements/comment-page-1/ | CC-MAIN-2019-13 | refinedweb | 3,122 | 72.97 |
The RDM rowid datatype API. The functions here are located in RDM Base Functionality. Linker option:
-l
rdmbase
#include <rdmrowidapi.h>
Decode a ROWID into a union number and slot.
This function will decode a ROWID into its parts: a union number and a slot number.
The union number is 0 for the first database and one higher for each additional database in the union. The union number is 0 for a single database.
The slot is the row ID as it is stored in the individual databases. For a single database the row ID and the slot are the same.
#include <rdmrowidapi.h>
Encode a union number and slot into a ROWID.
This function will encode a ROWID from its parts: a union number and a slot number. | https://docs.raima.com/rdm/14_1/group__rowid.html | CC-MAIN-2019-18 | refinedweb | 129 | 76.72 |
The MLAPI are the Application Program Interface of ML. MLAPI defines a MATLAB-like environment for rapid prototyping of new multilevel preconditioners, usually of algebraic type.
All MLAPI objects are defined in the MLAPI namespace. The most important objects are:
MLAPI can be used for both serial and parallel computations.
Class MLAPI::MultiVector contains one or more vectors. The general usage is as follows:
Space MySpace(128); MultiVector V; int NumVectors = 1; V.Reshape(V, NumVectors);
A new vector can be added to the already allocated ones as follows:
V.Add();
Equivalently, one vector can be deleted. For example, to delete the second multivector, one can write
V.Delete(2);
meaning that now
V contains just one vector.
One of the most powerful feature of C and C++ if the capability of allocating memory. Unfortunately, this is also the area where most bugs are found -- not to mention memory leaks. We have adopted smart pointers to manage memory. MLAPI objects should never be allocated using
new, and therefore never free them using
delete. The code will automatically delete memory when it is no longer referenced by any object. Besides, functions or methods that need to return MLAPI objects, should always return an instance of the required object, and not a pointer or a reference.
Let us consider three generic MLAPI objects. The assignment A = B means the following: all smart pointers contained by B are copied in A, both A and B point to the same memory location. However, A and B are not aliases: we can still write
B = C
meaning that A contains what was contained in B, and both B and C point to the same memory location. Should we need to create a copy of C in B, we will use the instruction
which is instead an expensive operation, as new memory needs to be allocated, then all elements in C need to be copied in B.
Although MLAPI is design to be a framework for development of new preconditioners, two classes already defines ready-to-use preconditioners:
Any Epetra_RowMatrix derived class can be wrapped as an MLAPI::Operator. (However, some restrictions apply, please check you Epetra_Map's for more details.)
An MLAPI::InverseOperator (and therefore preconditioners MLAPI::MultiLevelSA and MLAPI::MultiLevelAdaptiveSA) can be easily wrapped as an Epetra_Operator derived class, then used within, for instance, AztecOO. An example is reported in EpetraInterface.cpp. | http://trilinos.sandia.gov/packages/docs/r11.2/packages/ml/doc/html/ml_mlapi.html | CC-MAIN-2014-15 | refinedweb | 398 | 55.34 |
draw text label associated with a point More...
#include <vtkCaptionActor2D.h>
draw text label associated with a point.
To use the caption actor, you normally specify the Position and Position2 coordinates (these are inherited from the vtkActor2D superclass). (Note that Position2 can be set using vtkActor2D's SetWidth() and SetHeight() methods.) Position and Position2 define the size of the caption, and a third point, the AttachmentPoint, defines a point that the caption is associated with.).
The trickiest part about using this class is setting Position, Position2, and AttachmentPoint correctly. These instance variables are vtkCoordinates, and can be set up in various ways. In default usage, the AttachmentPoint is defined in the world coordinate system, Position is the lower-left corner of the caption and relative to AttachmentPoint (defined in display coordaintes, i.e., pixels), and Position2 is relative to Position and is the upper-right corner (also in display coordinates). However, the user has full control over the coordinates, and can do things like place the caption in a fixed position in the renderer, with the leader moving with the AttachmentPoint.
Definition at line 74 of file vtkCaptionActor2D.h.
Definition at line 77 of file vtkCaptionActor2D.
Define the text to be placed in the caption.
The text can be multiple lines (separated by "\n").
Set/Get the attachment point for the caption.
By default, the attachment point is defined in world coordinates, but this can be changed using vtkCoordinate methods.
Enable/disable the placement of a border around the text.
Enable/disable drawing a "line" from the caption to the attachment point.
Indicate whether the leader is 2D (no hidden line) or 3D (z-buffered).
Specify a glyph to be used as the leader "head".
This could be something like an arrow or sphere. If not specified, no glyph is drawn. Note that the glyph is assumed to be aligned along the x-axis and is rotated about the origin. SetLeaderGlyphData() directly uses the polydata without setting a pipeline connection. SetLeaderGlyphConnection() sets up a pipeline connection and causes an update to the input during render.
Specify the relative size of the leader head.
This is expressed as a fraction of the size (diagonal length) of the renderer. The leader head is automatically scaled so that window resize, zooming or other camera motion results in proportional changes in size to the leader glyph.
Specify the maximum size of the leader head (if any) in pixels.
This is used in conjunction with LeaderGlyphSize to cap the maximum size of the LeaderGlyph.
Set/Get the padding between the caption and the border.
The value is specified in pixels.
Get the text actor used by the caption.
This is useful if you want to control justification and other characteristics of the text actor.
Set/Get the text property.
Enable/disable whether to attach the arrow only to the edge, NOT the vertices of the caption border.
Reimplemented from vtkProp.
Definition at line 221 of file vtkCaptionActor2D.h.
Definition at line 234 of file vtkCaptionActor2D.h.
Definition at line 236 of file vtkCaptionActor2D.h.
Definition at line 237 of file vtkCaptionActor2D.h.
Definition at line 238 of file vtkCaptionActor2D.h.
Definition at line 239 of file vtkCaptionActor2D.h.
Definition at line 240 of file vtkCaptionActor2D.h.
Definition at line 242 of file vtkCaptionActor2D.h.
Definition at line 243 of file vtkCaptionActor2D.h. | https://vtk.org/doc/nightly/html/classvtkCaptionActor2D.html | CC-MAIN-2020-16 | refinedweb | 557 | 51.24 |
How Can I Pass Data To and Get Data From a Dialog Window?
Rev has built-in support for basic dialogs using the answer and ask commands. But sometimes your application needs to display a customized dialog to the user. The dialog may prompt for some user input or merely alert the user about something. In this case you need to create a stack that acts as your modal dialog (you can make the dialog stack as a substack of your main program stack).
This lesson will show you how to use the dialogData global property to pass data from the handler that opens the dialog to the modal dialog stack itself, and then back again. The dialogData is a special global property reserved especially for passing data back and forth between a dialog window and the handler that opens the dialog window.
The ScenarioThe Scenario
In order to see how the dialogData global property works I will show you how to open a dialog by clicking on a button (1). The dialog that opens will display a list of choices (2). The item that is initially selected (3) will be provided by the main application window when the button is clicked.
When the dialog window is closed (4) the item that was selected will be passed back to handler that opened the dialog.
Opening The DialogOpening The Dialog
Let's start by looking at the revTalk code that opens a dialog. When clicking on the Open Dialog button (1) the stack My Modal Window will be opened as a modal window (2). Before opening the window, however, the global property the dialogData will be assigned the name of the item that should be selected by default (3) when the dialog opens.
Selecting the Default Choice In The Modal Dialog ListSelecting the Default Choice In The Modal Dialog List
Because a global property (remember that the dialogData is a global property) is available in all of your scripts the preOpenCard handler in the My Modal Window card script (the only card of the My Modal Window stack) has access to it.
The modal dialog uses the value stored in the dialogData (1) to select the default choice in the list field (2).
Passing The Selected Choice Back To The Calling HandlerPassing The Selected Choice Back To The Calling Handler
Data can be passed from the dialog window back to the handler that opened the dialog window just as easily. Before closing the dialog window just set the dialogData to the value you want to return (1).
In this case the dialogData will be set to the text that is selected in the list (2). You can set the dialogData to any value though.
## Checkbox
set the dialogData to the hilite of button "MyCheckBox"
## Group with radio buttons
set the dialogData to the hilitedButtonName of group "MyRadioButtons"
## Text field
set the dialogData to the text of field "MyField"
If your dialog allows multiple inputs you can pass each value back on separate lines or using an array (go to the end of this lesson for more information on using arrays).
set the dialogData to the hilite of button "MyCheckBox" & cr & the hilitedButtonName of group "MyRadioButtons"
Displaying Selected ChoiceDisplaying Selected Choice
The ResultThe Result
Additional Notes: Using Arrays With The dialogDataAdditional Notes: Using Arrays With The dialogData
You can also pass arrays in the dialogData global property. Using arrays to pass data in the dialogData can be very useful when passing multiple values. The keys to using arrays are:
1) To assign an array to the dialogData create a variable that is an array and assign that variable to the dialogData.
2) To get an array out of the dialogData put the dialogData value into a variable and then use the variable.
The following revTalk will display the answer dialog pictured here.
-- Assign an array to the dialogData
put "a string" into theA["a string"]
put 0 into theA["a number"]
-- Store the array in the dialogData
set the dialogData to theA
-- Get an array from the dialogData
put the dialogData into theA
-- Display keys of the array
answer theA["a string"] & cr & theA["a number"] | http://lessons.livecode.com/s/lessons/m/4071/l/7388-how-can-i-pass-data-to-and-get-data-from-a-dialog-window | CC-MAIN-2017-47 | refinedweb | 694 | 54.05 |
Here you can find the source of writeToFile(String textToWrite, String fileName)
public static String writeToFile(String textToWrite, String fileName)
//package com.java2s; /*/*from w ww . j av a 2 s .co m*/ * Copyright (C) 2010-2012 Stichting Akvo (Akvo Foundation) * * This file is part of Akvo FLOW. * * Akvo FLOW is free software: you can redistribute it and modify it under the terms of * the GNU Affero General Public License (AGPL) as published by the Free Software Foundation, * either version 3 of the License or any later version. * * Akvo FLOW is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. * See the GNU Affero General Public License included below for more details. * * The full license text can also be seen at <>. */ import java.io.File; import java.io.FileWriter; import java.io.IOException; public class Main { /** * writes the contents of textToWrite to a file on the local filesystem identified by fileName. * * @param textToWrite * @param fileName * @return - the absolute path of the file written * @throws IOException */ public static String writeToFile(String textToWrite, String fileName) { File outFile = new File(fileName); try { if (!outFile.exists()) { outFile.createNewFile(); } FileWriter out = new FileWriter(outFile, true); out.write(textToWrite); out.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return outFile.getAbsolutePath(); } } | http://www.java2s.com/example/android-utility-method/text-file-write/writetofile-string-texttowrite-string-filename-996ff.html | CC-MAIN-2019-47 | refinedweb | 225 | 57.67 |
will
- Perform, ensure.
Download and use the free Visual Studio 2019 Community Edition. Make sure that you enable Azure development workload during the Visual Studio setup.
All the screenshots in this article have been taken using Microsoft Visual Studio Community 2019. If your system is configured with a different version, it is possible that your screens and options may not match entirely, but if you meet the above prerequisites this solution should work.
Step 1: Create an Azure Cosmos account
Let's start by creating an Azure Cosmos account. If you already have an Azure Cosmos DB SQL API account or if you are using the Azure Cosmos DB emulator for this tutorial, you can skip to Create a new ASP.NET MVC application section.
Select Create a resource > Databases > Azure Cosmos DB..
Now navigate to the Azure Cosmos DB account page, and click Keys, as these values are used in the web application you create next.
In the next section, you create a new ASP.NET Core MVC application.
Step 2: Create a new ASP.NET Core MVC application
In Visual Studio, from the File menu, choose New, and then select Project. The New Project dialog box appears.
In the New Project window, use the Search for templates input box to search for "Web", and then select ASP.NET Core Web Application.
In the Name box, type the name of the project. This tutorial uses the name "todo". If you choose to use something other than this name, then wherever this tutorial talks about the todo namespace, adjust the provided code samples to use whatever you named your application.
Select Browse to navigate to the folder where you would like to create the project. Select Create.
The Create a new ASP.NET Core Web Application dialog box appears. In the templates list, select Web Application (Model-View-Controller).
Select Create and let Visual Studio do the scaffolding around the empty ASP.NET Core MVC template.
Once Visual Studio has finished creating the boilerplate MVC application, you have an empty ASP.NET application that you can run.
The Azure Cosmos DB .NET SDK is packaged and distributed as a NuGet package. To get the NuGet package in Visual Studio, use the NuGet package manager in Visual Studio by right-clicking on the project in Solution Explorer and then select Manage NuGet Packages.
The Manage NuGet Packages dialog box appears. In the NuGet Browse box, type Microsoft.Azure.Cosmos. From the results, install the Microsoft.Azure.Cosmos package. It downloads and installs the Azure Cosmos DB package and its dependencies. Select I Accept in the License Acceptance window to complete the installation.
Alternatively, you can use the Package Manager Console to install the NuGet package. To do so, on the Tools menu, select NuGet Package Manager, and then select Package Manager Console. At the prompt, type the following command:
Install-Package Microsoft.Azure.Cosmos
After the package is installed, your Visual Studio project should contain the library reference to Microsoft.Azure.Cosmos.
Step 4: Set up the ASP.NET Core MVC application
Now let's add the models, the views, and the controllers to this MVC application:
Add a model
From the Solution Explorer, right-click the Models folder, select Add, and then select Class. The Add New Item dialog box appears.
Name your new class Item.cs and select Add.
Next replace the code; } } }
The data stored in Azure Cosmos DB is passed over the wire and stored as JSON. To control the way your objects are serialized/deserialized by JSON.NET, you can use the JsonProperty attribute as demonstrated in the Item class you created. Not only can you control the format of the property name that goes into JSON, you can also rename your .NET properties like you did with the Completed property.
Add a controller
From the Solution Explorer, right-click the Controllers folder, select Add, and then select Controller. The Add Scaffold dialog box appears.
Select MVC Controller - Empty and select Add.
Name your new controller, ItemController, and replace the code in that file. There is more to it than just adding this attribute, your views should work with this anti-forgery token as well. For more on the subject, and examples of how to implement this correctly, see Preventing Cross-Site Request Forgery. The source code provided on GitHub has the full implementation in place.
We also use the Bind attribute on the method parameter to help protect against over-posting attacks. For more details, please see Basic CRUD Operations in ASP.NET MVC.
Add views
Next, let's create the following three views:
Add a list item view
In Solution Explorer, expand the Views folder, right-click the empty Item folder that Visual Studio created for you when you added the ItemController earlier, click Add, and then click View.
In the Add View dialog box, update the following values:
- In the View name box, type Index.
- In the Template box, select List.
- In the Model class box, select Item (todo.Models).
- In the layout page box, type ~/Views/Shared/_Layout.cshtml.
After you add these values, select Add and let Visual Studio create a new template view. Once done, it opens the cshtml file that is created. You can close that file in Visual Studio as you will come back to it later.
Add a new item view
Similar to how you created a view to list items, create a new view to create items by using the following steps:
From the Solution Explorer, right-click the Item folder again, select Add, and then select View.
In the Add View dialog box, update the following values:
- In the View name box, type Create.
- In the Template box, select Create.
- In the Model class box, select Item (todo.Models).
- In the layout page box, type ~/Views/Shared/_Layout.cshtml.
- Select Add.
Add an edit item view
And finally, add a view to edit an item with the following steps:
From the Solution Explorer, right-click the Item folder again, select Add, and then select View.
In the Add View dialog box, do the following:
- In the View name box, type Edit.
- In the Template box, select Edit.
- In the Model class box, select Item (todo.Models).
- In the layout page box, type ~/Views/Shared/_Layout.cshtml.
- Select Add.
Once this is done, close all the cshtml documents in Visual Studio as you return to these views later.
Step 5: Connect to Azure Cosmos DB
Now that the standard MVC stuff is taken care of, let's turn to adding the code to connect to Azure Cosmos DB and perform CRUD operations.
Perform CRUD operations on the data
The first thing to do here is add a class that contains the logic to connect to and use Azure Cosmos DB. For this tutorial, we'll encapsulate this logic into a class called
CosmosDBService and an interface called
ICosmosDBService. This service performs the CRUD and read feed operations such as listing incomplete items, creating, editing, and deleting the items.
From Solution Explorer, create a new folder under your project named Services.
Right-click the Services folder, select Add, and then select Class. Name the new class CosmosDBService and select Add.
Add the following code to the CosmosDBService class and replace the code in that file) { ItemResponse<Item> response = await this._container.ReadItemAsync<Item>(id, new PartitionKey(id)); if (response.StatusCode == System.Net.HttpStatusCode.NotFound) { return null; } return response.Resource; } steps 2-3, but this time, for a class named ICosmosDBService, and add); } }
The previous code receives a
CosmosClientas part of the constructor. Following ASP.NET Core pipeline, we need to go to the project's Startup.cs and initialize the client based on the configuration as a Singleton instance to be injected through Dependency Injection. In the ConfigureServices handler, we define:
services.AddSingleton<ICosmosDbService>(InitializeCosmosClientInstanceAsync(Configuration.GetSection("CosmosDb")).GetAwaiter().GetResult());
Within the same file, we define our helper method InitializeCosmosClientInstanceAsync, which will read the configuration and initialize; }
The configuration is defined in the project's appsettings.json file. Open it and add a section called CosmosDb:
"CosmosDb": { "Account": "<enter the URI from the Keys blade of the Azure Portal>", "Key": "<enter the PRIMARY KEY, or the SECONDARY KEY, from the Keys blade of the Azure Portal>", "DatabaseName": "Tasks", "ContainerName": "Items" }
Now if you run the application, ASP.NET Core's pipeline will instantiate CosmosDbService and maintain a single instance as Singleton; when ItemController is used to process client side requests, it will receive this single instance and be able to use it to perform CRUD operations.
If you build and run this project now, you should now see something that looks like this:
Step 6: Run the application locally
To test the application on your local machine, use the following steps:
Press F5 in Visual Studio to build the application in debug mode. It should build the application and launch a browser with the empty grid page we saw before:
Click the Create New link and add values to the Name and Description fields. Leave the Completed check box unselected otherwise the new item is added in a completed state and doesn't appear on the initial list.
Click Create and you are redirected back to the Index view and your item appears in the list. You can add a few more items to your todo list.
Click Edit next to an Item on the list and you are taken to the Edit view where you can update any property of your object, including the Completed flag. If you mark the Complete flag and click Save, the Item will be displayed as completed in the list.
You can verify at any point the state of the data in the Azure Cosmos DB service using Cosmos Explorer or the Azure Cosmos DB Emulator's Data Explorer.
Once you've tested the app, press on the project in Solution Explorer and select Publish.
In the Publish dialog box, select App Service, then select Create New to create an App Service profile, or choose Select Existing to use an existing profile.
If you have an existing Azure App Service profile, select a Subscription from the dropdown. Use the View filter to sort by resource group or resource type. Next search the required Azure App Service and select OK.
To create a new Azure App Service profile, click Create New in the Publish dialog box. In the Create App Service dialog, enter your Web App name and the appropriate subscription, resource group, and App Service plan, then select Create.
In a few seconds, Visual Studio publishes your web application and launches a browser where you can see your project running in Azure!
Next steps
In this tutorial, you've learned how to build an ASP.NET Core MVC web application that can access data stored in Azure Cosmos DB. You can now proceed to the next article:
Feedback | https://docs.microsoft.com/en-us/azure/cosmos-db/sql-api-dotnet-application | CC-MAIN-2019-35 | refinedweb | 1,817 | 64.51 |
We continue from TFS Integration Tools – Where does one start? … part 1 (documentation) and TFS Integration Tools – Where does one start? … part 2 (try a simple migration). In this post we look what happened after “gently” selecting START.
Remember the following …
- We configured the session using no customizations, such as field or value mapping … out of the box.
- We have not worried about permissions.
… let’s see what happened after a few minutes of analysis…
Resolving the conflicts
WIT Conflict
The first “stop-the-bus” conflict was raised by the WIT session and had we read the configuration guide we would have noticed that by default the EnableBypassRuleDataSubmission rule is enabled, which requires the credential of the migration user to be a member of the Team Foundation Service Accounts group.
Using the TFSSecurity tool we can add the credentials to the Team Foundation Service Accounts group, by running the following command as shown below:
tfssecurity /g+ srv: @SERVER@\Administrator /server:@SERVER@, whereby we are using the Administrator credentials.
After this fix, the 1000+ entries wandered across the copper cable … or is that WiFi copper-less network?
VC Conflict
The VC session was the next to pull the migration hand-brake with the following conflict:
The conflict was thrown in our case, as the three template files exist in both the source project and the new target project, as created during the team project creation. Which is the right version? Well, the tool cannot make any assumptions and therefore stops the bus … or rather migration pipeline.
As shown above, there is a “click here” hyperlink, which takes us to the relevant version control conflict definition and suggested resolution:
In essence we have to look at both the team project we are migrating from to find the relevant changesets …
… and the team project we are migrating to:
What is worth highlighting is that this specific conflict dialog is probably VERY confusing, because the source changeset version refers to the local (to) team project and the target changeset to the other (from) team project. We have raised this anomaly (depending on which view of the system you have)with the product team and hope that we can rename the column headers and the field descriptors to something like “From” and “To” changeset information.
Take a look at the migration log
Scrolling through the 1.3MB log file would probably be very, very boring. for this blog post, but definitely worth a visit. It reports, in great details, the standard pipeline processing as documented in the architecture documentation:
- Generate Context Information Tables
- Generate Deltas on the originating point
- Generate Link Deltas on the originating point
- Generate Deltas on destination point
- Generate Link Deltas on destination point
- Generate Migration Instructions
- Post-Process Delta Changes
- Process Delta Changes
- Analyze Link Delta
- Process Link Changes
and conflicts if any:
[5/15/2011 10:51:32 AM] TfsMigrationShell.exe Information: 0 : VersionControl: Unresolved conflict:
[5/15/2011 10:51:32 AM] Session: e8853f21-3ab0-425c-817b-917b3d93ca60
[5/15/2011 10:51:32 AM] Source: 172f78a5-b891-4f7b-8f0e-f2cf4b4610cd
[5/15/2011 10:51:32 AM] Message: Cannot find applicable resolution rule.
[5/15/2011 10:51:32 AM] Conflict Type: VC namespace conflict type
[5/15/2011 10:51:32 AM] Conflict Type Reference Name: c1d23312-b0b1-456c-b6e4-af22c3531480
[5/15/2011 10:51:32 AM] Conflict Details: $/TiP_POC_Test_2/BuildProcessTemplates/DefaultTemplate.xaml
[5/15/2011 10:51:32 AM] TfsMigrationShell.exe Information: 0 : VersionControl: Stopping current trip for session: e8853f21-3ab0-425c-817b-917b3d93ca60
Take a look at target team project
The TFS Integration UI gives us a “thumbs up”, having moved 12 changesets and 1320 WIT items.
At the bottom of the UI we will also see the graphical chart. If we hover over one of the red bars, we will recognise the event where the VC conflict as reported above was reported:
Seeing is believing and therefore we should review the target team project and verify that everything has been migrated … which was the case.
Looking at one of the VC changesets, we notice that additional information was added to the description, reporting which (1) tool and who (2) moved the changeset:
What may not be apparent at a first glance, but is clearly documented as a limitation in the branching guidance, is the fact that the creation date is that date and time when the changeset was checked in by the migration tool, not the original check-in date you would find on the source (from) system. The migration guidance document defined this limitation as follows: .”
Looking at one of the WIT items, we also notice additional information on who moved the item (2) and the same date/time (3) limitation as outlined above.
The other limitation which you will noticed when doing a VC by VC changeset or WIT by WIT comparison is the following, as documented in the migration guidance document: .”
Lastly it is important to remind ourselves, as outlined in the previous blog post, that we are moving from one domain to another, not using value mapping and therefore it comes as no surprise that the “Assigned To” defines the credentials from the source (from) team project, which may not and in our case are not valid credentials on the target (to) team project.
In the next blog post we will demonstrate a simple field value mapping to change the “assigned to” field value to users that are known and valid on the target system. Also see the following blog posts for related information:
See you next time.
I just did a test run of only a Version Control migration and we do not see the CreationDate in the changset comment like in your screenshot. Is there a default setting that may have changed recently? Is there a way for us to easily add it back?
Please use the social.msdn.microsoft.com/…/tfsintegration forum to raise a query. Remember to add your configuration and log file if possible, so that we can verify that your session and adapters matches the environment I used when doing the blog post. I my case it was a TFS to TFS migration, using the out-of-the-box WIT and VC adapters. | https://blogs.msdn.microsoft.com/willy-peter_schaub/2011/05/16/tfs-integration-tools-where-does-one-start-part-3-dust-has-settled-did-it-work/ | CC-MAIN-2017-34 | refinedweb | 1,040 | 54.05 |
I am importing a csv file into python. As expected, it creates lists with every value as a string, however I want to avoid this. Is there a way for python to detect that a value is actually an int even though it looks like this '24'?
Thank you.
You may want to write a function something like this to do the job. You can expand it to cover other data type.
def return_str_type(str): possible_type = [int, float] for dtype in possible_type: try: str = dtype(str) break except: pass return type(str).__name__ print(return_str_type('4')) print(return_str_type('4.3')) print(return_str_type('s4'))
This will give OP
int float str
Though you will have to be careful with the order. e.g.
int check should always be before
float. | https://codedump.io/share/UiV4L1GaWCSw/1/detecting-the-type-of-data-we-have-python | CC-MAIN-2016-50 | refinedweb | 129 | 75.2 |
gomacro is an almost complete Go interpreter, implemented in pure Go. It offers both an interactive REPL and a scripting mode, and does not require a Go toolchain at runtime (except in one very specific case: import of a 3rd party package at runtime). press TAB to autocomplete a word, and press it again to cycle on possible completions.interpreter debugger eval repl macros generics
If you like this project, please checkout TODOs and open an issue if you'd like to contribute or discuss anything in particular. Each of these can be used with index operator, e.g. services[10], as well as first, last and any methonds. Any resource object can be converted to a JSON string with to_json method, or a Ruby object with to_ruby.kubernetes kubectl repl dsl
Wrap kubectl with namespace and variables. Download latest release for your platform from. It's recommended to use rlwrap in combination with kubectl-repl, such as rlwrap kubectl-repl. This adds prompt history, search, buffering etc.kubernetes repl kubectl terminal
Thanks to binder (mybinder.org), you can try lgo on your browsers with temporary docker containers on binder. Open your temporary Jupyter Notebook from the button above and enjoy lgo.jupyter-notebook-kernel jupyter-notebook repl data-science machine-learning
Box is a builder for docker that gives you the power of mruby, a limited, embeddable ruby. It allows for notions of conditionals, loops, and data structures for use within your builder plan. If you've written a Dockerfile before, writing a box build plan is easy..docker-image builder mruby repl docker dockerfile oci image containers
We have large collection of open source products. Follow the tags from
Tag Cloud >>
Open source products are scattered around the web. Please provide information
about the open source projects you own / you use.
Add Projects. | https://www.findbestopensource.com/tagged/repl?fq=Go | CC-MAIN-2020-24 | refinedweb | 305 | 65.42 |
I often hear from X++ developers, that the .Net garbage collector (GC) does not work correctly or that it isn’t as good as the one from Dynamics Ax because it is not known to you when objects are collected. This is of course nonsense not true and the reason will be exposed in this posting. My intention about this posting is, that with this basic knowledge about the .Net garbage collector, you’ll be able to avoid many problems and improve the quality of your applications. Please keep in mind that this is just a much simplified description of the BC. For further information, you should consult Jeffrey Richter's ”CLR via C#”.
The garbage collector in Dynamics Ax is very simple: it collects all unreferenced object every 3 seconds (ok, this is a little bit simplified, but it’s pretty much what the GC does). Consequently you know when the object is collected: about every 3 seconds and if this doesn’t happen you can use the Form SysHeapCheck to create a dump of the current heap, so you know how many references are currently held to that object.
Another point that differentiates X++ with C# is the existing of a destructor. In X++ this destructor is called "finalize()".:
In X++ it's the finalize method that contains all code that is used to clean up the instance (releases all objects that are held by this instance, ...). In C# this is done by the Dispose() method, but I'll describe this later. An important point is mentioned in the Msdn documentation:
Use finalize carefully. It will destruct an object even if there are references to it.
Use finalize carefully. It will destruct an object even if there are references to it.
In .Net you newer really know in advance when an object is collected, since the algorithm is much more complex and depends on much more variables than the one from Dynamics Ax. For example it depends on the currently available memory, the CPU usage or how old an object is. But not knowing when the objects are finally collected isn’t a problem at all because in most cases this stays completely transparent for the developer and, it might sound paradoxical, but this guarantees you best performance and an optimal use of resources because collecting objects is consuming resources, so whenever the GC collects it should be done economically and the system should have enough resources to handle this and if the system doesn’t have enough resources available, it should wait until enough resources will be free again.
In Dynamics Ax all objects without a reference are collected at once because the GC in Ax does not make any difference between the objects – they are all equal. The CLR in contrast differentiate objects.
Why does the GC differentiates objects? The idea behind this is that collecting objects in batches is more efficient than collecting all objects at the same time. For that the CLR is able to create ‘batches’ that are collected when it is opportune for the system. ‘Batches’ is not the real term, but this is it what’s done in reality.
But how to differentiate objects that should to be collected from those that can be collected later? To do this, the CLR is based on the assumption that younger objects have statistically a shorter lifetime then older objects. So the differentiation is based on its age: objects are belonging to generations. This is why the .Net GC is called a generational garbage collector. The CLR works with 3 generations: The first generation (called the generation 0) is the one that is collected frequently, because as I already mentioned) younger objects have statistically a shorter lifetime. The second one is collected by the GC under certain circumstances, and the third generation is collected when the memory is low. I know this is not precise, but I will come back to this later. As I wrote, I’m trying to keep this article very simple, but give you as many information as you need to understand the GC of the CLR.
But what exactly is a ‘generation’ in the CLR? A generation is first of all an attribute that shows how many cycles an object has survived. You can get the information of which generation your object (for example obj) belongs to by the static method GetGeneration of GC:
System.GC.GetGeneration(obj);
The first generation objects(called: generation 0 or gen0) , are objects that were recently created. 256KB of objects in the heap can belong to the gen0. This limit is called budget. If the total size of objects that belongs to gen0 exceeds this budget, the GC will automatically start collecting objects. 256KB is an approximate value, because this value depends of the L2 cache of your CPU. (If you like to dig very deep, read the article from Jan Gray).
In the following scheme we have a heap in three different states:
The first state shows 4 objects (A1,..,A4) that have been created recently. The flashes to these objects are indicating, that there are existing references to these objects. These four objects are all together smaller than then the budget for gen0, so there is no need for the GC to do anything.
The second state shows the heap with five objects. In the meantime some of the initial objects have lost their reference and with the creation of the fifth object (B5) they are bigger than the budget for gen0. So the creation of the new object A5 triggers the first collect of the GC with the consequence, that A2 and A4 (that are without reference) won’t survive gen0. All the others belongs now to gen1 (shown in the third state of the heap)
This scenario will be repeated many times and consequently increase the number of objects that belongs to gen1 as you can see in the following scheme:
Gen0 has a budget of 256KB and the gen1 a budget of 2MB (this is an approximate value). But, in contrast to the limit of gen0, exceeding the limit of gen1 will not automatically trigger a collection, but gen1 will nevertheless be collected, if the budget of gen0 will be exceeded the next time.
This is was happens in the next scheme. The first state of the heap shows a gen1 which exceeds 2MB budget, but the gen1 is only collected (as you can see in the second state) because gen0 exceeds the 256KB. All surviving objects of gen1 are belonging now to gen2.
The budget size for gen2 is 10MB and the behavior is the same as for gen1.
You can easily observe the described behavior with the perfmon. Maoni blogged about the GC performance counter some years ago and his posting might be much helpful if you’d like to simulate the described behavior of the GC. You'll find a really good article by Michael McIntyre here, too
Large objects are for the CLR all objects, that are bigger then 85000 bytes. This value might change in further versions of the CLR. Maoni Stephens from the CLR team wrote a really great article on msdn about this subject with a lot of details - maybe too much details for now. To make it short: The large objects belongs from its instantiation to generation 2 and they are held in a special heap called “large object heap” (LOH) that does not compress its objects… In a first time it is important for us to know that:
- large objects are treated differently
- they belong directly after the creation to gen2
- large objects are not compressed (risk of fragmentation)
The last point isn’t directly related to the GC, but it is worth to be mentioned, that large objects are often source of fragmented managed memory and this might result under certain circumstances in a System.OutOfMemoryException when there is not enough continuous memory available.
There is nothing easier for a programmer, than get rid of managed objects: Just wait until they get out of the scope and the GC will do all the rest for you in an extremely efficient way. You’ll never have problems with memory leaks and you can be sure that the GC will do the rest. Some kind of programmer’s heaven!
But even if this might be the programmer’s heaven, you should know what the GC does, because this will influence how you will program and it is very useful for troubleshooting your application.
The following scheme shows a heap before the collection and after the compact phase. The first state contains roots (static fields, method parameters, local variables and CPU registers) and unreachable objects:
In a first step, the collection will mark all roots. All unreachable objects (A1, A6 and A7) are considered to be garbage and they aren’t marked. In a second step, the GC is doing the compact phase, and walk through all objects in order to identify continuously non marked memory and shift them down in memory. That avoids fragmentation, and allows the CLR to know exactly where the next object is to be allocated: on top of the last object (here it would be A6).
The important point here to know is that managed resources are in good hands and that you don’t care about major problems like memory leaks and so on. Your application will be reliable and secured with managed code.
As we all know, there’s no programmer’s heaven and more than once we all were convinced of the existing of a programmer’s hell… I can assure you that there’s no such hell ;-)
Sometimes you will be challenged because you need to communicate with resources outside of the managed world (CLR), like accessing the file system, the Win32 (P/Invoke), COM unmanaged or unsafe code and so on. In all these cases there are resources initialized that are beyond the control of the GC and so it’s up to you to release these resources in order to prevent memory leaks or other messes. .Net gives you some tools to manage this, but at the end it’s up to you to implement them and write robust and secured code.
There are much more ways to assure the release of external resources, but that would go far beyond of what I intended with this article.
It might be helpful for you as X++ developer to know the difference between unmanaged and unsafe code since you will work with both when you’re using the BC.Net. On programmers-heaven you’ll find the following definition:
Un-managed code runs outside the Common Language Runtime (CLR) control while the unsafe code runs inside the CLR’s control. Both un-safe and un-managed codes may use pointers and direct memory addresses.
Un-managed code runs outside the Common Language Runtime (CLR) control while the unsafe code runs inside the CLR’s control. Both un-safe and un-managed codes may use pointers and direct memory addresses.
The Dynamics Ax resources are unmanaged and parts of the BC.Net are unsafe.
A paradox for a non experimented managed-code developer is the fact that you know perfectly when the constructor is called (you do this explicitly) but you don't know when the destructor is called. This is at least that what the destructor seems to be, since this is called the Finalize method (~ClassName). One of the reason why you don't call it destructor is what I mentioned before: It's the GC that determines the execution of this method and not you. Since it's up to you to manage unmanaged resources, it wouldn't be a great idea to implement the deallocation of those resources in a method of which you never know when it is called and you can't call it explicitly since it isn't a public method.
Instead of implementing the deallocation of unmanaged and unsafe resources in the Finalize method you implement that code in a public method called Dispose() and implement the interface IDisposable, so you can call the Dispose() method whenever you need to release the resources:
1: ExternalResources er = new ExternalResources();
2:
3: try
4: {
5: //do something with it
6: }
7: finally
8: {
9: er.Dispose();
10: }
By calling the Dispose() in line 13 you can be sure that in any case the resources from the instance "er" will be released. “Finally” will always be executed at the end of the try-scope: With or without exception. C# offers you the using-statement which will simplify the code from above:
1: using(ExternalResources er = new ExternalResources())
2: {
3: //do something
4: }
“Using” can be used if the class implements the Disposable interface. I would even say that you must use it (or at least the first method) if a class implements the IDisposable interface!
But what if for any reason the Dispose hasn't been executed? Without any additional code the resources will not be released!
An object should always be able to release all external resources that the object itself has allocated at the end of its lifetime. For that reason Microsoft defined the IDisposable-pattern
1: public class ExternalResources: IDisposable
3: ~ExternalResources()
4: {
5: Dispose(false);
6: }
7:
8: public void Dispose()
9: {
10: Dispose(true);
11: GC.SuppressFinalize(this);
12: }
13:
14: protected virtual void Dispose(bool disposing)
15: {
16: if (disposing)
17: {
18: // Clean up all managed resources
19: }
20:
21: // Clean up all external (unmanaged and unsafe) resources
22: }
23: }
Calling Dispose() will release the external resources, but without calling explicitly the Dispose, the resources will be released when the GC will call the Finalize method (~ExternalResources), too. Since calling the Finalizing method by the GC consumes resources, we want to avoid that last call when the Dispose() method has already been called. That's why we call the SuppressFinalize at the end of the Dispose() method. So with this instruction the GC is told that it don't need to call the Finalize method when he collects this objects since finalizable objects are treated in a different heap and need an additional cycle to be cleaned. You remember that in X++ the method "finalize" was the destructor of the class? Now you know that there is a Finalize in C#, too, but that has nothing in common with a destructor and the behavior is completely different.
Shawn Farkas wrote a great article about all this!
I started this posting with the assertion:
In .Net you newer really know in advance when an object is collected
In .Net you newer really know in advance when an object is collected
Well, this is true since you don’t know the certain time when the GC ‘decides’ to collect the objects, but you know the 5 conditions under which the GC will start collecting:
- Generation 0 is full: The GC collects automatically when the budget of gen0 has been exceeded (see 1.2.1)
- System has low memory: When the system signals "low memory", the GC will collect.
- AppDomain is unloading: When unloading an AppDomain the GC collects all objects first.
- CLR shuts down: The CLR tries to collect all objects in a friendly manner but after reaching a timeout (It is currently 40 seconds in the CLR2) it nevertheless shuts down. Unhandled resources might in this case be left open. In order to be able to debug this particular situation, read the blog I linked)
- GC.Collect: It is absolutely not recommended to ask the GC explicitly to collect, since the GC is self-tuning and already optimized. Calling GC.Collect explicitly results most of the time in less performing application and systems. So please do this with consideration and only if you precisely know what you are doing. Anyway, you can trigger the collection by calling:
GC.Collect();
This GC is used by console and WinForm (incl. WPF) applications and is optimized for low latency. Without getting more into details, low latency is the result when the application GC don’t pause in most cases the application. That’s what concurrent GC means: The GC can do it’s work while the application is still responsive for the user. You can get more information from Mark here and from Chris Lvon here.
ASP.Net applications are using the server GC, since it is optimized for multicore/multiprocessor and throughput. In contrast to the application GC, the server GC pauses the applications while collecting. In common Windows Form application scenarios, this might not an option.
But, the server garbage collection should be the fastest option for more than two processors. This might be important for you to know, since more and more workstations have more than 2 cores and in that case it might be interesting to activate the server GC, or at least test if that might improve the performance of your application, even if the server GC doesn’t support concurrent GC (until now). You find more information about this on Msdn.
The GC of the CLR is much more complex than the one from Dynamics Ax, but much more efficient and appropriate for server applications. Programming managed code is very easy and .Net offers you a number of tools to manage external resources.
3.1 Changing types (converting and casting) C# is an strongly-typed programming language (even if there | http://blogs.msdn.com/b/floditt/archive/2008/12/15/1-the-garbage-collector-in-x-and-the-clr.aspx | CC-MAIN-2013-20 | refinedweb | 2,910 | 58.32 |
Reeeed: the reader mode from feeeed
Reeeed is a Swift implementation of Reader Mode: you give it the URL to an article on the web, it extracts the content — without navigation, or any other junk — and shows it to you in a standard format. It’s faster, more consistent and less distracting than loading a full webpage. You can pass
Reeeed a URL, and get back simple HTML to display. Or you can present the all-inclusive SwiftUI
ReeeederView that handles everything for you.
Features
ReeeederView: a simple SwiftUI Reader View that works on iOS and macOS. Just pass a URL and present it.
Reeeederextractor: pass a URL and receive cleaned HTML. You also get metadata, like the page’s title, author and hero image.
- The generated HTML supports custom themes. Default and custom themes support dark mode out of the box.
Installation
- In Xcode’s menu, click File → Swift Packages → Add Package Dependency…
- Paste the URL of this repository:
Alternatively, add the dependency manually in your
Package.swift:
.package(url: "", from: "1.1.0")
Usage
Simplest implementation:
ReeeederView
For the simplest integration, just present the batteries-included
ReeeederView, like this:
import SwiftUI import Reeeeder struct MyView: View { var body: some View { NavigationLink("Read Article") { ReeeederView(url: URL(string: "")!) } } }
ReeeederView also supports a dictionary of additional options:
public struct ReeeederViewOptions { public var theme: ReaderTheme // Change the Reader Mode appearance public var onLinkClicked: ((URL) -> Void)? }
More flexible implementation
You can use
Reeeeder to fetch article HTML directly:
import Reeeeder import WebKit ... Task { do { let result = try await Reeeed.fetchAndExtractContent(fromURL: url, theme: options.theme) DispatchQueue.main.async { let webview = WKWebView() webview.load(loadHTMLString: result.styledHTML, baseURL: result.baseURL) // Show this webview onscreen } } catch { // We were unable to extract the content. You can show the normal URL in a webview instead :( } }
If you have more specific needs — maybe want to fetch the HTML yourself, or wrap the extracted article HTML fragment in your own template — here’s how to do it. Customize the code as necessary:
Task { // Load the extractor (if necessary) concurrently while we fetch the HTML: DispatchQueue.main.async { Reeeed.warmup() } let (data, response) = try await URLSession.shared.data(from: url) guard let html = String(data: data, encoding: .utf8) else { throw ExtractionError.DataIsNotString } let baseURL = response.url ?? url // Extract the raw content: let content = try await Reeeed.extractArticleContent(url: baseURL, html: html) guard let extractedHTML = content.content else { throw ExtractionError.MissingExtractionData } // Extract the "Site Metadata" — title, hero image, etc let extractedMetadata = try? await SiteMetadata.extractMetadata(fromHTML: html, baseURL: baseURL) // Generated "styled html" you can show in a webview: let styledHTML = Reeeed.wrapHTMLInReaderStyling(html: extractedHTML, title: content.title ?? extractedMetadata?.title ?? "", baseURL: baseURL, author: content.author, heroImage: extractedMetadata?.heroImage, includeExitReaderButton: true, theme: theme) // OK, now display `styledHTML` in a webview. }
How does it work?
All the good libraries for extracting an article from a page, like Mercury and Readability, are written in Javascript. So
reeeed opens a hidden webview, loads one of those parsers, and then uses it to process HTML. A page’s full, messy HTML goes in, and — like magic — just the content comes back out. You get consistent, simple HTML, and you get it fast.
Of course, these libraries aren’t perfect. If you give them a page that is not an article — or an article that’s just too messy — you’ll get nothing. In that case,
reeeed will fall back to displaying the full webpage.
Updating the Postlight Parser (formerly Mercury) JS
Last updated September 18, 2022 (v2.2.2)
- Replace the
Sources/Reeeed/JS/mercury.web.jsfile with a new one downloaded from the project repo
- Ensure the demo app works.
Things I’d like to improve
- Readability JS package is a few months old. They need to be updated. Ideally, this would be (semi) automated.
- The API could use a bit of cleanup. The naming and code structure is a bit inconsistent.
- Reeeed depends on two different HTML manipulation libraries: SwiftSoup and Fuzi. Fuzi is much faster, so I’d like to migrate the remaining
SwiftSoupcode to use it ASAP, and remove the dependency.
- Some day, I’d like to write a fully-native renderer for extracted content.
- Tests would be nice 😊 | https://iosexample.com/reader-mode-view-for-swiftui-based-on-the-feeeed-app/ | CC-MAIN-2022-40 | refinedweb | 697 | 59.7 |
Sending Email Using .NET
One thing that many applications need to do is to send email.
.NET has quite a robust set of classes available that allow you to do this very easily. The best part about it is that not only can it be used to send email by using a standard email/smtp server, but you also can use it to send email by using a Gmail account as well.
Setting Up Gmail to Allow External Access
To allow your .NET application to send email via your Gmail account, you'll need to do two things:
- You need to turn on 2 factor authentication. You can enable SMTP access without it, but the settings are global and not secured.
- Create an app-specific password.
Turning on 2 factor authentication is fairly straightforward. Open your Gmail inbox, click your avatar, and then click "Account", just under your name. Scroll down until you see "2 factor authentication"; click it and follow the instructions.
Once 2 step verification is enabled, you'll see that your security settings page now has an "App Specific Passwords" tab, as shown in Figure 1:
Figure 1: You have a new security settings tab
Click this tab, and then click the button marked "Manage App Specific Passwords". On the next screen that appears, select "Mail" on my "Windows Computer" and click generate.
You'll be shown the password that has been generated. At this point make sure you either add the password into your code, or write it down until you're ready to add it. Either way, once you dismiss the dialog, you'll be unable to get the password back, so you'll need to delete and then re-create it.
Once you've generated a password, you should see something like this:
Figure 2: The password has been generated
You can revoke the access any time you like and regenerate it to get new passwords.
Once you have this set up, you then can start to use the SMTP client classes in your applications.
The Simplest Email Is Always the First
To start using the SMTP classes, you need to first import 'System.Net' and 'System.Net.Mail'. This is as simple as adding:
using System.Net; using System.Net.Mail;
to your application using clause.
To use your Gmail account from .NET, you need to use the following settings:
Server Address: smtp.gmail.com SSL: Enabled Port: 587 User Name: gmail email address Password: password generated by app specific passwords
Pay particular attention to the port number here. In ALL the guides available, they tell you that the SSL/TLS port number is 465. That's correct for most applications. For .NET, however, you MUST use the alternative port; otherwise, your program will fail to connect and give you time out errors.
To send your first email, try the following:
SmtpClient smtp = new SmtpClient("smtp.gmail.com"); smtp.EnableSsl = true; smtp.Port = 587; smtp.Credentials = new NetworkCredential("email@gmail.com", "appspecificpassword"); smtp.Send("email@gmail.com","toaddress@somwhere.com", "Email Subject", "Email message");
Using the simple method of doing this, you quickly can send plain text emails in five lines of code (two if you don't have to enable Gmail settings).
However, there are a few more things you can do.
You can, for example, use the 'MailMessage' object to give you more control over your outgoing email such as adding multiple recipients and making the body of the email a HTML one. The following code shows how you might do this:
string myGmailAddress = "xxxxx"; string appSpecificPassword = "xxxxx"; SmtpClient smtp = new SmtpClient("smtp.gmail.com"); smtp.EnableSsl = true; smtp.Port = 587; smtp.Credentials = new NetworkCredential(myGmailAddress, appSpecificPassword); MailMessage message = new MailMessage(); message.Sender = new MailAddress(myGmailAddress, "Peter Shaw"); message.From = new MailAddress(myGmailAddress, "Peter Shaw"); message.To.Add(new MailAddress("aperson1@example.com", "Recipient Number 1")); message.To.Add(new MailAddress("aperson2@example.com", "Recipient Number 2")); message.CC.Add(new MailAddress("accaddress@example.com", "A CC Person")); message.Bcc.Add(new MailAddress("abccperson@example.com", "A BCC Person")); message.Subject = "My HTML Formatted Email"; message.Body = "<h1>HTML Formatted EMail</h1> <p>DO you like this <strong>EMail</strong> with HTML formatting contained in its body.</p>"; message.IsBodyHtml = true; smtp.Send(message);
You can also attach files to the email by using the following:
Attachment attachment = new Attachment("mypdffile.pdf", MediaTypeNames.Application.Pdf); message.Attachments.Add(attachment);
This is just the basics. There are lots of other options you have too, such as being able to support multiple body types. Have a read through the property lists on MSDN; you might be surprised at what's available.
If you have an idea or subject you'd like to see covered in this column, please feel free to hunt me down on Twitter as @shawty_ds, or come and find me on Linked-in where I help run one of the Larger .NET user groups called Lidnug, I'm always open to new suggestions.
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How send by not using appspecificpassword?Posted by (L)user on 04/10/2015 07:12pm
How can I send email by not using the AppSpecificPassword? Without secure code?
RE: How send by not using appspecificpassword?Posted by Peter Shaw on 04/22/2015 04:49pm
If your using GMail, you can't. Well actually you can, BUT... it means you have to turn off 2 factor authentication, and hunt down and change a number of different settings in your GMail account. All the things you have to change, Google don't want you to change, and have openly admitted that at some time in the future they will remove these un-secure settings. If you don't want to use GMail and it's secure settings, then the only other way is to set up and run your own Email server, which is what I do.Reply | https://www.codeguru.com/columns/dotnet/sending-email-using-.net.html | CC-MAIN-2019-26 | refinedweb | 1,141 | 65.83 |
I'm writing a function that returns the maximum element of an array. I made an array that had 10 elements. For some reason I keep getting these errors and im not sure why. Any help would be greatly appreciated, thank you.
These are my errors:
And the following is my code.And the following is my code.Code:max.cpp(25) : error C2065: 'size' : undeclared identifier (26)error C2065: 'a' : undeclared identifier (26) : error C2109: subscript requires array or pointer type
Code:#include <iostream> using namespace std; int max (void);//prototype int main() { const int size=10; int a[size]={1,2,3,4,5,6,7,8,9,10}; max();//call cout<<"The max number is"<<max<<endl; return 0; } int max(void)//function that returns maximum element of array { int MAX=10; int x=MAX; for (int i=0; i<size;i++) if (a[i]==x) return x; } | http://cboard.cprogramming.com/cplusplus-programming/54633-array-function-errors.html | CC-MAIN-2014-23 | refinedweb | 151 | 54.52 |
14 October 2011 06:25 [Source: ICIS news]
GUANGZHOU (ICIS)--?xml:namespace>
China’s food prices increased by 13.4% year on year, the highest rise among all products, according to data released by the National Bureau of Statistics (NBS).
The country’s producer price index (PPI), which is a measure of wholesale prices, increased by 6.5% year on year in September, the NBS said.
The producers’ PPI increased by 10% year on year in September, while that of raw chemicals and fuel increased by 12.7% and 12.3%, respectively.
However, the figures for September narrowed from previous months, NBS said.
Inflation | http://www.icis.com/Articles/2011/10/14/9500065/china-inflation-extends-into-september-cpi-up-by-6.1-year-on.html | CC-MAIN-2014-10 | refinedweb | 104 | 67.86 |
Released on June 10, Immer 7.0 includes lots of new innovations, optimizations, and breaking changes. In this guide, we’ll look at what’s new in the latest release of Immer.
We’ll walk through some of the most impactful changes, including:
- The introduction of
current
gettersand
settersare now handled consistently
produceno longer accepts non-draftable objects as the first argument
originalcan only be called on drafts
- Array patches computation
Let’s get started!
What is Immer?
Have you ever wanted to work with immutable state in JavaScript and ended up doing it in an inconvenient way or writing many lines of JavaScript code? Immer is a tiny package that allows you to work with immutable state in a more convenient way.
The basic idea is simple: Immer applies all your changes to a draft state, which is a proxy of the current state. Once you’re done changing/mutating the draft state, Immer produces the next state. That means your current state object is state from mutations and keeps all the benefits of immutability.
A working demo
Let’s walk through a simple demo.
Installation
First, upgrade to the latest version of Immer. At the time of writing, version 7.0.5 is the most current release.
yarn add immer // OR npm install immer
Open a JavaScript file and paste in the following.
import produce from "immer" const todos = [ //baseState { text: “learn Immer” done: false } { text: “learn cookimg done: true } ] const nextState = produce (todos, draftState) = { draftState.push ({text: “writing”, done: false}) draftState[0].done = true }); // Comparisons console.log(todos === nextState) //false console.log (todos[0].done === nextState[0].done) //false console.log(todos[1].done === nextState[0].done) // true
The
baseState will be untouched, but the
nextState will be a new, immutable tree that reflects all changes made to
draftState (and structurally shares the things that weren’t changed).
The above demo should give you a good sense of what Immer is all about. For more information, check out the documentation.
Now let’s dive into the latest updates.
5 key changes in Immer 7.0
Now let’s dive into the latest updates.
1.
current method
Immer exposes a named export,
current, that creates a copy of the current state of the draft. It takes a screenshot of the current state of a draft and finalizes it without freezing the object. This is a great utility for debugging the current state since those objects aren’t proxy objects.
Here’s an example:
const base = { x: 0 } const next = produce(base, draft => { draft.x++ const orig = original(draft) const copy = current(draft) console.log(orig.x) console.log(copy.x) setTimeout(() => { // this will execute after the produce has finised! console.log(orig.x) console.log(copy.x) }, 100) draft.x++ console.log(draft.x) }) console.log(next.x) // This will print // 0 (orig.x) // 1 (copy.x) // 2 (draft.x) // 2 (next.x) // 0 (after timeout, orig.x) // 1 (after timeout, copy.x)
You can see the effect of the
current method on the
draft.
2. Getters and setters handled consistently
If you’ve ever used Immer with Vue or React and tried to work with classes, you’re familiar with the error it always generates:
// Immer drafts cannot have computed properties.
In Immer 7.0, this error is officially extinct. Owned getters are involved in the copy process, just like
Object.assign would otherwise be.
You can read more about getters and setters in the docs.
3. Nondraftable objects
produce no longer accepts nondraftable objects as a first argument. Nondraftable objects are objects that are not JSON-serializable, such as the
Date object in JavaScript (except when converted to strings).
Immer 7.0 doesn’t support this type of object and throws an exception when it encounters one.
4. Original can only be called on drafts
Have you ever tried to call original on objects that cannot be proxied and gotten stuck with that ugly
undefined return type? For version 7, the Immer team added a catchable error to the original API, so instead of returning
undefined, it throws an error.
5. Array patches computation
The patches for array are now computed differently to fix various scenarios in which they were incorrect. In some cases, they’re more optimal now; in
others, less so. For instance, splicing or unshifting items into an existing array might result in a lot of patches. In Immer 7.0, this is no longer an issue.
Conclusion
In this guide, we walked through some exciting new features and four breaking changes in Immer 7.0. Below is a list of additional bug fixes and breaking changes that fell outside the scope of this article.
Bug fixes
- All branches of the produced state should be frozen
- Inconsistent behavior with nested
produce
- Does not work with polyfilled symbols
- Explicitly calling
useProxies(false)shouldn’t check for the presence of proxy
getownPropertyDescriptorsunavailable in Internet Explorer or Hermes
Head to GitHub for a complete list of bug fixes.
Breaking changes
- Nonenumerable and symbolic fields will never be frozen
The GitHub repo has a complete list of breaking. | https://blog.logrocket.com/whats-new-in-immer-7-0/ | CC-MAIN-2022-40 | refinedweb | 851 | 66.84 |
Library for scraping google search results
Project description
google-search
Library for scraping google search results.
Usage:
from googlesearch.googlesearch import GoogleSearch response = GoogleSearch().search("something") for result in response.results: print("Title: " + result.title) print("Content: " + result.getText())
Free software: MIT license
Features
Run a Google search and fetch the individual results (full HTML and text contents). By default the result URLs are fetched eagerly when the search request is made with 10 parallel requests. Fetching can be deferred until searchResult.getText() or getMarkup() are called by passing prefetch_results = False to the search method.
Pass num_results to the search method to set the maximum number of results.
SearchReponse.total gives the total number of results on Google.
Credits
This package was created with Cookiecutter and the audreyr/cookiecutter-pypackage project template.
History
1.0.0 (2017-05-06)
- First release on PyPI.
1.0.1 (2017-05-08)
- Minor corrections in documentation
1.0.2 (2017-05-12)
- Fixed duplicate result issue
- Added language parameter
Project details
Release history Release notifications
Download files
Download the file for your platform. If you're not sure which to choose, learn more about installing packages. | https://pypi.org/project/google-search/ | CC-MAIN-2019-18 | refinedweb | 193 | 53.07 |
Is there a ready way to use the Django admin page without any form of authentication? I know I can use this method, but that was for Django 1.3. Are there any changes that would let me do this more easily in Django 1.6?
My main motivation for this is that I want to have as few database tables as possible, and I am using this only locally, so there is no need for any sort of authentication (I'm only ever running the server on localhost anyways).
Create a module
auto_auth.py:
from django.contrib.auth.models import User class Middleware(object): def process_request(self, request): request.user = User.objects.filter()[0]
Edit
MIDDLEWARE_CLASSES in your
settings.py:
'django.contrib.auth.middleware.AuthenticationMiddleware'
'auto_auth.Middleware'
You can change
User.objects.filter()[0] to something else if you want a particular user.
In response to your comment: yes. Try this:
class User: is_superuser = True is_active = True is_staff = True id = 1 def return_true(*args, **kwargs): return True User.has_module_perms = return_true User.has_perm = return_true class Middleware(object): def process_request(self, request): request.user = User()
And remove
'django.contrib.auth' from
INSTALLED_APPS
But if you use any apps that depend on the auth app, you're going to have a bad time. | https://codedump.io/share/nJRJ7h0iqw4f/1/django-admin-without-authentication | CC-MAIN-2017-13 | refinedweb | 211 | 51.55 |
Eclipse CDT & JNI (Java Native Interface) with 64 bit MinGW - 2017
bogotobogo.com site search:
Knock, knock.
"Who's there?"
Very long pause.
...
...
"Java."
Eclipse CDT with MingW on Windows
Install
Following items are needed:
- Eclipse - Kepler 4.3
- We need compiler since CDT (C/C++ Development Tool) does not come with it.
Eclipse C/C++ IDE (CDT) for Kepler.
- To make it work (64 dll on 64 machine), we need 64-bit MinGW.
In my case, I put it here: C:\eclipse\MinGW
Also, we need to add the path (C:\eclipse\MinGW\bin) to environment variable
Eclipse Setup
- Put the source code:
- Window->Open Perspective->Others...->C/C++->OK.
- Project->Properties...
Check items under C/C++ Build.
For example, the PATH under Environment should lead us to the compiler and it should look like this:
${MINGW_HOME}\bin;
- Build project and run:
64-bit JNI (Java Native Interface) with Eclipse CDT
Creating Java Project
- Create a new Java project (HelloJNI)
- Make the HelloJNI.java Java class:
public class HelloJNI { static { // hello.dll on Windows or libhello.so on Linux System.loadLibrary("hello"); } private native void sayHello(); public static void main(String[] args) { // invoke the native method new HelloJNI().sayHello(); } }
Converting the Java Project to a C/C++ Project
- Right-click on the HelloJNI Java project->New->Other...
Under C/C++, Convert to a C/C++ Project (Adds C/C++ Nature)->Next.
- Then, the "Convert to a C/C++ Project" dialog will pop up. In "Project type", select "Makefile Project" ->In "Toolchains", select "MinGW GCC", and hit Finish.
- Now, we can run this project as a Java as well as a C/C++ project.
Generating C/C++ Header File
- Create a directroy called "jni" under the project to keep all the C/C++ codes:
right-click on the project->New->Folder. In "Folder name", enter "jni".
- Create a "makefile" under the "jni" directory:
Right-click on the "jni" folder->new->File. In "File name", enter "makefile", and hit Finish.
- Then, enter the following codes. Because it is makefile, we should use tab for the indent instead of spaces.
# Define a variable for classpath CLASS_PATH = ../bin # Define a virtual path for .class in the bin directory vpath %.class $(CLASS_PATH) # $* matches the target filename without the extension HelloJNI.h : HelloJNI.class javah -classpath $(CLASS_PATH) $*This makefile creates a target "HelloJNI.h", which has a dependency of "HelloJNI.class", and invokes the javah utiltiy on "HelloJNI.class" (under -classpath) to build the target header file: Right-click on the makefile->Make Targets->Create...
In "Target Name", enter "HelloJNI.h". Then, hit OK.
- Run the makefile for the target "HelloJNI.h":
Right-click on the makefile->Make Targets->Build...
Make sure all the files (HelloJNI.java and makefile) are saved.
Select the target "HelloJNI.h"->Build...
The header file "HelloJNI.h" shall be generated in the "jni" directory.
C File - HelloJNI.c
- Create a C program called "HelloJNI.c":
Right-click on the "jni" folder->New->Source file.
In "Source file", enter "HelloJNI.c".
Enter the following code:
#include <jni.h> #include <stdio.h> #include "HelloJNI.h" JNIEXPORT void JNICALL Java_HelloJNI_sayHello(JNIEnv *env, jobject thisObj) { printf("Hello World!\n"); return; }
- Modify the "makefile" as shown below to generate the shared library "hello.dll":
# Define a variable for classpath CLASS_PATH = ../bin # Define a virtual path for .class in the bin directory vpath %.class $(CLASS_PATH) all : hello.dll # $@ matches the target, $< matches the first dependancy hello.dll : HelloJNI.o gcc -m64 -Wl,--add-stdcall-alias -shared -o $@ $< # $@ matches the target, $< matches the first dependancy HelloJNI.o : HelloJNI.c HelloJNI.h gcc -m64 -I"C:\Program Files\Java\jdk1.7.0_21\include" -c $< -o $@ # $* matches the target filename without the extension HelloJNI.h : HelloJNI.class javah -classpath $(CLASS_PATH) $* clean : rm HelloJNI.h HelloJNI.o hello.dll
- Right-click on the "makefile"->Make Targets->Create...
In "Target Name", enter "all".
Repeat to create a target "clean".
- Run the makefile for the target "all": Right-click on the makefile->Make Targets->Build...
Select the target "all"->Build...
- The shared library "hello.dll" has been created in "jni" directory.
Finally, Running the Java JNI Program
- We need to provide the library path to the "hello.dll".
This can be done via VM argument -Djava.library.path:
Right-click on the project->Run As->Run Configurations...
Select (double-click) "Java Application"
In "Main" tab, enter the Main class "HelloJNI".
In "Arguments", "VM Arguments", enter "-Djava.library.path=jni"
- Run.
We should see the output "Hello World!" displayed on the console.
Note: 32-bit dll on 64-bit JVM?
In my case (AMD 64-bit, Windows8), initially, I had an error related to the 64bit JVM (or 32bit dll):
UnsatisfiedLinkError: C:\Users\KHyuck\workspaceJNI\HelloJNI\jni\hello.dll:
Can't load IA 32-bit .dll on a AMD 64-bit platform.
So, I checked my machine using java -d64 -version command:
C:\>java -d64 -version java version "1.7.0_21" Java(TM) SE Runtime Environment (build 1.7.0_21-b11) Java HotSpot(TM) 64-Bit Server VM (build 23.21-b01, mixed mode) C:\>java -d32 -version Error: This Java instance does not support a 32-bit JVM. Please install the desired version.
As expected, my JVM is 64-bit.
Regarding the complain: Can't load IA 32-bit .dll (hello.dll), I checked it with Dependency Walker.
Indeed, the CPU columns are not x64, x86_64 or amd64 (64-bit) but it is x86 (32-bit)!
So, I needed to get the 64-bit MinGW to make 64-bit dll. It has msys as well.
Here is the Environment variables for Project Properties that works with the MinGW 64-bit.
C++ with Eclipse on Linux
The steps are similar to the Windows case except that we do not have to install additional the compiler.
This example is running on Fedora 18.
Install Eclipse and Eclipse C/C++ Development Tools (CDT) plugin.
- yum install eclipse
- yum install eclipse-cdt | http://www.bogotobogo.com/cplusplus/eclipse_CDT_JNI_MinGW_64bit.php | CC-MAIN-2017-26 | refinedweb | 986 | 62.44 |
Welcome learning. They are actually just number-crunching libraries, much like Numpy is. The difference is, however, a package like TensorFlow allows us to perform specific machine learning number-crunching operations like derivatives on huge matricies with large efficiency. We can also easily distribute this processing across our CPU cores, GPU cores, or even multiple devices like multiple GPUs. But that's not all! We can even distribute computations across a distributed network of computers with TensorFlow. So, while TensorFlow is mainly being used with machine learning right now, it actually stands to have uses in other fields, since really it is just a massive array manipulation library.
What is a tensor? Up to this point in the machine learning series, we've been working mainly with vectors (numpy arrays), and a tensor can be a vector. Most simply, a tensor is an array-like object, and, as you've seen, an array can hold your matrix, your vector, and really even a scalar.
At this point, we just simply need to translate our machine learning problems into functions on tensors, which is possible with just about every single ML algorithm. Consider the neural network. What does a neural network break down into?
We have data (
X), weights (
w), and thresholds (
t). Are all of these tensors?
X will be the dataset (an array), so that's a tensor. The weights are also an array of weight values, so they're tensors too. Thresholds? Same as weights. Thus, our neural network is indeed a function of
X,
w, and
t, or
f(Xwt), so we are all set and can certainly use TensorFlow, but how?
TensorFlow works by first defining and describing our model in abstract, and then, when we are ready, we make it a reality in the session. The description of the model is what is known as your "Computation Graph" in TensorFlow terms. Let's play with a simple example. First, let's construct the graph:
import tensorflow as tf # creates nodes in a graph # "construction phase" x1 = tf.constant(5) x2 = tf.constant(6)
So we have some values. Now, we can do things with those values, such as multiplication:
result = tf.mul(x1,x2) print(result)
Notice that the output is just an abstract tensor still. No actual calculations have been run, only operations created. Each operation, or "op," in our computation graph is a "node" in the graph.
To actually see the result, we need to run the session. Generally, you build the graph first, then you "launch" the graph:
# defines our session and launches graph sess = tf.Session() # runs result print(sess.run(result))
We can also assign the output from the session to a variable:
output = sess.run(result) print(output)
When you are finished with a session, you need to close it in order to free up the resources that were used:
sess.close()
After closing, you can still reference that
output variable, but you cannot do something like:
sess.run(result)
...which would just return an error. Another option you have is to utilize Python's
with statement:
with tf.Session() as sess: output = sess.run(result) print(output)
If you are not familiar with what this does, basically, it will use the session for the block of code following the statement, and then automatically close the session when done, the same way it works if you open a file with the
with statement.
You can also use TensorFlow on multiple devices, and even multiple distributed machines. An example for running some computations on a specific GPU would be something like:
with tf.Session() as sess: with tf.device("/gpu:1"): matrix1 = tf.constant([[3., 3.]]) matrix2 = tf.constant([[2.],[2.]]) product = tf.matmul(matrix1, matrix2)
Code from: TensorFlow docs. The
tf.matmul is a matrix multiplication function.
The above code would run the calcuation on the 2nd system GPU. If you installed the CPU version with me, then this isn't currently an option, but you should still be aware of the possibility down the line. The GPU version of TensorFlow requires CUDA to be properly set up (along with needing a CUDA-enabled GPU). I have a few CUDA enabled GPUs, and would like to eventually cover their use as well, but that's for another day!
Now that we have the basics of TensorFlow down, I invite you down the rabbit hole of creating a Deep Neural Network in the next tutorial. If you need to install TensorFlow, the installation process is very simple if you are on Mac or Linux. On Windows, not so much. The next tutorial is optional, and it is just us installing TensorFlow on a Windows machine. | https://pythonprogramming.net/tensorflow-introduction-machine-learning-tutorial/ | CC-MAIN-2022-40 | refinedweb | 785 | 65.52 |
NAMEaccess, faccessat, faccessat2 -); /* But see C library/kernel differences, below */
#include <fcntl.h> /* Definition of AT_* constants */ #include <sys/syscall.h> /* Definition of SYS_* constants */ #include <unistd.h>
int syscall(SYS_faccessat2, int dirfd, const char *pathname, int mode, int flags);
faccessat():
Since glibc 2.10: _POSIX_C_SOURCE >= 200809L Before glibc 2.10: _ATFILE_SOURCE
DESCRIPTIONaccess()()faccessat()().
faccessat2()The description of faccessat() given above corresponds to POSIX.1 and to the implementation provided by glibc. However, the glibc implementation was an imperfect emulation (see BUGS) that papered over the fact that the raw Linux faccessat() system call does not have a flags argument. To allow for a proper implementation, Linux 5.8 added the faccessat2() system call, which supports the flags argument and allows a correct implementation of the faccessat() wrapper function.
RETURN VALUE to indicate the error.
ERRORS
- EACCES
- The requested access would be denied to the file, or search permission is denied for one of the directories in the path prefix of pathname. (See also path_resolution(7).)
- EBADF
- (faccessat()) pathname is relative but dirfd is neither AT_FDCWD (faccessat()) nor a valid file descriptor.
- EFAULT
- pathname points outside your accessible address space.
- EINVAL
- mode was incorrectly specified.
- EINVAL
- (faccessat()) Invalid flag specified in flags.
- EIO
- An I/O error occurred.
- ELOOP
- Too many symbolic links were encountered in resolving pathname.
- ENAMETOOLONG
- pathname is too long.
- ENOENT
- A component of pathname does not exist or is a dangling symbolic link.
- ENOMEM
- Insufficient kernel memory was available.
- ENOTDIR
- A component used as a directory in pathname is not, in fact, a directory.
- ENOTDIR
- (faccessat()) pathname is relative and dirfd is a file descriptor referring to a file other than a directory.
- EROFS
- Write permission was requested for a file on a read-only filesystem.
- ETXTBSY
- Write access was requested to an executable which is being executed.
VERSIONSfaccessat() was added to Linux in kernel 2.6.16; library support was added to glibc in version 2.4.
faccessat2() was added to Linux in version 5.8.
CONFORMING TOaccess(): SVr4, 4.3BSD, POSIX.1-2001, POSIX.1-2008.
faccessat(): POSIX.1-2008.
faccessat2(): Linux-specific.
NOTESWarning: reported.
C library/kernel differencesT, but see BUGS.
Glibc notes.
BUGSBecause the Linux kernel's faccessat() system call does not support a flags argument, the glibc faccessat() wrapper function provided in glibc 2.32 and earlier emulates the required functionality using a combination of the faccessat() system call and fstatat(2). However, this emulation does not take ACLs into account. Starting with glibc 2.33, the wrapper function avoids this bug by making use of the faccessat2() system call where it is provided by the underlying kernel.. | https://man.archlinux.org/man/faccessat2.2.en | CC-MAIN-2022-27 | refinedweb | 437 | 51.95 |
I have a csv files that I’m turning into a pandas dataframes (df), then manipulating the values in a couple of columns, and finally exporting the dataframe to a table in SQL Server.
The code is:
import pyodbc import sys df = pd.read_csv(f'../data/polreg/{sys.argv[3]}', usecols=[0, 1, 2, 3, 4, 5, 8, 10, 11, 17, 18, 20]) # trim leading and trailing white space from all string type columns df_obj = df.select_dtypes(['object']) df[df_obj.columns] = df_obj.apply(lambda x: x.str.strip()) # drop all non-alphanumeric values at end policy numbers using regex df['a'].replace(to_replace = '[W^]+$', value='', regex=True, inplace=True) df.loc[df['b'] == 'rn', ['b']] = None df.loc[df['b'] == 'cn', ['b']] = df['c'] df.loc[df['b'] != None, ['c']] = None #define connection string to database and create connection cursor "cur" conn = pyodbc.connect('Driver={SQL Server};' f'Server={sys.argv[1]};' f'Database={sys.argv[2]};' 'Trusted_Connection=yes;') cur = conn.cursor() cur.execute('EXEC src.CreateJob;') #Execute stored procedure src.CreateJob #get most recent jobId value from src.ExtractJob, create new column in csv_df called jobId, fill all values of jobId column with jobId value. cur.execute('SELECT TOP(1) jobId FROM src.ExtractJob ORDER BY jobId DESC;') extractJob_info = cur.fetchall() jobId = extractJob_info[0][0] df["jobId"] = jobId # execute src.Update stored procedure for each row in df Update_query = """EXEC src.Update @a=?, @b=?, @c=?, @d=?, @e=?, @f=?, @g=?, @h=?, @i=?, @j=?, @k=?, @l=?, @jobId=?""" for index, row in df.iterrows(): values = (row['a'], row['b'], row['c'], row['d'], row['e'], row['f'], row['g'], row['h'], row['i'], row['j'], row['k'], row['l'], jobId) cur.execute(Update_query, values) cur.execute(f'EXEC src.FinishJob @jobID = {jobId}') # execute src.FinishJob sotred procedure cur.commit()
When I wrote the code originally it worked fine, but then realized I needed to manipulate columns "b" and "c" so I added the 3 lines of code that start with df.loc[…] = value (they are right before I create the connection cursor). When I check the values of df after those 3 lines of code they do exactly what I want them to do so I thought everything was set to go, but then when I run my code I get the error message.
"Traceback (most recent call last):
File "C:" line 48, in
cur.execute(Update_query, values)
pyodbc.ProgrammingError: (‘42000’, ‘[42000] [Microsoft][ODBC SQL Server Driver][SQL Server]The incoming tabular data stream (TDS) remote procedure call (RPC) protocol stream is incorrect. Parameter 13 ("@b"): The supplied value is not a valid instance of data type float. Check the source data for invalid values. An example of an invalid value is data of numeric type with scale greater than precision. (8023) (SQLExecDirectW)’)"
I can not for the life of me figure out what changed in the dataframe that is making this error occur. If I take out the 3 lines of code stated earlier everything works fine but the values are obviously not right in columns ‘b’ and ‘c’ because I still need to manipulate them. Does using df.loc[…] = value somehow change the indexing of the dataframe? I’m really lost here, any help will be greatly appreciated.
Source: Python Questions | https://askpythonquestions.com/2021/06/11/why-cant-i-transfer-dataframe-values-to-sql-server-after-manipulating-dataframe-data-using-iloc/ | CC-MAIN-2021-31 | refinedweb | 541 | 59.5 |
Does the world need yet another programming language? After reviewing Curl, I'm still not sure. Most languages start out as an attempt to simplify overly complex and cruft-filled older languages. But as they develop, these new kids on the block are beset by many of the same ills that plague their older siblings.
Curl began optimistically in 1995. The language was devised as a way of addressing vexing client-side problems that were troublesome after many years of browser development. These problems were mainly due to disparate development directions with limited standardization for two and three dimensional graphics, file access, multimedia support, and XML, for example.
Curl is enabled via a plug-in that works with either Internet Explorer or Netscape Navigator 4.x (and is mostly compatible with Netscape 6/Mozilla). Curl currently supports Windows only. Both Mac and Linux ports, and a server version are planned.
The language is noteworthy for its license. While the development licenses are free, Curl supports itself by charging on a per-use basis in full production environments, making it an early contender in the subscriber space that initiatives like Microsoft .Net are striving to fill. Licensing fees are set by usage ($0.0005/KB of data transferred).
The goal of Curl is simplicity, although I'm leery of any languages that are supposedly designed for non-programmers. The basic code examples look like slightly twisted LISP after a few run-ins with XML. I wrote Listing 1 as a routine that converts between miles and kilometers. This routine is fairly easy to follow if you're familiar with programming, but Curl isn't that much friendlier than JavaScript. And a strong data typing structure can make for very efficient code, but at the expense of more complex development—a questionable trade-off in scripting.
However, Curl does exhibit some interesting concepts. The structure of the language in general follows the convention:
{operation [parameterName = ] expression[:type] [,[parameterName = ] expression[:type]]}
Operation is the action (
let,
set,
define-proc,
paragraph, and so
on),
expression is a contained operation/expression/type triplet (or the result of same),
parameterName is the name of the parameter that's being operated on, and
type gives the expression data type. The elements within square brackets indicate optional elements (the bracket itself isn't included), while the integral curly braces group expressions.
Curl also distinguishes between declaration and assignment of a scalar value, which can make your code more efficient, but adds the complexity of deciding whether a given expression is a constant, a parameter, or a function—much more challenging than loosely typed languages like JavaScript.
Functions in Curl are relatively straightforward once you get used to the stack-like order of operations. For instance, consider Listing 2, the converter from Listing 1. The function defines an input parameter,
miles_in, as a floating point number, and specifies that the output type should also be a float. It then defines an expression as a float that performs the actual conversion to a temporary variable (called
k). The final line returns the variable's contents to the calling function. The line delimiter is a carriage return.
An additional aspect of this approach is that you use Curl to create HTML-like output functionally, rather than through markup. For instance, this code creates a paragraph that's sent to the display:
{paragraph {value myMiles & " miles = " & {m2k myMiles} & " kilometers"}}
It's worth noting that there isn't any HTML in this code. Curl creates its own display region and outputs its content to that region, rather than creating content for a browser. This gives you much finer control over the output, but at the expense of the very real benefits provided by the massive HTML infrastructure (more on this later).
The event-handling mechanism follows a model similar to that of DHTML. Each Curl object can add one or more event handlers that can be used to either invoke specific method calls or to set properties for the handler or other objects. To test this, I wrote the code in Listing 3, which creates two rectangles and adds them to a flow container (much like a layout container in Java). The code then attaches event handlers to each rectangle that set different colors when the mouse enters or leaves it. (Note that Curl uses
|| to delineate comments, rather than
// or
#.) The add-event-handler method takes an event object
(the
PointerEnter or
PointerLeave objects) and performs the commands given after the
do keyword. This model of treating the events themselves as distinct objects, which can then be caught by the appropriate event handlers, is gaining currency with most languages.
Surge Lab, the Curl IDE, is adequate. However, it isn't Curl's strongest feature by any stretch. Curl, like most compiled languages, supports the idea of packages. These are compiled sets of Curl programs that together provide a unified set of functionality. Unlike more sophisticated IDEs, Surge Lab doesn't let you see packages through an object viewer or via pop-ups while you're typing. Nor can you select a specific object and see its definition. Thus, you're reliant upon the Help system, which is also written in Curl. It's a surprisingly good resource for showcasing Curl's capabilities. Clearly, Surge Lab's strength is the ability to produce document-oriented code. The resulting code flows in a way that's reminiscent of HTML, and it doesn't rely upon absolute positioning as you'd expect with C++ (even though this is possible if needed). The Help system is broken into an API document that makes the packages and their enclosed objects, methods, and properties somewhat reminiscent of the Javadoc system.
working with text, graphics, sound, and 3d
Many of the critical packages (like graphics handling) are implicitly loaded by the environment itself, but you can add your own or third-party packages using the
import command from within your scripts. The graphics model that Curl uses is built upon the creation of graphical objects rather than simply rendering content to a graphical space. This feature makes Curl useful for developing interfaces, because it lets you create complex objects out of simple ones through inheritance and aggregation. This also applies to text. Many of the properties for specifying text follow the CSS conventions, as Listing 4 demonstrates. You can also create sophisticated custom flow output (as in Listing 5).
Curl supports a fairly impressive set of libraries. Beyond the basic two-dimensional features, Curl has a rich 3D-rendering environment, including the ability to animate 3D scenes, create scene graphs, and work with basic renderers, 3D text, and particle systems. The language also supports one of my favorite features: filters. These let you apply precise effects onto a graphic image, such as introducing blur effects, posterizing and embossing graphics on the fly, and twirling content. In addition, Curl supports both external .WAV files and generated sounds (via frequency envelopes), and includes image loading and manipulation capabilities.file systems and networking
Curl was intended as a client language for working with external Web services and HTTP. You can read files (and HTTP file headers) from remote Web servers, although currently there's limited support for writing to external files. The code in Listing 6 retrieves the headers from a specific Web page (initially,). The routine creates a Web-stream object, which can then receive Web content and extract the relevant headers.
Curl also works explicitly with Web services that use SOAP. It currently supports the (latest) version 1.1 SOAP specification. Understanding this spec itself isn't necessary. However, you do need to know enough to set up the requisite data types in your argument calls. Once you set up these services, you can call them transparently as remote procedure calls.
The Curl packages also include an XML SAX parser for handling simple XML work. The parser is useful for evaluating commands based upon specific XML elements, but it has several limitations when querying XML or retaining a DOM object in memory. It doesn't support XSLT or XPath, so you can't do any native transformations upon it. As an ardent XML practitioner, this omission disappointed me.
Finally, Curl has a full complement of file and directory routines, but this is a mixed blessing. These capabilities work well when the client is used locally (for example, looking at a Curl file located on your hard drive rather than on a server). However, they don't work when the Curl application is talking to a server, for sandbox security reasons.
swimming back
Some aspects of Curl, like the 2D and 3D graphics integration, offer some interesting potential for development, especially with XML. The Curl language can be a bit cryptic at first, but once you get a feel for it, it's internally consistent and supports object-oriented development among its many design features.
However, Curl has its fair share of negatives. It's especially frustrating as a client language. The type system that Curl uses seems curiously antiquated in an age when Python, Perl, and JavaScript all demonstrate that weakly typed languages offer many advantages in client systems.
Curl also doesn't provide much in the way of interoperability with other environments, even as a component embedded in an HTML Web page. The IDE needs to be radically improved before it can be taken seriously as a development environment. It's stable (which isn't something you can take for granted), but the bar has been raised on IDEs: after several years of working with IDEs such as Microsoft Visual Studio, Sun Forte, Borland JBuilder, and so on, the expectations of developers for such features as dropdown APIs, good project management tools, and context-sensitive help mean that anything less will be seen as substandard.
Curl has the potential to be very powerful. Its ability to work with interpreted, instead of compiled languages means that Curl can be used for sophisticated applications in response to just-in-time changes on the server and access privileges. Curl's LISP-like structure is also making a comeback in the computing world as systems become more complex and distributed. With future SVG support, Curl's graphic generation abilities will provide an alternative to developing interactive SVG graphics on Internet Explorer.
Curl has cool features and it could very well become important over time. Curl may be the next Java, especially because its designers have solved one of the big headaches that Java hasn't: they've developed a good client-side programming language.
Kurt is an author and a developer who specializes in Web technologies and XML. You can contact Kurt at kurt@kurtcagle.net.
{curl 1.7 applet} {applet license="development"} {let miles : float, kilometers:float} {define-proc {m2k miles_in:float}:float let k:float = (miles_in * 1.6) asa float {return k} } {set kilometers={m2k 100}} {title "Miles To Kilometers"} {paragraph {value "100 miles = " & kilometers & " kilometers"}} {paragraph {value "200 miles = " & {m2k 200} & " kilometers"}} {let myMiles :float = 300} {paragraph {value myMiles & " miles = " & {m2k myMiles} & " kilometers"}}
</code> {define-proc {m2k miles_in:float}:float let k:float = (miles_in * 1.6) asa float {return k} }
{curl 1.7 applet} {applet license="development"} {value let left = {RectangleGraphic width=100pt, height=50pt} let right = {RectangleGraphic width=100pt, height=50pt} let my-hbox = {HBox left, right} || attach first event handler to left rectangle {left.add-event-handler {on PointerEnter do set right.fill-color = "green" } } || attach second event handler to left rectangle {left.add-event-handler {on PointerLeave do set right.fill-color = "red" } } my-hbox }
{paragraph font-size=24pt,font-family="san-serif",font-weight="bold", font-style="italic", The Curl Help System}
Listing 5
{curl 1.7 applet} {applet license = "development"} {define-text-proc {blink ...}:any let color-str:String = "blue" let flash:TextFlowBox = {TextFlowBox font-weight = "bold", color = color-str, {value ...} } {Timer interval = 0.25s, {on TimerEvent do {if color-str == "white" then set color-str = "blue" else set color-str = "white" } set flash.color = color-str } } {return {text {value flash}}} } {paragraph font-size=24pt,font-family="san-serif",font-weight="bold", font-style="italic",
> {value let url-text:TextField = {TextField width=3in, value=""} let web-buffer:VBox = {VBox} let connect-button:CommandButton = {CommandButton label = "Get it!", || when button is clicked ... {on Action do || convert string to Url let web-url:Url = {url url-text.value} let http-file:HttpFile = {web-url.instantiate-File} asa HttpFile || open the Url let web-stream:HttpTextInputStream = {http-file.http-read-open || don't redirect auto-redirect? = false, || return response headers even if error status always-return-response-headers? = true} || display status {web-buffer.add "Status: " & web-stream.response-headers.status} || display response headers {for value:String key name:String in web-stream.response-headers do {web-buffer.add name & {if value == "" then "" else ": " & value} } } {web-stream.close} web-buffer } } {spaced-vbox {spaced-hbox {text URI to get:}, url-text, connect-button}, {HBox {text {bold Response Headers:}}}, {HBox width=5in, web-buffer} } } | http://www.drdobbs.com/yet-another-programming-language/184413224 | CC-MAIN-2016-22 | refinedweb | 2,163 | 55.24 |
>> Then again it's these people, Peter first, who enhance Ant to
>> support better models for the future, so power to you guys ;-)
Cool, so we can expect 'auto-download' to be a feature of 1.7.1?
Serious, just to pull off some kind of demo implementation: is there some
kind of
namespace interceptor in Ant's source code? I'm just asking cause I have
never
seen such a beast...
Regards,
Wolfgang Häfelinger
Research & Architecture | Dir. 2.7.0.2
European Patent Office
Patentlaan 3-9 | 2288 EE Rijswijk | The Netherlands
Tel. +31 (0)70 340 4931
whaefelinger@epo.org
"Dominique Devienne" <ddevienne@gmail.com>
14-11-2007 17:40
Please respond to
"Ant Developers List" <dev@ant.apache.org>
To
"Ant Developers List" <dev@ant.apache.org>
cc
Subject
Re: ApacheCon Presentation
On Nov 14, 2007 9:50 AM, Peter Reilly <peter.kitt.reilly@gmail.com> wrote:
> On Nov 14, 2007 3:18 PM, Dominique Devienne <ddevienne@gmail.com> wrote:
> > | http://mail-archives.apache.org/mod_mbox/ant-dev/200711.mbox/%3COFF92CFCC8.CC89BC60-ONC1257393.005C2B4C-C1257393.005CA28F@epo.org%3E | CC-MAIN-2016-22 | refinedweb | 163 | 59.4 |
Using Line Integral Convolution to Render Effects on Images
- Anastasia Simon
- 1 years ago
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Transcription
1 Using Line Integral Convolution to Render Effects on Images Ricardo David Castañeda Marín VISGRAF Lab Instituto Nacional de Matemática Pura e Aplicada A thesis submitted for the degree of Master in Mathematics-Computer Graphics Feb 2009
2 ii
3 Dedicated To My Family...
4 Acknowledgements I am very grateful to my parents Mariela and Gildardo, my sisters Eliana and Andrea and my friends Alejandro Mejia, Julian Lopez and Andres Serrano who have supported all my studies and have encouraged me to carry on with my academic and personal life; this monograph is dedicated to all them. Many thanks to my academic advisor Dr. Luiz Henrique de Figueiredo who accepted my request on working in this topic. Thank you for all the suggestions and for helping me in writing this dissertation. Particular thanks go also to Dr. Luiz Velho for his valuable tips and time we spent discussing new ideas. Those sessions were very helpful, thank you. Also I am in debt with Emilio Ashton Vital Brazil who gave generously his time to offer explanations especially with the pencil effect approach of Section 4.3.
5 Contents List of Figures v 1 Introduction 1 2 Line Integral Convolution DDA Convolution LIC Formulation A Fast LIC algorithm Final Considerations Vector Field Design Basic Design Another Approach - Distance Vector Fields Effects Using LIC Ideas Blur LIC Silhouette Pencil Rendering Painterly Rendering Conclusions and Future Work A Implementation in C++ 29 A.1 Getting Started with CImg A.2 LIC in C++ using CImg A.3 A Basic Vector Field Design System using CImg A.4 LIC effects in C A.4.1 LIC Pencil Effect iii
6 CONTENTS A.4.2 Painterly Rendering B Gallery 41 References 51 iv
7 List of Figures 2.1 LIC algorithm overview DDA convolution LIC Different Values for L FastLIC Image Domain Overflowing Singularities Classification Distance Vector Fields Blur Effect Warping a dithered image Automated Silhouette LIC Silhouette LIC Pencil Effect Examples LIC Spray-Like Effect LIC Pencil Effect Process Painterly Rendering A.1 Color to gray conversion A.2 Basic Vector Field Design example using CImg B.1 Pigeon Point Lighthouse, California B.2 Plymouth Hoe, England B.3 Landscape B.4 Girl Playing Guitar v
8 LIST OF FIGURES B.5 Shoes in the Grass B.6 Cows B.7 Garden IMS, Rio de Janeiro B.8 Live Performance B.9 Live Performance Continued B.10 Live Performance Continued vi
9 1 Introduction In this monograph we are going to expose the use of some ideas involved in the Line Integral Convolution (LIC) algorithm for the generation of many Non-Photorealistic Renditions on arbitrary raster images. In other words, our main objective is to create images that could be considered as pieces of visual art generated using ideas from the LIC algorithm. From this point of view, the output of our algorithms does not need to be considered as right or wrong, an aesthetic judgement will be more appropriate. That is what we are expecting from the reader. It is well known that even since its roots Computer Graphics procedures have been used by artists for both aesthetics and commercial purposes. Our motivation comes from the original paper on LIC (1) which explores another kind of applications considered as realistic effects, more specifically blur-warping. In a similar way, we searched for other uses of these LIC ideas mixing the already known NPR techniques like painterly rendering and pencil sketches. This monograph is then the result of such experiments. The material presented demands basic knowledge of ordinary differential equations and vector calculus. Chapter 2 defines and explains the LIC algorithm to visualize the structure of planar vector fields using white noise as the input image. Since our approach uses arbitrary vector fields to guide the effects, two methods for designing these vector fields are given in chapter 3. Chapter 4 discusses the actual NPR effects results. There is also an appendix A which exposes the implementation of our procedures using the CImg library for image processing and visualization of the results, and an appendix B which is a gallery with our results. 1
10 1. INTRODUCTION 2
11 2 Line Integral Convolution This chapter is about the main algorithm of this text: Line Integral Convolution (LIC). It was introduced in (1) by B. Cabral and L. Leedom at the SIGGRAPH conference in LIC was designed primarily to plot 2D vector fields that could not be visualized with traditional arrows and streamlines, i.e., fields with high density. Due to the low of performance of the original algorithm on large images, over the years several alternatives of the same calculations have been published to increase the speed and the details of the visualization. We will discuss a fast procedure briefly. Since every other algorithm here will be an extension or a derivation from LIC, it is important to have a good understanding of how it works. 2.1 DDA Convolution The LIC algorithm takes as input an image and a vector field defined on the same domain. The output image is computed as a convolution of the intensity values over the integral curves of the vector field (see Figure 2.1). In the case we want to visualize the topology and structure of this field, the input image needs to have pixels uniformly distributed and with mutually independent intensities (6). A simple white noise as input image will be enough for what we want here. On the other hand, the input image can be arbitrarily chosen, and the output image will have an effect depending on the input vector field. We will turn to this subject later. As stated in the original paper, LIC is a generalization of what is known as DDA convolution. The DDA algorithm performs convolution on a line direction rather than 3
12 2. LINE INTEGRAL CONVOLUTION Figure 2.1: LIC algorithm overview - Left to right: White noise, input vector field and output LIC visualization. on integral curves. For each pixel location (i, j) on the input image I, we want to compute the pixel intensity in the output image O(i, j). For this, DDA takes the normalized vector V (i, j) corresponding to that location and moves in its positive and negative directions some fixed length L. This generates a line of locations l(s) = (i, j) + sv (i, j), s { L, L + 1,..., 0,..., L 1, L and a line of pixels intensities I(l(s)) of length 2L + 1. Choosing a filter kernel K : R R with Supp(K) [ L, L], the line function I(l(s)) is filtered and normalized to generate the intensity output O(i, j): O(i, j) = 1 2L + 1 L s= L I(l(s))K(l 1 (i, j) s) 1 2L + 1 I l(i,j) K The symbol stands for discrete convolution and is responsible for the name of the algorithm. So for each pixel we perform a discrete convolution of the input image with some fixed filter kernel. As a special case, when K is chosen to be a box kernel (K 1 on [ L, L] and K 0 everywhere else), the convolution becomes the average sum of the pixels I(l(s)): O(i, j) = 1 2L + 1 L s= L I(l(s)) Fig 2.2 depicts the process. As expected, DDA is very sensitive to the fixed length L, since we are assuming not only that the vector field can be locally approximated by 4
13 2.2 LIC Formulation a straight line, but also that this line has fixed length L everywhere, generating a uneven visualization: linear parts are better represented than vortices or paths with high curvature. Line integral convolution remedies this by performing convolution over integral curves. Figure 2.2: DDA convolution - Convolution over a line of pixels. Picture adapted from (1). 2.2 LIC Formulation LIC can be performed on 2D and 3D spaces. Because we are only concerned with the generation of effects on 2D images, our vector field will have a planar domain. integral curve of the vector field v : Ω R 2 R 2, passing over x 0 Ω at time τ 0, is defined as a function c x0 : [ L, L] R 2 with: d dτ c x 0 (τ) = v(c x0 (τ)), c x0 (0) = x 0 that is, a curve solution of the initial value problem d dτ c(τ) = v(c(τ)), c(0) = x 0 Uniqueness of the solution of this ODE is reached when the field locally satisfies a Lipschitz condition. When d dτ c x(τ) 0 for all x Ω and for all τ [ τ, τ], every c x can be reparametrized by arc length s (2). An easy computation of this reparametrization leads to an alternate definition of integral curves: An 5
14 2. LINE INTEGRAL CONVOLUTION d ds c x 0 (s) = v(c x 0 (s)) v(c x0 (s)), c x 0 (s 0 ) = x 0 Basically the generalization from DDA to LIC is done when one changes the line l(s) involved, for the integral curve c l(0) c (i,j). The new output pixel O(i, j), with s 0 such that c (i,j) (s 0 ) = (i, j), is computed by LIC as: O(i, j) = 1 2L + 1 s 0 +L s=s 0 L and simplifying with a box filter: O(i, j) = I(c (i,j) (s))k(s 0 s) 1 2L + 1 s 0 +L s=s 0 L I(c (i,j) (s)) 1 2L + 1 I c (i,j) K Figure 2.3 shows this process. Notice that we are restricting the integral curve to the interval [ L, L] for some fixed length L like in DDA. In general a good L depends on the vector field and its density. Figure 2.4 show some examples for different values of L and the same vector field. Figure 2.3: LIC - Convolution over a integral curve of pixels. Picture adapted from (1). To compute the integral curves of the input vector field, the solution of the ODE is obtained by integration: s c x0 (s) = x 0 + v(c x0 (s ))ds s 0 6
15 2.2 LIC Formulation Figure 2.4: Different Values for L - From top to bottom and left to right: Values for L: 1,3,5,10,20, and 50. The next pseudocode performs a discretization of this equation, storing in an array C the pixel locations of the integral curve. The function vector field(p) returns the vector at point p. The constant ds is the sample rate for the integral curve, see section 2.4 for an explanation. Computing the integral curve for a pixel p = (x, y): 1 function compute_integral_curve(p){ 2 V=vector_field(p) 3 add p to C 4 for (s=0;s<l;s=s+1){ // positive calculations 5 x=x+ds*v.x 6 y=y+ds*v.y 7 add the new (x,y) to C 8 compute the new V=vector_field(x,y) 9 10 (x,y)=p V=vector_field(p) //return to original point and original vector 11 for (s=0;s>-l;s=s-1){ // negative calculations 7
16 2. LINE INTEGRAL CONVOLUTION 12 x=x-ds*v.x 13 y=y-ds*v.y 14 add the new (x,y) to C 15 compute the new V=vector_field(x,y) return C 18 used: To compute the convolution with a box kernel a simple average of the intensities is Computing the convolution along integral curves: 1 function compute_convolution(image,c){ 2 sum=0 3 for each location p in C { 4 sum=sum+image(p) 5 6 sum=sum/(2*l+1) // normalization 7 return sum 8 Next is the pseudocode of the final LIC algorithm. LIC Pseudocode with a box kernel: 1 function LIC(image){ 2 create an empty image O_img 3 for each p on image{ 4 array C=compute_integral_curve(p) 5 sum = compute_convolution(image,c) 6 set pixel p on O_img to sum 7 8 return O_img 9 Note that for a point on a particular integral curve c, its own integral curve is highly related to c. The low performance of the LIC algorithm can be seen there: for 8
17 2.3 A Fast LIC algorithm each pixel location we have to compute the integral curve passing through that location (without using the already computed integral curves) and perform a convolution with some filter kernel. In the next section we will see how this relations can be explored to increase speed of the LIC algorithm. 2.3 A Fast LIC algorithm Given that when computed, an integral curve covers lot of pixels, uniqueness of the solution of the ODE implies that the convolution involved in LIC can be reused. Choose a box filter kernel and suppose we have an integral curve of a location (i, j), say c (i,j) and another location along it c (i,j) (s), then their output values are related by O(c (i,j) (s)) = O(i, j) s 0 L+s s =s 0 L I(c (i,j) (s )) + s 0 +L+s s =s 0 +L I(c (i,j) (s )) Figure 2.5 illustrates this relation. In practice, to reuse an already computed convolution for a set of pixels, a matrix of the same size of the image is created such that each entry stores the number of times that pixel has been visited. The order in which the pixels are analyzed is important for the efficiency of this process. The goal is to hit as many uncovered pixels with each new integral curve to reuse the convolutions as possible, and thus it is not a good choice to make it in a scanline order. Nevertheless, we can adopt another approach in which the image is subdivided in blocks and process the pixels in scanline order on each block. For instance, we take the first pixel of each block and make the calculations, then the second pixel and so on 1. Figure 2.5: FastLIC - Integral curves relation involved in the FastLIC approach. The shaded region of the convolution could be reused. 1 There are other methods to compute the order to process the pixels, see for example (6; 11). 9
18 2. LINE INTEGRAL CONVOLUTION The following is a pseudocode of the basic FastLIC algorithm (5). This code is used on each block, as stated in the previous paragraph, to ensure reusability of the integral curves. FastLIC Pseudocode: 1 for each pixel p 2 if p hasn t been visited then 3 compute the integral curve with center p=c(0) 4 compute the LIC of p, and add result to O(p) 5 m=1 6 while m<l 7 update convolutions for c(m) and c(-m) 8 set output pixels: O(c(m)) and O(c(-m)) 9 set pixels c(m) and c(-m) as visited 10 m=m+1; Final Considerations As you can see from the previous sections, LIC is a simple but powerful tool for visualizing vector fields. In this section I want to make explicit some considerations regarding the implementation of this algorithm. This section is optional for the readers whose interest is the implementation rather than the applications. The already given material is enough for what we want to develop with LIC. The first consideration is about the space of the variable s. In section 2.1 we define the DDA convolution for discrete values: s { L, L + 1,..., 0,..., L 1, L. However, in general s is a real variable on the interval [ L, L]. The line of locations l(s) is in general generated by sampling this interval, with l(0) = (i, j). It is clear that for some sampling rates this line is not injective, given that our image is a raster image with integer locations (i, j). The DDA line is computed as l(k s) = (i, j) + k sv (i, j) with integer k [ L s, L s ]. If s 1 we will be back in our original definition. Practical experience (6) shows that using a s of about a third or half an image pixel width is enough for good visualizations. The same sampling consideration is applied for integral curves in the general LIC algorithm. 10
19 2.4 Final Considerations Another thing one should consider when implementing LIC is that the domain of the input I and output image O can be taken as continuous domains rather than a grid of pixels (i, j). Basically we take a continuous rectangular domain and define a set of cells with center a pixel location (i, j). Then to compute the output pixel at location (i, j) one choose a number of samples locations within its correspondent cell, perform the computations and compute an average intensity value. Because increasing the number of samples on each cell increases the run time of the algorithm, a small number is recommended. Finally, when performing the convolution on pixels near the boundary of the image domain, sometimes the algorithm will try to retrieve an intensity value of a invalid pixel location, because generally the integral curve will leave the image domain. Figure 2.6 illustrates this. One solution is to pad the image with zeros on the boundary. This however will cause sometimes black regions at the image boundaries. In the case we have a vector field defined only on the image grid, we simply extend it arbitrarily and smoothly on the domain (e.g., by repeating values). Figure 2.6: overflowing. Image Domain Overflowing - A padding with zeros is used to avoid 11
20 2. LINE INTEGRAL CONVOLUTION 12
21 3 Vector Field Design In the previous chapter we saw how planar vector fields with high density can be visualized using the LIC algorithm. We now turn on the subject to design the input vector field. This is motivated by many graphics applications including texture synthesis, fluid simulation and, as we will see in the next chapter, NPR effects on images. 3.1 Basic Design In section 2.2 we saw that a vector field v : Ω R 2 R 2 defines the differential equation d c(τ) = v(c(τ)) dτ such that for each point x 0 Ω, the solution, with intial condition c x0 (s 0 ) = x 0, is the integral curve c x0 (τ). A singularity of the vector field v is a point x Ω such that v(x) = 0. A very basic vector field design consists of local linearizations and a classification of the singularities. Explicitly, if v is given by the scalar functions F and G, i.e v(x) = (F (x), G(x)), then the local linearization of v at a point x 0 is V (x) = v(x 0 ) + Jv(x 0 )(x x 0 ) ( F x where Jv(x 0 ) = (x F 0) y (x ) 0) G x (x G 0) y (x is the Jacobian matrix evaluated at the point 0) x 0. When x 0 is a singularity we have V (x) = Jv(x 0 )(x x 0 ) 13
22 3. VECTOR FIELD DESIGN We will assume that for singularities x 0 its corresponding Jacobian matrix has full rank and thus that it has two non zero eigenvalues. This implies also that the only element on the null space of the Jacobian is zero, and so the only singularity of the vector field V is x 0. We know from linear algebra that in this case the eigenvalues of the Jacobian are both real or both complex. When they are real, we have three cases: 1. Both are positive. In this case the singularity is called a source. 2. Both are negative. In this case the singularity is called a sink. 3. One is positive and the other is negative. In this case the singularity is called a saddle. On the other hand, when the eigenvalues are complex, we have a center when the real part of both are zero. Figure 3.1 shows this classification for the singularities of our vector field. Figure 3.1: Singularities Classification - Top and left to right: A sink, a source and a saddle. Bottom and left to right: A center, and a mix of a saddle a sink and a center. 14
23 3.1 Basic Design The basic design consists of providing locations and types of singularities on the image domain. For instance, to create the center at (0, 0) shown in figure 3.1, we defined the vector field as V (x, y) = ( ) ( x y In general the type of singularity can be stored as the Jacobian matrix JV, that we can define as: ( ) k 0 JV = for a sink. 0 k ( ) k 0 JV = for a saddle. 0 k ( ) k 0 JV = for a source. 0 k ( ) 0 k JV = for a counter-clockwise center. k 0 ( ) 0 k JV = for a clockwise center. k 0 where k > 0 is a constant representing the strength of the singularity. In practice, if we want a vector field with a singularity of any type at position p 0 = (x 0, y 0 ), then one defines the vector field as: ( ) V (p) = e d p p 0 2 x x0 JV y y 0 choosing the desired JV and where d is a decay constant that controls the influence of the vector field on points near and far from the singularity. This is essential when one wants to design a vector field which is a composition of many basic fields with singularities. To construct such vector field, we define a simple vector field separately for each singularity, and then we define the final vector field as their sum. For example a vector field with a sink at q 1 = (10, 10) and a center at q 2 = ( 5, 4) can be modeled as: V (p) = e d 1 p q 1 2 ( k1 0 0 k 1 or more compactly: ) ( x 10 y 10 ) ) + e d 2 p q 2 2 ( 0 k2 k 2 0 ) ( x + 5 y 4 ) 15
24 3. VECTOR FIELD DESIGN V (p) = V q1 (p) + V q2 (p) Note that each V qi has just one singularity, namely q i. This is not the case for our final vector field, in which new singularities are present when V q1 (p) = V q2 (p). In particular, choosing each d i properly, each q i is a singularity of the final vector field, but it could happen that V (p) = 0 for points p where V q1 (p) 0 and V q2 (p) 0. There is a method to control this undesired new singularities using Conley indices (4) but it falls out of the scope of this monograph. 3.2 Another Approach - Distance Vector Fields In the previous section we saw how to design planar vector fields classifying its singularities: the user chooses a location and type and a linear vector field its created by choosing some other parameters like strength and influence. In this section we are interested in constructing vector fields using gestures. The idea is to create a vector field that resembles the direction of a given planar curve. vector field which is explained next. We use a distance-based Given a parametrized curve C : [a, b] R R 2 the distance from a point p R 2 to the curve is given by d(p, C) min {d(p, C(t)) t [a,b] The parameter t for which the equality holds in the equation above may be not unique. Indeed, when C is a circumference and p is taken as the center of the circumference, this equation will hold for every value of t. Nevertheless we obtained pleasant results choosing an aleatory value from all the candidates. We will note this value by τ p. Also we took the Euclidean distance function d(x, y) = x 2 + y 2 for simplicity. To a curve C and a distance function d, we associated two vector fields V : R 2 R 2 and W : R 2 R 2, each perpendicular to the other by definition: V (p) C(τ p ) p, W (p), V (p) 0 Assuming that C is differentiable with C (t) 0 for all t [a, b], from the definition it is clear that for a point p R 2 with p C(t) for all t [a, b], the vector W (p) has 16
25 3.2 Another Approach - Distance Vector Fields the direction (up to sign) of the tangent vector of the curve at τ p. In fact the function f : R R defined by f(t) = C(t) p, C(t) p which measures the square of the distance from p to C(t) for each t [a, b], has a minimmun at τ p. On the other hand, we have and thus f (τ p ) = 0 implies that f (t) = 2 C (t), C(t) p C (τ p ), V (p) = 0 leading to W (p) = λc (τ p ) for λ R as claimed. From this we see that the vector field W could be a good option to accomplish the design of a vector field that resembles a given curve. However, given that in practice the curve C could be not differentiable (creating it interactively for example), numerous artifacts in the final vector field appear. Figure 3.2 show some examples of V and W for different polylines created with a mouse. Note also how all the points in the curve C became singularities of V and W, which is obvious from their definition. 17
26 3. VECTOR FIELD DESIGN Figure 3.2: Distance Vector Fields - Left to right: White noise with the curve C in red and distance vector fields V and W. 18
27 4 Effects Using LIC Ideas Computational art can be thought as studies concerned in creating and producing pieces of art by means of a computer 1. In this monograph we are not going to discuss the creative process that leads to a piece of art from the initial white canvas. These subjects, I think, fall into the context of artificial intelligence and cognition and are out of the scope of this text. The creativity involved here will be then of another kind; we will be given an input digital image and we will create and use modifications of the LIC algorithm to process it and generate a new digital image. The result image needs not be compared to any other, since we will be creating rather than imitating styles. Since the results are in some sense non-real, they are called NPR or non-photorealistic rendering effects on images. Nevertheless we will be also including the original real effects blur-warping for completeness. 4.1 Blur A warping or blur effect can be achieved when using LIC on an arbitrary image rather than on white noise. In this case the vector field will drive the warping effect in its directions. To guarantee visual coherence on the result image, each RGB channel is processed separately. A code in C++ using CImg can be found in the appendix section A.2. Figure 4.1 shows some results. As you may notice, the deformation on the final image depends strongly on the input image and the vector field used. Also notice that in chapter 2 we were able to 1 We will be referring just to graphic arts like painting, drawing and photography. This point of view is independent from the definition of art, which we are not going to discuss here. 19
28 4. EFFECTS USING LIC IDEAS Figure 4.1: Blur Effect - Left-Original Image, Middle-LIC on white noise of the vector field used. Right-LIC of the original image. 20
29 4.2 LIC Silhouette visualize the structure of the vector field because of the uniformly distribution of the white noise input image. In general, we compute as a preprocessing step a dithered version of the input image to ensure this charactheristic and then perform the LIC to generate a warping effect. Figure 4.2 shows an example. Another application of blur-warping is to generate an animation that advects the colors on the image in the direction of the input vector field. This is achieved by iterating LIC several times with the same vector field. This technique could be used to flow visualization not only for steady vector fields but unsteady aswell. However some considerations need to be made to control the color advection at the image boundaries (section 2.4). This black regions can be avoided with a technique called Image Based Flow Visualization (10). Figure 4.2: Warping a dithered image - From left to right images: dithered, and warping the dithered image 4.2 LIC Silhouette We can generate a silhouette image automatically with LIC. For this, a threshold is defined to control the value of the convolution of a given pixel. The first step is to convert the image to gray to avoid color incoherences. Then for each pixel we proceed 21
30 4. EFFECTS USING LIC IDEAS as in LIC, but the output pixel is set depending on the value of the convolution and the thresholds predefined. This process can be used also to generate a dithered version of the visualization of a vector field. Below is a pseudocode of this process. Figure 4.3 show examples of this method. Figure 4.3: Automated Silhouette - Left-Original image, Middle-Dithered LIC, Right- Automated Silhouette using LIC function Silhouette(image){ convert image to gray(image) for each pixel p in image C=compute_integral_curve(p) I=compute_convolution(image,C) if (val 1<I< val 2) { set OutputImage(p)=color 1 if (I<val 1){ set OutputImage(p)=color 2 else{ set OutputImage(p)=color 3 22
31 4.2 LIC Silhouette This approach can be thought as a quantification of the image guided by the values of the line integral convolution. We subdivide the interval [0, 1] in three parts, and we choose an arbitrary color to each part to achieve different effects including the silhouette. We obtained good results setting color i as the color of the first pixel p in the original image that belongs to the i part of the subdivision.the thresholds val1 and val2 can be set arbitrarily. However we found interesting results computing the mean intensity value M of the LIC blurred image and then set val1 = M M/3, val2 = M + M/3. Sometimes when the image is too dark we invert colors as a preprocessing step to ensure a good silhouette visualization. Figure 4.4 show some results with this settings. Figure 4.4: LIC Silhouette - Setting color i as the color of the first pixel in the original image belonging to the i part of the [0, 1] subdivision. It is important to note also the role of the vector field in this approach. Observe that high (low) values of I correspond to convolutions over integral curves on regions with high (low) intensities. Thus for vector fields with integral curves passing from high intensity to low intensity regions we will have an I close to the mean value. That is the reason for edges to appear in the final result for vector fields in directions of discontinuities in the original image. 23
32 4. EFFECTS USING LIC IDEAS 4.3 Pencil Rendering We adapted the algorithm described on (8; 9) to create a pencil effect. Below are some results. Figure 4.5: LIC Pencil Effect Examples - Some results of the interactive pencil rendering with LIC Our procedure is set to interactively paint pencil strokes in the direction of an input vector field. Strokes are then integral curves with a fixed length L predefined. As a preprocessing step we compute the gradient image of a grayscale version of the original I(x,y) image as E(x, y) = I(x,y) x + y to perform edge detection. The output energy image is used as the height image and paper is modeled in the same way described in (8). After this when the user clicks on the image, we process a predefined quantity of pixels in the perpendicular direction, rather than this pixel alone. This is done to 24
33 4.3 Pencil Rendering create strokes with width greater than one pixel, ideal for this kind of effect. Figure 4.7 shows the process step by step. The pseudocode follows: function Interactive_Pencil_rendering(image){ convert image to gray(image) compute the energy image E(gray image) create paper with E array C=compute_integral_curve(mouseX, mousey); array PP=compute_perpendicular_path(mouseX,mouseY); for each location p in C and PP { paper_draw(p, presure); As in (8), the parameter presure is a value in the interval [0, 1] to model the presure of the pencil in the paper. The paper draw function is guided by the height input image (in this case our energy image) and a sampling function that perturbs locally and uniformly the presure to imitate a hand-made effect. The method above can be trivially generalized for color images to create an spraylike effect. Here we can choose to process all the colors by pixel or process each RGB channel separately. The latter will create an image with aleatory colors uniformly distributed from the original image. See Figure 4.6. Figure 4.6: LIC Spray-Like Effect - Images from left to right: Processing all colors at once, and processing each RGB channel separately. 25
34 4. EFFECTS USING LIC IDEAS Figure 4.7: LIC Pencil Effect Process - Images: Original, LIC blur, grayscale, energy, interactive pencil rendering and final result. 26
35 4.4 Painterly Rendering 4.4 Painterly Rendering To create an image with a hand-painted appearance from an input photograph we used the algorithm described in (7). The method uses curved brush strokes of multiples sizes guided automatically by the contours of the gradient image. We adapted the mentioned algorithm to create strokes in the directions of an input vector field. These strokes are computed as integral curves like in LIC. The stroke length is controlled by the style stroke maximum length like in the original algorithm. A pseudocode the stroke computations procedure follow. Figure 4.8 shows an example. LIC Strokes Procedure: function makelicstroke(pixel p, R,reference_img){ array C=compute_integral_curve(p) with L=style max length strokecolor= reference_img.color(p) K= new stroke with radius R, with locations C, and color strokecolor Figure 4.8: Painterly Rendering - Left-Vector Field Image, Right- Painterly rendering. 4.5 Conclusions and Future Work As we can see from this whole monograph, the Line Integral Convolution algorithm ideas can be used not only to visualize high density planar vector fields, but also to 27
36 4. EFFECTS USING LIC IDEAS render non-realistic effects on arbitrary images by mixing already know NPR methods like painterly rendering and pencil drawing. The vector field design stage is fundamental in this approach, allowing the user to create a vector field to use as a guide for a determined effect. There are many ways to continue the work done here by either improving our results or by creating totally new algoritms and experiments. For instance, given that our interactive design is still slow, a GPU implementation for a real-time design will enhance the experimentation process when creating new effects. Given that our painterly rendering algorithm is not interactive, it could be a good experiment to create a system to interactively paint strokes similarly to the pencil and spray effects of section 4.3. Here some considerations with the layers of the original method need to be considered: When the user clicks, is that pixel going to be approximated by which level of detail?. Other future work could be a generalization to 3D spaces. For this, a tensor field design system will be more appropriate as suggested by the literature (3) increasing the flexibility of the whole system and extending the range of visual effects. An interesting next step of our system could be also the use of a Tangible User Interface for the design and visualization of the results. Out of the topic of this monograph, but still my main interest on flow and vector visualization could be considered as future work. Scientific visualization is a growing area that creates visual representations of complex scientific concepts to improve or discover new understandings from a set of data information. However at this time it is not clear a direct application into the field of computer music. The challenge is to create a new visualization of a piece of music that could gives us an alternative way to understand the basic sound components, or then an artistic visualization that could be used in computer music composition: Given our new visualization of a particular song, can we create another image that has the same characteristics in order to create music from it?. The suggestion is to make a connection between two art components: Graphics and music. Thus, can we use the LIC ideas to create this new visualization?, what information could we retrieve from a song which advects an 1D white noise? and can we visualize this advection?. These are examples of questions that could guide a future work on scientific visualization and computer music. 28
37 Appendix A Implementation in C++ This appendix is included to expose the main algorithms presented all along the chapters making use of the CImg Library, which is an open source C++ image processing toolkit created by David Tschumperlé at INRIA 1. For a better understanding, we will introduce briefly some of its characteristics before going into our procedures. A.1 Getting Started with CImg The CImg Library consist of a single header file CImg.h that contains all the C++ classes and methods. This implies among other things, that a simple line of code is needed to use it, namely... #include "lib_path/cimg.h"... using namespace cimg_library;... given that we had already downloaded the standard package from the website and had placed it into lib path. All the classes and functions are encapsulated in the cimg library namespace, so it is a good idea to use the second line of code too 2. The main classes of the CImg Library are: CImg<T> for images, CImgList<T> for a list of 1 2 This is different from the cimg namespace which implements functions with the same name as standard C/C++ functions! Never use by default the cimg namespace. 29
38 A. IMPLEMENTATION IN C++ images, and CImgDisplay which is like a canvas to display any image. The template parameter T specify the type of the pixels, for example a raster image with entries of type double is defined as CImg<double>. Possible values of T are float, double and unsigned char. As you may expect displaying an image with CImg is as simple as with MAT LAB. Here is the code to load and display an image called myimage.jpg which is in the same directory as our code: #include "lib_path/cimg.h" using namespace cimg_library; int main(){ CImg<unsigned char>("myimage.jpg").display(); return 0; // needed by the compiler To load an image and put it into our code as a variable I, we use the code: CImg<unsigned char> I("myimage.jpg"). To display an already loaded image I, we use its display method: I.display(). The code above is a compact version of these two steps: loading and displaying. We also could load an image and display it on a CImgDisplay. This is useful when doing applications with interactivity, given that the CImgDisplay class allows control to define the user callbacks like mouse clicks and keyboard inputs. The correspondent code using a CImgDisplay is next: #include "lib_path/cimg.h" using namespace cimg_library; CImgDisplay main_disp; int main(){ main_disp.assign( CImg<unsigned char>("myimage.jpg"),"my very first display!!"); while (!main_disp.is_closed){ main_disp.wait(); return 0; 30
39 A.1 Getting Started with CImg The assign method takes as first argument the image we want to display. We could re-assign any other loaded image at any moment. The second argument will be the title of the window. The while loop is necessary to tell the program to wait for user events. Here is where we should put the code to control user events. If this is ommited the program will run normally but will close after displaying the image which ocurs in a small fraction of time, so you will barely see the image!. Each CImgDisplay has its own parameters to control the user events which can be retrieved like any other field of the class with a point, some of them are:.mouse x or.mouse y to retrieve the integer coordinates (x, y) of a user click on the display,.key to retrieve keyboard inputs and.button which is of boolean type to indicate whether or not there was a click on the display. To control the different buttons of the mouse separately we use.button&1 for the left button and.button&2 for the right button. For more on this check the CImg documentation. Once we load an image on a variable, say I, we can retrieve the values of its pixel (x,y,z) like we were handling a matrix, that is: I(x,y,z,v). The parameter v refers to the type of image: v=1 for gray scale images, and v=3 for color images. CImg can handle 3D images, in our case for 2D images we will have always z=1 when declaring a 2D image and z=0 when retrieving pixel values. Remember that indices on C++ begins at 0, thus to retrieve the RGB components of a 2D image at pixel (10,10) we will have: I(10,10,0,0) for red, I(10,10,0,1) for green and I(10,10,0,2) for blue. Finally to retrieve any of the dimensions of I we can call.dimx() for the x dimension,.dimv() for the v dimension and so on. As an application the next function convert a color image to a grayscale image: CImg<unsigned char> to_gray(cimg<unsigned char> img){ if (img.dimv()==1) return img; //already gray CImg<unsigned char> gray(img.dimx(),img.dimy(),1,1); for (int x=1;x<img.dimx()-1;x++){ for (int y=1; y<img.dimy()-1;y++){ gray(x,y,0,0)=.2989*img(x,y,0,0)+.5870*img(x,y,0,1)+.1140*img(x,y,0,2); 31
40 A. IMPLEMENTATION IN C++ return(gray); Figure A.1: Color to gray conversion - Converting from color to grayscale using the CImg library. A.2 LIC in C++ using CImg Section 2.2 exposed a general pseudocode of LIC with a box kernel. Basically, the algorithm was composed of two functions: computing the integral curve, and computing the convolution. The next code is a mix of these two functions to perform LIC with a box kernel for an arbitrary input image using CImg. Our data type vector was defined to store the vector values (vx, vy) of the (x, y) position. The vector field function will be explained in the next section. LIC-Box kernel with CImg: CImg<double> LIC(CImg<double> img){ int n_chn=img.dimv(), n=img.dimx(), m=img.dimy(); CImg<double> OutputImg(n,m,1,n_chn); double u, v, Vi, Vj, x, y, sum, ds; int u1,v1,l; ds=1; L=10; for (int h=0;h<n_chn; h++){ for (int i=0;i<n;i++){ for (int j=0;j<m;j++){ vector V=vector_field(x,y); u=i; v=j; Vi=V.x; Vj=V.y; 32
41 A.3 A Basic Vector Field Design System using CImg sum=0; for (int s=0;s<=l;s++){ //positive); u=i; v=j; V.x=Vi; V.y=Vj; for (int s=0;s<=-l;s=s-1){ //negative); OutputImg(i,j,0,h)=sum/(2*L+1); return(outputimg); A.3 A Basic Vector Field Design System using CImg We can use CImg to create a system that can handle the basic vector field design ideas of section 3.1. For this we use the classes vector and singular point to store vector components and singular points with its respectives fields: parameters, type (Jacobian) and position. The code looks like this: typedef struct {double x, y; vector; class singular_point { public: vector pos; //position vector W1,W2; //rows of the jacobian matrix 33
42 A. IMPLEMENTATION IN C++ double d, k; //parameters public: singular_point(vector poss,vector W11, vector W22, double k1, double d1){ pos=poss; W1=W11; W2=W22;k=k1;d=d1; ; singular_point(){; // constructor by default ; // end of class singular_point We store all the singularities in an simple array LIST OF SING with a global variable length to control its length. The system begins loading an image stored globally as image and waiting for user events. A click on the display will add a singularity at this position. The type of the singularity to add is controled by the global variables V1, V2 which correspond to the rows of the jacobian of the actual singularity. This varibles are initialized for a type sink by default, and can be modified with the keyboard: S for a sink, O for a source, D for a saddle, C for a clockwise center and W for a couter-clockwise center. The main function is next: int main() { load_img(); while (!main_disp.is_closed) { main_disp.wait(); if(main_disp.button && main_disp.mouse_x>=0 && main_disp.mouse_y>=0){ int u0 = main_disp.mouse_x, v0 = main_disp.mouse_y; vector pos; pos.x=u0; pos.y=v0; singular_point s(pos,v1,v2,k,d); length++; LIST_OF_SING[length-1]=s; cout<<"calculating LIC...\n"; image=lic(image); cout<<"done.\n"; image.display(main_disp); if (main_disp.key){ switch (main_disp.key){ case cimg::keyq: exit(0); break; case cimg::keys: V1.x=-k; V1.y=0.0; V2.x=0.0; V2.y=-k; break; case cimg::keyo: V1.x=k; V1.y=0.0; V2.x=0.0; V2.y=k; break; 34
43 A.3 A Basic Vector Field Design System using CImg case cimg::keyd: V1.x=k; V1.y=0.0; V2.x=0.0; V2.y=-k; break; case cimg::keyc: V1.x=0.0; V1.y=-k; V2.x=k; V2.y=0.0; break; case cimg::keyw: V1.x=0.0; V1.y=k; V2.x=-k; V2.y=0.0; break; // end while return 0; The additional function load img used to load the image and perform the variables initialization: void load_img(void){ char name[50]; cout<<"please enter the image name (ex: dog.jpg):\n"; cin>>name; CImg<double> im(name); image=im; main_disp.assign(image,"basic Vector field Design"); d=0.0001; k=0.5; // by default V1.x=-k; V1.y=0.0; V2.x=0.0; V2.y=-k; // sink by default length=0; //no singular points so far Finally, the actual normalized vector field computation for a point (x, y) is done as sums of vector field influences of each singularity, see section 3.1. Here is the code: vector vector_field(double x, double y) { vector OUT; double d,k,x0,y0; vector U1,U2; OUT.x=OUT.y=0.0; for (int i=0;i<length;i++){ double t; d=list_of_sing[i].d; k=list_of_sing[i].k; U1=LIST_OF_SING[i].W1; U2=LIST_OF_SING[i].W2; x0=list_of_sing[i].pos.x; y0=list_of_sing[i].pos.y; t=exp(-d*((x-x0)*(x-x0)+(y-y0)*(y-y0))); OUT.x=OUT.x+t*(U1.x*k*(x-x0)+U1.y*k*(y-y0)); OUT.y=OUT.y+t*(U2.x*k*(x-x0)+U2.y*k*(y-y0)); 35
44 A. IMPLEMENTATION IN C++ double NV=sqrt(OUT.x*OUT.x+OUT.y*OUT.y); if (NV!=0){OUT.x=OUT.x/NV; OUT.y=OUT.y/NV; else{out.x=out.y=0; return OUT; The figure below shows an example of this system. Figure A.2: Basic Vector Field Design example using CImg - A simple combination of a sink a saddle and a center A.4 LIC effects in C++ This section concludes the implementation in C++ of the LIC effects presented in chapter 4. We already saw the blur-warp effect on section A.2, and the silhouette algorithm is straight forward from that code and the observations of section 4.2. We will proceed then with the pencil effect and painterly rendering. A.4.1 LIC Pencil Effect The main class involved in the pencil effect is of course the paper class which stores the height image (in our case the energy image) and the initial white canvas. The drawing 36
45 A.4 LIC effects in C++ function is called interactively with a certain presure perturbed by a sampling function. The final value for a pixel p on the canvas depends linearly on this perturbed presure and the intensity of the pixel p in the height image. For all our results prs=0.005: class Paper{ public: CImg<double> height_img; CImg<double> canvas; public: Paper(int resx, int resy, CImg<double> H); //constructor void draw(int coordx, int coordy, double prs); double sampling(double pres, int res =10); ; Paper::Paper(int resx, int resy, CImg<double> H){ this -> height_img =H; CImg<unsigned char> grain(resx,resy,1,1,1); this -> canvas=grain; void Paper::draw( int coordx, int coordy, double prs ){ coordx=(coordx>0)?coordx:0; coordy=(coordy>0)?coordy:0; double d, h, g; h=this->height_img(x,y,0); h*=0.65; g = this->sampling(prs); d = h+g; canvas(coordx,coordy,0)-=d; canvas(coordx,coordy,0)=(canvas(coordx,coordy,0)<0)? 0.0:canvas(coordX,coordY,0); double Paper::sampling(double pres, int res){ int aux = 0 ; for (int i = 0 ; i < res ; ++i ){ double p = (double)std::rand()/(double)(rand_max); if ( p < pres ) ++aux; 37
46 A. IMPLEMENTATION IN C++ return (double)aux/(double)res ; Next is the pencil effect main procedure using the above class of paper and the CImg library. For this effect we set the length of the integral curves to L = 100 and process lgd = 10 pixels in the perpendicular direction (see section 4.3). void pencil_effect(cimg<double> original){ CImg<double> Height=to_gray(original); Height=invert_colors(Height); Height=energy(Height); Height=normalize_0_1(Height); int n=original.dimx(), m=original.dimy(); Paper paper( n, m, Height,1); CImgDisplay main_disp(height,"pencil Effect"); int const lgd=10; while (!main_disp.is_closed){ main_disp.wait(); if (main_disp.mouse_x>=0 && main_disp.mouse_y>=0){ int startx = main_disp.mouse_x, starty = main_disp.mouse_y; vector V=vector_field(startx,starty,LIST_OF_SING); vector Vppd; Vppd.x=-V.y; Vppd.y=V.x; for (int i=0;i<lgd;i++){ double u=startx+i*vppd.x, v=starty+i*vppd.y; double u0=u,v0=v; vector Vstart=V=vector_field(u,v,LIST_OF_SING); for (int s=0;s<100;s++){ // positive); u= u0, v=v0; V=Vstart; 38
47 A.4 LIC effects in C++ for (int s=0;s<100;s++){ // negative); paper.height.display(main_disp); // end while A.4.2 Painterly Rendering We implemented the algorithm of section 2.1 in (7) replacing the makestroke procedure with our new make LIC Stroke to paint strokes in the direction of the input vector field, see section 4.4. Next is the code: stroke make_lic_stroke(int x0,int y0,double R){ int n=image.dimx(), m=image.dimy(); int r=floor(ref_img(x0,y0,0,0)); int g=floor(ref_img(x0,y0,0,1)); int b=floor(ref_img(x0,y0,0,2)); int* strokecolor= new int[3]; strokecolor[0]=r; strokecolor[1]=g; strokecolor[2]=b; stroke K= stroke(r,strokecolor); point p,q; vector V; double ds=1.0; p.x=q.x=x0; p.y=q.y=y0; K.pts[K.lgth]=p; K.lgth++; vector float_pt, float_qt; float_pt.x=p.x; float_pt.y=p.y; float_qt.x=p.x; float_qt.y=p.y; V=vector_field(x0,y0); for (int so=0; so<r+sty.maxlgth*0.3;so++){ float_pt.x+=ds*v.x; float_pt.y+=ds*v.y; p.x=(int)float_pt.x; p.y=(int)float_pt.y; 39
48 A. IMPLEMENTATION IN C++ float_qt.x-=ds*v.x; float_qt.y-=ds*v.y; q.x=(int)float_qt.x; q.y=(int)float_qt.y; if (!(p.x<0 p.x>n p.y<0 p.y>m)){ K.pts[K.lgth]=p; K.lgth++; V=vector_field(float_pt.x,float_pt.y); if (!(q.x<0 q.x>n q.y<0 q.y>m)){ K.pts[K.lgth]=q; K.lgth++; V=vector_field(float_qt.x,float_qt.y); //end for return K; 40
49 Appendix B Gallery Here are some of our results. All the images in full color and the source code can be found in the website rdcastan/visualization. Figure B.1: Pigeon Point Lighthouse, California - Images from top to bottom and left to right: Original, warp, LIC on a spray image with each RGB processed separately and painterly 41
50 B. GALLERY Figure B.2: Plymouth Hoe, England - From top and left to right: Original, vector field visualization, spray and LIC of the spray image. 42
51 Figure B.3: Landscape - Painterly Rendering. 43
52 B. GALLERY Figure B.4: Girl Playing Guitar - LIC Silhouette effect. 44
53 Figure B.5: Shoes in the Grass - LIC pencil effect. 45
54 B. GALLERY Figure B.6: Cows - LIC after spray effect. 46
55 Figure B.7: Garden IMS, Rio de Janeiro - Painterly Rendering. Garden of the Instituto Moreira Salles 47
56 B. GALLERY Figure B.8: Live Performance - Top to Bottom-Original (Anita Robinson from Viva Voce), painterly and LIC pencil. 48
57 Figure B.9: Live Performance Continued... - Top to Bottom-LIC silhouette, spray on each RGB and simple spray. 49
58 B. GALLERY Figure B.10: Live Performance Continued... - Top to Bottom-Dithered and LIC on dithered 50
Texture Screening Method for Fast Pencil Rendering
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Virtual Mouse Using a Webcam
1. INTRODUCTION Virtual Mouse Using a Webcam Since the computer technology continues to grow up, the importance of human computer interaction is enormously increasing. Nowadays most of the mobile devices | http://docplayer.net/884280-Using-line-integral-convolution-to-render-effects-on-images.html | CC-MAIN-2017-22 | refinedweb | 11,155 | 53.31 |
April 15, 2016David Isbitski
By Josh Skeen, software developer at Big Nerd Ranch
This is part four of the Big Nerd Ranch series. Click here for part three..
We'll go over how to write Alexa skill data to storage, which is useful in cases where the skill would time out or when the interaction cycle is complete. You can see this at work in skills like the 7-Minute Workout skill, which allows users to keep track of and resume existing workouts, or when users want to resume a previous game in The Wayne Investigation.
For this experiment, we'll build upon an existing codebase and improve it. The skill, a cooking assistant called CakeBaker, guides users in cooking a cake, step by step. A user interacts with CakeBaker by asking Alexa to start a cake, then advances through the steps of the recipe by saying "next" after each response, like so:
.
This continues until the user reaches the last step. But what if the skill closes before the user is able to finish a step? By default, Alexa skills close if a user doesn’t respond within 16 seconds. Right now, that means that a user would be forced to start over at the first step, losing the progress made.
Let’s fix that by implementing two new methods in our skill, called saveCakeIntent and loadCakeIntent, which will allow users to save and load their current progress to and from a database. We'll also test the database functionality in our local environment using the alexa-app-server and alexa-app libraries we discussed in our post on implementing an intent in an Alexa Skill.
This experiment will use Node.js and alexa-app-server to develop and test the skill locally, so we will need to set up those dependencies first. If you haven't yet done so, read our posts on setting up a local environment and implementing an intent—they will guide you in setting up a local development environment for this skill, which will involve more advanced requirements.
Let’s get started by downloading the source code for CakeBaker. We’ll be improving this source code so that it supports saving and loading cakes to the database.
To complete the experiment, we’ll need a working installation of alexa-app-server and Node.js. If you haven’t done so, install Node.js and then install alexa-app-server, using the instructions outlined in the linked posts.
Clone CakeBaker into the alexa-app-server/examples/apps directory by opening a new terminal window and entering the following within the alexa-app-server/examples/apps directory:
git clone
Change directories into alexa-app-server/examples/apps/alexa-cakebaker and run the following command:
npm install
This will fetch the dependencies the project requires in order to work correctly.
The database we will use to store the state of the cake is Amazon's DynamoDB, a NoSQL-style database that will ultimately live in the cloud on Amazon's servers. To facilitate testing, we'll install a local instance of DynamoDB. We will use the brew package manager to add DynamoDB to our local development environment.
Install Homebrew if you haven’t already done so:
/usr/bin/ruby -e "$(curl -fsSL)"
Once this command completes, install a local version of DynamoDB via Homebrew:
brew install dynamodb-local
On Windows? Follow these steps.
When the brew command completes, open a new tab in your terminal and run the following command:
dynamodb-local -sharedDb -port 4000
You should see something similar to the following:
Initializing DynamoDB Local with the following configuration: Port: 4000 InMemory: false DbPath: null SharedDb: true shouldDelayTransientStatuses: false CorsParams: *
Now we can begin developing our database functionality and test db behaviour in our local environment. Leave the tab open while you work.
At this point, the CakeBaker skill is cloned locally and our test database instance is set up, so we're ready to begin adding the save and load features. In order to implement them, we need two new intents for these actions: saveCakeIntent and loadCakeIntent. Let's begin by adding the intent definitions to the bottom of the index.js file.
One for saving the cake:
skillService.intent('saveCakeIntent', { 'utterances': ['{save} {|a|the|my} cake'] }, function(request, response) { //code goes here! } );
And one for loading the cake:
skillService.intent('loadCakeIntent', { 'utterances': ['{load|resume} {|a|the} {|last} cake'] }, function(request, response) { //code goes here! } );
Here's a diagram of how the save command will work:
In the diagram, the user's utterance is resolved to the saveCakeIntent and then processed by the skill service. The skill service saves the cake data to the database, and once this operation completes the service, it responds to the skill interface, indicating that the write to the database succeeded.
The CakeBaker source code we checked out contains a helper called database_helper.js. Open this file, and you should see the following:
'use strict'; module.change_code = 1; var _ = require('lodash'); var CAKEBAKER_DATA_TABLE_NAME = 'cakeBakerData'; var dynasty = require('dynasty')({}); function CakeBakerHelper() {} var cakeBakerTable = function() { return dynasty.table(CAKEBAKER_DATA_TABLE_NAME); }; CakeBakerHelper.prototype.createCakeBakerTable = function() { return dynasty.describe(CAKEBAKER_DATA_TABLE_NAME) .catch(function(error) { return dynasty.create(CAKEBAKER_DATA_TABLE_NAME, { key_schema: { hash: ['userId', 'string' ] } }); }); }; CakeBakerHelper.prototype.storeCakeBakerData = function(userId, cakeBakerData) { return cakeBakerTable().insert({ userId: userId, data: cakeBakerData }).catch(function(error) { console.log(error); }); }; CakeBakerHelper.prototype.readCakeBakerData = function(userId) { return cakeBakerTable().find(userId) .then(function(result) { return result; }) .catch(function(error) { console.log(error); }); }; module.exports = CakeBakerHelper;
This file contains the basic logic for creating a new table in DynamoDB we will name cakeBakerData to write cake data to. It also contains methods for reading and writing the cake data to the DynamoDB instance.
Our first task, saving a cake, will be aided by the storeCakeBakerData method the helper contains. Notice storeCakeBaker's signature: it expects a userId and cakeBakerData. The userId is a unique identifier provided by the Alexa service upon a user enabling a skill. We will pull the userId from the request received by our service from the skill interface, and it will uniquely identify the Alexa account that the Skill is attached to so that the skill can keep track of data for different users. It is also the key we will use to look up a user’s cakeBakerData on the database.
The helper also makes use of Dynasty, an open-source library for interacting with the DynamoDB instance. Because we are developing locally, the first code change we will make is to the connection settings for the Dynasty object.
For testing locally, we will use our local machine's DynamoDB instance. In order to do that we will need to edit the database_helper.js file and comment the line:
//var dynasty = require('dynasty')({}); and add: //var dynasty = require('dynasty')({}); var localUrl = ''; var localCredentials = { region: 'us-east-1', accessKeyId: 'fake', secretAccessKey: 'fake' }; var localDynasty = require('dynasty')(localCredentials, localUrl); var dynasty = localDynasty;
This will enable us to test against the local DynamoDB instance we started in the terminal using port 4000.
Before we can save or read cake data from DynamoDB, we'll first need to ask DynamoDB to create a table to store it in. We can use a helpful feature of alexa-app called a "pre" hook, which will execute before the intent handlers in the skill are executed.
Open the index.js file in the alexa-cakebaker folder and add the following at line 9, right below var databaseHelper = new DatabaseHelper();:
skillService.pre = function(request, response, type) { databaseHelper.createCakeBakerTable(); };
This will execute before any intent is handled. If the table doesn't exist, and if it's already created, Dynasty will simply return an error, which we handle in the DatabaseHelper class.
Let's implement a saveCake function, at the bottom of the index.js file before the module.exports = CakeBakerHelper; :
var saveCake = function(cakeBakerHelper, request) { var userId = request.userId; databaseHelper.storeCakeBakerData(userId, JSON.stringify(cakeBakerHelper)) .then(function(result) { return result; }).catch(function(error) { console.log(error); }); };
The method pulls the userId from the request, passing it and a stringified version of the cake data to be written to the database.
Now we’ll put the saveCake method to use. Update the saveCakeIntent intent handler we defined earlier in the index.js file:
skillService.intent('saveCakeIntent', { 'utterances': ['{save} {|a|the|my} cake'] }, function(request, response) { var cakeBakerHelper = getCakeBakerHelperFromRequest(request); saveCake(cakeBakerHelper, request); response.say('Your cake progress has been saved!'); response.shouldEndSession(true).send(); return false; } );
Perfect! This should write the cake’s progress to the database when a user explicitly requests it from the skill.
We will also need to update the advanceStepIntent to make use of the saveCake method as well. When a user requests “next,” the cake should be saved implicitly to avoid any lost progress due to a timeout or the skill’s request cycle ending.
Update the advanceStepIntent to call saveCake, just after the cakeBakerHelper is incremented:
skillService.intent('advanceStepIntent', { 'utterances': ['{next|advance|continue}'] }, function(request, response) { var cakeBakerHelper = getCakeBakerHelperFromRequest(request); cakeBakerHelper.currentStep++; saveCake(cakeBakerHelper, request); cakeBakerIntentFunction(cakeBakerHelper, request, response); } );
A user should be able to load the cake after the skill has exited. Once the cake is loaded, the skill should pick back up at the step that the user left from, eliminating the pain of starting over from the beginning.
In order to enable this, we will have the skill read the cake from the database after looking it up with our userId and set up the CakeBakerHelper object from the persisted state. Then we'll call cakeBakerIntentFunction to generate the response that should be sent to Alexa. Edit the index.js file and replace the loadCakeIntent Intent with the following:
skillService.intent('loadCakeIntent', { 'utterances': ['{load|resume} {|a|the} {|last} cake'] }, function(request, response) { var userId = request.userId; databaseHelper.readCakeBakerData(userId).then(function(result) { return (result === undefined ? {} : JSON.parse(result['data'])); }).then(function(loadedCakeBakerData) { var cakeBakerHelper = new CakeBakerHelper(loadedCakeBakerData); return cakeBakerIntentFunction(cakeBakerHelper, request, response); }); return false; } );
Now we can test that the new functionality works against the local database. First, let’s start the alexa-app-server. Change to the alexa-app-server/examples directory and run the local development server:
node server
Now, visit the test page at. We want to mimic a cake that has advanced several steps, so we’ll send several requests on the server. Configure the type to IntentRequest, and the Intent to cakeBakeIntent and hit "Send Request". This should start a new cake.
Next, change the Intent to advanceStepIntent and hit "Send Request"—this mimics a user saying "next" in order to move the recipe along to the next step. Hit "Send Request" three more times. In the response area of the test page, you should see:
>" } } },
Great! Now we can test that saving to the database works. Switch the Intent to saveCakeIntent and click “Send Request”. You should see the following in the response area:
{ "version": "1.0", "sessionAttributes": { "cake_baker": { "started": false, "currentStep": 4, "steps": [ //removed for brevity ] } }, "response": { "shouldEndSession": true, "outputSpeech": { "type": "SSML", "ssml": "<speak>Your cake progress has been saved!</speak>" } }
Our cake has now been saved to the database! To verify whether the skill service is working, reload the test page, then set the Intent to loadCakeIntent. Click "Send Request". This mimics a user saying "Alexa, ask Cake Baker to load the cake."
The response should pick up where the user left off with the fourth step in the cake recipe.
{ "version": "1.0", "sessionAttributes": { "cake_baker": { "started": false, "currentStep": 4, "steps": [ //removed for brevity ] } }, >" } } }, "dummy": "text" }
Now that we've tested the skill locally, let's deploy it live! Fortunately, because DynamoDB is already wired to work easily with an AWS Lambda skill, we will have to do very little to deploy.
First, let's change database_helper.js to production mode. Open database_helper.js. Uncomment:
var dynasty = require('dynasty')({});
Then comment the local development configuration we added. The top of our database_helper.js file should look like this:
'use strict'; module.change_code = 1; var _ = require('lodash'); var CAKEBAKER_DATA_TABLE_NAME = 'cakeBakerData'; var dynasty = require('dynasty')({}); // var localUrl = ''; // var localCredentials = { // region: 'us-east-1', // accessKeyId: 'fake', // secretAccessKey: 'fake' // }; ...
Now, we will follow the usual Alexa Skill deployment process—but with two big differences. First, we will run through setting up the skill service on AWS Lambda. Visit the Lambda dashboard and click "Create Lambda Function". Click "skip" on the resulting page.
Zip the files within the cakebaker directory and click the "Upload a ZIP file" option in the Lambda configuration, keeping in mind that your index.js file should be at the parent level of your archive. Click "Upload" and select the archive you created.
It’s important to note that the Lambda function handler and role selection are different here than they are in an AWS Lambda skill without a database. Rather than "Basic Execution Role", select "Basic with DynamoDB". This will redirect to a new screen, where you should click "Allow". This step allows our AWS Lambda-backed skill service to use a DynamoDB datastore on our AWS Account.
Here is what your configuration should now look like:
Click "Next" and then "Create Function".
Note the long “ARN” at the top right of the page. This is the Amazon Resource Name, and it will look something like arn:aws:lambda:us-east-1:333333289684:function:myFunction. You will need it when setting up the skill interface, so be sure to copy it from your AWS Lambda function.
Finally, click on the "Event sources" tab and click "Add event source". Select "Alexa Skills Kit" in the Event Source Type dropdown and hit "Submit".
Next, we'll set up the skill interface. Visit and click "Add a New Skill". In the Skill Information tab, enter “Cake Baker” for the “Name” and “Invocation Name” fields. Leave “Custom Interaction Model” selected for the Skill Type.
Click "Next".
Now we need to set up the interaction model. Copy the intent schema and utterances from the alexa-app-server test page into the respective fields.
For the “Intent Schema” field, use:
{ "intents": [ { "intent": "advanceStepIntent", "slots": [] }, { "intent": "repeatStepIntent", "slots": [] }, { "intent": "cakeBakeIntent", "slots": [] }, { "intent": "loadCakeIntent", "slots": [] }, { "intent": "saveCakeIntent", "slots": [] } ] }
and for the “Sample Utterances” field, use:
advanceStepIntent next advanceStepIntent advance advanceStepIntent continue cakeBakeIntent new cake cakeBakeIntent start cake cakeBakeIntent create cake cakeBakeIntent begin cake cakeBakeIntent build cake cakeBakeIntent new a cake cakeBakeIntent start a cake cakeBakeIntent create a cake cakeBakeIntent begin a cake cakeBakeIntent build a cake cakeBakeIntent new the cake cakeBakeIntent start the cake cakeBakeIntent create the cake cakeBakeIntent begin the cake cakeBakeIntent build the cake loadCakeIntent load cake loadCakeIntent resume cake loadCakeIntent load a cake loadCakeIntent resume a cake loadCakeIntent load the cake loadCakeIntent resume the cake loadCakeIntent load last cake loadCakeIntent resume last cake loadCakeIntent load a last cake loadCakeIntent resume a last cake loadCakeIntent load the last cake loadCakeIntent resume the last cake saveCakeIntent save cake saveCakeIntent save a cake saveCakeIntent save the cake saveCakeIntent save my cake
Click “Next”.
On the Configuration page, select "Lambda ARN (Amazon Resource Name)" and enter the ARN you copied when you set up the Lambda endpoint. Click “Next”. You can now test that the skill behaves as it did in local development. If you have an Alexa-enabled device registered to your developer account, you can now test the save and load functionality with the device. Amazon has more information on registering an Alexa-enabled device for testing, if you’re not familiar with the process.
Try the following commands, either in the test page or against a real device: "Alexa, ask Cake Baker to bake a cake", "next", "next", and "Save Cake".
Wait for a moment while the skill times out, and then say, "Alexa, ask Cake Baker to load the cake". The skill should pick up where we left off, on the third step of Cake Baker.
Congratulations; you've implemented basic persistence in an Alexa Skill! In the next post, we'll cover submitting your custom skills for certification so that they can be used by anybody with an Alexa-enabled device. | https://developer.amazon.com/fr/blogs/alexa/post/Tx1T3KH2O7K8AOP/big-nerd-ranch-series-developing-alexa-skills-locally-with-node-js-implementing-persistence-in-an-alexa-skill-part-4-of-6 | CC-MAIN-2020-10 | refinedweb | 2,664 | 54.93 |
First week at the new job, so I get do delve into currently-unkown code. And I get to reload my Django knowledge back into my head: it has been a year since I “did” my till-now-only-one django project.
And I got the job of introducing proper python packaging.
“Proper python packaging” for me means two things:
setup.pythat you can easy_install.
In the Django context I’d add one more aspect to proper packaging:
Without packaging, you basically end up with one directory structure for your project. One main directory and the libraries (Django: applications) inside it. When you take those libraries and package them independently, you get several advantages:
setup.pycontains the name of the package, the version number, a short explanation.
long_description. It is customary to take the readme, changelog and possible other files and use those as long description. Basically what you see on the pypi page of a project (but usable outside pypi of course). For me, the “it is customary” is what helps.
Coming from a Zope and Plone background, I’m used to packages like zest.releaser, plone.app.something, z3c.anotherthing. Namespaces. Handy to keep zest.releaser out of collective.releaser’s hair. And to keep the generic openid package, plone’s openid package and your company’s openid package out of each others hair: you cannot call all of them “openid”.
We’ve got two main product lines at our company. And the first subdirectory
that I tackled was called “base”. So
firstproductline.base was born.
Raargh, Django doesn’t like namespaces. You get errors like “application firstproductline not found” when you expect it to load “firstproductline.base”. And from what I read, namespaces are actively discouraged in Django.
So what I settled with, after some googling for examples, was to name the
package
firstproductline-base (with a dash). The svn url is something
like. And inside that, the actual
code is in a
firstproductline_base directory (with an underscore).
firstproductline_base is thus the module name that you import.
Well, I’ll have to see how well such a scheme holds up. Feedback): | https://reinout.vanrees.org/weblog/2010/01/08/proper-django-packaging.html | CC-MAIN-2019-04 | refinedweb | 354 | 67.45 |
If there are any problems, let me know. If you want to develop, I'll get you set up.
CODE:
- Code: Select all
"""This is a simple Markov chain text algorithm
that uses a user-defined corpus. This project is based on,
but is not a fork of, tedlee/markov on GitHub."""
import random
class Markov:
def __init__(self, corpus):
"""Initializer function
"""
self.corpus = corpus
self.cache = {}
self.word_list = self.corpus.split(" ")
self.list_size = len(self.word_list)
def words_iter(self):
if len(self.word_list) < 3:
print("I'm sorry, the corpus is too short.")
return # end function
tuple_list = zip(self.word_list, self.word_list[1:], self.word_list[2:])
for tupl in tuple_list:
yield tupl
def setup_cache(self):
for word1, word2, word3 in self.words_iter():
key = word1, word2
# if key already exists, append word to key
if key in self.cache:
self.cache[key].append(word3)
# if key doesn't exist, make a new one
else:
self.cache[key] = [word3]
def generate(self, size=50):
self.setup_cache()
# first word picker
seed = random.randrange(0, self.list_size - 2)
word1, word2 = self.word_list[seed] + self.word_list[seed+1]
# corpus generator
new_corpus = []
# maker function
for i in range(size):
# append word to the corpus and pick the next one
new_corpus.append(word1)
word1, word2 = word2, random.choice(self.cache[(word1, word2)])
# add last word
new_corpus.append(word2)
# put all the words together and print them
print(" ".join(new_corpus))
# test code
corpus = """.
"""
markov_corpus = Markov(corpus)
size = 80
markov_corpus.generate(size) | http://www.python-forum.org/viewtopic.php?f=11&t=11136 | CC-MAIN-2016-30 | refinedweb | 244 | 62.44 |
We are about to switch to a new forum software. Until then we have removed the registration on this forum.
I've used this code for multiple projects at this point without many issues but am now running into an unexpected problem which I am unsure how to solve. I have little to no experience with Processing but was getting some help from people a few months back ago when I started to use this code.
The project is a large LED panel installation on 40 panels, the code will run through processing on a raspberry pi so I am using this pi compatible version someone helped me find. I have one video which almost successfully runs on these 40 panels with a bit of lag (which isn't the worst for the project) but it is not the video I intend to use! In comparing it to the video which I do want to use I am not sure what the difference is. I made the first video which works a few months ago so I can't remember if I did anything different but both videos are made in final cut (mov) and then converted to mp4 online. In final cut I made the dimensions of both videos 640 x 360 and both were H264. The first video moves a bit slower and looks more lo-res but I believe those to be qualities from the original source before I imported and edited in FinalCut.
I believe the problem to be related to the amount/size of data being processed. I should mention that both videos will work according to processing and be recognized by the panels but the issue is that the video I want to use does not play consistently. One teensy may send part of the video to the LEDs mostly correct while another teensy's LEDs start to pick up after 10 seconds and then flickers a spectrum of random colors. None of the teensys seem to be synced up with this second video (though all teensys are mounted on the OctoBoards and connected to each other to sync.)
I'm wondering if anyone has any advice for what to do to the video to make it play correctly.
I have tried using HandBrake to also change some qualities of the video but have no clue what I'm doing really and all of my test have yielded no results.
I also noticed that the flickering happens more when theres a bigger change in color supposed to be happening
I suppose the problem could relate to how many rows I have, not sure, but the other video does seem to be working mostly properly. I am inserting some photos that show the project, some of the panels still need some work so thats why one is pink (wrong RGB ordered lights) and the all white ones just have no data input yet.
Anyone have any ideas?
I hope I entered this code correctly...
`/* OctoWS2811 movie2serial.pde - Transmit video data to 1 or more Teensy 3.0 boards running OctoWS2811 VideoDisplay.ino Copyright (c) 2013 Paul Stoffregen, PJRC.COM,. */ // To configure this program, edit the following sections: // // 1: change myMovie to open a video file of your choice ;-) // // 2: edit the serialConfigure() lines in setup() for your // serial device names (Mac, Linux) or COM ports (Windows) // // 3: if your LED strips have unusual color configuration, // edit colorWiring(). Nearly all strips have GRB wiring, // so normally you can leave this as-is. // // 4: if playing 50 or 60 Hz progressive video (or faster), // edit framerate in movieEvent(). //import processing.video.*; import gohai.glvideo.*; import processing.serial.*; import java.awt.Rectangle; GLMovie myMovie;; float framerate=0; void setup() { String[] list = Serial.list(); delay(20); println("Serial Ports List:"); println(list); //serialConfigure("/dev/ttyACM1"); // change these to your port names //serialConfigure("/dev/cu.usbmodem3550481"); serialConfigure("/dev/tty.usbmodem3999691"); //serialConfigure("/dev/cu.usbmodem3550481"); //serialConfigure("/dev/ttyACM0"); serialConfigure("/dev/tty.usbmodem3645941"); serialConfigure("/dev/tty.usbmodem3694501"); serialConfigure("/dev/tty.usbmodem3766451"); if (errorCount > 0) exit(); for (int i=0; i < 256; i++) { gammatable[i] = (int)(pow((float)i / 255.0, gamma) * 255.0 + 0.5); } size(480, 400, P2D); // create the window String mpath = sketchPath() + "/../../../media/x.mp4"; println(mpath); myMovie = new GLMovie(this, mpath); myMovie.loop(); // start the movie :-) } // movieEvent runs for each new frame of movie data void movieEvent(GLMovie m) { // read the movie's next frame m.read(); //if (framerate == 0) framerate = m.getSourceFrameRate(); framerate = 30; // TODO, how to read the frame rate??? for (int i=0; i < numPorts; i++) { // copy a portion of the movie's image to the LED image int xoffset = percentage(m.width, ledArea[i].x); int yoffset = percentage(m.height, ledArea[i].y); int xwidth = percentage(m.width, ledArea[i].width); int yheight = percentage(m.height, ledArea[i].height); ledImage[i].copy(m, xoffset, yoffset, xwidth, yheight, 0, 0, ledImage[i].width, ledImage[i].height); // convert the LED image to raw data byte[] ledData = new byte[(ledImage[i].width * ledImage[i].height * 3) + 3]; image2data(ledImage[i], ledData, ledLayout[i]); if (i == 0) { ledData[0] = '*'; // first Teensy is the frame sync master int usec = (int)((1000000.0 / framerate) * 0.75); ledData[1] = (byte)(usec); // request the frame sync pulse ledData[2] = (byte)(usec >> 8); // at 75% of the frame time } else { ledData[0] = '%'; // others sync to the master board ledData[1] = 0; ledData[2] = 0; } // send the raw data to the LEDs :-) ledSerial[i].write(led, boolean layout) { int offset = 3; int x, y, xbegin, xend, xinc, mask; int linesPerPin = image.height / 8; int pixel[] = new int[8]; for (y = 0; y < linesPerPin; y++) { if ((y & 1) == (layout ? 0 : 1)) { // even numbered rows are left to right xbegin = 0; xend = image.width; xinc = 1; } else { // odd numbered rows are right to left xbegin = image.width - 1; xend = -1; xinc = -1; } for (x = xbegin; x != xend; x += xinc) { for (int i=0; i < 8; i++) { // fetch 8 pixels from the image, 1 for each pin pixel[i] = image.pixels[x + (y + linesPerPin * i) * image.width]; pixel[i] = colorWiring(pixel[i]); } // convert 8 pixels to 24 bytes for (mask = 0x800000; mask != 0; mask >>= 1) { byte b = 0; for (int i=0; i < 8; i++) { if ((pixel[i] & mask) != 0) b |= (1 << i); } data[offset++] = b; } } } } // translate the 24 bit color from RGB to the actual // order used by the LED wiring. GRB is the most common. int colorWiring(int c) { int red = (c & 0xFF0000) >> 16; int green = (c & 0x00FF00) >> 8; int blue = (c & 0x0000FF); red = gammatable[red]; green = gammatable[green]; blue = gammatable[blue]; return (green << 16) | (red << 8) | (blue); // GRB - most common wiring } // ask a Teensy board for its LED configuration, and set up the info for it. void serialConfigure(String portName) { if (numPorts >= maxPorts) { println("too many serial ports, please increase maxPorts"); errorCount++; return; } try { ledSerial[numPorts] = new Serial(this, portName); if (ledSerial[numPorts] == null) throw new NullPointerException(); ledSerial[numPorts].write('?'); } catch (Throwable e) { println("Serial port " + portName + " does not exist or is non-functional"); errorCount++; return; } delay(250); String line = ledSerial[numPorts].readStringUntil(10); if (line == null) { println("Serial port " + portName + " is not responding."); println("Is it really a Teensy 3.0 running VideoDisplay?"); errorCount++; return; } String param[] = line.split(","); if (param.length != 12) { println("Error: port " + portName + " did not respond to LED config query"); errorCount++; return; } // only store the info and increase numPorts if Teensy responds properly ledImage[numPorts] = new PImage(Integer.parseInt(param[0]), Integer.parseInt(param[1]), RGB); ledArea[numPorts] = new Rectangle(Integer.parseInt(param[5]), Integer.parseInt(param[6]), Integer.parseInt(param[7]), Integer.parseInt(param[8])); ledLayout[numPorts] = (Integer.parseInt(param[5]) == 0); numPorts++; } // draw runs every time the screen is redrawn - show the movie... void draw() { if (myMovie.available()) { movieEvent(myMovie); } // show the original video image(myMovie, 0, 80); // then try to show what was most recently sent to the LEDs // by displaying all the images for each port. for (int i=0; i < numPorts; i++) { // compute the intended size of the entire LED array int xsize = percentageInverse(ledImage[i].width, ledArea[i].width); int ysize = percentageInverse(ledImage[i].height, ledArea[i].height); // computer this image's position within it int xloc = percentage(xsize, ledArea[i].x); int yloc = percentage(ysize, ledArea[i].y); // show what should appear on the LEDs image(ledImage[i], 240 - xsize / 2 + xloc, 10 + yloc); } } // respond to mouse clicks as pause/play boolean isPlaying = true; void mousePressed() { if (isPlaying) { myMovie.pause(); isPlaying = false; } else { myMovie.play(); isPlaying = true; } } // scale a number by a percentage, from 0 to 100 int percentage(int num, int percent) { double mult = percentageFloat(percent); double output = num * mult; return (int)output; } // scale a number by the inverse of a percentage, from 0 to 100 int percentageInverse(int num, int percent) { double div = percentageFloat(percent); double output = num / div; return (int)output; } // convert an integer from 0 to 100 to a float percentage // from 0.0 to 1.0. Special cases for 1/3, 1/6, 1/7, etc // are handled automatically to fix integer rounding. double percentageFloat(int percent) { if (percent == 33) return 1.0 / 3.0; if (percent == 17) return 1.0 / 6.0; if (percent == 14) return 1.0 / 7.0; if (percent == 13) return 1.0 / 8.0; if (percent == 11) return 1.0 / 9.0; if (percent == 9) return 1.0 / 11.0; if (percent == 8) return 1.0 / 12.0; return (double)percent / 100.0; }`
Answers
so like I said, a few of these panels (marked with Xs--ignore them) just aren't wired right yet... and the rest of the panels are somewhat out of order right now. The problem is the video is not being displayed consistently in the panels which are being fed data. The first photo is the problem video version. The second image shows the video x.mp4 playing correctly.
:(
I have one obvious idea
Other than that, the less compressed a video is the faster, generally, it decompresses (and the larger the file, obviously). So try older formats like mpg4 or mpg2. mjpeg, even.
Doesn't the pi have hardware video decoding for certain formats? Try those. You might need a license.
You might even try replacing the percentage and inverse percentage methods with a lookup table the way you do for the gamma.
And that problem video looks like an incomplete file, like when I try and watch something before handbrake has finished.
Thanks koogs! I tried your recommendations with the mjpeg/ mpg4 /mpg2 and its still about the same... all seem to still have a data date over 100 Mbit/s. I'll try some more throughout the day with handbrake trying to reduce the bitrate/ quality... doesn't seem to change that much so far though.
I don't think they're incomplete files and they are showing clearly in the processing window but maybe there is something else wrong with them? I really wish I knew more about this stuff.
Not sure what the percentage/ inverse methods refer to but ill try to look that up as well.
Anyone else have any other ideas on how to reduce the amount of data / data speed?
I could also run this from a Mac mini instead of a pi... I just don't want to haha. I've tried it running from both the pi and my laptop at this point and its practically the same problems. maybe the pi even works better, but maybe theres a solution that would work on a Mac that wouldn't work on a pi?
Really great advice though! Wish it fixed my weird problem.
Lines 244, 251, 260
actually perhaps part of my problem is the Arduino part?
I've changed the way the teensys feed to panels from the default format... im breaking up the video vertically into 5 strips, placing my x offset 20 percent over each time (I think) ... I assumed this was a percentage, maybe its not?
I've used this on the teensys:
this being the edited part that I am using, editing only the offset by 20 for each board | https://forum.processing.org/two/discussion/comment/116895/ | CC-MAIN-2020-34 | refinedweb | 2,017 | 64.71 |
public class DigestInputStream extends Filter one of the
read methods
results in an update on the message digest. But when it is off,
the message digest is not updated. The default is for the stream
to be on.
Note that digest objects can compute only one digest (see
MessageDigest),
so that in order to compute intermediate digests, a caller should
retain a handle onto the digest object, and clone it for each
digest to be computed, leaving the orginal digest untouched.
MessageDigest,
DigestOutputStream
in
available, close, mark, markSupported, read, reset, skip
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
protected MessageDigest digest
public DigestInputStream(InputStream stream, MessageDigest digest)
stream- the input int read() throws IOException
on), this method will then call
updateon the message digest associated with this stream, passing it the byte read.
readin class
FilterInputStream
IOException- if an I/O error occurs.
MessageDigest.update(byte)
public int read(byte[] b, int off, int len) throws IOException
lenbytes from the input stream into the array
b, starting at offset
off. This method blocks until the data is actually read. If the digest function is on (see
on), this method will then call
updateon the message digest associated with this stream, passing it the data.
readin class
FilterInputStream
b- the array into which the data is read.
off- the starting offset into
bof where the data should be placed.
len- the maximum number of bytes to be read from the input stream into b, starting at offset
off.
lenif the end of the stream is reached prior to reading
lenbytes. -1 is returned if no bytes were read because the end of the stream had already been reached when the call was made.
IOException- if an I/O error occurs.
MessageDigest.update(byte[], int, int)
public void on(boolean on)
readmethods results in an update on the message digest. But when it is off, the message digest is not updated.
on- true to turn the digest function on, false to turn it. | http://docs.oracle.com/javase/7/docs/api/java/security/DigestInputStream.html | CC-MAIN-2017-13 | refinedweb | 334 | 61.56 |
TypeName
AvoidUninstantiatedInternalClasses
CheckId
CA1812
Category
Microsoft.Performance
Breaking Change
NonBreaking
An instance of an assembly-level type is not created by code within the assembly. The following types are not examined by this rule:
Value types.
Abstract types.
Enumerations.
Delegates.
Compiler-emitted array types.
Uninstantiable types that define static methods only.
This rule tries to locate a call to one of the type's constructors, and reports a violation if no call is found.).
It is safe to exclude a warning from this rule, but there are no known scenarios where this is required.
Avoid uncalled private code
Review unused parameters
Remove unused locals
Currently, if you have the InternalsVisibleToAttribute applied to the assembly being analyzed, this rule will not fire on any constructors marked as internal (Friend in Visual Basic, public private in C++) as it cannot be sure that a field is not being used by another friend assembly.
While it is not possible to work around this limitation in Visual Studio Code Analysis, the external standalone FxCop will fire on internal constructors if every friend assembly is present in the analysis.
Although this rule states that there are no known scenarios where it is required to exclude (or suppress) this warning, there a couple of instances where this rule will incorrectly fire a false positive:
[C#]
internal class Foo{ public Foo() { }}
public class Bar<T> where T : new(){ public T Create() { return new T(); }}
[...]
Bar<Foo> bar = new Bar<Foo>();
bar.Create();
In these situations it is safe (and recommended) to simply suppress the warning.
This rule will also fire on types that are only ever instantiated by unused methods on that exist on the same type. This is by-design.
For example, the following type will fire this rule:
internal class Book{ public static Book Create() { return new Book(); }}
[Visual Basic]
Friend Class Book
Public Shared Function Create() As Book Return New Book() End Function
End Class | http://msdn.microsoft.com/en-us/library/ms182265(VS.80).aspx | crawl-002 | refinedweb | 321 | 50.36 |
This page was copied from. Once we're done here the content should be put back to XML and published on the website.
Back to FOPProjectPages.
Authors:
VictorMote (wvm)
JeremiasMaerki (jm)
Glossary
output handler: A set of classes making up an implementation of an output format (i.e. not just the renderer, but for example the PDF Renderer plus the PDF library)
rendering run: One instance of the process of converting an XSL:FO document to a target format like PDF (or multiple target formats at once)
rendering instance: One instance of the process of converting an XSL:FO document to exactly one target format. Note that there may be multiple rendering instances that are part of one rendering run.
typeface: A set of bitmap or outline information that define glyphs for a set of characters. For example, Arial Bold might be a typeface. This concept is often also called a "font", which we have defined somewhat differently (see below).
typeface family: A group of related typefaces having similar characteristics. For example, one typeface family might include the following typefaces: Arial, Arial Bold, Arial Italic, and Arial Bold Italic. A typeface family may be named in a way ambiguous with its members -- for example, the family mentioned in the previous sentence might also be named "Arial".
font: A typeface rendered at a specific size. For example -- Arial, Bold, 12pt.
Goals
- refactor existing font logic for better clarity and to reduce duplication
- The design should be in concert with the considerations for Avalonization
- parse registered font metric information on-the-fly (to make sure most up-to-date parsing is used??)
resolve whether the { { { FontBBox, StemV, and ItalicAngle } } } font metric information is important or not -- if so, parse the .pfb (or .pfa file) file to extract it when building the FOP xml metric file (Adobe Type 1 fonts only) [1]
- handle fonts registered at the operating system (through AWT)
handle fonts that are simply available on the target format (Base 14 fonts for PDF and PostScript, Pre-installed fonts for PCL etc.)
- Support various file-based font formats:
- Allow for font substitution [3]
- We probably have to support fixed-size fonts for several renderers: Text, maybe PCL, Epson LQ etc.
- Optional: Make it possible to use multiple renderers in one run (create PDF and PS at the same time)
- How important is that?
Issues
- Why are we using our own font metric parsing and registration system, instead of the AWT system provided as part of Java?
- Answer 0: We must handle default fonts for the target format, like the standad PDF fonts or default PS printer fonts, which may not be available either from the system/AWT nor as a file.
Answer 1: Many of our customers use FOP in a so-called "headless" server environment -- that is, the operating system is operating in character mode, with no concept of a graphical environment. We need some mechanism of allowing these environments to get font information.12
- Answer 2: At some level, we don't yet fully trust AWT to handle fonts correctly. There are still unresolved discrepancies between the two systems.
- What about fonts for output formats using the structure handler (RTF, MIF)? Do they need access to the font subsystem? [4]
- Supporting multiple output formats per rendering run has a few consequences.
The layout (line breaks, line height, page breaks etc.) is influenced by font metrics. Two fonts with the same name (but one TrueType and one Type 1) may have different font metrics, thus leading to a different layout. [5]
- The set of available fonts cannot be provided by the renderers anymore. A central registry is needed. A selector has to decide which fonts are available for a set of renderers to be used. [6]
- Two renderers (although using the same area tree) may produce slightly different looking output.
- What to do when a font is not available to one of the say two target output formats? Or what to do when a font is available from two font sources but each output handler supports only one of these (and the font metrics are different)? [7]
- Font subsitution: PANOSE comes to my mind. What's that exactly? [8] Can we use/implement that?
Design
Concern areas
There are several concern areas within FOP:
- provision of font metrics to be used by the layout engine
- registration and embedding of fonts by the output handlers (such as PDF)
- Management of multiple font sources (file-based, AWT...)
- Selection of fonts (fonts that can be used in a rendering run, substituted fonts)
Parsing of file-based fonts ({ { { Type 1, TrueType, OpenType etc. } } })
Thoughts
Central font registry
{ { { Until now each renderer set up a FontInfo object containing all available fonts. Some renderers then used the font setup from other renderers (ex. PostScript the one from PDF). That indicates that there are merely various font sources from which output handlers support a subset. } } }
{ { { So the font management should be extracted from the renderers and made standalone, hence the idea of a central font registry. The font registry would manage various font sources (AWT fonts, Type 1 fonts, TrueType fonts). Then, there's an additional layer needed between the font registry and the layout engine. I call it the font selector (for now), because it determines the subset of fonts available to the layout engine based on the set of output handlers (one or more) to be used in a rendering run. It could also do font substitution as the layout engine looks up fonts and selects the most appropriate font. If a font is available from more than one font source the font selector should select the one favoured by the output handler(s). This means that we need some way for the output handlers to express a priority on font sources. } } }
The font selector will have to pass to the output formats which fonts have been used during layout.
Common Resources
There are some possible efficiencies to be gained by using one FOP session to generate multiple documents, and by generating multiple output formats for one document. However, to accomplish this, we probably need to explicitly distinguish which resources are available to / used by a Session, a Document (rendering run), and a Rendering Instance.
Proposed Interface for Fonts (wvm)
We wish to design a unified font interface that will be available to all other sections of FOP. In other words, the interface will provide all needed information about the font to other sections of FOP, while hiding all details about what type of font it is, etc.
{ { { /** {{{ * Hidden from FOP-general
*/ }}}
/** {{{ * Hidden from FOP-general.
- Implementations of this for AWT, Base14 fonts, Custom, etc.
- All implementations of this interface are hidden from FOP-general
*/ }}}
package interface TypeFace package getEmbeddingStream() {}
public class Font {{{ private TypeFace typeface;
- /**
Consults list of available TypeFace, and Font objects in the Session,
- and returns appropriate Font if it exists, otherwise creates it, updating Session
- and Document lists to keep track of available fonts and embedding information
- /
public static StreamOfSomeSort getFontRendering(Document document) {} }}}
/** some accessor methods **/ {{{ String getTypeFace();
- String getStyle(); int getWeight(); int getSize(); }}}
/** The following methods are either computed by the implementations of the TypeFace {{{ interface, or are computed based on information returned from the TypeFace interface
- */
- //These methods already take font size into account int getAscender(); int getDescender(); int getCapHeight(); //more... int getWidth(char c); boolean hasKerningAvailable(); //more... } } } }}}
Jeremias and I (wvm) have gone around a bit about whether the Font should be a class or an interface. The place where the interface is needed is at the { { { TypeFace } } } level, which is where the differences between AWT, { { { TrueType } } } custom, { { { PostScript } } } custom, etc. exist. The rest of FOP needs only the following:
- the provideFont() method to obtain a Font object which can provide metrics information
a way to get the actual font for embedding purposes. This is done through the { { { FontFamily } } } interface, which has methods for returning needed embedding information. However, the interface is never exposed to FOP-general. Instead a static method is (in Font) to handle all of that.
- collections of fonts used, fonts to be embedded, etc. are stored in the Session and Document concept objects respectively, where they can be obtained by { { { getFontRendering() } } }
So while the interface for { { { TypeFace } } } is good (to handle the many variations), any attempt to expose it to FOP-general makes FOP-general's interaction with fonts more complex than it needs to be.
Hardware fonts
Definition: "hardware" fonts are fonts implicitly available on a target platform (printer or document format) without the need to do anything to make them available. Examples: PDF and { { { PostScript } } } specifications both define a Base 14 font set which consists of Helvetica, Times, Courier, Symbol and ZapfDingbats. PCL printers also provide a common set of fonts available without uploading anything.
The Base 14 fonts are already implemented in FOP. We have their font metrics as XML files that will be converted to Java classes through XSLT. The same must be done for all other "hardware" fonts supported by the different output handlers. The layout engine simply needs some font metrics to do the layout.
OpenType Fonts
OpenType font files come in three varieties: 1) TrueType font files, 2) TrueType collections, and 3) Wrappers around CFF (PostScript) fonts. The first two varieties can be treated just like normal TTF and TTC files. The fonts metric information for all three is stored in identical (i.e. TrueType) tables. The CFF files require a small amount of additional logic to unwrap the contents and find the appropriate tables.
How to define a "font" in various contexts
A "font" can have various definitions in different contexts:
- The layout engine needs a font defined as: font-family (Helvetica), font-style (oblique), font-weight (bold), font-size (12pt). In this context the layout engine will also use information like text-decoration (underline etc.).
- Font sources will probably deal with fonts defined by: font-family, font-style, font-weight. But there are things to consider:
Type 1 fonts normally define a font exactly this way (Example: The files FTR_.pfb and FTR_.pfm together define the "Frutiger 55 Roman" font).
But the Type 1 spec defines a multiple master extension allowing more than one flavour of a font in one font file (ex. a regular and a bold font). I think, the same is possible for TrueType. To handle fonts like this in a family/style/weight manner, we would need a facade that points to a particular flavour of a multiple master font, so one such font would result in multiple facades point to it. [9]10
These fonts are generally scalable (at least AWT, T1, TT and OT are). What if we need to support fixed-size fonts for a text, PCL or Epson LQ renderer?11
[1] It is important. Because these values are used to create the font descriptor in PDF. If these values are wrong you get error messages from Acrobat Reader. (jm) See where this issue is discussed in a note. If I understand the note correctly, we need to read in the pfb file to get this information. (wvm)
[2] Actually OpenType is the unified next generation font format that also replaces Type 1 Fonts. An OpenType font contains more information than either a Type 1 or TrueType font contains. It can wrap either of the two methods for describing the font outline information. (wvm)
[3] Please define what is meant by this term. Are we talking about which font to use when we can't find the one that is requested? (wvm)
[4] I am not sure about RTF, but I think that MIF will need some access to this information. (wvm) <wvm date="20030718"> OK, I think I was wrong about this. The StructureRenderers should be able to get everything they need about fonts directly from the XSL-FO input. If they need to aggregate similar fonts, or track which ones have been used, they should do that themselves.</wvm>
[5] My thought is that this should never happen. If the font registry is centralized, then when "XYZ, bold, 12pt" is requested, the same font should be selected every time. (wvm)
[6] I envision this information to be stored in the appropriate objects -- Session, Document, or RenderingInstance (these are concepts, not class names, because classes filling these concepts may already exist). Session should either be static or a singleton, and includes a list of all fonts (actually probably typefaces) used in this session. Document may not need to list anything, but RenderingInstance needs to know which fonts need to be embedded, among other things. (wvm)
[7] I think I am against allowing this. We would first need to first resolve how to register hardware fonts & get their metric information, which seems almost impossible. Then we would have to build a mechanism that maps font sources to output media -- PDF can use software fonts, but not hardware. PCL can use hardware, and depending on the printer, perhaps can use downloadable software fonts as well. This seems like an ugly, slippery slope, at least for a 1.0 release. I think it better to say that we support only soft fonts, and let the user build a workaround. The other really ugly aspect of this is that if you allow two different fonts to be used for two different rendering contexts, I think you have to have two different area trees to handle the layout differences. (wvm)
[8] See. (wvm)
[9] Actually, multiple masters are used to generate specific instances of .pfm and .pfb files, so these live in separate files. We do have an issue with .cff (Compact Font Format, which contain multiple Type 1 faces), and .ttc (TrueType Collection, which contain multiple TrueType faces). Until we have parsing tools, these are really unusable to us. OpenType fonts have native support for multiple typefaces within a font file, and I think they support both of these formats. (wvm)
10 With regard to the design aspect, when a font object is requested by the layout classes, the same object should always be returned for the same basic information that is passed. (wvm)
11 A fixed-size font can be thought of as merely an instance at a specific point size of a typeface. So, for text, we probably need to take the first point size passed to us & use that throughout, spitting out an error if other point sizes are subsequently used. For the others, I suppose we have to first resolve the issues of whether/how to support hardware fonts. (wvm)
12 I don't think this is really a strong argument unless we refrain from using Batik for SVGs too. (pij) Response from wvm: <wvm> I don't understand this comment. The point is that we use our own registry for fonts because it is the only way to get font information in a headless environment. </wvm> | https://wiki.apache.org/xmlgraphics-fop/FOPFontSubsystemDesign | CC-MAIN-2017-09 | refinedweb | 2,482 | 61.56 |
27 June 2012 10:50 [Source: ICIS news]
LONDON (ICIS)--Technip has been awarded two front end engineering and design (FEED) contracts by ZapSibNeftekhim, a subsidiary of Russia-based petrochemical company Sibur, the French engineering firm said on Wednesday.
Technip said it will carry out the work on two plants located in Tobolsk, in the ?xml:namespace>
“The first contract concerns a linear low/high density gas phase polyethylene plant; the second one is for a high density slurry phase polyethylene plant,” it added.
Each plant will consist of two parallel production trains with a total capacity of 1.5m tonnes/year of polyethylene, said Technip.
It added that the two plants will be developed using licences of Switzerland-headquartered INEOS Technologies.
“Technip’s operating centres in
Financial details of the contracts were not disclosed.
On 21 June, Sibur said it had entered into an agreement | http://www.icis.com/Articles/2012/06/27/9572904/frances-technip-awarded-feed-contracts-for-petchem-complex-in-russia.html | CC-MAIN-2014-41 | refinedweb | 146 | 54.12 |
This paper describes a portable electronic mail bouncer which
sends detailed information back to the sender when a mail message can
not be delivered to it's intended recipient. The bouncer was
originally written to handle a large merger between multiple DNS
domains, and is implemented entirely in Perl5 as a mail delivery
agent. The bouncer operates under the concept of "least privilege" so
it's safe to run directly from mail transport agents such as sendmail.
The bouncer is designed to make the human processes and interactions
in dealing with undeliverable E-mail easier for both postmasters and
end-users alike.
Most large networks are in a constant state of flux when it
comes to account management and electronic mail routing. New users are
added daily as old users are removed, often without thought of
potential future consequences in an ever expanding electronic world.
As more and more computer neophytes start using the Internet, handling
mail delivery problems and bounces will become a much larger problem
for any large site's postmaster.
Like postmasters at most sites with several thousand users, our
bounced mail is run through multiple filters in an attempt to either
auto-respond to problems or to sort the problems into related issues
for easier handling. The rapid increase in the amount of unsolicited
commercial E-mail is making this even more important. This paper
examines the other side of these issues - what an end-user sees in an
undeliverable message, rather than what a postmaster sees. Hopefully
by improving the end-user interface, we will lower the number of
undeliverable messages a postmaster must deal with directly.
This
spring, Collins Avionics & Communication Division merged with it's
sister company, Collins Commercial Avionics, to form Rockwell Collins,
Inc. The new combined enterprise network contains over 10,000 active
network users, and several thousand old accounts which no longer
exist, but whose userid's can not be re-used in an effort to prevent
mis-delivered electronic mail. One of the first steps in merging
networks of this size are to correct any namespace collisions, both
hostnames and login IDs. Forcing uniqueness of existing usernames
generally isn't looked upon favorably by the person whose address is
changing; they may have their old address printed on business
correspondence and recorded in thousands of ``From:'' headers
scattered across the Internet. In an enterprise network, even a
collision rate of less than 5% can make a user-friendly solution a
value-added task. In an effort to help our users and customers do
business more efficiently, we're notifying senders when an address
changes with a clearly written explanation of what happened and why.
This bounced message gives the sender the recipient's new address,
similar to the sendmail redirect [1] feature, but with more detailed
information.
In most cases it is possible to use alias maps on mail hubs
and gateways to re-route electronic mail to the user's new address
automatically, but usually the user has no way to control how long
this forwarding is enabled. When it is removed, the old address
suddenly generates undeliverable messages with brief errors such as
those shown in Listing 1. While this tells the user why the message
was returned, it doesn't explain why the username they're sending to
is now unknown, nor does it suggest any corrective actions. While the
above example makes perfect sense to any Postmaster or System
Administrator, many end-users simply don't understand how to interpret
many computer-generated error messages like this, and then must
contact a System Administrator or attempt to contact the person
they're trying to send the E-mail to via alternate means to get the
new E-mail address.
... while talking to mailhost.domain.com.:
>>> RCPT To:<user@mailhost.domain.com>
<<< 550 <user@mailhost.domain.com>... User unknown
550 user@mailhost.domain.com... User unknown
Newer versions of sendmail (Berkeley v6.25
and later) can be configured to take advantage of a feature called
redirect which is used to provide forwarding addresses in the returned
message, rather than just saying ``User unknown.'' A sample redirect
bounce might look like Listing 2. Once again sufficient for System
Administrators, this time the error message communicates the
recipient's new address. However, these terse error messages often
confuse end users who may wonder if this is just informational and
whether or not their message was delivered to the new address provided
or not.
... while talking to mailhost.domain.com.:
>>> RCPT To:<user@mailhost.domain.com>
<<< 551 User not local; please try <user@elsewhere.com>
551 User not local; please try <user@elsewhere.com>
With a user community of over 10,000 people, we wanted to
develop a methodology for returning undeliverable messages to senders
with concise, plain English explanations of why the message is being
returned, and suggest corrective actions they should take to ensure
their message is delivered successfully in the future. The bouncer
needs to handle many potential reasons for a userid change such as
namespace collisions, legal name changes, employees who have left the
company, etc. In order to facilitate rapid communications, in addition
to returning a mail message to the sender, where possible an attempt
is made to deliver the message to the user's new address if permitted
by local security policies.
The final implementation language was
also given careful consideration. First and foremost, because of our
migration schedules we needed a language which would facilitate rapid
prototyping and development. Ideally, the language would also allow us
to easily secure the bouncer. Perl [2] meets both of these
requirements for several reasons:
The initial implementations of the bouncer program ran with
minimal privileges as a simple mail filter. Users who were to have
their mail bounced would receive an alias similar to:
oldname: newname,bouncer or
oldname: bouncer
In this way, the recipient would receive a copy of the message if
permitted by local security restrictions, and the bouncer account
would also receive a copy. The bouncer account contained a simple
.forward file which reset IFS for security purposes, executed the
bouncer script, and if it failed, returned an exit status of 75 so
that sendmail would bounce the message as it normally would have. The
.forward file read:
|IFS=' ' & exec /path/bouncer.pl\
|| exit 75 #bouncer
The other problem with the filter
implementation is that if the original recipient appears only in a
Bcc: header, the recipient is hidden from the filter; only the
delivery agent knows who to deliver the message to. By the time the
message reaches the bouncer, the Bcc: headers have been removed for
privacy reasons by the mail transfer or delivery agent.
Because of these problems, the bouncer was re-written as a
mail delivery agent. This required the addition of a few lines to the
mail system's sendmail.cf configuration file, and a re-write of the
bouncer code for security reasons. At the same time, the code was
moved to the mail server's local file systems, rather than the bouncer
account's home directory (in fact, the bouncer account is no longer
needed; the delivery agent can be run as any unprivileged user, such
as ``nobody''). Because the bouncer is running as a delivery agent, it
must run under the same assumptions a SUID [3] program would run,
since it's launched via sendmail with system privileges. Since the
bouncer doesn't actually have to do any local mail delivery, it can
relinquish these privileges immediately (running instead as
``nobody''), which minimizes the risk of security issues. In addition,
it carefully ``untaints'' all user input that is passed back to
external programs, to prevent a shell from interpreting malicious
data.
Configuration of the delivery agent requires the addition
of two lines to the sendmail.cf file. The first addition is a mail
delivery agent command line, such as:
Mbouncer, P=/bin/bouncer,
F=DFMPlms S=10, R=20,
A=bouncer -a $f -d $u
Once the delivery agent has been established, ruleset 0 must be
modified in order to enable it. If addresses of the form
user@bouncer are to be handled, the line in Listing 3 is added
to ruleset 0.
R$+<@bouncer> $#bouncer $:$1<@bouncer> user@bouncer
R$+<@$+.bouncer> $#bouncer $:$1<@$2.bouncer> user@*.domain.com.bouncer
The bouncer code has several configurable options within the
code itself. These options are all defined at the beginning of the
program and allow the administrator to set:
The address configuration file is relatively straight
forward and allows the administrator to specify the old address, new
address, some personal contact information for the recipient, and a
configuration code used to determine which explanatory text is sent in
the bounced messages for each user.
In an attempt to prevent mail
loops, the bouncer follows RFC 822 [4] conventions for returning
undeliverable mail. Additionally, in order to deal with mailing list
programs which put the list maintainer's address in the Errors-To:
header, it is given precedence. If there is no Error-To: header, the
Sender: header is used to determine how to send the bounce to. In the
absence of a Sender: header, the From: header will be used, and if the
From: header does not exist, a last ditch effort is made using the
sender's address from the SMTP message envelope.
Finally, any
message with a Precedence: header matching an administrator-
configurable setting will be handled by sending a separate not to the
recipient, rather than replying to the sender. In this way, users will
be reminded to update their mailing list subscriptions with their new
address, and there is a much smaller risk of starting mail loops
between the bouncer and a mailing list program. By default,
Precedence: headers which trigger this behavior are any that match
bulk, junk, list [5].
Logging of all bounced mail is handled by sendmail itself,
which will create an entry in the syslog output just as if the normal
local delivery agent had been run. In this case however, the local
delivery agent will be the bouncer, so it's relatively easy to pull a
list of all bounced E-mail messages from the syslog output. A sample
syslog entry is shown in Listing 5.
Sep 6 10:57:35 mailhub sendmail[527]: AA186621431: from=<user@somedomain.com>
Sep 6 10:57:35 mailhub sendmail[527]: AA186621431: size=80, class=0,
pri=10080, nrcpts=2
Sep 6 10:57:35 mailhub sendmail[527]: AA186621431:
msgid=<9708068735.AA873561403@somedomain.com>
Sep 6 10:57:35 mailhub sendmail[527]: AA186621431: relay=somehost [127.0.0.1]
Sep 6 10:57:36 mailhub sendmail[527]: AA186621431: to=jdsmith@bouncer,
delay=00:00:01, stat=Sent, mailer=bouncer
For a simple example of how the bouncer is configured,
assume there is someone named John D Smith on one network, and another
user named Jeff D Smith on a second network. John's E-mail address is
jdsmith@domain1.com and Jeff's address is
jdsmith@domain2.com. When the two networks are combined, it is
desirable for each to answer for the new network (domain3.com) as well
as both old networks (domain1.com and domain2.com) for backward
compatibility. In this manner the same mail servers may be used to
provide redundant delivery hubs for the same domain.
In order to implement this improved delivery system, one or both
of the addresses above much change. Sendmail's redirect can't
be used in this case because it only handles the case where one user
changes their address; in this case, both users should change their
addresses to avoid confusion, since different people may remember
either Jeff or John as jdsmith@[someplace].com. If only Jeff
were to change his userid, then John would likely start receiving mail
in the future which the sender actually intended for Jeff, not
realizing that Jeff had changed his userid.
The solution in this
case is to change both addresses to something like
jdsmith1@newdomain.com for John, and
jdsmith2@newdomain.com for Jeff. In this way, both are unique
and neither maintains the original address. Prior to changing the
userid's, the bouncer is configured to respond to any of the following
addresses:
jdsmith@domain1.com
jdsmith@domain2.com
jdsmith@newdomain.com
Due to the consolidation of networks between domain1.com and
domain2.com to form a common network newdomain.com, some Electronic
Mail addresses were changed. This message is automatically generated
in response to your E-mail to one of the persons listed below. In
this case, we were unable to determine which user you intended to
send to, and request that you re-send your E-mail message to the
new address listed after the person's name below:
John D Smith (Phone Number) [jdsmith1@newdomain.com]
Jeff D Smith (Phone Number) [jdsmith2@newdomain.com]
For your convenience, a copy of your original message is included below.
====================================================================
[original message including headers]
The
configuration of the bouncer program's reply is contained within a
single ASCII file. The format of the file is:
code=user1,user2,[...]: \
text (address1@[domain]), \
text (address2@[domain]),[...]
01=jdsmith: John D Smith \
(555-1212) (jdsmith1@), \
Jeff D Smith (555-1234) \
(jdsmith2@)
01=jdsmith: John D Smith \
(555-1212) (jdsmith1@), \
Jeff D Smith (555-9875) \
(jdsmith2@elsewhere.com)
# Users who've had their address changed because of a namespace
# collision in the domain merger
01=jdsmith: John D Smith (555-1212) (jdsmith1@),\
Jeff D Smith (555-1234) (jdsmith2@)
# Users who've had their address changed because of a name change
02=jadoe: Jane A Smith (formerly Jane A Doe, 555-1111) (jasmith@)
# Users who're no longer valid on this network
03=jsbrown: John S Brown (moved to Div XYZ) (jsbrown@xyz.domain.com)
jdsmith: jdsmith@bouncer # can't tell who they want to send to here;
# just bounce it
jadoe: jasmith,jadoe@bouncer # forward and notify sender of new address
jsbrown: jsbrown@bouncer # dont fwd -- may have confidential
# information: just bounce it
As currently written, the bouncer behaves in a similar
manner to the vacation [6] program. However, the bouncer is
centrally managed and has finer control over what happens with each
recipient's messages. The only configuration which needs to be done is
to initially set the administrator options in the bouncer code, update
the address information inside the single ASCII address configuration
file, and configure the aliases for old usernames so they will be
directed at the bouncer. If vacation were to be used for this
implementation, each old account would need to be maintained, have a
.forward file, and an individual vacation configuration. In the
sample case provided earlier, vacation would not be a viable
long-term solution when the password maps between domain1 and domain2
are eventually merged, because of the username conflict. While this
problem can be circumvented with the creative use of aliases and
sendmail.cf rules, the configuration of the bouncer is much simpler
and obviates the need to maintain multiple configurations for each
account that's changed.
Another alternative would be to take
advantage of sendmail's #error delivery agent. However, this
would require further modification of the sendmail.cf file in order to
provide multiple error conditions, and tends to produce terse error
messages. This would not meet the design goals of the bouncer - simple
configuration and detailed explanations - and is more difficult to
maintain, especially by junior administrators. The advantage to the
bouncer is that once the sendmail.cf is initially set up, no further
modifications need be made. Junior System Administrators can modify
the bouncer.cfg and mail.aliases maps to configure new bouncer
entries.
If enough traffic is being directed through the bouncer, it
might be better implement in a compiled language such as C, to prevent
the startup costs of Perl. However, the current delivery agent
implementation takes less than 1 second to execute, so it would take a
very large site to justify this more complex task. For example, our
site contains over 10,000 accounts. If a namespace collision rate of
5% is assumed, this means that 500 usernames are going to be handled
by the bouncer. If each address receives 10 pieces of E-mail per day,
this is only 5,000 messages to handle. Most modern gateways can handle
much more than this without any performance problems in an average
day; ours typically process 75,000 to 100,000 messages in an average
day with no noticeable performance problems. With the load balancing
provided by MX record preferences [7], only extremely large sites may
ever need to re-implement the bouncer for performance reasons.
The main feature lacking from the bouncer is the ability to auto-
detect and stop mail loops. As much care as possible was invested in
determining sender information and handling mailing list processors,
but there is still small possibility that the bouncer program could
get into a loop with another mail delivery agent such as a mailing
list processor. While this shouldn't happen with such popular mailing
list packages such as majordomo or listserv, not everyone uses these
to process heir mailing lists, and not all mailing list processors
follow the RFC's and use the correct header formats. An algorithm for
detecting and preventing these types of mail loops will be added to
future releases of the bouncer code.
Please contact the author directly for further information
and program availability information.
Rich Holland is the Technical Lead for the Enterprise E-mail
Team at Rockwell Collins, Inc. where he is responsible for technical
leadership and future direction in merging multiple mail systems into
a common system for use by over 10,000 end users worldwide. Before
coming to Rockwell, he was a Senior System Administrator for Synopsys
where he oversaw the care and feeding of the Synopsys Porting Center
machines. Reach him via U.S. Mail at Rockwell Collins, Inc.; M/S
106-193; 400 Collins Rd. NE; Cedar Rapids, IA 52498. His E-mail
addresses are <rjhollan@collins.rockwell.com> and
<holland@pobox. com>. | http://static.usenix.org/publications/library/proceedings/lisa97/full_papers/23.holland/23_html/main.html | crawl-003 | refinedweb | 3,012 | 51.18 |
Issue
I have used the following code to create a temporary file in my android app:
public File streamToFile (InputStream in) throws IOException { File tempFile = File.createTempFile("sample", ".tmp"); tempFile.deleteOnExit(); FileOutputStream out = new FileOutputStream(tempFile); IOUtils.copy(in, out); return tempFile; }
Now the problem is
Cannot resolve symbol 'IOUtils'. I did a little bit of googling and discovered that for using IOUtils I need to download and include a jar file. I downloaded the jar file from here(commons-io-2.4-bin.zip). I added the jar named
commons-io-2.4.jar from the zip to my bundle and when I tried to import it using:
import org.apache.commons.io.IOUtils;
It is showing error
Cannot resolve symbol 'io'. So I tried to import it like:
import org.apache.commons.*
But still I am getting the error
Cannot resolve symbol 'IOUtils'.
Question 1 : Why am I getting this error? How to resolve it?
Question 2 : Is there any way to create a temp file from an InputStream without using an external library? Or is this the most efficient way to do that? I am using android studio.
Solution
Right clicking on the
commons-io-2.4.jar file in project navigator and clicking ‘Add to project’ solved the issue.
Answered By – Harikrishnan
This Answer collected from stackoverflow, is licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0 | https://errorsfixing.com/cannot-resolve-symbol-ioutils/ | CC-MAIN-2022-33 | refinedweb | 240 | 69.38 |
ncl_frstd man page
FRSTD — Defines the first of a sequence of points through which a curve is to be drawn.
Synopsis
CALL FRSTD (X,Y)
C-Binding Synopsis
#include <ncarg/ncargC.h>
void c_frstd (float x, float y)
Description
- X
(an input expression of type REAL) defines the X user coordinate of the starting point of the curve.
- Y
(an input expression of type REAL) defines the Y user coordinate of the starting point of the curve.
C-Binding Description
The C-binding argument descriptions are the same as the FORTRAN argument descriptions.
Usage
One way to draw a curve with Dashline is to call FRSTD once to define the first point of the curve and then to call VECTD repeatedly to define the second and all following points of the curve.
If three or more distinct points are given, and if one of the smoothing versions of Dashline is being used, and if the internal parameter that suppresses smoothing is not set, then splines under tension are used to generate a smooth curve; the number of points actually used to draw the curve will depend on its length. In all other cases, the "curve" will be approximated by just connecting the user-given points in the specified order.
After the call to VECTD defining the last point of the curve, you may call LASTD, which flushes any portions of smoothed curves that are defined by coordinates saved in internal buffers of FRSTD and VECTD and that have not yet been drawn. Calls to LASTD are not always required - for example, when a non-smoothing version of Dashline is used (no buffering) or when the next call to an NCAR Graphics routine will be to FRSTD (which flushes the buffers) - but unnecessary calls do no harm. If you judge that one of the smoothing versions of Dashline may be used, it is best to put in the calls to LASTD.
Examples
Use the ncargex command to see the following relevant examples: tdashc, tdashl, tdashp, tdashs, fdldashc, fdldashd.
Access
To use FRSTD or c_frstd load the NCAR Graphics libraries ncarg, ncarg_gks, and ncarg_c, preferably in that order.
See Also
Online: dashline, dashline_params, curved, dashdb, dashdc,. | https://www.mankier.com/3/ncl_frstd | CC-MAIN-2017-43 | refinedweb | 364 | 62.61 |
On 04/18/2010 09:53 PM, Satoru SATOH wrote: > This patch adds the files implements dnsmasq (hostsfile) module. > > Signed-off-by: Satoru SATOH <satoru satoh gmail com> In addition to Jim's comments: > > --- > src/util/dnsmasq.c | 326 ++++++++++++++++++++++++++++++++++++++++++++++++++++ > src/util/dnsmasq.h | 59 ++++++++++ > 2 files changed, 385 insertions(+), 0 deletions(-) > create mode 100644 src/util/dnsmasq.c > create mode 100644 src/util/dnsmasq.h > > diff --git a/src/util/dnsmasq.c b/src/util/dnsmasq.c > new file mode 100644 > index 0000000..b46654e > --- /dev/null > +++ b/src/util/dnsmasq.c > @@ -0,0 +1,326 @@ > +/* > + * Copyright (C) 2010 Satoru SATOH <satoru satoh gmail com> > + * Copyright (C) 2007-2009 Red Hat, Inc. You did the right thing in preserving the Red Hat copyright from src/iptables.c, since that was your template. However, it makes maintenance easier if you list the Red Hat line first, and extend its copyright to 2010, since emacs copyright updating hooks only catch the first copyright line. > + > +#ifdef HAVE_PATHS_H > +#include <paths.h> > +#endif This fails 'make syntax-check' if you have cppi installed. Indent the include line: #ifdef HAVE_PATHS_H # include <paths.h> > +static int > +hostsfileWrite(const char *path, dnsmasqDhcpHost *hosts, int nhosts) > +{ > + char tmp[PATH_MAX]; > + FILE *f; > + int istmp; Make this 'bool istmp', for how you are using it. > + > +typedef struct > +{ > + int nhosts; > + dnsmasqDhcpHost *hosts; > + > + char path[PATH_MAX]; /* Absolute path of dnsmasq's hostsfile. */ > +} dnsmasqHostsfile; Jim didn't mention this use of PATH_MAX, but it is worth refactoring. In particular, PATH_MAX can cause problems if we ever try to port to GNU Hurd, where there is no limit (I know that the current libvirt code base already has uses of PATH_MAX, but we shouldn't be adding more). -- Eric Blake eblake redhat com +1-801-349-2682 Libvirt virtualization library
Attachment:
signature.asc
Description: OpenPGP digital signature | https://www.redhat.com/archives/libvir-list/2010-April/msg00850.html | CC-MAIN-2015-18 | refinedweb | 301 | 67.76 |
ROLAND FANTOM S
All of the Akai MPC2000/XL Sounds Import Perfectly into the Roland Fantom S! Get All New Fantom Samples!
Format Name: Fantom S
Company: Roland
Extensions:
Description:
To order Roland Fantom S sounds, choose the ‘Fantom’ option under ‘Format’ and the ‘Shipping’ CD-ROM ($2) or Download Option (instant download) when checking out.
Since the Roland Fantom Series keyboards have a complex file system, it is easier to load wav samples into the Roland Fantom S, Roland Fantom X, or Roland Fantom Xa. Loading instructions are simple in expanding your Roland Fantom Sound library.
Get more information on how to import samples into the Roland Fantom S and Roland Fantom X Keyboards. Get more information about importing samples into the Roland Fantom Xa Keyboard.
import them into your Roland Fantom S | https://www.gotchanoddin.com/home/roland-fantom-s/?v=1d20b5ff1ee9 | CC-MAIN-2019-22 | refinedweb | 134 | 63.19 |
The code in this article and an implementation of
zipLongest are in this gist.
The built-in
zip function is ubiquitous in python. It allows highly readable iteration over multiple iterables:
def naturals(): n = 1 while True: yield n n += 1 for n, c in zip(naturals(), "Hello!"): print(n, c) # 1 H # 2 e # 3 l # 4 l # 5 o # 6 !
Now, with Mapped Types in typescript, we can do the same thing, all while keeping our lovely types too!
With mapped types, we can make an
Iterableify type, which will take a type, and change it so that its members are of type Iterable:
type Iterableify<T> = { [K in keyof T]: Iterable<T[K]> }
For example
type T1 = Iterableify<string[]> // Iterable<string>[] type T2 = Iterableify<{a: number, b: string}> // {a: Iterable<number>, b: Iterable<string>} type T3 = Iterableify<[number, string][]> // Iterable<[number, string]>[]
We can then make a simple zip function like so:
function* zip<T extends Array<any>>( ...toZip: Iterableify<T> ): Generator<T> { // Get iterators for all of the iterables. const iterators = toZip.map(i => i[Symbol.iterator]()) while (true) { // Advance all of the iterators. const results = iterators.map(i => i.next()) // If any of the iterators are done, we should stop. if (results.some(({ done }) => done)) { break } // We can assert the yield type, since we know none // of the iterators are done. yield results.map(({ value }) => value) as T } }
Since the mapped types affect typescript tuples as well, we can now do something like this:
for (const [a, b] of zip([1, 2, 3], "abc")) { // type of a is number! // type of b is string! // This has no compilation errors! console.log(b.repeat(a)) }
Discussion (1)
Nice,
zipin python is really convenient, thank you for this type safe implementation in typescript! | https://practicaldev-herokuapp-com.global.ssl.fastly.net/chrismilson/zip-iterator-in-typescript-ldm | CC-MAIN-2021-17 | refinedweb | 296 | 63.09 |
Move viewport camera from plugin
- mortenjust last edited by m_adam
I'm playing around with an idea for a 3D mouse.
I have this working Mouse > USB > my macOS app - and just need the last few steps: > Cinema 4D plug-in > Cinema 4D camera/rig rotation
I'm wondering if I can write a plug-in that takes a set of rotation parameters (in any format, really, quarternion, euler angles, transform) and rotate the camera (or its rig parent node) to look from that angle.
Is that even possible? I looked at the docs, and I could only find direct dragging functions.
Also, what would be a good way to pass in the rotation parameters from my macOS app to the plugin? I'm thinking maybe a websocket. Ideally I'd pass in the rotation 60 times per second, but 15 could probably work, too.
- mortenjust last edited by
So! It looks like this might work for the rotation part, as long as there is a rig node.
import c4d obj = GetCameraRigNode() def rotate(eulerX, eulerY, eulerZ): rot = c4d.Vector(eulerX, eulerY, eulerZ) obj.SetAbsRot(rot)
For the transport I'm thinking about running a websockets server which the Python app will connect to and listen for rotation events.
Unless there's something simpler I could do, like calling a url scheme, or passing parameters to C4D from cocoa.
Hi @mortenjust first of all welcome in the plugin cafe community.
Don't worry since it's your first post, but please next time try to follow these rules:
- Q&A New Functionality.
- How to Post Questions especially the tagging part.
I've set up this post correctly, but please for the next ones.
Regarding your question, there is no building option in Cinema 4D, so the best way would be to have a TCP/Socket server to communicate across multiple application.
Finally, in case you are not aware, there is already a plugin for handling 3D mouse called CallieMouse, but is not yet ported in R20, for more information see 3D Mouse Slider Focus
Cheers,
Maxime.
- mortenjust last edited by
Sorry if I did something wrong in my post, and thanks for the pointers.
I made it work using Websocket. It's using augmented reality to orbit the camera live in Cinema. Here's a couple of videos if anyone's interested
wow! i love that.
great job! | https://plugincafe.maxon.net/topic/11464/move-viewport-camera-from-plugin/5 | CC-MAIN-2019-47 | refinedweb | 398 | 64 |
Keystone IdP SAML metadata insufficient for websso flow
Bug Description
The metadata generated by Keystone IdP includes a binding of type URI. From https:/
def single_
return md.SingleSignOn
Looking at the Shibboleth SessionInitiator code, this is not a valid binding for a default websso configuration. The accepted bindings are defined at https:/
// No override, so we'll install a default binding precedence.
string prec = string(
@Marek: ++
This should be tracked if we want to implement fully enabled SAML IdP in Keystone.
unassigning due to inactivity
Since we don't suppor K2K with websso workflow it's not a bug, but definitely worth having it here so we can track this. | https://bugs.launchpad.net/keystone/+bug/1470205 | CC-MAIN-2019-22 | refinedweb | 111 | 53.41 |
You can subscribe to this list here.
Showing
7
results of 7
On 3/8/06, A. Pagaltzis <pagaltzis@...> wrote:
> * Lars Lindner <lars.lindner@...> [2006-03-07 22:25]:
> >The problem is how to render the GNOME error icon inside the
> >HTML widget.
>
> The gtk+ stock icon API lets your retrieve the image data for any
> stock icon you want. Maybe you could register a `stock:` protocol
> in the HTML widget? The resolver code would then ask gtk+ for the
> corresponding pixmap and return it.
>
> Btw, is there interest in getting rid of the presentational
> tables in the HTML passed to the HTML widget, so that it can be
> styled more freely with CSS? The problem, of course, will be
> GtkHTML2, whose CSS support is=85 uh, let's call it rudimentary.
>
> I have some styles in `.liferea/liferea.css` to make the basic
> styling a little prettier; they won't work very well in GtkHTML2,
> but as minimal as they are, I find they really add something to
> the look in Gecko. Any interest in those?
>
> Finally, the stylesheets that come with Liferea are way verbose,
> with a lot of completely unnecessary repetition. Any interest in
> cleaned up versions?
If the functional result is the same: yes. The current CSS style sheets
are pretty ugly and need some love. But before optimizing lets finalize
the new rendering changes. After finishing the rendering lets optimize
the HTML and CSS (timeline: two weeks from now).
And the plan is to fully support GtkHTML2, which means no CSS that's
not supported by GtkHTML2 because the warnings GtkHTML2 issues
woud mess up the command line.
Lars
I just made a branch to start the unit testing code. And stuck an old
file that I had lying around into it as a start.
-Nathan
On Wed, Mar 08, 2006 at 05:12:10AM +0100, A. Pagaltzis wrote:
> Hi guys,
>=20
> check out this approach in use by the DivMod project:
>=20
>
>=20
> The upshot of working that way is that the code in the trunk HEAD
> always works; it has a number of additional advantages but
> they=E2=80=99re all just gravy in comparison.
>=20
> Regards,
> --=20
> Aristotle Pagaltzis // <>
Yes... some tests would be great. I know that the feedparser python
script has a bunch of tests that we could try. I looked at the wiki
that started this thread, and its xml:base test feed seemed, well,
incomplete.
Could you make a good complete test feed?
I'm not entirely sure about how one should go about making the driver
for the unit tests. Do you have ideas of a good way to structure it?
Maybe write a small C driver program that outputs the parsed feed
structure in XML, and check it using some python (or perl, or
whatever) script?
-Nathan
On Wed, Mar 08, 2006 at 05:08:55AM +0100, A. Pagaltzis wrote:
> * // <>
Hi guys,
The upshot of working that way is that the code in the trunk HEAD
always works; it has a number of additional advantages but
they’re all just gravy in comparison.
Regards,
--
Aristotle Pagaltzis // <>
* // <>
* Nathan Conrad <conrad@...> [2006-03-08 02:40]:
>I've added another patch to the code that I think might actually
>bring it to the state that "still needs a minor amount of work"
>as this email's subject states.
>
>I've not yet converted the text-construct code, but the
>content-construct code should work. RSS parser still needs to be
>worked on.
>
>Please let me know what you think of the current state of the
>code.
Okay…
In `pie_feed.c`:
• I don’t understand why you picked the arbitrary
`` as the base in `pie_feed.c`.
Shouldn’t that be just NULL?
In `atom10.c`:
• The content construct parser got a lot simpler. That’s great.
:-)
• You set `defaultBase` to the feed’s URI. That’s fine, but you
must still do `xmlNodeGetBase` on `atom:content` because every
element in the feed may have its own `xml:base`.
The way I would handle this is to do `xmlNodeSetBase` on the
root `atom:feed` element in `atom10_parse_feed`. Then you can
simply use `xmlNodeGetBase` everywhere and let libxml2 handle
everything for you. Fewer special cases and less code to write
that way.
So far it all looks okay. However…
In `common.c`:
• You rolled everything into `extractHTMLnode`. It now has two
large sections of code (and your design in fact expects three)
that share nothing except a few lines of cleanup at the end of
the code. Which section is executed is decided by the value of
a parameter.
This strikes me as an odd design. It seems better to have two
(or three) completely separate functions, and to just put the
tiny shared bit of code in another function (say,
`dump_document_element`) which all of them then call.
• You wrote:
divNode = xmlNewNode(NULL, BAD_CAST "div");
xmlNewProp(divNode, BAD_CAST "xmlns", BAD_CAST "";);
That is So Very Wrong. The right way is like so:
xmlNsPtr htmlns = xmlNewGlobalNs(newDoc, BAD_CAST "";);
divNode = xmlNewNode(htmlns, BAD_CAST "div");
• For `xhtmlMode == 0`, you unconditionally copy
`->xmlChildrenNode` into the `newDoc`. But what document does
`common_parse_html` create for the following string?
<p>Okay so far.</p> <p>But what now?</p>
This does not have a single document element and
`common_html_doc_find_body` won’t find a body tag here either.
Are you sure you want still want `->xmlChildrenNode` in that
case?
• In the case of `xhtmlMode == 2` you still need to do the
copy-node-to-new-document-before-dumping dance, because it is
otherwise not guaranteed that the resulting dumped node will be
namespace-wellformed.
I have to say the changes to `common.c` look pretty problematic
overall.
Regards,
--
Aristotle Pagaltzis // <>
I've added another patch to the code that I think might actually bring
it to the state that "still needs a minor amount of work" as this
I've not yet converted the text-construct code, but the
content-construct code should work. RSS parser still needs to be
worked on.
Please let me know what you think of the current state of the code.
-Nathan
On Tue, Mar 07, 2006 at 05:02:58PM +0100, A. Pagaltzis wrote:
> * Nathan Conrad <conrad@...> [2006-03-06 23:50]:
> >I've added code to convert the html into xhtml in the atom
> >parser, and plan to do so in the other parsers. It _seems_ to
> >work, and I've even found some bugs in the HTML code that
> >Liferea generates.
>=20
> Cool! But the code currently in there is looking for
> `/html/body` and bails if it doesn=E2=80=99t find that=E2=80=A6 are you=
use
> that=E2=80=99s what you mean or is that a copy-paste vestige?
>=20
> >I'm thinking that I'm going to wrap all the items in an extra
> >pair of div tags that contain the xml base for the item (using
> >the libxml2 function to get the base for that item).
>=20
> I think the best place to do that would be in
> `common_html_to_xhtml` and in `extractHTMLnode`. I started
> working on a patch to add a `baseURL` parameter to both, but then
> I stumbled over that `/html/body` XPath in `common_html_to_xhtml`
> and stopped.
>=20
> Another thing: `extractHTMLnode` should not simply `xmlDumpNode`
> the node, it should instead `xmlDocCopyNode` to a fresh document
> and then dump *that*. The code looks like this:
>=20
> xmlBufferPtr buf =3D xmlBufferCreate();
> xmlDocPtr temp_doc =3D xmlNewDoc( BAD_CAST "1.0" );
> {
> xmlNodePtr copied_node =3D xmlDocCopyNode( cur, temp_doc, 1 );
> xmlDocSetRootElement( temp_doc, copied_node );
> if( baseURI && !( xmlNodeGetBase( temp_doc, copied_node ) ) )
> xmlNodeSetBase( copied_node, baseURI );
> xmlNodeDump( buf, temp_doc, copied_node, 0, 0 );
> printf( "%s\n", ( char * ) xmlBufferContent( buf ) );
> }
> xmlBufferFree( buf );
> xmlFreeDoc( temp_doc );
>=20
> That will make libxml2 create the necessary namespace
> declarations in `copied_node` to ensure that is namespace-
> wellformed. It will also set the appropriate base URI, making
> sure that it doesn=E2=80=99t override an existing base URI if the XHTML
> fragment defines one itself.
>=20
> For the whole thing to work, there *has* to be a root element
> wrapping all the children, so I was going to replace the
> `children` boolean with a `rewrap` boolean; if `rewrap` is true,
> I was going to force the document element to be a `div` in the
> `` namespace. That would also allow
> easy support of `html:body` embdedded in RSS 2.0 items. :-)
>=20
> But I didn=E2=80=99t do that yet, because I was going to add the same
> sort of logic to `common_html_to_xhtml` at that point, when I
> discovered that it doesn=E2=80=99t seem to be correct yet, as noted
> above.
>=20
> With all that in place, you would simply drop the `if(baseURL)`
> part in `atom10_parse_content_construct` et al, and would instead
> simply pass the `baseURL` as a parameter to `extractHTMLnode` and
> `common_html_to_xhtml`, and these functions would then internally
> take care of the base URI. That would simplify the feed parsers
> and keep the logic where it belongs.
>=20
> With all that in place and with Gecko running in XHTML mode,
> Liferea should pass all the XML namespace conformance tests from
> the Atom wiki, which means inline MathML and SVG in feed entries
> would render correctly. It should also pass all the XML base
> conformance tests. That would make Liferea one of the most
> advanced aggregators available for any platform. (Only Shrook and
> Snarfer are currently as conformant.) :-)
>=20
> Regards,
> --=20
> Aristotle Pagaltzis // <>
>=20
>=20
> -------------------------------------------------------
> This SF.Net email is sponsored by xPML, a groundbreaking scripting lang=
uage
> that extends applications into web and mobile media. Attend the live we=
bcast
> and join the prime developer group breaking into this new coding territ=
ory!
>
=3D121642
> _______________________________________________
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> Liferea-devel@...
> | http://sourceforge.net/p/liferea/mailman/liferea-devel/?viewmonth=200603&viewday=8 | CC-MAIN-2014-41 | refinedweb | 1,611 | 71.95 |
Derived from IRC +Log
7 items remaining on the agenda: Approval of May 29 telcon minutes [0] (12.40 + 5) Review action items, see [1] (12.45 + 5) Status reports. In general, reporters should be able to describe what is GETF report (1.15 + 30) Shall we publish the Part 1 and Part 2 documents [2] and [3] as WD's? Comments against Test Collection docs (1.45 + 15) LC decisions(2.00 + 30) AOB f2f host is Software AG
<Yves> Editors: DONE <Yves> Editors: DONE <Yves> Editors: pending( was first Editors AI) <Yves> MarkB: Pending <Yves> Yin Leng & PaulD: DONE <Yves> Yin Leng: DONE df: thanks to Yin-Leng and PaulD for work on charmod review
primer update: no news df: update available when? nilo: couple of weeks df: GETF discussion will highlight some changes needed in primer conformance: can we cover that under #8? ak: yes usage: john's not here email: no updates media type: markB not here
df: noah? nm: GETF on rush program to produce a proposal, discussed architecture issues w/http binding and RPC issues nm: few days ago GETF drafted me to integrate the changes into the spec, cf helped with HTTP binding and MEP <DavidF> re. primer update - nilo simply signalled he will be available over the next couple of weeks nm: all changes made and handed off to hfn to incorporate email comments nm: should we go into architectural points? df: yes please:) <DavidF> "a little bit of architecture would be a good thing" nm: introduced sections covering 1) call out simple feature that describes "web methods", references HTTP spec (GET, POST, PUT, DELETE, etc.) nm: suggests you should use GET or POST nm: useful independent of RPC nm: 2) RPC layer, based largely on proposal I circulated one or two weeks ago nm: should know which arguments identify the resource as distinct from those that represent state nm: when you use RPC on the Web, you SHOULD, where practical, make sure that identifying information appears in the URI nm: we don't say how that encoding should be done nm: take a step back nm: we used to have one MEP - request/response 3) added new MEP called SOAP response nm: if operation you are doing is "safe" retrieval, no body to be sent, no headers, etc. then RPC is sent using new MEP, use new feature to specify web method GET nm: other circumstances, use request/response and POST web method nm: anything else? hfn: no, good enough df: notes that document is very shortly forthcoming to WG for review/approval jacek: what is status of consensus of the name of the new MEP df: consensus in GETF is that it will be called "SOAP Response" Jacek: have expressed some concern that it may carry some significant data nm: it does df: does that answer your question jacek: yes df: here's what we're suggesting we do in terms of rolling this out df: see my email on additional info for agenda item #7 df: we think this is about ready to go to TAG, signal to them that we'd like a fast turnaround df: suggest we ask for review by this time next week df: send heads up email to TAG today is email under discussion df: we'll go through comments/concerns and roll into a document based on current ed-copy snapshot df: tomorrow pm, WG can see fully integrated version of part 2 df: as ed copy df: WG is encouraged to look at that, evaluate it and if you need to make a decision as to whether this should go to a wider audience... e.g. this document represents a consensus df: if I don't see any negative comments on the list, i'll inform the TAG df: is that schedule okay with WG? No objections raised. Chair asserts the schedule is OK with the WG. df: one additional point, WG gets 'til Tuesday to get any specific feedback and we deal with those on telcon next week df: I'll ask WG if the disposition of the comments and document are ready to go out as LC WD df: TAG, we really need to make sure they get a chance to review (monday is when they meet) df: is that okay? nilo: its really part 2 that we're talking about, not primer changes, right? df: correct df: one of the things that GETF will have to do in short order df: GETF to figure out what goes in primer on tomorrow's call df: has been some concern expressed as to need for education df: first part of plan is to get closure with WG, GETF and TAG df: need to figure out how to handle conformance document df: we really just arrived at this point, still trying to figure out what all of the implications are df: going to take silence as acceptance of first part of plan df: critical part is WG review comments due by Tuesday EOB df: to editors, can we make changes with change bars in it? hfn: yup nm: we're not doing anything beyond what style sheet used today? not 100% reliable nm: style sheet needs to be updated mh: I can hack that tomorrow nm: great df: I'm hearing no pushback on comments on revisions in time for next week's telcon No objections raised. df: i take that as acceptance by WG then ak: will hacked stylesheet show diffs in tables? mh: yup df: going to need to figure out how to cascade changes to conformance and primer df: i am disinclined to do that now, take off line with editors of various documents
df: shall we publish current part1 and part 2 as WDs? df: unclear to me (before) how long GETF would be able to address the TAG issues, really concerned to get closure so stuff didn't dribble in and out of those docs df: given we've agreed to plan for GETF, i am inclined now NOT to pose question, because i think it'll take time away from them cranking through GETF changes df: on other hand, if TAG can't respond with their comments for 2 weeks... are there any opinions from the WG? hfn: as one of the editors with limited amount of time, strongly encourage us not to publish hfn: not sure who customers of such a WD would be... docs already ~public as editors draft df: anyone feel strongly that we should publish now? silence df: okay, move on to #8
ak: don mullen's comments incorporated ak: put in significant amount of editorial changes, that's current status. not published as yet ak: issue 194... spec text says something different than resolution ak: encoding style attribute allowed on SOAP elements hfn: we came to pretty clear resolution that it may not ak: but spec doesn't say that explicitly sect 5.1.1 hfn: fwiw, think it is reasonable to write it up more clearly, but... jjm: don't think it was me who put it in mh: could have been me ak: is this included in current ed copy? hfn: yup looking... ak: don't see it <DavidF> <DavidF> is 5.1.1 in 31 may hfn: i think that's right, whther it would be useful to say MUST NOT appear, I'm fine with that df: so what's there is okay, but clarification that it must not appear elsewhere is okay? hfn: yes df: URI points to section we're discussing df: anyone unhappy about adding line to 5.1.1 saying MUST NOT appear elsewhere mh: for consistency, we've been saying where things *can* go, not where they *cannot* df: why then is it an issue for this particular test? ak: because resolution text says something different df: can we change the assertion in the spec text to say "MAY ONLY appear ...."? <DavidF> changing "The encodingStyle attribute information item MAY ONLY appear on:" df: any objections? silence Chair asserts the WG has agreed to make the change to the spec. ACTION 1=Editors to fix assertion in 5.1.1 to say MAY ONLY or something like that, to better reflect the spirit of issue 194 resolution that can be tested as an assertion ak: thinking of adding section about...??? hfn: yes, there's a bunch of choices to be made... hfn: think we have to be careful df: I'm confused hfn: rpc:procedure not found e.g. says MAY, but we don't say what's right way to do it nm: occasions where spec says you MAY but if you do you MUST do it this way ak: agree with noah df: e.g. if RPC used, then assertion ak: not exactly, we say that it is not required for conformance df: so there's just a blanket statement in beginning that says ... df: one way to categorize which tests are obligatory and which are not ak: at beginning of collection, add paragraph which lists things like procedure not present, fault reason and mention that these are in the test collection, but conformance to the collection, you don't have to use these values hfn: or things like reason, and others that are used in specific tests? hfn: think that is editorial ak: but issue you raised applies to more than procedure not present df: unless there are other opinions, suggest we leave this as editorial decision, you deal as you think best df: other questions for anish? none df: <puts on scheduler hat> df: what's timeline for rolling these changes into test collection doc? ak: Lynne and I think that EOD saturday, we should be able to roll these changes in, is this okay? ak: this doesn't include GETF changes df: right silence df: would be super useful to look at what impact GETF would have on test collection df: wonder if there are people on call that could volunteer to review GETF changes and noodle on how that would impact test collection No one volunteers. nm: one of the decisions we reached this morning was to take some of the SHOULDs and make them mushier nm: takes these off the table nm: do we have tests that test binding, like HTTP binding? ak: yes nm: for MEPs or features? df: some of RPC tests may disappear? nm: don't think so, just in new sections we've added df: i see df: back to the original question, think it would speed us up lots if someone could look at what we publish tomorrow and figure out what might be needed to change df: please contact me directly after the call, otherwise we'll have to serialize this activity ak: question w/r/t spec version, currently synched up with 31-May, do editors know when next version will be available? df: the only changes to the 31-May version will be GETF ak: looking at ed copy and do see changes in there, wondering if these are w/r/t 31-May or changes w/r/t 14-May hfn: there was one issue we found today, change yes to true has been fixed, only change I know of df: so that's the only diff between 31-May? hfn: yes df: 31-May is stable version? hfn: yup df: other questions? otherwise expect to see revised test collections doc over w/e ak: yes ACTION: Lynne and Anish to publish new test collections doc over this w/e
df: okay, on to LC decision df: number of things we need to figure out df: and other types of information we need to capture, see #9, 4 subparts df: I) a list of documents for LC, also listed type (e.g. WD, ID, etc.) and type of review we are requesting and comments to be sent df: we need to agree that is what we are going to do II) list of groups we are asking feedback from df: want to know if that's the right list df: III) we are going to try to go from LC to PR skipping CR, so we need to provide right evidence of impls df: need to signal our intent to the world df: and conditions under which WG will make that jump IV) announce for LC review needs a date when period ends, suggests date <Noah> Do we have implementation issues with the new RPC and HTTP GET stuff? prolly df: we can do this via email or now df: or next week nm: think its in spirit of this to demonstrate GET ala GETF changes nm: (MEP and RPC suggestions/recommendations, etc.) df: in terms of impls?? nm: yes df: lets wait to we get to III nm: okay df: okay, I)... df: re Parts 0, 1, 2 of the spec, I guess that's noncontroversial, any comments? silence Chair asserts the WG has decided to accept the publication of Parts 0,1,2 of the spec as stated in the agenda. df: re. test collection, any comments? silence Chair asserts the WG has decided to accept the publication of the Test Collection document as stated in the agenda. df: i believe with that decision we can close issue #36 whcih we had deferred until we decided to publish the Test Collection document df: agree to publish test collection ACTION 3=DF to send closing text for issue #36 to xmlp-comments df: re. the "Email Binding" document, we publish it as Note, but we don't specifically ask for comments df: note the change to its name, and its publication as a Note... df: any objections? silence df: i take that as agreement Chair asserts the WG has decided to accept the publication of an Email Binding document as stated in the agenda. df: next proposal is that we mention in our LC announcement that we plan on writing a non-normative document during LC that describes an attachment feature... we decided this a while back hfn: we don't promise we'll be done, do we? df: was going to say "we plan to create" hfn: we plan to start work? <Noah> How about we plan to consider deciding whether to start thinking about possibly creating an attachments document? df: i'd like to signal that we plan to complete work hfn: no particular reason we want to say we have another spec ready df: you're using words like spec, making it sound bigger than I intended df: imagine it would be a Note hfn: well... df: would you be happier saying by Recommendation? hfn: yes, that would be fine okay by me df: okay then, any other comments? Silence. df: next, we make reference to appl/soap+xml ID df: mb would not submit to IANA until we had a stable namespace URI hfn: also because we didn't know whether GETF impacts this or not hfn: little tricky hfn: might very well be that we're ready to move forward with SOAP1.2, but have cross dependency with IANA df: okay, I'll take this one out then, and we'll bring it back later hfn: okay ACTION 4= Chair to chat with Mark B to figure out what to say about ID in LC announce df II) list of WGs cf: suggests add XKMS and XMLEnc cf: also asks if webont is part of S/W yl: says yes df: okay, we'll add these two (XKMS and XML Enc) nm: how bout TAG? df: okay, I'll add TAG df: thanks, on to III) df: exit criteria for advancing to PR df: this doesn't guarantee we move from LC to PR df: one friendly amendment, jacek points out that it should say there are two, interoperating and different implementations of all non-optional features df: any other comments? nm: more as a warning to ourselves, w/r/t GETF and RPC changes... nm: hope we would see implementation experience during LC, warning should be if we want to get out of LC, we need to see implementations. jacek: so you are saying we should list things we want to see implemented and those we don't? <DavidF> s/all non-optional/non-optional and optional/ nm: text df has proposed is fine, just reminding the group that last time we looked at this and asked if there were impls, there were a bunch that said that they were very close and if we set this criteria (then) we could achieve our objective. just reminind the WG that the changes for GETF weren't part of that consideration jacek: don't want to see us leave LC without some impl experience df: we wouldn't meet out exit criteria then df: we could have our exit criteria only mandatory features df: any objections to accepting revised text as exit criteria? silence Chair asserts the WG has decided to accept the text in the agenda and as amended by Jacek's recent email. df: okay then df: if we get towards the end of july, we have option for extending LC period jacek: or go to CR? df: becomes academic at that point jacek: agree df: on to IV) really just a note that we decided to hold a f2f last week of july * JacekK notices that iv) does mention CR. 8-) df: we really want to finish the week before cf: that was me df: that would put end of comment period july 19 df: that makes for 5 week LC period df: okay? silence Chair asserts the WG has decided to accept end of LC as being July 19. df: that's all she wrote, we can adjourn early unless there is anything else | http://www.w3.org/2000/xp/Group/2/06/05-pminutes.html | CC-MAIN-2017-04 | refinedweb | 2,976 | 66.61 |
The ADO.NET framework is made of two distinct groups of constituent classes: the generic container classes and the data source-aware classes. The data source-aware classes are still part of the System.Data namespace but are tightly integrated with a specific data source. Although data source-aware classes provide general-purpose functionality, their implementation is based on the features of a particular data source. So ADO.NET command classes, for example, might have a different set of methods depending on whether they work against an OLE DB provider or Microsoft SQL Server.
The container group of ADO.NET classes are abstracted from the physical data source. Although they represent data tables, rows, columns, and primary keys, nothing in their programming interface keeps track of the content source. Thus, a DataTable object or a DataSet object can be filled with data retrieved from a commercial database server as well as filled with packets of data read from a connected device.
The point of contact between data source-aware classes and container classes is represented by a new breed of component: the .NET data provider. Such managed data providers in .NET play the same role as OLE DB providers in the COM world. In the past few years, companies invested a lot of money in the OLE DB technology. OLE DB turned the vision of a universal data access strategy, theorized in the Universal Data Access (UDA) specification, into concrete programming calls. OLE DB is built on the idea of using a suite of COM interfaces to read and write the contents of data sources irrespective of their relational, hierarchical, or flat architecture.
Maybe the C++ oriented design that OLE DB came up with is a bit too complex for widespread use, but it definitely provides great flexibility when exposing proprietary data in a standardized way. OLE DB supplies a common COM-based API that enables consumer applications to talk to data provider modules without knowing about internal details. Each provider encapsulates a particular data store such as a commercial database, a system component such as Active Directory, or, more simply, the manager of proprietary data with a custom format. According to the UDA specification, OLE DB is the tool of choice to universalize data access.
The advent of .NET pushed all COM-based technologies to the side, and OLE DB was no exception. All .NET applications that want to access data by using OLE DB providers must bust out of the common language runtime environment and rely on COM interoperability and enterprise services. Such a move creates overhead that of course never benefits overall application performance. To ameliorate these issues, which are at the core of data access, .NET introduced managed data providers. Managed data providers are patterned after OLE DB providers but also access data within the context of the common language runtime in a simpler and more effective way.
In the pre-.NET era, OLE DB providers were your primary option for making your proprietary data publicly available—that is, available in a widely accepted format. For relatively simple data formats (such as comma-separated files), you also had the option of using the OLE DB Simple Provider Toolkit. The Simple Provider Toolkit provides tools for writing (even in Microsoft Visual Basic) shrink-wrapped OLE DB providers with limited functionality. In .NET, exposing proprietary data requires a more sophisticated approach, and you have multiple and equally powerful options from which to choose. | http://etutorials.org/Programming/Web+Solutions+based+on+ASP.NET+and+ADO.NET/Part+III+Interoperability/Exposing+Data+to+.NET+Applications/ | CC-MAIN-2018-09 | refinedweb | 575 | 53.71 |
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Even better, Python allows you to construct your data structures, making it a tremendously versatile language. While data structures may not appear to be very relevant to a newbie, believe us when we say that the deeper you go, the more critical your data structure choice becomes.
Python allows you to automate almost anything. From sending emails and filling up PDFs and CSVs (if you’re not familiar with this file format, it’s used by Excel, for example) to connecting with external APIs and performing HTTP requests, there’s a lot you can do with it. Whatever your concept is, Python and its modules and tools are more than likely to help you realize it.
Python’s libraries make the language extremely strong, allowing developers to tackle everything from machine learning and web scraping to operating system management.
Python also has a good support structure and a massive community of users. The language’s popularity continues to grow, and articles covering virtually all of the language’s concepts continue to appear on the web — a quick search is bound to turn up some exciting blog or StackOverflow posts. Alternatively, post your query to any Python forums.
You won’t be alone with your dilemma for long.
A vibrant community surrounds Python, and the language itself is constantly evolving. Plus, new third-party libraries appear regularly.
Python has found application in various professions and businesses, including science, data analysis, mathematics, networking, and more, despite not being a darling of the software development industry.
What can Python be used to automate?
Nearly anything!
You may automate almost any repetitious task with a bit of effort.
To do so, all you need is Python installed on your computer. We wrote all of the examples herein Python 3.9 and the relevant libraries. We’re not going to teach you Python; I’m just going to show you how easy it is to automate with it. We used iPython in the examples below, which is a tool that allows you to develop code interactively and step by step.
Python’s built-in libraries should be enough for basic automation. In other circumstances, we’ll tell you what needs to be installed.
File reading and writing
Reading and writing files is an activity that Python can help you automate quickly. First, all you need to know is where the files in your filesystem are located, their names, and which mode to open them in.
We used the statement to open a file in the example below, which is a method we highly suggest. Then, when the block code is complete, the file is automatically closed, and the cleanup is taken care of for us. More information is available in the official documentation.
Let’s use the open() method to load the file. The first input to open () is a file path, and the second is an opening mode. The file is loaded by default in read-only mode (‘r’).
with open(“text_file.txt”) as f: print(f.read())
Try the readlines() function to read the material line by line; it saves the data to a list.
with open(“text_file.txt”) as f: print(f.readlines())
The file’s contents are also changeable. However, this overwrites the original material! Loading it in write (‘w’) mode is one of the alternatives for doing so. The open () method’s second argument selects the mode.
with open("text_file.txt", "w") as f: f.write("Some content") with open("text_file.txt") as f: print(f.read())
One excellent approach is to open the file in append (‘a’) mode, which means that the new material is appended to the end of the file while the previous content is preserved.
with open("text_file.txt", "a") as f: f.write("\nAnother line of content") with open("text_file.txt") as f: print(f.read())
As you can see, Python makes reading and writing files a breeze. Feel free to learn more about the subject, particularly the file-opening modes, which are combined and extended! Combining writing to a file with Web scraping or interacting with APIs opens up a world of possibilities for automation! As a next step, you might want to look into an excellent library CSV that can help you read and write CSV files.
Sending emails is another Python operation that you can easily automate. Python includes the fantastic smtplib library, which allows you to send emails via the Simple Mail Transfer Protocol (SMTP). Continue reading to learn how to use the library and Gmail’s SMTP server to send emails.
Naturally, you’ll need a Gmail account, and we strongly advise you to create a separate account for the sake of this script.
Why?
Because you’ll need to turn on the Allow less secure apps option, which makes it simpler for outsiders to access your personal information, set up your account today, and then let’s get started with the code. First and foremost, we must establish an SMTP connection.
import getpass import smtplib HOST = "smtp.gmail.com" PORT = 465 username = "username@gmail.com" password = getpass.getpass("Provide Gmail password: ") Provide Gmail password: server = smtplib.SMTP_SSL(HOST, PORT)
We use getpass to securely prompt the password and smtplib to create a connection and deliver emails, and we import the required built-in modules at the top of the program. The variables are set in the steps that follow. Gmail requires both HOST and PORT – they’re constants, which is why they’re written in caps.
Then you type in the password and your Gmail account name, which are saved in the username variable. It’s best to use the getpass module to enter the password. It asks for a password and does not repeat it back to you when you type it in. The script then uses the SMTP_SSL() function to establish a secure SMTP connection. The server variable holds the SMTP object.
server.login(username, password) (235, b'2.7.0 Accepted') server.sendmail( "from@domain.com", "to@domain.com", "An email from Python!", ) {} server.quit() (221, b'2.0.0 closing connection s1sm24313728ljc.3 – gsmtp')
Finally, you use the login() method to verify your identity, and that’s all! The sendmail() method will now be available for sending emails. Please remember to use the quit() method to clean up after yourself.
Scraping the internet
Web scraping is a technique for extracting data from Web pages and saving it to your computer. Assume that part of your job entails pulling data from a regularly visited website. Scraping could be highly effective in this situation since once code is developed, it can be executed multiple times, making it particularly useful when dealing with massive amounts of data.
Manually extracting data takes a long time and lots of clicking and searching.
Scraping data from the web has never been easier than using Python. However, before you can analyze and extract data from HTML code, you must first download the target website. The requests library will take care of everything – install it.
In your console, type the following:
pip install requests
Now that the page has been downloaded, we may extract the data we need. BeautifulSoup comes in handy here. The library aids in the parsing and extraction of information from structured files. The library must, of course, be installed first. Type the following in your console, just like before:
pip install beautifulsoup4
Let’s look at a simple example to learn how the automation feature works. The HTML code of a webpage we chose for processing is concisely understandable, considering its function is to display the current week of the year. Right-click anywhere on the page and select View page source to study the HTML code.
Then start the interactive Python by typing ipython in the console and begin fetching the page using requests:
import requests response = requests.get(" response.status_code
The page is then downloaded and saved in a response variable after that. In the interactive terminal, type response.content to see the contents. The HTTP status (200) shows that the request is completed successfully.
It’s now up to BeautifulSoup to finish the job. We begin by importing the library and then constructing the soup BeautifulSoup object. The fetched data is used as an input to generate the soup object. We also tell the library which parser to use, which is html.parser for HTML pages.
from bs4 import BeautifulSoup soup = BeautifulSoup(response.content, "html.parser") print(soup)
The HTML file has now been saved to the soup object. It is shown as a nested structure (its fragment is printed above). There are a few different ways to get around the structure. The following are a handful of them.
soup.title soup.title.string soup.find_all("p")
You can quickly extract the page’s title or locate all of the content tags found in the data. The easiest way to acquire a sense of it is to play about with the thing.
When looking for data hidden in a table under the heading tag, we may use find to extract the table from the soup object and store it in a variable. It’s straightforward to get all the tags that store the information once the table has been saved. When you use find_all() on table_content, you’ll get a list of tags like . Iterate through the list and get_text() from each item to output them in a nice-looking format.
table = soup.find("table") print(table) table_content = table.find_all("td") for tag in table_content: print(tag.get_text())
We extracted exciting content from the page using only a few commands thanks to the beautiful BeautifulSoup package and simple steps. Libraries are great and beneficial when working with more significant, hierarchical HTML texts.
Interacting with a Programming Interface (API)
API interaction grants you superpowers! Let us explore this application’s example: pulling air quality data updates from the web.
Various APIs are accessible, but the Open AQ Platform API appears to be the most appealing because it does not require authentication (the relevant documentation can be found here: Open AQ Platform API ). The API returns air quality data for the provided location when queried. We used the requests library the same way we did in the previous example to get the data.
import requests response = requests.get(" response.status_code response_json = response.json()
The code above retrieved Paris air quality statistics, focusing solely on the PM25 figure. You can personalize the search in any way you like; if you want to learn more about it, consult the API documentation.
The json() method on the response object is used. The script then saved the extracted data in key-value JSON format, which is more readable and cleaner. The sample response is shown below.
print(response_json)
The actual values drawn are concealed under the results key, with the most recent pulls near the head of the list, allowing us to extract the most recent value by reading the list’s first element with index zero. We can retrieve the PM25 concentration in the air in Paris on Feb 19, 2022, using the code below.
print(response_json["results"][0])
Data Compilation
It can take a long time to look through reports, PDFs, Excel spreadsheets, and other papers that contain information and data. Whether you need to extract data from a document or a webpage, you may use Python code to compile the information you need.
Python includes several modules that assist with data reading. You can develop a Python script to swiftly scan through a document and compile the data you need to extract no matter what sort of document or data source you’re dealing with. You may even use Python to generate the data you need in any format you wish.
How many hours have you spent traveling between papers and web pages while manually inputting information and formatting it to match your organization’s needs? If you learn Python, you can say goodbye to copying and pasting massive amounts of data.
Produce Reports
This duty is similar to data collection, but if you’ve ever had to prepare a regular report for coworkers or bosses, you know how time-consuming it can be. Creating reports entails more than simply data collection. You must put information into context. Your company’s preferred reporting format is likely to be the same.
Python can help you save time by compiling the data you need for your report and generating it. You can program your Python script to create reports on a specified timetable. The parameters you’d like to consider and your Python code will take care of the rest.
If you usually email your reports to the people who need to know, you may use your email automation to do so as well.
It is a real-world example of how Python automation may help a firm become more efficient by simplifying and expediting essential activities and workflow.
Python has the advantage that if the people who receive your reports are also Python users, they can automate the reading of the report and extract any actionable data. Imagine the efficiency of a company that is completely automated using Python.
Conclusion
Scripts written in Python are used to automate a variety of tasks. Humans or bots can execute Python scripts. Executing a task or sequence with little or no human intervention is called automation. A bot refers to a software code that automates the execution of Python scripts. Automation, especially for repeated processes, can save you time and boost productivity.
These are just a handful of Python’s time-consuming chores that can help you automate. Python’s automation capabilities and uses are, of course, nearly limitless. Python scripts are also used to automate web building and other more complicated activities.
You don’t need to be a software developer or have a lot of programming knowledge to construct sophisticated, time-saving automation scripts with Python. However, the more you understand Python automation, the more you will benefit from it. | https://www.codeunderscored.com/how-to-automate-repetitive-tasks-in-python/ | CC-MAIN-2022-21 | refinedweb | 2,702 | 65.12 |
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Chapter 8. Bump Mapping
This chapter enhances the per-fragment lighting discussion in Chapter 5 with texture-encoded normals to create an effect known as bump mapping. This chapter has the following five sections:
- "Bump Mapping a Brick Wall" introduces bump mapping of a single rectangle.
- "Bump Mapping a Brick Floor" explains how to make bump mapping consistent for two planes.
- "Bump Mapping a Torus" shows how to bump map curved surfaces that have mathematical representations, such as the torus.
- "Bump Mapping Textured Polygonal Meshes" shows how to apply bump mapping to textured polygonal models.
- "Combining Bump Mapping with Other Effects" combines bump mapping techniques with other textures, such as decals and gloss maps, for more sophisticated shading.
8.1 Bump Mapping a Brick Wall
The earlier presentation of lighting in Chapter 5 discussed per-vertex and per-fragment light computations. This chapter introduces an advanced lighting approach commonly called bump mapping. Bump mapping combines per-fragment lighting with surface normal perturbations supplied by a texture, in order to simulate lighting interactions on bumpy surfaces. This effect is achieved without requiring excessive geometric tessellation of the surface.
As an example, you can use bump mapping to make surfaces appear as if they have bricks protruding from them, and mortar between the bricks.
Most real-world surfaces such as brick walls or cobblestones have small-scale bumpy features that are too fine to represent with highly tessellated geometry. There are two reasons to avoid representing this kind of fine detail using geometry. The first is that representing the model with sufficient geometric detail to capture the bumpy nature of the surface would be too large and cumbersome for interactive rendering. The second is that the surface features may well be smaller than the size of a pixel, meaning that the rasterizer could not accurately render the full geometric detail.
With bump mapping, you can capture the detailed surface features that influence an object's lit appearance in a texture instead of actually increasing the object's geometric complexity. Done well, bump mapping convinces viewers that a bump-mapped scene has more geometry and surface richness than is actually present. Bump mapping is most compelling when lights move in relation to a surface, affecting the bump-mapped surface's illuminated appearance.
Benefits of bump mapping include:
- A higher level of visual complexity in a scene, without adding more geometry.
- Simplified content authoring, because you can encode surface detail in textures as opposed to requiring artists to design highly detailed 3D models.
- The ability to apply different bump maps to different instances of the same model to give each instance a distinct surface appearance. For example, a building model could be rendered once with a brick bump map and a second time with a stucco bump map.
8.1.1 The Brick Wall Normal Map
Consider a wall made of bricks of varying texture stacked on top of each other in a regular pattern. Between the bricks is mortar that holds the bricks together. The mortar is set into the wall. Though a brick wall may look flat from a distance, on closer inspection, the brickwork pattern is not flat at all. When the wall is illuminated, the gaps between bricks, cracks, and other features of the brick surface scatter light quite differently than a truly flat surface.
One approach to rendering a brick wall would be to model every brick, mortar gap, and even individual cracks in the wall with polygons, each with varying surface normals used for lighting. During lighting, the surface normals at each vertex would alter the illuminated surface appearance appropriately. However, this approach may require a tremendous number of polygons.
At a sufficiently coarse scale, a brick wall is more or less flat. Aside from all the surface variations that we've mentioned, a wall's geometry is quite simple. A single rectangle can adequately represent a roughly flat rectangular section of brick wall.
8.1.2 Storing Bump Maps As Normal Map Textures
Before you encounter your first Cg program that lights surfaces with bump mapping, you should understand how textures for bump mapping are created and what they represent.
Conventional Color Textures
Conventional textures typically contain RGB or RGBA color values, though other formats are also available. As you know, each texel in an RGB texture consists of three components, one each for red, green, and blue. Each component is typically a single unsigned byte.
Because programmable GPUs allow arbitrary math and other operations to be performed on the results of texture lookups, you can use textures to store other types of data, encoded as colors.
Storing Normals in Conventional Color Textures
Bump maps can take a variety of forms. All the bump mapping examples in this book represent surface variations as surface normals. This type of bump map is commonly called a normal map, because normals, rather than colors, are stored in the texture. Each normal is a direction vector that points away from the surface and is usually stored as a three-component vector.
Conventional RGB texture formats are typically used to store normal maps. Unlike colors that are unsigned, direction vectors require signed values. In addition to being unsigned, color values in textures are typically constrained to the [0, 1] range. Because the normals are normalized vectors, each component has a [-1, 1] range.
To allow texture-filtering hardware for unsigned colors to operate correctly, signed texture values in the [-1, 1] range are range-compressed to the unsigned [0, 1] range with a simple scale and bias.
Signed normals are range-compressed this way:
colorComponent = 0.5 * normalComponent + 0.5;
After conventional unsigned texture filtering, range-compressed normals are expanded back to their signed range this way:
normalComponent = 2 * (colorComponent - 0.5);
By using the red, green, and blue components of an RGB texture to store the x, y, and z components of a normal, and range-compressing the signed values to the [0, 1] unsigned range, normals may be stored in RGB textures.
Recent GPUs support signed floating-point color formats, but normal maps are still often stored in unsigned color textures because existing image file formats for unsigned colors can store normal maps. Recent GPUs have no performance penalty for expanding range-compressed normals from textures. So whether you store normals in a range-compressed form (using an unsigned texture format) or use a signed texture format is up to you.
Generating Normal Maps from Height Fields
Authoring normal maps raises another issue. Painting direction vectors in a computer paint program is very unintuitive. However, most normal maps are derived from what is known as a height field. Rather than encoding vectors, a height field texture encodes the height, or elevation, of each texel. A height field stores a single unsigned component per texel rather than using three components to store a vector. Figure 8-1 shows an example of a brick wall height field. (See Plate 12 in the book's center insert for a color version of the normal map.) Darker regions of the height field are lower; lighter regions are higher. Solid white bricks are smooth. Bricks with uneven coloring are bumpy. The mortar is recessed, so it is the darkest region of the height field.
Figure 8-1 A Height Field Image for a Brick Bump Map
Converting a height field to a normal map is an automatic process, and it is typically done as a preprocessing step along with range compression. For each texel in the height field, you sample the height at the given texel, as well as the texels immediately to the right of and above the given texel. The normal vector is the normalized version of the cross product of two difference vectors. The first difference vector is (1, 0, Hr – Hg ), where Hg is the height of the given texel and Hr is the height of the texel directly to the right of the given texel. The second difference vector is (0, 1, Ha – Hg ), where Ha is the height of the texel directly above the given texel.
The cross product of these two vectors is a third vector pointing away from the height field surface. Normalizing this vector creates a normal suitable for bump mapping. The resulting normal is:
This normal is signed and must be range-compressed to be stored in an unsigned RGB texture. Other approaches exist for converting height fields to normal maps, but this approach is typically adequate.
The normal (0, 0, 1) is computed in regions of the height field that are flat. Think of the normal as a direction vector pointing up and away from the surface. In bumpy or uneven regions of the height field, an otherwise straight-up normal tilts appropriately.
As we've already mentioned, range-compressed normal maps are commonly stored in an unsigned RGB texture, where red, green, and blue correspond to x, y, and z. Due to the nature of the conversion process from height field to normal map, the z component is always positive and often either 1.0 or nearly 1.0. The z component is stored in the blue component conventionally, and range compression converts positive z values to the [0.5, 1] range. Thus, the predominant color of range-compressed normal maps stored in an RGB texture is blue. Figure 8-1 also shows the brick wall height field converted into a normal map. Because the coloration is important, you should refer to the color version of Figure 8-1 shown in Plate 12.
8.1.3 Simple Bump Mapping for a Brick Wall
Now that you know what a normal map is, you're ready for your first bump mapping example. The example will show how to use the brick wall normal map in Figure 8-1 to render a single bump-mapped rectangle to look like a brick wall. When you interactively move a single light source, you will change the appearance of the wall due to the brick pattern in the normal map, as shown in Figure 8-2. The figure shows the effect of three different light positions. In the left image, the light is at the lower left of the wall. In the center image, the light is directly in front of the wall. And in the right image, the light is at the upper right of the wall.
Figure 8-2 A Bump-Mapped Brick Wall with Different Light Positions
To keep things simple, this first example is quite constrained. We position the rendered wall rectangle in the x-y plane, with z equal to 0 everywhere on the wall. Without bump mapping, the surface normal for the wall would be (0, 0, 1) at every point on the wall.
The Vertex Program
The C8E1v_bumpWall vertex program in Example 8-1 computes the object-space vector from a vertex to a single light source. The program also transforms the vertex position into clip space using a conventional modelview-projection matrix, and it passes through a 2D texture coordinate set intended to sample the normal map texture.
Example 8-1. The C8E1v_bumpWall Vertex Program
void C8E1v_bumpWall(float4 position : POSITION, float2 texCoord : TEXCOORD0, out float4 oPosition : POSITION, out float2 oTexCoord : TEXCOORD0, out float3 lightDirection : TEXCOORD1, uniform float3 lightPosition, // Object space uniform float4x4 modelViewProj) { oPosition = mul(modelViewProj, position); oTexCoord = texCoord; // Compute object-space light direction lightDirection = lightPosition - position.xyz; }
The Fragment Program
The dot product of the light vector and the normal vector for diffuse lighting requires a unit-length light vector. Rather than implement the normalization directly with math operations, the C8E2f_bumpSurf fragment program in Example 8-2 normalizes the interpolated light direction vector using a normalization cube map, which will be explained shortly. For now, think of a normalization cube map as a way to take an unnormalized vector that is interpolated as a texture coordinate set and generate a normalized and range-compressed version of it. Because the program implements normalization with a cube map texture access, this style of per-fragment vector normalization is fast and well suited for the broadest range of GPUs.
In addition to normalizing the interpolated light vector, the C8E2f_bumpSurf program samples the normal map with conventional 2D texture coordinates. The result of the normal map access is another range-compressed normal.
Next, the program's helper function, named expand , converts both the range-compressed normalized light direction and the range-compressed normal into signed vectors. Then the program computes the final fragment color with a dot product to simulate diffuse lighting.
Example 8-2 illustrates how the appearance of the brick wall changes with different light positions. The wall's surface, rendered with the C8E1v_bumpWall and C8E2f_bumpSurf programs, really looks like it has the texture of a brick wall.
Example 8-2. The C8E2f_bumpSurf Fragment Program
float3 expand(float3 v) { return (v - 0.5) * 2; // Expand a range-compressed vector } void C8E2f_bumpSurf(float2 normalMapTexCoord : TEXCOORD0, float3 lightDir : TEXCOORD1, out float4 color : COLOR, uniform sampler2D normalMap, uniform samplerCUBE normalizeCube) { // Normalizes light vector with normalization cube map float3 lightTex = texCUBE(normalizeCube, lightDir).xyz; float3 light = expand(lightTex); // Sample and expand the normal map texture float3 normalTex = tex2D(normalMap, normalMapTexCoord).xyz; float3 normal = expand(normalTex); // Compute diffuse lighting color = dot(normal, light); }
Constructing a Normalization Cube Map
Chapter 7 explained how you could use cube maps for encoding environment maps as a way to give objects a reflective appearance. To simulate surface reflections, the 3D texture coordinate vector used for accessing the environment cube map represents a reflection vector. But cube map textures can encode other functions of direction vectors as well. Vector normalization is one such function.
The Cg Standard Library includes a routine called normalize for normalizing vectors. The routine has several overloaded variants, but the three-component version is most commonly used. The standard implementation of normalize is this:
float3 normalize(float3 v) { float d = dot(v, v); // x*x + y*y + z*z return v / sqrt(d); }
The problem with this implementation of normalize is that basic fragment profiles provided by second-generation and third-generation GPUs cannot directly compile the normalize routine that we just presented. This is because these GPUs lack arbitrary floating-point math operations at the fragment level.
The normalization cube map—a fast way to normalize vectors supplied as texture coordinates—works on all GPUs, whether or not they support advanced fragment programmability.
Note
Even on GPUs supporting advanced fragment profiles, using normalization cube maps is often faster than implementing normalization with math operations, because GPU designers highly optimize texture accesses.
Figure 8-3 shows how a cube map normalizes a vector. The vector (3, 1.5, 0.9) pierces the cube map on the positive x face of the cube map, as shown. The faces of the normalization cube map are constructed such that the texel pierced by any given direction vector contains the normalized version of that vector. When signed texture components are unavailable, the normalized version of the vector may be stored range-compressed and then expanded prior to use as a normalized vector. This is what the examples in this chapter assume. So the range-compressed texel pierced by (3, 1.5, 0.9) is approximately (0.93, 0.72, 0.63). When this vector is expanded, it is (0.86, 0.43, 0.26), which is the approximate normalized version of (3, 1.5, 0.9).
Figure 8-3 Using Cube Maps to Normalize Vectors
A resolution of 32x32 texels is typically sufficient for a normalization cube map face with 8-bit color components. A resolution of 16x16, and even 8x8, can also generate acceptable results.
The electronic material accompanying this book includes a normalization cube map, as well as source code for constructing normalization cube maps. All of your Cg programs can share just one normalization cube map.
8.1.4 Specular Bump Mapping
You can further enhance the preceding programs by adding specular and ambient lighting terms and by adding control over the diffuse material, specular material, and light color. The next pair of programs illustrate this.
The Vertex Program
Example 8-3 extends the earlier C8E1v_bumpWall example to compute the half-angle vector, which the rasterizer interpolates as an additional texture coordinate set. The C8E3v_specWall program computes the half-angle vector by normalizing the sum of the vertex's normalized light and eye vectors.
Example 8-3. The C8E3v_specWall Vertex Program
void C8E3v_specWall(float4 position : POSITION, float2 texCoord : TEXCOORD0, out float4 oPosition :) { oPosition = mul(modelViewProj, position); oTexCoord = texCoord; lightDirection = lightPosition - position.xyz; // Add the computation of a per-vertex half-angle vector float3 eyeDirection = eyePosition - position.xyz; halfAngle = normalize(normalize(lightDirection) + normalize(eyeDirection)); }
The Fragment Program
The corresponding fragment program, shown in Example 8-4, requires more modifications. In addition to normalizing the light vector with a normalization cube map as before, the updated fragment program also normalizes the half-angle vector with a second normalization cube map. Then, the program computes the dot product of the normalized half-angle vector with the perturbed normal obtained from the normal map.
Example 8-4. The C8E4f_specSurf Fragment Program
float3 expand(float3 v) { return (v - 0.5) * 2; } void C8E4f_specSurf(float2 normalMapTexCoord : TEXCOORD0, float3 lightDirection : TEXCOORD1, float3 halfAngle : TEXCOORD2, out float4 color : COLOR, uniform float ambient, uniform float4 LMd, // Light-material diffuse uniform float4 LMs, // Light-material specular uniform sampler2D normalMap, uniform samplerCUBE normalizeCube, uniform samplerCUBE normalizeCube2) { // Fetch and expand range-compressed normal float3 normalTex = tex2D(normalMap, normalMapTexCoord).xyz; float3 normal = expand(normalTex); // Fetch and expand normalized light vector float3 normLightDirTex = texCUBE(normalizeCube, lightDirection).xyz; float3 normLightDir = expand(normLightDirTex); // Fetch and expand normalized half-angle vector float3 normHalfAngleTex = texCUBE(normalizeCube2, halfAngle).xyz; float3 normHalfAngle = expand(normHalfAngleTex); // Compute diffuse and specular lighting dot products float diffuse = saturate(dot(normal, normLightDir)); float specular = saturate(dot(normal, normHalfAngle)); // Successive multiplies to raise specular to 8th power float specular2 = specular * specular; float specular4 = specular2 * specular2; float specular8 = specular4 * specular4; color = LMd * (ambient + diffuse) + LMs * specular8; }
In the original C8E2f_bumpSurf program, the program outputs the diffuse dot product as the final color. The final color's COLOR output semantic implicitly clamps any negative dot product results to zero. This clamping is required by the diffuse lighting equation, because negative illumination is physically impossible. The C8E4f_specSurf program combines the diffuse and specular dot products, so the program explicitly clamps negative values to zero with the saturate Standard Library function:
Basic fragment profiles such as fp20 and ps_1_3 lack support for true exponentiation. To simulate specular exponentiation and support a broad range of fragment profiles, the program uses three successive multiplications to raise the specular dot product to the eighth power. Advanced profiles could use the pow or lit Standard Library functions for more generality.
Finally, the output color is computed by modulating the ambient and diffuse terms by a uniform parameter, LMd . The application supplies LMd , which represents the light color premultiplied by the material's diffuse color. Similarly, the LMs uniform parameter modulates the specular illumination and represents the light color premultiplied by the material's specular color.
Further Improvements
The C8E4f_specSurf program compiles under basic and advanced fragment profiles. Although this makes the bump mapping effect portable to a wider variety of GPUs, various improvements are possible if you target an advanced fragment profile. Following are a few examples.
C8E4f_specSurf binds the same normalization cube map texture into two texture units. As you saw in Chapter 7, this duplicate binding is required because basic fragment profiles can only sample a given texture unit with that texture unit's corresponding texture coordinate set. Advanced fragment profiles do not have this limitation, so a single normalizeCube cube map sampler can normalize both the light vector and half-angle vector.
C8E4f_specSurf also computes the specular exponent by raising the specular dot product to the eighth power using successive multiplies, because basic fragment profiles do not support arbitrary exponentiation. An advanced profile version could use the following code:
color = Kd * (ambient + diffuse) + Ks * pow(specular, specularExponent);
where specularExponent is a uniform parameter, or even a value from a texture.
C8E3v_specWall computes a per-vertex half-angle vector. Ideally, you should compute the half-angle vector from the light and view vectors at every fragment. You could modify the vertex program to output the eyeDirection value rather than the half-angle vector. Then you could modify C8E4f_specSurf to compute the half-angle vector at each fragment, as shown:
// Fetch and expand normalized eye vector float3 normEyeDirTex = texCUBE(normalizeCube, eyeDirection).xyz; float3 normEyeDir = expand(normEyeDirTex); // Sum light and eye vectors and normalize with cube map float3 normHalfAngle = texCUBE(normalizeCube, normLightDir + normEyeDir); normHalfAngle = expand(normHalfAngle);
As explained in Chapter 5, computing the half-angle vector at every fragment creates more realistic specular highlights than computing the half-angle vector per-vertex, but it is more expensive.
8.1.5 Bump Mapping Other Geometry
You have learned how to bump map a brick wall, and the results in Figure 8-2 are quite promising. However, bump mapping is not as simple as these first examples might have you believe.
The wall rectangle rendered in Figure 8-2 happens to be flat and has a surface normal that is uniformly (0, 0, 1). Additionally, the texture coordinates assigned to the rectangle are related to the vertex positions by a uniform linear mapping. At every point on the wall rectangle, the s texture coordinate is different from the x position by only a positive scale factor. The same is true of the t texture coordinate and the y position.
Under these considerably constrained circumstances, you can directly replace the surface normal with the normal sampled from the normal map. This is exactly what the prior examples do, and the bump mapping looks fine.
However, what happens when you bump map arbitrary geometry with the C8E1v_bumpWall and C8E2f_bumpSurf programs? What if the surface normal for the geometry is not uniformly (0, 0, 1)? What if the s and t texture coordinates used to access the normal map are not linearly related to the geometry's x and y object-space positions?
In these situations, your rendering results may resemble correct bump mapping, but a closer inspection will show that the lighting in the scene is not consistent with the actual light and eye positions. What happens is that the object-space light vector and half-angle vectors used in the per-fragment bump mapping math no longer share a consistent coordinate system with the normals in the normal map. The lighting results are therefore noticeably wrong.
Object-Space Bump Mapping
One solution is to make sure that the normals stored in your normal map are oriented so that they directly replace the object-space surface normals for the geometry rendered. This means that the normal map effectively stores object-space normals, an approach known as object-space bump mapping. This approach does work, which is why our earlier bump-mapped wall example (Figure 8-2) is correct, though only for the particular wall rectangle shown.
Unfortunately, object-space bump mapping ties your normal map textures to the specific geometry that you are bump mapping. Creating a normal map requires knowing the exact geometry to which you will apply the normal map. This means that you cannot use a single brick-pattern normal map texture to bump map all the different possible brick walls in a scene. Instead, you end up needing a different normal map for every different brick wall you render. If the object animates its object-space vertex positions, every different pose potentially requires its own object-space normal map. For these reasons, object-space bump mapping is very limiting.
Texture-Space Bump Mapping
Correct bump mapping requires that the light vector and half-angle vector share a consistent coordinate system with the normal vectors in the normal map. It does not matter what coordinate system you choose, as long as you choose it consistently for all vectors in the lighting equations. Object space is one consistent coordinate system, but it is not the only choice.
You do not need to make all the normals in the normal map match up with the object-space coordinate system of the object to be bump mapped. Instead, you can rotate the object-space light vectors and half-angle vectors into the normal map's coordinate system. It is a lot less work to rotate two direction vectors into an alternative coordinate system than to adjust every normal in a normal map. The coordinate system used by the normal map texture is called texture space, so this approach is known as texture-space bump mapping (sometimes called tangent-space bump mapping).
Vertex programs are efficient at transforming vectors from one coordinate system to another. The vector transformations required for texture-space bump mapping are akin to transforming positions from object space to clip space with the modelview-projection matrix.
You can program your GPU to transform each object-space light and half-angle vector into the coordinate system that matches your normal map texture.
However, a modelview-projection matrix is fixed for a given rendered object. In contrast, the transformation required to rotate object-space light and half-angle vectors into the coordinate system that matches your normal map typically varies over the surface you render. Every vertex you render may require a distinct rotation matrix!
Although it may require a distinct rotation matrix for each vertex, texture-space bump mapping has one chief advantage. It allows you to apply a single normal map texture to multiple models—or to a single model being animated—while keeping the per-fragment mathematics required for bump mapping simple and efficient enough for GPUs that support only basic fragment profiles.
8.2 Bump Mapping a Brick Floor
Before we consider bump mapping polygonal meshes, consider an only slightly more complicated case. Instead of rendering a bump-mapped brick wall that has an object-space surface normal (0, 0, 1), consider rendering the same brick-textured rectangle repositioned so it becomes a brick floor rather than a wall. The surface normal for the floor is (0, 1, 0), straight up in the y direction.
In this floor example, apply the same brick normal map to the floor that you applied to the wall in the last example. However, "straight up" in the normal map is the (0, 0, 1) vector, while "straight up" for the floor in object space is (0, 1, 0). These two coordinate systems are not consistent.
What does it take to make these two coordinate systems consistent? The floor has the same normal at every point, so the following rotation matrix transforms the floor's object-space "straight up" vector to the normal map's corresponding "straight up" vector:
Sections 8.3 and 8.4 will explain the details of how to construct this 3x3 matrix for arbitrary textured rectangles and triangles. For now, the important thing is that such a matrix exists and provides a way to transform vectors from object space to the normal map's texture space.
We can use this matrix to rotate the object-space light and half-angle vectors for the floor rectangle so they match the coordinate system of the normal map. For example, if L is the light vector in object space (written as a row vector), then L' in the normal map coordinate system can be computed as follows:
To perform specular texture-space bump mapping, you must also rotate the half-angle vector in object space into texture space the same way. Although this example's rotation matrix is trivial, the same principle applies to an arbitrary rotation matrix.
About Rotation Matrices
You can always represent a 3D rotation as a 3x3 matrix. Each column and each row of a rotation matrix must be a unit-length vector. Moreover, each column vector is mutually orthogonal to the other two column vectors, and the same applies to the row vectors. The length of a vector transformed by a rotation matrix does not change after transformation. A 3D rotation matrix can act as the bridge between direction vectors in two 3D coordinate systems.
The columns of a rotation matrix used to transform object-space direction vectors into a normal map's texture space are named tangent (T), binormal (B), and normal (N), respectively. So rotation matrix entries can be labeled as in Equation 8-1.
Equation 8-1 A Rotation Matrix Formed by Tangent, Binormal, and Normal Column Vectors
Given two columns (or rows) of a rotation matrix, the third column (or row) is the cross product of the two known columns (or rows). For the columns, this means that the relationship in Equation 8-2 exists.
Equation 8-2 Cross-Product Relationships Between Tangent, Binormal, and Normal Vectors
8.2.1 The Vertex Program for Rendering a Brick Floor
You can enhance the C8E1v_bumpWall example so that it can bump map using texture-space bump mapping. To do this, pass the tangent and normal vectors of the rotation matrix needed to transform object-space vectors into texture-space vectors.
Example 8-5's C8E5v_bumpAny vertex program, in conjunction with the earlier C8E2f_bumpSurf fragment program, can bump map the brick wall and brick floor with the same normal map texture. But to do this, you must supply the proper normal and tangent vectors of the rotation matrix that maps between object space and texture space. You must specify these two vectors for each vertex. The program computes the binormal with a cross product. Rather than requiring the binormal to be passed as yet another per-vertex parameter, the program computes the binormal in order to reduce the amount of dynamic data that the GPU must read for each vertex processed. Computing the binormal also avoids having to precompute and devote memory to storing binormals.
Example 8-5. The C8E5v_bumpAny Vertex Program
void C8E5v_bumpAny(float3 position : POSITION, float3 normal : NORMAL, float3 tangent : TEXCOORD1, float2 texCoord : TEXCOORD0, out float4 oPosition : POSITION, out float2 normalMapCoord : TEXCOORD0, out float3 lightDirection : TEXCOORD1, uniform float3 lightPosition, // Object space uniform float3 eyePosition, // Object space uniform float4x4 modelViewProj) { oPosition = mul(modelViewProj, float4(position, 1)); // Compute the object-space light vector lightDirection = lightPosition - position; // Construct object-space-to-texture-space 3x3 matrix float3 binormal = cross(tangent, normal); float3x3 rotation = float3x3(tangent, binormal, normal); // Rotate the light vector using the matrix lightDirection = mul(rotation, lightDirection); normalMapCoord = texCoord; }
Texture-space bump mapping is also known as tangent-space bump mapping because a tangent vector to the surface, in conjunction with the surface normal, establishes the required rotation matrix.
Figure 8-4 compares two images of a simple scene with the same bump-mapped wall and floor arrangement, the same normal map texture, the same light position, and the same C8E2f_bumpSurf fragment program. But each image uses a different vertex program. The lighting in the left image is consistent and correct because it uses the C8E5v_bumpAny vertex program with the correct object-space-to-texture-space rotation for correct texture-space bump mapping. However, the lighting in the right image is inconsistent. The lighting on the wall is correct, but the lighting on the floor is wrong. The inconsistent lighting arises because the image on the right uses the C8E1v_bumpWall vertex program for both the wall and the floor.
Figure 8-4 Consistent Texture-Space Bump Mapping vs. Inconsistent Object-Space Bump Mapping
Conventionally, we write position vectors as column vectors and direction vectors as row vectors. Using Equation 8-2, C8E5v_bumpAny computes the binormal as a cross product of the per-vertex tangent and normal vectors:
float3 binormal = cross(tangent, normal);
The cross routine for computing the cross product of two vectors is part of Cg's Standard Library.
The program then constructs a rotation matrix with the float3x3 matrix constructor:
float3x3 rotation = float3x3(tangent, binormal, normal);
The rows of the constructed rotation matrix are the tangent, binormal, and normal, so the constructed matrix is the transpose of the matrix shown in Equation 8-1. Multiplying a row vector by a matrix is the same as multiplying the transpose of a matrix by a column vector. The C8E5v_bumpAny example's multiply is a matrix-by-vector multiply because the rotation matrix is really the transpose of the intended matrix, as shown:
lightDirection = mul(rotation, lightDirection);
Enhancing the C8E3v_specWall program in the same way requires also rotating the half-angle vector, as shown:
eyeDirection = mul(rotation, eyeDirection); halfAngle = normalize(normalize(lightDirection) + normalize(eyeDirection));
The scene in Figure 8-4 has only flat surfaces. This means that the rotation matrix required for the wall, and the other rotation matrix required for the floor, are uniform across each flat surface. The C8E5v_bumpAny program permits distinct tangent and normal vectors for every vertex. A curved surface or a mesh of polygons would require this support for varying the tangent and normal vectors that define the rotation from object space to texture space at every vertex. Figure 8-5 shows how a curved triangular shape requires distinct normal, tangent, and binormal vectors at each vertex. These vectors define distinct rotation matrices at each vertex that rotate the light vector properly into texture space. In the figure, the light vectors are shown in gray.
Figure 8-5 Per-Vertex Texture Space Bases
The next two sections explain how to generalize texture-space bump mapping to support curved surfaces and polygonal meshes.
8.3 Bump Mapping a Torus
Note
This section and the next are for readers who want a more mathematically based understanding of texture space. In particular, these sections explain the mathematics of how to construct the rotation matrices for transforming object-space vectors to and from texture space. These topics are not essential if you are content to rely on 3D authoring tools or other software to generate the rotation matrices for texture-space bump mapping. If you are not interested in this level of detail, you are encouraged to skip ahead to Section 8.5.
In this section, we describe how to bump map a tessellated torus, as depicted in Figure 8-6. Bump mapping a torus is more involved than bump mapping a brick wall because the surface of a torus curves. That curvature means that there isn't a single, fixed rotation from object space to texture space for the entire torus.
Figure 8-6 A Tessellated Torus
8.3.1 The Mathematics of the Torus
For bump mapping, the torus provides a well-behaved surface with which to develop your mathematical intuition before you apply these ideas to the more general case of an arbitrary polygonal model in Section 8.4.
Bump mapping a torus is more straightforward than bump mapping an arbitrary polygonal model, because a single set of parametric mathematical equations, shown in Equation 8-3, defines the surface of a torus.
Equation 8-3 Parametric Equations for a Torus
The parametric variables (s, t)
[0, 1] map to 3D positions (x, y, z) on the torus, where M is the radius from the center of the hole to the center of the torus tube, and N is the radius of the tube. The torus lies in the z=0 plane and is centered at the origin.
By defining the surface of a torus with a set of parametric equations, you can determine the exact curvature of a torus analytically, using partial differential equations.
The analytic definition of the torus in Equation 8-3 lets you determine an oriented surface-local coordinate system, the texture space we seek for bump mapping, in terms of the parametric variables (s, t) used to define the torus. These same parametric variables also serve as texture coordinates to access a normal map texture for bump mapping.
In practical terms, this provides a way to convert an object-space light vector and an object-space view vector into a surface-local coordinate system that is consistently oriented for normals stored in a normal map texture. Once you have a set of normal, light, and view vectors in this consistent coordinate system, the lighting equations explained in Chapter 5 work correctly. As discussed in Section 8.1.5, the trick to bump mapping is finding a consistent coordinate system and properly transforming all vectors required for lighting into that space.
If we assume that a surface is reasonably tessellated, we need to compute only the light and view vectors required for lighting at each vertex, and then interpolate these vectors for computing the lighting equations for every rasterized fragment. This assumption holds well for a uniformly tessellated torus.
As with the flat brick wall, we seek a rotation, in the form of a 3x3 matrix, that we can use to convert object-space vectors to a surface-local coordinate system oriented according to the (s, t) parameterization of the torus. Because of the curvature of the torus, the 3x3 matrix must be different for every vertex of the torus.
Constructing the rotation matrices requires the partial derivatives of the parametric equations that define the torus. These are shown in Equation 8-4.
Equation 8-4 Partial Derivatives of the Parametric Torus
We call the three-component vector formed from the partial derivatives in terms of either s or t an inverse gradient because it resembles the per-component reciprocal of a conventional gradient. An inverse gradient indicates the instantaneous direction and magnitude of change in surface position in terms of a single parametric variable.
You can use these inverse gradients to define a surface-local coordinate system. Forming a 3D coordinate system takes two orthogonal vectors. One vector that is essential for any surface-local coordinate system is the surface normal. By definition, the surface normal points away from the surface. You can construct the surface normal at a point on a surface by computing the cross product of two noncoincident inverse gradients to the surface at that point.
For our torus example, the surface normal N is given by Equation 8-5.
Equation 8-5 The Normal of a Surface Expressed in Terms of Its Parametric Inverse Gradients
By picking the inverse gradient in terms of s as your tangent vector, in conjunction with the surface normal, you fashion a surface-local coordinate system.
The rotation matrix required to transform object-space vectors into the texture-space coordinate system for any particular torus vertex is
where the
notation indicates a normalized vector, and given the equations shown in Equation 8-6.
Equation 8-6 The Tangent, Binormal, and Normal on a Surface
You form the rotation matrix entirely of normalized vectors. This means that you can ignore the constant scale factors 2p and 2Np in Equation 8-4 for the inverse gradients in terms of s and t, respectively.
Furthermore, the normalized surface normal N of the torus based on Equation 8-5 simplifies to
8.3.2 The Bump-Mapped Torus Vertex Program
Example 8-6 shows the vertex program C8E6v_torus for rendering a bump-mapped torus. This program procedurally generates a torus from a 2D grid specified over (s, t)
[0, 1], as shown in Figure 8-7. Besides generating the torus, the program constructs the correct per-vertex rotation matrix, as described in Section 8.3.1. The program also rotates the uniform object-space light vector and half-angle vector parameters into texture space for consistent texture-space bump mapping.
Figure 8-7 Procedural Generation of a Torus from a 2D Grid
Figure 8-8 (on page 224) shows two bump-mapped tori rendered with the C8E6v_torus vertex program and the C8E4f_specSurf fragment program. The example applies the brick normal map from Figure 8-1. The bricks bump outward consistently, and a specular highlight is visible in each case.
Figure 8-8 Two Bump-Mapped Brick Tori Rendered with and
Example 8-6. The C8E6v_torus Vertex Program
void C8E6v_torus(float2 parametric : POSITION, out float4 position :, uniform float2 torusInfo) { const float pi2 = 6.28318530; // 2 times Pi // Stretch texture coordinates counterclockwise // over torus to repeat normal map in 6 by 2 pattern float M = torusInfo[0]; float N = torusInfo[1]; oTexCoord = parametric * float2(-6, 2); // Compute torus position from its parametric equation float cosS, sinS; sincos(pi2 * parametric.x, sinS, cosS); float cosT, sinT; sincos(pi2 * parametric.y, sinT, cosT); float3 torusPosition = float3((M + N * cosT) * cosS, (M + N * cosT) * sinS, N * sinT); position = mul(modelViewProj, float4(torusPosition, 1)); // Compute per-vertex rotation matrix float3 dPds = float3(-sinS * (M + N * cosT), cosS * (M + N * cosT), 0); float3 norm_dPds = normalize(dPds); float3 normal = float3(cosS * cosT, sinS * cosT, sinT); float3 dPdt = cross(normal, norm_dPds); float3x3 rotation = float3x3(norm_dPds, dPdt, normal); // Rotate object-space vectors to texture space float3 eyeDirection = eyePosition - torusPosition; lightDirection = lightPosition - torusPosition; lightDirection = mul(rotation, lightDirection); eyeDirection = mul(rotation, eyeDirection); halfAngle = normalize(normalize(lightDirection) + normalize(eyeDirection)); }
8.4 Bump Mapping Textured Polygonal Meshes
Now consider the more general case of a textured polygonal model, such as the kind used for characters and other objects in 3D computer games. In general, objects are not strictly flat like a brick wall, nor easily described with a convenient mathematical expression, like a torus. Instead, an artist models such objects as a mesh of textured triangles.
Our approach is to explain how to bump map a single triangle from a textured polygonal mesh and then generalize this method to the entire mesh.
8.4.1 Examining a Single Triangle
Figure 8-9 shows a wireframe model of an alien head, along with a height-field texture for constructing the head's normal map. The figure shows the same triangle three times. The version of the triangle on the left lies in 2D on the height-field texture. The version of the triangle on the right is shown in 3D object space in relation to other triangles forming the head. The middle version of the triangle appears on the head as rendered with bump mapping.
Figure 8-9 The Same Triangle Exists in Object Space and Texture Space
Each vertex of this textured triangle has a 3D object-space position and a 2D texture coordinate set. Think of the combination of these five coordinates as a 5D vertex. You can then describe the triangle's vertices v 0, v 1, and v 2 this way:
Because all these coordinates lie in the plane of the same triangle, it is possible to derive plane equations for x, y, and z in terms of s and t:
For each of these three equations, you can compute the values of the coefficients A, B, C, and D using the triangle's vertex coordinates. For example, A 0, B 0, C 0, and D 0 would be computed as shown in Equation 8-7.
Equation 8-7 Plane Equation Coefficients for (x, s, t) Plane for a Single-Textured Triangle
Rewriting the plane equations allows you to express x, y, and z in terms of s and t:
These three equations provide a means to translate texture-space 2D positions on the triangle to their corresponding 3D positions in object space. These are simple linear functions of s and t that provide x, y, and z. The equations are similar to Equation 8-3 for the torus. As in the case of the torus, we are interested in the partial derivatives of the vector <x, y, z> in terms of s and t:
Equation 8-8 Object-Space Partial Derivatives for a Texture-Space Triangle in Terms of the Texture Coordinates
This equation provides inverse gradients analogous to those in Equation 8-4, but these inverse gradients are much simpler. Indeed, every term is a constant. That makes sense because a single triangle is uniformly flat, having none of the curvature of a torus.
Normalized versions of these inverse gradients form a rotation matrix in the same manner as the torus. Use the normalized inverse gradient in terms of s as the tangent vector, and use the normalized inverse gradient in terms of t as the binormal vector. You can use the cross product of these two inverse gradients as the normal vector, but if the model supplies a per-vertex normal for the vertices of the triangle, it is best to use the model's per-vertex normals instead. That's because the per-vertex normals ensure that your bump map lighting of the model is consistent with non-bump-mapped per-vertex lighting.
Normalizing the cross product of the two inverse gradients would give each triangle a uniform normal. This would create a faceted appearance.
8.4.2 Caveats
The Orthogonality of Texture Space with Object Space
There is no guarantee that the inverse gradient in terms of s will be orthogonal to the inverse gradient in terms of t. This happened to be true for every point on the torus (another reason the torus was used in Section 8.3), but it is not generally true. In practice, the two inverse gradients tend to be nearly orthogonal, because otherwise the artist who designed the model would have had to paint the associated texture accounting for a skew. Artists naturally choose to apply textures to models by using nearly orthogonal inverse gradients.
Beware of Zero-Area Triangles in Texture Space
It is possible that two vertices of the triangle will share the same (s, t) position in texture space (or very nearly the same position), or the three texture-space positions may all be collinear. This creates a degenerate triangle with zero area in texture space (or nearly zero area). This triangle may still have area in object space; it may only be degenerate in texture space. Artists should avoid authoring such triangles if the texture coordinates are intended for bump mapping.
If zero-area triangles in texture space are present on a bump-mapped model, they have a single perturbed normal for the entire triangle, leading to inappropriate lighting.
Negative-Area Triangles in Texture Space
Artists often mirror regions of a texture when applying texture coordinates to a polygonal model. For example, a texture may contain just the right half of a face. The artist can then apply the face's texture region to both the right and the left half of the face. The same half-face image applies to both sides of the face because faces are typically symmetric. This optimization more efficiently uses the available texture resolution.
Because decals have no sense of what direction they face, this technique works fine when applying a decal texture. However, normal maps encode direction vectors that flip when polygons mirror regions of the normal map in this manner.
This issue can be avoided either by requiring artists to forgo mirroring while applying texture coordinates to models, or by automatically identifying when a triangle is mirrored in texture space and appropriately flipping the per-vertex normal direction. The latter approach is preferable, because you can use software tools to flip (negate) the normal whenever a triangle has a negative area in texture space, and adjust the mesh appropriately (for example, using NVIDIA's NVMeshMender software, which is freely available from NVIDIA's Developer Web site, developer.nvidia.com ).
Nonuniform Stretching of Bump Map Texture Coordinates
Artists can sometimes stretch a texture when assigning the texture coordinates for a model in a nonuniform manner. Again, this is usually fine for decals, but stretching creates issues for bump mapping. Nonuniform scaling of textures means that the inverse gradient in terms of s may have a much larger magnitude than the inverse gradient in terms of t. Typically, you automatically generate normal maps from height fields without reference to a particular model. Implicitly, you are assuming that any stretching of the normal map, when it applies to the model, is uniform.
You can avoid this issue either by requiring artists to avoid nonuniform stretching, or by accounting for the stretching when converting the height-field texture to a normal map.
8.4.3 Generalizing to a Polygonal Mesh
You can apply the approach described in the previous section on a polygon-by-polygon basis to every polygon in your polygonal mesh. You compute the tangent, binormal, and normal for every triangle in the mesh.
Blending Bases at Shared Vertices
However, in a mesh, more than one triangle may share a given vertex in the mesh. Typically, each triangle that shares a particular vertex will have its own distinct tangent, binormal, and normal vectors. Consequently, the basis—formed by the tangent, binormal, and normal vectors—for each triangle sharing the particular vertex is likewise distinct.
However, if the tangents, binormals, and normals for different triangles at a shared vertex are similar enough (and they often are), you can blend these vectors together without creating noticeable artifacts. The alternative is to create a copy of each vertex for each triangle shared by the original vertex. Generally, blending the bases at such vertices is the best approach if the vectors are not too divergent. This approach also helps to avoid a faceted appearance when a model is not optimally tessellated.
Mirroring, as discussed previously, is a situation in which the vectors are necessarily divergent. If mirroring occurs, you need to assign each triangle a distinct vertex with the appropriate tangent, binormal, and normal for each differently mirrored triangle.
8.5 Combining Bump Mapping with Other Effects
8.5.1 Decal Maps
The same texture coordinates used for your bump map are typically shared with decal map textures. Indeed, the discussion in Section 8.4 presumes that the texture coordinates assigned for applying a decal texture are used to derive the tangent and binormal vectors for bump mapping.
Often, when a game engine doesn't support bump mapping, artists are forced to enhance decal textures by painting lighting variations into the textures. When you bump map a surface, the bump mapping should supply these lighting variations. Artists constructing bump maps and decals must be careful to encode diffuse material variations alone, without lighting variations, in the decal map. Artists should encode geometrical surface variations in the height field from which the normal map is generated.
For example, an artist should paint a green solid shirt as solid green in the decal map. In contrast, the artist should paint the folds in the fabric of the shirt that account for the lighting variations in the height field, rather than in the decal. If artists are not careful about this, they can inadvertently create double lighting effects that make bump-mapped surfaces too dark.
8.5.2 Gloss Maps
It's common for some regions of an object to be shiny (such as belt buckles and armor) and other regions to be duller (such as fabric and flesh). A gloss map texture is a type of control map that encodes how specularity varies over a model. As with the decal map and normal map, the gloss map can share the same texture coordinate parameterization with these other texture maps. The gloss map can often be stored in the alpha component of the decal map (or even the bump map), because RGBA textures are often nearly as efficient as RGB textures.
This fragment of Cg code shows how a decal texture can provide both the decal material and a gloss map:
float4 decalTexture = tex2D(decal, texCoord); color = lightColor * (decal.rgb * (ambient + diffuse) + decal.a * specular);
8.5.3 Geometric Self-Shadowing
Geometric self-shadowing accounts for the fact that a surface should not reflect a light if the light source is below the plane of the surface. For diffuse illumination, this occurs when the dot product of the light vector and the normal vector is negative. In this case, the dot product's result is clamped to zero. You can implement this in Cg as follows:
diffuse = max(dot(normal, light), 0);
Chapter 5 explained how the specular term should also account for geometric self-shadowing by clamping the specular term to zero either when the dot product of the half-angle vector and the normal vector is negative or when the diffuse contribution is clamped to zero. You can implement this in Cg as follows:
specular = dot(normal, light) > 0 ? max(dot(normal, halfAngle), 0) : 0;
When you bump map, there are actually two surface normals: the conventional interpolated normal and the perturbed surface normal supplied by the normal map. One way to think about these two normals is that the interpolated normal is a large-scale approximation of the surface orientation, and the perturbed normal is a small-scale approximation of the surface orientation.
If either normal faces away from the incoming light direction, then there should be no illumination from the light. When you're lighting in texture space for bump mapping, the light vector's z component indicates whether the light is above or below the horizon of the geometric (or large-scale) normal. If the z component is negative, the geometric orientation of the surface faces away from the light and there should be no illumination from the light on the surface. You can implement this in Cg as follows:
diffuse = light.z > 0 ? max(dot(normal, light), 0) : 0;
The ?: test enforces geometric self-shadowing for the large-scale surface orientation; the max function enforces geometric self-shadowing for the small-scale surface orientation. You can implement the geometric self-shadowing for specular bump mapping in Cg this way:
specular = dot(normal, light) > 0 && light.z > 0 ? max(dot(normal, halfAngle), 0) : 0;
Whether or not you account for geometric self-shadowing in your bump mapping is a matter of personal preference and a performance trade-off. Accounting for geometric self-shadowing caused by the large-scale surface orientation means that a light source will not illuminate some fragments that might otherwise be illuminated. However, if you do not account for geometric self-shadowing caused by the large-scale surface orientation, then lights on bump-mapped surfaces (particularly surfaces with considerable variation of surface normals) do not provide a clear cue for the direction of the incoming light.
An abrupt cut-off might cause illumination on a bump-mapped surface to flicker unnaturally because of large-scale geometric self-shadowing when the scene is animating. To avoid this problem, use a function such as lerp or smoothstep to provide a more gradual transition.
8.6 Exercises
Try this yourself: Use an image-editing program to replace the normal map used in Example 8-6 with a cobblestone pattern. Hint: You can edit the file that contains the normal map. You should not need to modify any code.
Try this yourself: When generating a normal map from a height field, you can scale the difference vectors by some scalar factor s as shown:
What happens visually when you regenerate a normal map from its height field with an increased value for the s scale factor? What happens when you decrease the scale factor? What happens if you use one scale factor to scale Hg - Ha and another scale factor to scale Hg - Hr ?
Try this yourself: Implement bump mapping for multiple light sources by using a rendering pass per light contribution. Use "depth equal" depth testing and additive blending to combine contributions from multiple lights for a bump-mapped surface.
8.7 Further Reading
Jim Blinn invented bump mapping in 1978. Blinn's "Simulation of Wrinkled Surfaces" (ACM Press) is a seminal SIGGRAPH computer graphics paper.
Mark Peercy, John Airey, and Brian Cabral published a SIGGRAPH paper in 1997 titled "Efficient Bump Mapping Hardware" (ACM Press), which explains tangent space and its application to hardware bump mapping.
In 2000, Mark Kilgard published "A Practical and Robust Bump-Mapping Technique for Today's GPUs." The white paper explains the mathematics of bump mapping and presents a technique appropriate for third-generation GPUs. You can find this white paper on NVIDIA's Developer Web site ( developer.nvidia.com ).
Sim Dietrich published an article titled "Hardware Bump Mapping," in Game Programming Gems (Charles River Media, 2000), that introduced the idea of using the texture coordinates of polygonal models for texture-space bump mapping. | https://developer.nvidia.com/content/cg-tutorial-chapter-8-bump-mapping?display[%24ne]=defaultnppopenaccuser%2Flogincuda-example-introduction-general-purpose-gpu-programmingcategory%2Fzone%2Fcuda-zone | CC-MAIN-2014-10 | refinedweb | 9,330 | 50.26 |
*
2D array battleship
Haani Naz
Greenhorn
Joined: May 30, 2010
Posts: 23
posted
Oct 29, 2011 20:00:36
0
Hi,
been reading up head first
java
. there's a bit about creating a battleship game and i just jumped ahead and tried doing it myself.
so far i managed to create a grid which populates ships denoted by 'x' in 3 cells. i'm having trouble getting the checks right if it tries to populate it in the same cells.
here is my code. please assist in giving me advice is getting it to work, i'd really appreciate it.
import java.util.*; import java.math.*; public class Array2DTest { public static void main(String[] args) { //create the grid final int rowWidth = 5; final int colHeight = 5; Random rand = new Random(); String [][] board = new String [rowWidth][colHeight]; //fill the grid for (int row = 0; row < board.length; row++) { for (int col = 0; col < board[row].length; col++) { board[row][col] = "-"; //rand.nextInt(10); } } // System.out.println("Board length: " + board[1].length); //to randomly decide if the ships are assigned to the grid via row or column int toss; int row_pos; int column_pos; int count = 0; // run through the grid 3 times and create 3 ships while (count < 3){ //i'm forcing it only use rows at this point. toss = 1; //rand.nextInt(2) if (toss == 1){ row_pos=rand.nextInt(5); //random row is assigned System.out.println("row position: " + row_pos); count++; int temp; int rowSpace; int i=0; int col=0; //creating a ship. 3 'x' markers on the board. loop 3 times. while( i < 3){ //if row already has a 'x'. move to next column while ( board[row_pos][col] == "x"){ col++; System.out.println("col increment: " + col); } //System.out.println("board length marker 1: " + board[row_pos].length); if ((rowSpace=( 1 + board.length) - col) >= 3 ) { System.out.println("board length marker 2: " + rowSpace ); board[row_pos][col]= "x"; col++; i++; } else { //if no more cells available in row, generate a new row position while ( (temp = rand.nextInt(5)) != row_pos) { row_pos = temp; } } }//end-i < 3 } /* else if (toss == 0) { column_pos=rand.nextInt(5); System.out.println("column position: " + column_pos); count++; int i=0; int row=0; while( i < 3){ board[row][column_pos]= "x"; row++; i++; } }*/ }//end-count < 3 System.out.println("Printing starts here.."); //display output for(int i = 0; i < board.length; i++) { for(int j = 0; j < board[i].length; j++) { System.out.print(board[i][j] + " "); //System.out.println(); } System.out.println(); } } //end of main }
here's a working output for me:
row position: 2
board length marker 2: 6
board length marker 2: 5
board length marker 2: 4
row position: 0
board length marker 2: 6
board length marker 2: 5
board length marker 2: 4
row position: 4
board length marker 2: 6
board length marker 2: 5
board length marker 2: 4
Printing starts here..
x x x - -
- - - - -
x x x - -
- - - - -
x x x - -
non-working output:
row position: 2
board length marker 2: 6
board length marker 2: 5
board length marker 2: 4
row position: 1
board length marker 2: 6
board length marker 2: 5
board length marker 2: 4
row position: 1
col increment: 1
col increment: 2
col increment: 3
board length marker 2: 3
As you can see as soon as its the same row it fails to work. it also fails to print the grid : /
Thanks in advance.
Stephan van Hulst
Bartender
Joined: Sep 20, 2010
Posts: 3362
9
posted
Oct 30, 2011 09:40:58
0
The problem is that in your while loop, you check for three placed ships. i only gets increased if rowSpace >= 3, which will never happen if two ships are in the same row, because col gets incremented to 3, then once more to 4, and after that (5+1-col) will never be >= 3. So you're stuck in an infinite loop.
An important note about your code. NEVER use assignment expressions within another expression, like you do with rowSpace. Assign the value to rowSpace in the line before it, and then use rowSpace in the expression afterwards. When I saw the code I immediately thought your bug was there, because you had intended it to be an == instead of an =. So don't do it.
I agree. Here's the link:
subject: 2D array battleship
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Why I abandoned Java in favour of Kotlin.
Eight months into the Python project, I had to build a system in Java for a freelance project. I had no idea about how to get started, but the more I started messing around with it, the more I loved it. It was like watching poetry unfold and an orchestra perform a software ritual right in front of my eyes. As an ex-Delphi developer, who became accustomed to code that reads almost like English, the ceremony Java provided was beautiful and I was hooked.
Source : Feast of Music, Flickr
Let’s say you are an opera singer performing the same play every day and every night, after some time, you get tired of performing the same ceremony every day and just want to get down to performing - screw the announcements, screw the pre-show drinks, screw the credits, screw the standing ovations you just want to sing, enjoy the singing and not get bogged down by everything else.
For me, the case with Java, was similar. I enjoyed writing code in Java, but all the boilerplate bothered me. You'll see in the next few sections — how then, my intro to Kotlin was a breath of fresh air.
It was quite strange back in the days when Java introduced a 4 letter extension,
.java, when every other file-extension at the time was only 3 letters long.
Kotlin cuts it down to two letters,
.kt, almost as if they're making a statement saying,
"we're tired of boilerplate".
Now let's check out some interesting use cases where Kotlin outperforms Java.
Main method
Look at all the ceremony Java gives you before you get to write a single line of code whereas Kotlin gets straight to the performance!
Java:
public class MyClass { public static void main(String... args) { // code goes here; } }
Kotlin (doesn't even require that main method be in a class):
fun main(args: Array<String>) { // code goes here }
Declaring variables and constants
Java:
private String s1 = "my string 1"; private final String s2 = "my string 2"; private static final String s3 = "my string 3";
Kotlin:
var s1 = "my string 1" val s2 = "my string 2" val s3 = """my string 3""" // requires companion object
Also note the lack of semicolons in Kotlin! Semicolons are optional in Kotlin and can be used if you want to write two lines of code on the same line, otherwise you can just ignore it.
Unlike Java which forces you to use double-quotes everywhere, you can use triple quotes in Kotlin! Triple quotes allow you to put anything in there without having to escape strings, let me demonstrate …
Java:
String" + s2 + "</div>";
Kotlin:
val html = """<div class=”text”>$s2</div>"""
Note the
$s2, this allows you to place any Kotlin / Java value directly in your String without
having to break the string and without having to plus parts of strings, this is really awesome!
Alternatively, you can also use
${} which allows you to do things to that value inline, like
${s2.trim()}.
Getters and Setters
Java forces you to use getters and setters everywhere to encapsulate private variables; in Kotlin, anything that is not private, will automatically be exposed via properties making your code more concise and readable - this feature alone got me to try out Kotlin. Furthermore, the null-safety in Kotlin is beyond awesome. If you’re a Java developer, you’ll probably be familiar with endless null-pointer exceptions in your logs or bloated code that does endless null-checks, let me demonstrate with an imaginary HTML class.
Java:
HTML html = myHelperClass.getHtml(); String text = ""; if (html != null){ Body body = html.getBody(); if (body != null){ Div div = body.getDiv(); if (div.getText() != null){ text = div.getText(); } } } System.out.println(text);
Kotlin:
val html = myHelperClass.html val text = html?.body?.div?.text ?: "" println(text)
Or in short, in a single line:
println(myHelperClass.html?.body?.div?.text ?: "")
Notice the lack of getters in Kotlin (getting the job done without the ceremony),
the
? does the null check for you and returns
null at any point the
?
encounters a null and the elvis operator,
?:, checks if the result is
null
and if so, offers a default value.
Null checking in Kotlin is just sooooo much better than Java.
Method extensions
It really closed the deal for me, in Java you have gazillions of helper classes, just think Apache Commons for example or java.utils.Collections, let me give a simple example ...
Java:
public class Helper { public static String stripUnwantedSlashes(final String input) { if (input == null){ return null; } if (input.isEmpty()){ return ""; } String s = input.replaceAll("\\\\'", "'").replaceAll("\\\\\"", "\"").replaceAll("\\\\`", "`"); if (s.length() != input.length()){ return stripUnwantedSlashes(s); } return s; } }
Now every time you want to make use of this helper function, you have to do use the
Helper
class which bloats your code pretty quickly.
System.out.println(Helper.stripUnwantedSlashes(text));
Kotlin fixes this by allowing you to extend the String class injecting your own method.
Note that I don’t need to do a null check on input, by defining it as type
String,
the compiler won't allow it to be null; it won't even compile if it can be null.
If you want to allow null, you need to define the type as
String? instead and handle
the null, otherwise, once again, it won’t even compile.
Kotlin:
fun String.stripUnwantedSlashes() : String { if (this.isEmpty()){ return "" } val s = this.replace("\\\\'".toRegex(), "'").replace(("\\\\\"").toRegex(), "\"").replace(("\\\\`").toRegex(), "`") if (s.length != this.length){ return s.stripUnwantedSlashes() } return s }
See the difference, no
Helper. bloat:
println(text?.stripUnwantedSlashes() ?: "");
So instead of doing
Collections.sort(mylist);, you can get straight down to business and just do
mylist.sort()
Instead of bloating your code with
Integer.parseInt("1"), get straight down to business and do
"1".toInt()
Smart casting in Kotlin
This is another awesome feature that you don’t get in Java!
Following is a Java class that we'll extend, and use in both Java and Kotlin:
public abstract class Param<T> { private T value; public Param(T value) { this.value = value; } public T getValue() { return value; } } public class Password extends Param<String> { public Password(String value) { super(value); } public String getMaskedValue() { // code that masks password and returns it } } public class Username extends Param<String> { public Username(String value) { super(value); } }
Java:
List<Param> params = Arrays.asList(new Password("password1"), new Password("password2"), new Username("dude")); params.forEach((param) -> { if (param instanceof Password){ System.out.println("Password=" + ((Password) param).getMaskedValue()); } else if (param instanceof Username){ System.out.println("Username=" + ((Username) param).getValue()); } });
Kotlin:
val params = mutableListOf(Password("password1"), Password("password2"), Username("dude")) params.forEach { param -> if (param is Password){ println("Password=${param.maskedValue}") } else if (param is Username){ println("Username=${param.value}") } }
Notice how in the Java code, you need to cast your param every time you want to use it! Kotlin on the other hand, once you've confirmed param's type, you're free to use it as if it is of that type!
Kotlin also allows you to tell it what type param is in which case you can also just use it
as if it is of that type. Example, let's assume that list only contained
Password objects
Kotlin:
params.forEach { param -> param as Password println(param.maskedValue) println(param.maskedValue) println(param.maskedValue) }
Primary Constructors and named arguments
Another awesome feature I wish Java had, is the way you can more precisely call methods and constructors with named arguments.
Java:
Java, defining a class, typically looks like this:
public class User { private String firstName; private String lastName;; } }
To make use of this class in Java, you'll typically write this boilerplate:
User user = new User(); user.setFirstName("Graham"); user.setLastName("Spencer");
Kotlin:
Kotlin allows you to firstly get rid of the getters and setters, but also allows you to set variables in your class directly from the constructor
class User( var firstName: String = "", var lastName: String = "", var email: String = "") { override fun toString(): String { return "FirstName=${firstName}, LastName=${lastName}, Email=${email}" } }
To make use of this class in Kotlin, you can either do what Java did and set the variables individually, or you can passs the variables into the constructor or you can make use of named parameters (the one which I prefer most)
Kotlin (option1):
val user1 = User() user1.firstName = "Graham" user1.lastName = "Spencer"
Kotlin (option2) (notice that we can skip the last parameter since it has a default value):
val user2 = User("Graham", "Spencer")
Kotlin (option3) (notice that we can now pass in the parameters in any order):
var user3 = User(lastName = "Spencer", firstName = "Graham")
Methods in Kotlin also allows you to either call them via sequential arguments, or named arguments. The latter is great for when you want to make a method call much more readable, example, which looks better?
findUser("Graham", "Spencer", "0841234567", 33, 40, "Mr.")
or
findUser( title = "Mr", firstName = "Graham", lastName = "Spencer", phoneNumber = "0841234567", minAge = 33, maxAge = 40)
Using named parameters, you can even omit parameters that does not make sense to provide (assuming you provide default values for them in the method declaration) instead of providing empty strings or null. How many times have you seen long strings of null being sent into a method and not even knowing if the method will handle it correctly?
Java:
findUser(null, null, null, 33, 40, "Mr");
Kotlin:
findUser(title="Mr", minAge=33, maxAge=40)
Operator overloading
This is something Kotlin has which Java does not! There’s been many attempts to get operator overloading into Java, but the founders seems to kick back against it. Operator overloading is a feature I enjoyed very much in Python and I’m happy to see that Kotlin has it as well.
Instead of writing
a.contains(b) in Java, you can overload the contains
method or use method extensions to inject a contains method which will
allow you to write Kotlin
a in b
And this can be done for any operator that you can apply on an integer, like
+,
-,
++, etc
Kotlin:
Let's override the
compareTo operator in User:
operator fun compareTo(user: User): Int { return firstName.compareTo(user.firstName) }
Now which one reads easier?
if (user1.compareTo(user2) > 0)
or
if (user1 > user2)
Better Switch Case
Haven't you always wished for a switch case that is a little more powerful?
Java’s switch case is really simplistic, Kotlin gives you
when which allows
you to do anything an if-else can do, without the boilerplate.
Kotlin:
when (x) { 1 -> println("x == 1") 2 -> println("x == 2") 3,4 -> { println("x == 3") println("x == 4") } in 5..10 -> println("x >= 5 and x <= 10") is String -> println("x is actually a string") else -> { println("this is the else block") } }
The first question I asked on Kotlin's Slack channel (which is very active by the way) was
about whether Kotlin offered something similar to Dart's double-dot operator and some
guy told me that I can use DSLs to write my own
.. syntax, but he would suggest
I stick to
with. With allows you to switch the scope, let me demonstrate.
with (user1){ firstName = "Graham" lastName = "Spencer" println("First=${firstName}, Last=${lastName}") if (this > user2){ println("user1 > user2") } }
Without
with, you'd have to type user1 out every time and if you had nested properties,
you'd have to chain
user1.a.b.c.d.e them which reads very hard when you're integrating
into complex APIs with many levels of nested objects.
user1.firstName = "Graham" user1.lastName = "Spencer" println("First=${user1.firstName}, Last=${user1.lastName}") if (user1 > user2){ println("user1 > user2") }
Getting rid of equals()
I think the biggest win for Kotlin is getting rid of having to use
equals everywhere!!!
In Java, when using
== on objects (even
Strings), you are comparing pointers,
something which I've never seen anyone use in any real-world code and instead you are forced to
write
string1.equals(string2) everywhere.
Kotlin decided that since hardly anyone ever wants to compare pointers, why not make
==
actually compare values and instead, if you REALLY want to compare pointers, use
===.
So instead of
user1.firstName.equals(user2.firstName), you can write
user1.firstName == user2.firstName.
To existing Kotlin users, I know I know, I'm just shaving the tip of the iceberg here. There's plenty more to cover, but to cut a long story short, if you're already a Scala developer and are liking it, you'll probably not find many new things in Kotlin that you don't have already (except for the zero-overhead null-safety). But if you're a Java developer and are tired of the boilerplate and all the ceremonies before you get to do any real work, then Kotlin is for you.
If you're a Java dev & are tired of the ceremonies before doing any real work, then Kotlin is for you.
Click to Tweet
Kotlin is literally a better Java and I've already said goodbye to Java many months ago, not writing any new code in Java. For existing Java projects, I simply continue writing all new code in Kotlin while keeping the old code in Java, and keeping them both in the same project.
Cheers to the Kotlin team for making Java better!
Finally! Kudos for the effort and time to compile this HNO.
I'm currently looking into Kotlin and my plan to ditch Java is getting delayed. But with more and more I read about Kotlin, I grow more and more into it. As I mentioned before, it wouldn't be long before I left Java for Kotlin, and thanks for putting out all information which I needed.
The most interesting thing is, how quick I can write the same code in Kotlin with far more less code. And this is what I was looking for. Another good thing is, it is coming under JVM family IIRC!
Once again, thank you for writing this, so that people like me, who thought Java was the end of the world can get more idea about this Insane language!!
What material would you suggest for learning?
Interesting. Reminds me of some of the similar reasons Groovy was created.
I used to code in Java for a couple years and really never had any love for it. I did find JavaScript to be much more fun for me, although it is lacking in many aspects as a robust language. Python was something that really had my attention but still to me was not complete when comparing to Java. Kotlin really caught my eye and actually got me back into the Java realm.
Great article about some of the many questions I have been looking up answers for.
The Dev Community
(Free, friendly and inclusive)
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October 25, 2016 Update: Now able to put TestingAppDelegate in test target, even in Swift
The biggest benefit of Test Driven Development is fast feedback. And so one of the best ways to keep your TDD effective is to make sure you get that feedback as fast as you can.
But most iOS folks use their production app delegate when testing. This is a problem.
That’s because when you run your tests, it first fires up your app — which probably does a lot. A bunch of slow stuff. And that’s a bunch of slow stuff we don’t need or want for our tests.
How can we avoid this?
[This post is part of the series TDD Sample App: The Complete Collection …So Far]
The testing sequence
Apple used to segregate unit tests into two categories: application tests and logic tests. The distinction was important because in the bad old days, application tests could only run on device, unless you used a completely different third-party testing framework.
But this distinction diminished when Apple made it possible to run application tests on the simulator. It took a while for their documentation to catch up, but in their latest Testing with Xcode, Apple now talks about “app tests” and “library tests.” This simplifies things down to whether you’re writing an app or writing a library. And Xcode sets up a test target for you that is usually what you need.
If I’m writing an app (or a library that requires a running app), I’m always to going to run the app tests anyway, so I stopped trying to distinguish between the two types of tests. But because Xcode executes app tests within the context of a running app, the testing sequence goes like this:
- Launch the simulator
- In the simulator, launch the app
- Inject the test bundle into the running app
- Run the tests
What can we do to make this faster? We can make step 2, “launch the app,” as fast as possible.
The normal app delegate
In production code, launching an app may fire off a number of tasks. Ole Begemann’s post Revisiting the App Launch Sequence on iOS goes into more detail, but basically, UIApplicationMain() eventually calls the app delegate to have it execute application:didFinishLaunchingWithOptions:. What that does depends on your app, but it’s not unusual for it to do things like:
- Set up Core Data.
- Configure the root view controller.
- Check network reachability.
- Send a network request to some server to retrieve the latest configuration, such as what to show in the root view controller.
That’s a lot of stuff to do before we even start testing. Wouldn’t it be better to not bother, if all we want is to run our tests?
Let’s set things up that way. Here’s how.
Change main
Let’s change our main function, which looks like this in Objective-C:
#import "AppDelegate.h"
int main(int argc, char *argv[])
{
@autoreleasepool {
return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
}
}
We now want it to check if we are running tests. And if so, we want it to use a different app delegate. We can do that like this:
For Objective-C: Put the TestingAppDelegate in the test target. If we can load it, we use it.
#import "AppDelegate.h"));
}
}
For Swift: First, remove the @UIApplicationMain annotation from AppDelegate.swift. Then create a new file main.swift:
let appDelegateClass: AnyClass? =
NSClassFromString("TEST_TARGET.TestingAppDelegate") ??!))
replacing TEST_TARGET with the name of the target containing TestingAppDelegate.
Provide TestingAppDelegate
This requires creating a new TestingAppDelegate class. In Objective-C, it’s nothing more than this:
TestingAppDelegate.h
@interface TestingAppDelegate : NSObject
@property (nonatomic, strong) UIWindow *window;
@end
TestingAppDelegate.m
@implementation TestingAppDelegate
@end
(In earlier versions of iOS, I had to add more code so that the TestingAppDelegate would create a window, give that window a do-nothing root view controller, and make the window visible. It looks like that’s no longer necessary.)
For Swift, it’s simply:
TestingAppDelegate.swift
class TestingAppDelegate: NSObject {
var window: UIWindow?
}
Bare bones for fast feedback
The important thing is that we’ve reduced the “launch the app” step of testing to a bare minimum. There’s still some overhead, but not much. This is an important step for fast feedback so that we can get the most from TDD.
Even if you’re starting a brand-new project, I recommend taking this step early because your real app delegate will eventually grow. Let’s nip that in the bud, and keep the feedback fast.
Another benefit is that now we can write unit tests against the production app delegate, with complete control over what parts of it are exercised, and when. It’s win-win!
Have you used this technique, or something different? You can share your thoughts by clicking here.
This post is part of a series on What Is the Most Important Benefit of TDD? Did you find it useful? Subscribe today to get regular posts on clean iOS code.
Nice! I was using a more complex mechanism to identify if the app is running tests:
{
NSDictionary *environment = [[NSProcessInfo processInfo] environment];
NSString *injectBundle = environment[@"XCInjectBundle"];
return [[[injectBundle lastPathComponent] stringByDeletingPathExtension] isEqualToString:@"MyTargetTests"];
}
Also, I’m not doing the logic on main but instead on didFinishLaunchingDirectly so I have a if to check if it’s not running tests and only in that case I run all the necessary bootstrap.
One advantage of keeping the short-circuit outside the app delegate: you can write unit tests against your app delegate.
Great article, Jon. Thanks.
I have still been using a combination of both Application and Library tests for testing applications, but I’m going to switch over to this approach. Thanks for sharing it with us.
Nice of you to talk about this topic, is super important.
I’ve been using this works with old and new Xcodes, and works with Travis CI
{
NSDictionary *environment = [NSProcessInfo processInfo].environment;
NSString *serviceNameValue = environment[@"XPC_SERVICE_NAME"];
NSString *injectBundleValue = environment[@"XCInjectBundle"];
BOOL runningOnTravis = (environment[@"TRAVIS"] != nil);
return ([serviceNameValue.pathExtension isEqualToString:@"xctest"] ||
[serviceNameValue isEqualToString:@"0"] ||
[injectBundleValue.pathExtension isEqualToString:@"xctest"] ||
[injectBundleValue isEqualToString:@"0"] ||
runningOnTravis);
}
You put it in your AppDelegate and boom! Works!
One downside is that it doesn’t work with storyboards, weird.
I used to have calls to some kind of +isUnitTesting method, sprinkled here and there. Sometimes this is an okay starting point with legacy code, but it quickly created its own pain. I’d rather move to a single switch, moved as far outside as I can.
IMO, the easiest and more correct-ish way is to create separated target for testing.
This approach has at least two advantages:
– the ‘main’ target is clean and know nothing about tests
– you don’t have to compile parts that you’re not going to test (e.g. some view controllers, views, whatnot)
So do you put the code you want to test into two targets: your app, and your test target (where your test target doesn’t link against your app)?
Yes, some parts included in both targets. Also, this approach shows which parts could be completely decoupled from the codebase into ‘submodules’.
That’s an interesting approach Alex.
How do you feel about having to add the classes under test, and their dependencies into the test target as well? I personally don’t like having to tick those checkboxes every time.
Also why do you think your approach highlights components that can be decoupled?
I was going to say the same thing. I have separate targets for the app and for testing. That Way I just have to include the AppDelegate with nothing on it on my test target and the regular one on the main target.
It’s also easier to have dependencies that are needed just for testing on my Podfile this way.
This is great John – Thanks.
We’re using swift here so I’ve had quick go at implementing the same idea:
1: Comment out @UIApplicationMain in AppDelegate.swift
2: Make your empty TestingAppDelegate.swift
class TestingAppDelegate: UIResponder, UIApplicationDelegate {
var window: UIWindow?
}
3: Make a new file called ‘main.swift’ and add the following code:
import UIKit
let isRunningTests = NSClassFromString("XCTestCase") != nil
if isRunningTests {
UIApplicationMain(C_ARGC, C_ARGV, nil, NSStringFromClass(TestingAppDelegate))
} else {
UIApplicationMain(C_ARGC, C_ARGV, nil, NSStringFromClass(AppDelegate))
}
Thanks! There was a discussion on Twitter about “How do I do that in Swift?” so it’s good to have an example.
Thanks Paul Booth, you’ve put me on right track with ‘main.swift’ tip.
Some things have changed in Xcode 7/Swift 2. Following is what I’ve ended up with. Turns out you can just pass
and skip creating empty
.
private func delegateClassName() -> String? {
return NSClassFromString("XCTestCase") == nil ? NSStringFromClass(AppDelegate) : nil
}
UIApplicationMain(Process.argc, Process.unsafeArgv, nil, delegateClassName())
Nice shot. we are actually making return YES early in the didFinishLaunching.
Does the TestingAppDelegate needs to be compiled into the app ?
I used to use an early return in didFinishLaunching. But I found that by moving the test outside to main, it simplified the app delegate — and many more people work in the app delegate, while nobody really touches main. So it’s harder for people to accidentally break. But also, this makes it possible to write unit tests against your app delegate!
Yes, TestingAppDelegate does need to be compiled into the app. That’s a little smelly, but avoiding the need to link makes the code more complicated. I’d rather go with simple code.
Hey Jon, thanks for sharing this. I’ve been using early returns so far too, but I prefer this approach. We can look at it from the SRP point of view, and the AppDelegate should be responsible to find out whether it’s running for testing or not. I’ll convert all my current tests suites now 🙂
Hi Jon, I didn’t get your reply by email (I wish I had).
To no more have to have “two” delegate compiled :
@autoreleasepool {
Class appDelegateClass = NSClassFromString(@”XYZTestingAppDelegate”);
if( appDelegateClass == nil ) {
appDelegateClass = [DOAAppDelegate class];
}
return UIApplicationMain(argc, argv, nil, NSStringFromClass(appDelegateClass));
}
So I prefer this one, as the XYZTestingAppDelegate is no part of the test bundle.
@Gio : I think the SRP is more respected this way : one AppDelegate for App, without any relationship/test for returning earlier because of tests.
Just seen the “Notify me of followup comments via e-mail” tickbox which is just after the post coment button 🙂
Oh, this is better! I’ve updated my post to use this… thanks!
Couple things to note from doing this myself:
– If you’re using storyboards, you’ll need to make sure that your storyboard is not set to load automatically when the app starts up.
– If you’re using KIF tests or other UI tests, make sure that you’re checking for the existence of those classes in main before you swap out the app delegate. I generally keep my UI tests in a separate bundle from my non-UI tests, so I was able to keep the startup check in main.
If you want to take a look at how this is set up, I got it working in the TestingPlayground app I put together for my most recent talk:
Awesome stuff! Love your blog.
Why not to use for example UIResponder class instead of adding TestingAppDelegate?
Because UIResponder will always be present. But see this comment for a better way.
UIResponder could be like a stub for AppDelegate.
If we do not use our AppDelegate like a singleton in a production code, tests won’t call it and this means that we are able to stub delegate with an instance of any class (I’m using UIResponder).
And there are no need to create fake AppDelegate in production or test target.
Fake AppDelegate is a must only if our tested production code doing something like this:
This code work form me (little adjusments) in main.swift:
let isRunningTests = NSClassFromString(“XCTestCase”) != nil
if isRunningTests {
UIApplicationMain(Process.argc, Process.unsafeArgv, nil, NSStringFromClass(TestingAppDelegate))
} else {
UIApplicationMain(Process.argc, Process.unsafeArgv, nil, NSStringFromClass(AppDelegate))
}
This technique fails for me in Xcode 7 beta, it is no longer finding the TestAppDelegate. Any pointers how to solve this?
If your TestAppDelegate is a member of your unit test bundle target, remove it and add it to your main target.
Compare what you have against my MarvelBrowser project, which works in Xcode 7:
Thanks Jon,
When I try your technique on my code, with my test app delegate in my unit test target, it fails to load my test app delegate (NSClassFromString returns nil when called with my test app delegate name).
I cloned your MarvelBrowser project to try to test it there as well, but I couldn’t build it due to a missing file: “MarvelKeys.m”.
A follow-up: I commented out the code preventing the build of MarvelBrowser, and when running I experience the same result. TestingAppDelegate is never loaded. AppDelegate is used regardless if I’m running the app or the unit tests.
You’re quite correct. I suspect that the test bundle is being injected too late. I filed a Radar.
Hi Jon, what is the radar number, is it posted on openradar? I’d like to dupe it please!
I just copied it to openradar. It’s 22101460
Hi Jon, Apple replied to me that my radar is duplicating yours, and that it is closed.
Can you update what they did please?
Thanks
Basically, they said “Sorry, that’s depending on an implementation detail that can change, so this won’t work anymore.”
As recently observed, testing for the injected delegate does not work as of Xcode 7 beta 6.
However, I’ve addressed the problem similarly as the first commenter, by simply testing for the presence of an environment variable. Furthermore, I’m not even providing a substitute delegate; just passing nil as the last parameter to UIApplicationMain works fine.
{
NSString *appDelegateClassName = nil;
if (![NSProcessInfo processInfo].environment[@"XCTestConfigurationFilePath"])
{
appDelegateClassName = NSStringFromClass([KashooAppDelegate class]);
}
return UIApplicationMain(argc, argv, nil, appDelegateClassName);
}
Oops, I forgot to close a tag properly up there. Oh well.
I fixed it 🙂
@Ben solution does not work with Xcode 6.4 🙁
I suspect this also has something to do with the strange memory errors I’m seeing when running my existing unit tests that were fine before Xcode 7, in terms of the test bundle being injected “too late”.
There’s always the possibility of creating a blank class at runtime:
static void ApplicationDidFinishLaunching(id self, SEL _cmd)
{
NSLog(@"TestingAppDelegate finished launching!");
}
static UIWindow *window()
{
UIWindow *window = [[UIWindow alloc] initWithFrame:CGRectZero];
window.rootViewController = [[UIViewController alloc] init];
return window;
}
static Class createTestingAppDelegate()
{
Class class = objc_allocateClassPair([NSObject class], "TestingAppDelegate", 0);
class_addMethod(class, @selector(applicationDidFinishLaunching:), (IMP)ApplicationDidFinishLaunching, NULL);
class_addMethod(class, @selector(window), (IMP)window, "@@:");
objc_registerClassPair(class);
return class;
}
int main(int argc, char *argv[])
{
@autoreleasepool {
BOOL isTesting = NSClassFromString(@"XCTestCase") != nil;
Class appDelegateClass = (isTesting) ? createTestingAppDelegate() : [AppDelegate class];
return UIApplicationMain(argc, argv, nil, NSStringFromClass(appDelegateClass));
}
}
In my case under Xcode 7 I had to add the AppDelegateForTesting to the project target since NSClassFromString always returned nil when AppDelegateForTesting was added to the test target.
Here is the code that worked for me:
BOOL isRunningTests = ([NSProcessInfo processInfo].environment[@"XCTestConfigurationFilePath"] != nil);
if (isRunningTests) {
appDelegateClass = NSClassFromString(@"AppDelegateForTesting");
}
return UIApplicationMain(argc, argv, nil, NSStringFromClass(appDelegateClass));
This is exactly the approach I used to take before learning about testing for classes injected via the test bundle. Now that injection is delayed on Xcode 7, we need to go back to the technique you show.
Hi there. This is not working for me. I get crashes because ‘Default context is nil! Did you forget to initialize the Core Data Stack?’ is now missing from the AppDelegate
Core data initialization has nothing to do in your app delegate (put this in another object, more respectful to the SRP).
I agree with Kenji that Core Data initialization should be handled elsewhere. And for unit tests, you’ll probably want an in-memory stack that you configure for the tests.
But that aside… the basic idea of having a TestingAppDelegate is that you can customize it if necessary, mimicking any “must-haves” from your real app delegate.
Found the solution (thanks @Simon Lucas to give me the idea to look into env vars) :
NSString *testBundlePath = [NSProcessInfo processInfo].environment[@"TestBundleLocation"];
if( testBundlePath )
{
NSBundle *testBundle = [NSBundle bundleWithPath:testBundlePath];
NSError *error = NULL;
[testBundle loadAndReturnError:&error];
if( error )
{
NSLog(@"error : %@", error);
}
appDelegateClassName = @"XYZTestingAppDelegate";
}
return UIApplicationMain(argc, argv, nil, appDelegateClassName);
I think this solution is better than relying on runtime object creation.
Arg… work only in simulator.
On a device :
(BOOL) $2 = NO
TestBundleLocation is location of the xctest bundle on the Mac side, not device one.
So I fixed it as the bundle is in the tmp directory of the app :
NSString *appDelegateClassName = NSStringFromClass([AppDelegate class]);
NSString *testBundlePath = [NSProcessInfo processInfo].environment[@"TestBundleLocation"];
#if !TARGET_IPHONE_SIMULATOR
NSString *testBundleName = [testBundlePath lastPathComponent];
testBundlePath = [[NSTemporaryDirectory() stringByAppendingPathComponent:testBundleName] stringByStandardizingPath];
#endif
if( testBundlePath )
{
NSError *error = nil;
NSBundle *testBundle = [NSBundle bundleWithPath:testBundlePath];
[testBundle load];
if( testBundle == nil || error )
{
NSLog(@"error loading bundle %@ : %@", testBundle, error);
}
appDelegateClassName = @"MBCTestingAppDelegate";
}
return UIApplicationMain(argc, argv, nil, appDelegateClassName);
}
Tested on two devices (8.4 and 9.1)
@jon, can you edit code above to put #if !TARGET_IPHONE_SIMULATOR block inside the if( testBundlePath ) one ?
I run unit tests only on simulator.
I just updated the post for what I use now in Xcode 7.
If you want to omit the default view controller too, you can do that by providing it in the fake app delegate
var window: UIWindow? = UIWindow(frame: UIScreen.mainScreen().bounds)
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
window?.rootViewController = UIViewController()
return true
}
}
Yes, once we substitute the app delegate, we have lots of control. Thanks for the example!
Love this approach, but do you know of any technique for detecting if we are running UI tests? As in this scenario we would want to load the original app delegate (the one that actually has the UI to test).
The only way I know of is less automatic. Make sure your UI tests scheme sets up an environment variable. Then in main, test for this variable with getenv.
This approach also has the added benefit of fixing some holes in the default way that Xcode calculates code coverage. I wrote about on my blog:
Nice blog post Andy, thanks for sharing! You’re absolutely right, the coverage stats would be skewed by the normal app launch sequence — something that doesn’t reflect the test content in any way. We reached the same conclusion, for different purposes.
Hello, so what is the current working and preferred approach for testing AppDelegate? I’ve read that the approach described in the beginning in this blog does not work anymore. Or does it still work?
I’m currently trying to set up my testing environment based on Kiwi. I quickly learned that accessing AppDelegate directly in tests via [[UIApplication sharedApplication] delegate] does not give me enough control. So now I’m looking for any kind of ways to isloate AppDelegate for testing.
It does work. The current contents of the post are accurate at this time.
I think theres a mistake in your post. In the section “Provide TestingAppDelegate” you just have the main.swift code and not a TestAppDelegate.swift file.
Oh I see, I mistakenly repeated the main.swift part. Thanks. I also updated main.swift for Xcode 8 beta, which currently complains about Process.unsafeArgv unless it has those crazy casts.
As part of the mass Swift renaming, etc. in Swift 3 Xcode Beta 6, Process.argc and Process.unsafeArgv have been renamed to CommandLine.argc and CommandLine.unsafeArgv (link), and the UnsafeMutablePointer ‘init’ has been replaced ‘withMemoryRebound(to:capacity:_)’ (link). Still trying to understand what that means for the code in main.swift, but know it won’t work until fixed.
This seems to work in main.swift for Xcode 8 beta 6.
let appDelegateClass: AnyClass = isRunningTests ? TestingAppDelegate.self : AppDelegate.self
let argsCount = Int( CommandLine.argc )
let argsRawPointer = UnsafeMutableRawPointer( CommandLine.unsafeArgv )
let args = argsRawPointer.bindMemory( to: UnsafeMutablePointer<Int8>.self, capacity: argsCount )
UIApplicationMain( CommandLine.argc,
args,
nil,
NSStringFromClass( appDelegateClass )
)
Nice idea, I do this:
if let _ = NSClassFromString("XCTestCase") {
return true
} else {
return false
}
}
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
// app init
// required init
guard testingMode() == false else {
return true
}
// regular init
return true
} | http://qualitycoding.org/app-delegate-for-tests/ | CC-MAIN-2017-13 | refinedweb | 3,396 | 57.16 |
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Tell us what questions you have trouble with or doubt your correct answer. If it is from an online test or paper, show the link to the test so we can look it up for easier reference.
Ah great. So I can get help. :-) Here is all the questions with my answers on it. Is something wrong?
abel: It is not an online test. This is a paper that we could use to study questions for coming tests....the stupied thing is that we dont get the correct answers with the paper. I dont want to learn the questions if they a wrong. :-)
1. When an "is a" relationship exists between objects, it means that the specialized object has
a.
some of the characteristics of the general class, but not all, plus additional characteristics.
b.
some of the characteristics of the general object, but not all.
c.
none of the characteristics of the general object.
d.
all the characteristics of the general object, plus additional characteristics.
ANS: ___B__
2. Which of the following statements declares Salaried as a derived class of PayType?
a.
public class Salaried : PayType
b.
public class Salaried :: PayType
c.
public class Salaried derivedFrom(Paytype)
d.
public class PayType : Salaried
ANS: __A___
3. If ClassA is derived from ClassB, then
a.
public and private members of ClassB are public and private, respectively, in ClassA
b.
public members in ClassB are public in ClassA, but private members in ClassB cannot be directly accessed in ClassA
c.
neither public or private members in ClassB can be directly accessed in ClassA
d.
private members in ClassB are changed to protected members in ClassA
ANS: _B____
4.___
5. If a derived class constructor does not explicitly call a base class constructor,
a.
it must include the code necessary to initialize the base class fields.
b.
the base class fields will be set to the default values for their data types.
c.
C# will automatically call the base class's default constructor immediately after the code in the derived class's constructor executes.
d.
C# will automatically call the base class's default constructor just before the code
in the derived class's constructor executes.
ANS: _D____
6. A protected member of a class may be directly accessed by
a.
methods of the same class
b.
methods of a derived class
c.
methods in the same namespace
d.
All of the above.
ANS: ___D__
7. When declaring class data members, it is best to declare them as
a.
private members
b.
public members
c.
protected members
d.
restricted members
ANS: ___A__
8. If a class contains an abstract method,
a.
you cannot create an instance of the class
b.
the method will have only a header, but not a body, and end with a semicolon
c.
the method must be overridden in derived classes
d.
All of the above
ANS: __D___
9. All fields declared in an interface
a.
are const and static
b.
have protected access
c.
must be initialized in the class implementing the interface
d.
have private access
ANS: __C___
10. When one object is a specialized version of another object, there is this type of relationship between them.
a.
"has a"
b.
"is a"
c.
direct
d.
"contains a"
ANS: __A___
11. A derived class can directly access
a.
all members of the base class
b.
only public and private members of the base class
c.
only protected and private members of the base class
d.
only public and protected members of the base class
ANS: __D___
12. In the following statement, which is the base class?
public class ClassA : ClassB , ClassC
a.
ClassA
b.
ClassB
c.
ClassC
d.
Cannot tell
ANS: __B___
13.__
14. If a base class does not have a default constructor or a no-arg constructor,
a.
then a class that inherits from it, must initialize the base class values.
b.
then a class that inherits from it, must call one of the constructors that the base class does have.
c.
then a class that inherits from it, does not inherit the data member fields from the base class.
d.
then a class that inherits from it, must contain the default constructor for the base class.
ANS: __C___
15. Protected members are
a.
not quite private
b.
not quite public
c.
Both A and B
d.
Neither A or B
ANS: __C___
16. Protected class members are denoted in a UML diagram with the symbol
a.
*
b.
#
c.
+
d.
-
ANS: __D___
17. In a class hierachy
a.
the more general classes are toward the bottom of the tree and the more specialized
are toward the top.
b.
the more general classes are toward the top of the tree and the more specialized are toward the bottom.
c.
the more general classes are toward the left of the tree and the more specialized are toward the right.
d.
the more general classes are toward the right of the tree and the more specialized are toward the left.
ANS: __C___
18. If a class contains an abstract method,
a.
you must create an instance of the class
b.
the method will have only a header, but not a body, and end with a semicolon
c.
the method cannot be overridden in derived classes
d.
All of the above.
ANS: __A___
19. In an interface all methods have
a.
private access
b.
protected access
c.
public access
d.
namespace access
ANS: ___C__
20. Which of the following statements correctly specifies three interfaces:
a.
public class ClassA : Interface1, Interface2, Interface3
b.
public class ClassA : [Interface1, Interface2, Interface3]
c.
public class ClassA : (Interface1, Interface2, Interface3)
d.
public class ClassA : Interface1 Interface2 Interface3
ANS: __A___
TRUE/FALSE
1. It is not possible for a base class to call a derived class method.
ANS: __T___
2. If a method in a derived class has the same signature as a method in the base class, the derived class method overloads the base class method.
ANS: __F___
3. Every class is either directly or indirectly derived from the Object class.
ANS: ___T__
4. An abstract class is not instantiated, but serves as a base class for other classes.
ANS: __T___
5. In an inheritance relationship, the derived class constructor always executes before the base class constructor.
ANS: ___F__
6. If two methods in the same class have the same name but different signatures, the second overrides the first.
ANS: __T___
7. All methods in an abstract class must also be declared abstract.
ANS: ___T__
8. When an interface variable references an object, you can use the interface variable to call all the methods in the class implementing the interface.
ANS: __F___
you had:
1B should be 1D
2A
3B
4C should be 4A (depends on what asker means by "open", picture of uml inheritance)
5D... impossible to answer, answers (c,d) do not match question and (a,b) are wrong, however, D is closest to correct imo...
6D, not correct, but there's no correct answer. Both A and B are good.
7A depends on your school of thought... the term for "data members" should be "fields"
8D no correct answer exists, both A and C are correct, however, a class cannot only have an abstract member, it must also be declared an abstract class, hence the question is wrong (again)
9C this is total rubbish! Interfaces cannot contain fields (try it, you get a CS0525 in C#)
10A i think should be B, but "specialized version of" is not an OO term and hence this this is a guessing game (inheritance? aggregation?)....
11D
12B, should be D, because the statement is illegal with classes
13C should be 13A (same as q. 4)
14C should be B
15C q. is total rubbish, there's no reasonable answer
16D should be B (the minus symbol is for private accessor)
17C should be B (ridiculous question without a context (UML?), and even then, depends, your answer can also be good)
18A is wrong, but there are no correct answers
19C
20A
that was more work then I thought, because there were very few correct questions/answers (that has all to do with the questionnaire, nothing with the answers you tried to give, you couldn't know), some talk even total nonsense... Now on with the true/false, see if those questions are better:
1T should be F. This depends on what the question means by "calling a method". There are many ways to call a derived classes method, though not through the inheritance tree...
2F should be T, but this process is called shadowing or hiding in C#. Not "overriding". The question is not correct here and will give a compiler warning. Use the override or new modifiers.
3T
4T
5F
6T should be F (this is called overloading)
7T should be F (abstract classes can contain concrete methods)
8F question is total rubbish, there's no such thing as an interface variable.
Conclusion:
Very strange questionnaire, could've been made by somebody who only read an introductory chapter on C# and UML. Most questions are unanswerable and some are even total rubbish. Sorry to be so harsh, but it's the first time I see a questionnaire so bad as this, most of the times there's still some sense in them somehow or at least the questions are somehow correct.... but not here.
I suggest you try to contact the creator of these questions and have him contact me for attending a course or something :)
-- Abel --
:)
Glad I could've been of some help.
indeed
>5D... impossible to answer, answers (c,d) do not match question and (a,b) are wrong, however, D is closest to correct imo...
actually, 5D is correct AFAIK
>6D, not correct, but there's no correct answer. Both A and B are good.
actually, option C is good also, so 6D is correct for me
>7A depends on your school of thought... the term for "data members" should be "fields"
I do agree on 7A, as by default, data members should not be visible to "outside world" unless you need to have a different behavior
>8D no correct answer exists, ...
actually, 8D is correct!
>9C this is total rubbish! Interfaces cannot contain fields (try it, you get a CS0525 in C#)
well, you have to remember that you are answering a microsoft-style questionaire.
I am not sure if it will raise a compile error or not, but from the docs, I would deduct that the fields have private access (and hence are completely useless, actually)
my choice would hence by 9D.
>10A i think should be B, but "specialized version of" is not an OO term and hence this this is a guessing game (inheritance? aggregation?)....
10B indeed.
>12B, should be D, because the statement is illegal with classes
12B is correct. the name ClassB does not make it a class (remember, it's ms trapping :)
same link:
>>When a base type list contains a base class and interfaces, the base class must come first in the list.
>15C q. is total rubbish, there's no reasonable answer
15C is correct, IMHO.
private = nobody else can see/use the method/property
public = everybody else can see/use the method/property
protected = some specific code can see/use the method
not rocket science question, I do agree !
>18A is wrong, but there are no correct answers
18B is correct. only a abstract class can have abstract methods, hence the description of B is correct.
anyhow, A and C are definitively wrong, so B would have been my choice by exclusion
>1T should be F. This depends on what the question means by "calling a method". There are many ways to call a derived classes method, though not through the inheritance tree...
I disagree here. the base class (A) cannot call a method of a class (B) that inherits (A), as (A) has to be compiled "before" (B) in order to have the "interface" ready. trying to do this would be a cyclic reference problem.
>2F should be T,
agreed
>6T should be F (this is called overloading)
agreed
>7T should be F (abstract classes can contain concrete methods)
Agreed.
>Abstract method declarations are only permitted in abstract classes
does not exclude that abstract classes have non-abstract methods
>8F question is total rubbish, there's no such thing as an interface variable.
8F would be my choice.
I presume what is meant is a variable that is declared with the data type of the interface.
which does not allow you to directly call the derived class methods (at least not without casting)
aka:
IInterface var = new ClassImplementingIInterfac
var.MethodofClassImplement
(ClassImplementingIInterfa
@5 you say: actually, 5D is correct AFAIK
I said: "does not match the question". Because a default constructor is a private constructor in C#, unless you make it explicitly public or protected. So, it depends on the code and the question needs tweaking. The following example will not compile:
public class TestBase
{
public TestBase(string bla) { }
}
public class TestChild : TestBase
{
public TestChild(int someInt) { } // error CS1729
}
@6 you say: actually, option C is good also, so 6D is correct for me
and I said that only a and b are good. C says "protected member is accessible to any class in the namespace". There is no access modifier that restricts to a namespace:
public: no restriction
protected: restricted to containing class and derived classes
internal: restricted to classes in assembly (note that this is different from "namespace")
protected internal: restricted to any class in assembly and any derived classes
private: only containing class
See also:
@7 you say: I do agree on 7A, as by default, data members should not be visible to "outside world" unless you need to have a different behavior
and I said it depends on your school of thought. I take that back. It depends onmany things: whether you use constant fields or constant statics, which can and should be public (see Uri, String and Int class). Non-constant fields can also be internal or even protected, depending on your design (see Int (m_value) and TimeSpan (ticks)). Where internal will often have the preference (it is impossible to access by people having your assembly, even if they derive from your class).
@8: you say: actually, 8D is correct!
and I said: no correct answer exists, but A & C are correct. That was wrong. C is only partially correct: you can have derived classes that do not overload the abstract methods.
And B is partially correct also: "a class cannot contain an abstract method, unless the class itself is called abstract", which is not what is said in the question: "if a class contains an abstract method ...": it will not compile. Q.E.D. ;-)
@9 you refer to, which says:
interface SomeInterface
{
public static const string bla = ""; // CS0525 "Interfaces cannot contain fields"
}
!
@15 you think C (not quite public/private).
I said: this is rubbish. There's no definition for "not quite". Does it mean more private or less private? If this definition is correct, then "internal" is also "not quite public/private". Deduction then gives us "internal == protected"???? Anyway, I stick to mine "it's rubbish" lol
@18 you say: 18B is correct. only a abstract class can have abstract methods, hence the description of B is correct.
I think you mean here: "hence the description of B is incorrect", because there's no mention of an abstract class in the question, hence "a class cannot have an abstract method", only "an abstract class can have zero or more abstract methods/properties etc".
If you have to answer the question, I agree that B i most likely meant as correct answer...
//// TRUE / FALSE questions \\\\
@1 amongst more, you say "trying to do this would be a cyclic reference problem."
in my answer, I say "it depends on what you mean by calling a method". Consider this example, it will compile and run and there's no cyclic reference problem; the base class can call a method of a derived class:
public class TestBase
{
public TestBase() { }
public void DoSomethingWithChild(TestC
someChild.someProp = "test";
}
}
public class TestChild : TestBase
{
public string someProp { get; set; }
public void DoSomething()
{
DoSomethingWithChild(this)
}
}
@8 you have a different reading of the question. I said there's no such thing as in interface variable, and you say that it is a variable declared with the type of an interface, which of course is possible.
Making matters worse: in the Java world, an interface variable is a constant that is declared on an interface (as I noted earlier, in Java you can have constants and statics on an interface). In C# that is not possible, which is why I said there's no such thing.
I like your reading of that last question, though I still consider it a poor question that requires out-of-band thinking beyond the question definition, which is something that half of all the questions here required.... :S
-- Abel --
@6: the issue is the understanding of the question and it's answers.
the "protected" does not "limit" to the namespace, actually. however, all classes that are in the namespace have access. there might be other classes in other namepaces, but that case is not excluded by answer C... so, 6C is good also (at least, it's not wrong)
@8: as for @6: as long as a "answer" is not wrong, it has to be considered correct. you might name it "partially correct"...
@9: I am not sure if it compiles or not, maybe that behavior has changed between versions.
!
call it trap if you wish, the issue is that the questionnaires are built that way. also, to exclude people that do just learn brain-dumps trying to pass the exams without understanding the material.
only by having understood the concepts that you can pass those questions
@18 I will rephrase to "hence the description of B can be applied
T/F@1: interesting example... I wonder how that could be compiled, from the point of view of a compiler
I presume the compiler would first build up the interface of TestBase (pass), then TestChild (pass), and the compiles each method code, which will also pass.
I really doubt any real-life implementation scenario for this...
T/F@8: resp all the comments:
as I have taken plenty of MS (and other software exams, check my profile to see which status I got, not all individual exams though), and I managed to pass them all on the first "try" except 2, where I was send before I finished my preparations, I think I am kind of an expert of understanding how the exams "work".
it does not mean that I am 200% sure of all the answers I give here, but at least, I can answer plenty of the question by cross-checking some knowledge from all my different preparations, along with a good basic understanding of general programming concepts.
I don't (and won't) agree on all being correct. but at least, I am aware of both the concept and the issues around them.
regards,
But apart from knowing what the possible answer should be, I think it is also good to step aside and look at the questions. Some of them just talk nonsense (in the light of C#, I mean) and maybe that's on purpose, but still... Anyway, discussing them is good and reveals some of the misunderstandings that are around coding in C#.
Mainly the first one above (@5): I wouldn't have said what I said if I hadn't tested and verified it. Even though it is called implicitly, the compiler will complain (with an error, not a warning) and you cannot compile.
Another thing on @6: I agree to your reading of the question (though I do not agree to the question, it is still plain wrong imo), but don't mix things up: "all classes in the namespace have access to protected members" is just not true:
public classA {
protected void doSomething() {}
}
public classB {
private void callDoSomething{
classA clsa = new classA();
clsa.doSomething(); // compile error
}
}
I will leave it now to that. To the other points I second your thoughts, anyway.
You seem to have one question yourself though, on T/F nr 1: the circular reference. Yet it is quite common, consider this DOM example, which works in most OO languages, and contains loads of circular references:
XmlDocument doc = new XmlDocument();
doc.Load("some.xml");
XmlNode node = doc.DocumentElement.FirstC
which will return the document element :)
Regards,
-- Abel -- | https://www.experts-exchange.com/questions/24320076/20-questions-A-B-C-and-D.html | CC-MAIN-2018-05 | refinedweb | 3,472 | 73.37 |
Gets a value indicating whether the test point is over a group.
public virtual bool InGroup { get; }
Overridable Public ReadOnly Property InGroup As Boolean
You can also use the InGroupCaption property to determine whether the test point is over a group caption. Note that if the test point is over a group caption, both the InGroupCaption and InGroup properties return true.
You can also determine whether the test point is over a group caption button (this is not supported in all paint styles). Use the HitTest property for this purpose.
Use the Group property to obtain the group over which the test point rests.
The following sample code represents a handler for the MouseMove event. It calculates hit information for the mouse pointer's position via the NavBarControl.CalcHitInfo method. Then the group that is hovered over is accessed.
using DevExpress.XtraNavBar;
private void navBarControl1_MouseMove(object sender, MouseEventArgs e) {
NavBarHitInfo hitInfo = navBarControl1.CalcHitInfo(new Point(e.X, e.Y));
if (hitInfo.InGroup) {
NavBarGroup group = hitInfo.Group;
// perform operations on the group here
//...
}
}
Imports DevExpress.XtraNavBar))
If HitInfo.InGroup Then
Dim Group As NavBarGroup = HitInfo.Group
' perform operations on the group here
'...
End If
End Sub | https://documentation.devexpress.com/WindowsForms/DevExpress.XtraNavBar.NavBarHitInfo.InGroup.property | CC-MAIN-2018-39 | refinedweb | 195 | 52.26 |
Build a class library with Visual Basic and the .NET Core SDK in Visual Studio 2017
A class library defines types and methods that are called by an application. A class library that targets the .NET Standard 2.0 allows your library to be called by any .NET implementation that supports that version of the .NET Standard. When you finish your class library, you can decide whether you want to distribute it as a third-party component or whether you want to include it as a bundled component with one or more applications.
Note
For a list of the .NET Standard versions and the platforms they support, see .NET Standard.
In this topic, you'll create a simple utility library that contains a single string-handling method. You'll implement it as an extension method so that you can call it as if it were a member of the String class.
Creating a class library solution
Start by creating a solution for your class library project and its related projects. A Visual Studio Solution just serves as a container for one or more projects. To create the solution:
On the Visual Studio menu bar, choose File > New > Project.
In the New Project dialog, expand the Other Project Types node, and select Visual Studio Solutions. Name the solution "ClassLibraryProjects" and select the OK button.
Creating the class library project
Create your class library project:
In Solution Explorer, right-click on the ClassLibraryProjects solution file and from the context menu, select Add > New Project.
In the Add New Project dialog, expand the Visual Basic node, then select the .NET Standard node followed by the Class Library (.NET Standard) project template. In the Name text box, enter "StringLibrary" as the name of the project. Select OK to create the class library project.
The code window then opens in the Visual Studio development environment.
Check to make sure that the library targets the correct version of the .NET Standard. Right-click on the library project in the Solution Explorer windows, then select Properties. The Target Framework text box shows that we're targeting .NET Standard 2.0.
Also in the Properties dialog, clear the text in the Root namespace text box. For each project, Visual Basic automatically creates a namespace that corresponds to the project name, and any namespaces defined in source code files are parents of that namespace. We want to define a top-level namespace by using the
namespacekeyword.
Replace the code in the code window with the following code and save the file:
Imports System.Runtime.CompilerServices Namespace UtilityLibraries Public Module StringLibrary <Extension> Public Function StartsWithUpper(str As String) As Boolean If String.IsNullOrWhiteSpace(str) Then Return False End If Dim ch As Char = str(0) Return Char.IsUpper(ch) End Function End Module End Namespace
The class library,
UtilityLibraries.StringLibrary, contains a method named
StartsWithUpper, which returns a Boolean value that indicates whether the current string instance begins with an uppercase character. The Unicode standard distinguishes uppercase characters from lowercase characters. The Char.IsUpper(Char) method returns
true if a character is uppercase.
On the menu bar, select Build > Build Solution. The project should compile without error.
Next step
You've successfully built the library. Because you haven't called any of its methods, you don't know whether it works as expected. The next step in developing your library is to test it by using a Unit Test Project. | https://docs.microsoft.com/en-us/dotnet/core/tutorials/vb-library-with-visual-studio | CC-MAIN-2018-51 | refinedweb | 570 | 66.74 |
0
im having a problem with making stack with array converted to linked list
so far this is my code ...
import java.util.*; public class Nkakainis { public static void main(String[] args){ Stack <String> istak = new Stack<String>(); String[] names = {"john", "mark", "peter"}; List<String> list1 = Arrays.asList(names); System.out.println("pushed " + istak.push(list1)); } }
i dont have an idea on how to push those strings..how can i display john, mark, peter?
and how can i make other stack operations show on the output (i.e. pop(), peek(), search(), isEmpty())?
corrections are greatly appreciated ... i really need ur help badly :( | https://www.daniweb.com/programming/software-development/threads/284387/stack-with-array-to-linkedlist | CC-MAIN-2017-34 | refinedweb | 102 | 68.67 |
A few years ago, I wrote a series of posts discussing how to use Ajax in the WordPress Frontend. The purpose of the series is simple:
We're going to give a very brief overview of what Ajax is, how it works, how to set it up on the front, and understanding the hooks that WordPress provides. We'll also actually build a small project that puts the theory into practice. We'll walk through the source code and we'll also make sure it's available on GitHub, as well.
Generally speaking, the series holds up well but, as with all software under constant development, techniques, APIs, and approaches change. Furthermore, as years pass and we continue to refine our skills, we get better at development and we get better at employing new APIs.
Because of all of the above, I want to revisit the concept of Ajax in WordPress so you see some of the new APIs and how to employ them in your day-to-day work or how to refactor some of the code you may be working with right now.
A word of caution before you go too far into this tutorial: I assume that you have already read through the series linked in the introduction of this article, and that you have some experience with building WordPress plugins.
Defining the Plugin
As with any WordPress plugin, it's important to make sure you define the header so WordPress will be able to read the file in order to introduce the new functionality into the core application.
I'm calling this variation of the plugin Simple Ajax Demo, and it's located in
wp-content/plugin/wp-simple-ajax. The first file I'm creating resides in the root directory of
wp-simple-ajax and is called
wp-simple-ajax.php.
It looks like this:
<?php /** * Plugin Name: Simple Ajax Demo * Description: A simple demonstration of the WordPress Ajax APIs. * Version: 1.0.0 * Author: Tom McFarlin * Author URI: * License: GPL-2.0+ * License URI: */
The code should be self-explanatory, especially if you're used to working with WordPress Plugins; however, the most important thing to understand is that all of the information above is what will drive what the user sees in the WordPress dashboard.
That is, users will see the name, description, and version of the plugin as well as the author's name (which will be linked to the specified URL) when they are presented with the option to activate the plugin.
Adding WordPress's Ajax File
At this point, the plugin will appear in the WordPress Plugin dashboard but it won't actually do anything because we haven't written any code. In order to make that happen, we'll be approaching this particular plugin using the procedural programming approach rather than the object-oriented approach I've used in most of my tutorials..
Ultimately, this series will be covering both types of programming supported by PHP and WordPress.
Most likely, if you've worked with Ajax in the past, then you've done something like this in order to give your plugin the support to make asynchronous calls:
<?php add_action( 'wp_head','acme_add_ajax_support' ); function acme_add_ajax_support() { ?> <script type="text/javascript"> var ajaxurl = '<?php echo admin_url( 'admin-ajax.php' ); ?>'; </script> <?php }
This particular method isn't inherently wrong, but it does neglect some of the newer APIs I'll cover momentarily. It also mixes PHP, HTML, and JavaScript all in a single function.
It's not great as it gets the job done, but there is a cleaner way to do this.
How We Add Ajax Support
First, to make sure the plugin can't be directly accessed by anyone, add the following conditional just under the plugin's header:
<?php // If this file is called directly, abort. if ( ! defined( 'WPINC' ) ) { die; }
Note the opening PHP tag will not be necessary since this code will come later in a pre-existing PHP file (it's necessary for syntax highlighting right now).
Next, let's set up a function to include WordPress support for Ajax through the use of some of the existing APIs that don't involve mixing languages.
Here's what we'll need to do:
- We're going to create a function responsible for adding Ajax support.
- We'll hook the function into the
wp_enqueue_scriptaction.
- We will take advantage of the
wp_localize_scriptAPI call in order to enqueue WordPress's support for Ajax (which comes from
admin-ajax.php).
It seems straightforward enough, doesn't it? Note if you have any questions, you can always add them in the comments. Check out the following code to see if you can follow along:
<?php add_action( 'wp_enqueue_scripts', 'sa_add_ajax_support' ); /** * Adds support for WordPress to handle asynchronous requests on both the front-end * and the back-end of the website. * * @since 1.0.0 */ function sa_add_ajax_support() { wp_localize_script( 'ajax-script', 'sa_demo', array( 'ajaxurl' => admin_url( 'admin-ajax.php' ) ) ); }
Again, note the opening PHP tag will not be required in the final version of the plugin, as it is here only to take advantage of the syntax highlighting functionality.
With that said, take a look at
wp_localize_script. Before examining each parameter, let's review the purpose of this function. From the Codex, the short version is as follows:
Localizes a registered script with data for a JavaScript variable.
The longer description is important, though:
This lets you offer properly localized translations of any strings used in your script. This is necessary because WordPress currently only offers a localization API in PHP, not directly in JavaScript.
Though localization is the primary use, it can be used to make any data available to your script that you can normally only get from the server side of WordPress.
Now review the parameters it accepts:
-
dataparameter. It refers to an array that will be sent to the browser as a JavaScript object. Since we're passing the URL of a path to a file, Ajax support will be provided.
Notice the first parameter is
ajax-script. Keep this in mind when we turn our attention to writing and enqueuing our own JavaScript, as we'll need to use this handle one more time.
Also remember to make note of the name you've selected for your call to the API, as we'll be using this when working with the client-side code later in this tutorial.
An Important Note About Ajax Support
Notice we're only using the
wp_enqueue_script hook and we're not using
admin_enqueue_script. This is because
ajaxurl is already defined in the dashboard.
This means if you're looking to make Ajax requests in the administration area of WordPress, then you don't need to enqueue anything. Everything we're doing in the context of this tutorial is specifically for the front-end of the website.
Setting Up Your Server-Side Code
Now it's time to write a function your JavaScript will call via Ajax. This can be anything you want it to be, but for the purposes of this plugin we're going to set up a function that will return information about the user who is logged into the site.
The plugin will do the following:
-
Now that we've outlined exactly how the code is going to work whenever a user makes an Ajax request to the server, let's start writing a function for doing exactly that. We'll call it
sa_get_user_information.
<() { }
The function's implementation will come later in this tutorial, but the primary takeaway from the code above is that we've hooked into both
wp_ajax_get_current_user_info and
wp_ajax_nopriv_get_current_user_info.
These two hooks are well documented in the Codex, but the first hook will allow those who are logged in to the site to access this function. The second hook will allow those who are not logged in to this site to access this function.
Also note everything after
wp_ajax_ and
wp_ajax_nopriv_ is up to you, as the developer, to define. This will be the name of the function you call from the client-side as you'll see later in this tutorial..
It's highly unlikely the second case will be true, but it will help us to learn more about a few more of the WordPress APIs and how we can take advantage of them for handling erroneous requests.
The first thing to understand is
WP_Error. As with many APIs, this is available in the Codex:
Instances of WP_Error store error codes and messages representing one or more errors, and whether or not a variable is an instance of WP_Error can be determined using the is_wp_error() function.
The constructor will accept up to three parameters (though we'll only be using the first two):
-.
Next, we'll be sending the results of the errors back to the client using a function called
wp_send_json_error. This is really easy to use:
Send a JSON response back to an Ajax request, indicating failure. The response object will always have a success key with the value false. If anything is passed to the function in the $data parameter, it will be encoded as the value for a data key.
By combining both
WP_Error and
wp_send_json_error, we can create functions that will help us provide error codes to the JavaScript calling the server-side.
For example, let's say we have a function providing an error if the user isn't logged in to the website. This can be achieved using the following function:
<?php /** * Determines if a user is logged into the site using the specified user ID. If not, * then the following error code and message will be returned to the client: * * -2: The visitor is not currently logged into the site. * * @access private * @since 1.0.0 * * @param int $user_id The current user's ID. */ function _sa_user_is_logged_in( $user_id ) { if ( 0 === $user_id ) { wp_send_json_error( new WP_Error( '-2', 'The visitor is not currently logged into the site.' ) ); } }
Notice the function is marked as private even though it's in the global namespace. It's prefixed with an underscore in order to denote this function should be considered private.
We'll revisit this in the next article.
Secondly, we need to handle the case if the user doesn't exist. To do this, we can create a function that does the following:
<?php /** * Determines if a user is logged into the site using the specified user ID. If not, * then the following error code and message will be returned to the client: * * -3: The visitor does not have an account * * @access private * @since 1.0.0 * * @param int $user_id The current user's ID. */ function _sa_user_exists( $user_id ) { if ( 0 === $user_id ) { wp_send_json_error( new WP_Error( '-3', 'The visitor does not have an account with this site.' ); ); } }
We now have two functions, each of which will send information back to the client if something has failed, but what do we do if both of these functions pass?
Handling Successful Requests
If the functions above do not yield any errors, then we need to have a way to send the request back to the client with a successful message and the information that it's requesting.
Namely, we need to send the information back to the client that includes the current user's information in the JSON format.
To do this, we can take advantage of the
wp_send_json_success message. It does exactly what you think it would do, too:
Send a JSON response back to an Ajax request, indicating success. The response object will always have a success key with the value true. If anything is passed to the function it will be encoded as the value for a data key.
Let's combine the work we've done thus far to write a function the JavaScript will eventually call and that leverages the two smaller functions we've placed above. In fact, this will be the implementation of the function we left out earlier in this tutorial:
<() { // Grab the current user's ID $user_id = get_current_user_id(); // If the user is logged in and the user exists, return success with the user JSON if ( _sa_user_is_logged_in( $user_id ) && _sa_user_exists( $user_id ) ) { wp_send_json_success( json_encode( get_user_by( 'id', $user_id ) ) ); } }
If the user is logged in and the user exists, then we will send a success message to the client containing the JSON representation of the user. At this point, it's time to write some JavaScript.
The Client-Side Request
First, add a file called
frontend.js to the root of your plugin directory. Initially, it should include the following code:
;(function( $ ) { 'use strict'; $(function() { }); })( jQuery );
The function implementation will be covered momentarily, but we need to make sure we're enqueuing this JavaScript file in the plugin, as well. Return to the function
sa_add_ajax_support and add the following above the call to
wp_localize_script:
<?php wp_enqueue_script( 'ajax-script', plugin_dir_url( __FILE__ ) . 'frontend.js', array( 'jquery' ) );
Remember this script must have the same handle as the one defined in
wp_localize_script. Now we can revisit our JavaScript file and make a call to the server-side code we've been working on throughout this entire article.
In
frontend.js, add the following code:
/** * This file is responsible for setting up the Ajax request each time * a WordPress page is loaded. The page could be the main index page, * a single page, or any other type of information that WordPress renders. * * Once the DOM is ready, it will make an Ajax call to the server where * the `get_current_user_info` function is defined and will then handle the * response based on the information returned from the request. * * @since 1.0.0 */ ;(function( $ ) { 'use strict'; $(function() { /* Make an Ajax call via a GET request to the URL specified in the * wp_enqueue_script call. For the data parameter, pass an object with * the action name of the function we defined to return the user info. */ $.ajax({ url: sa_demo.ajax_url, method: 'GET', data: { action: 'get_current_user_info' } }).done(function( response ) { /* Once the request is done, determine if it was successful or not. * If so, parse the JSON and then render it to the console. Otherwise, * display the content of the failed request to the console. */ if ( true === response.success ) { console.log( JSON.parse( response.data ) ); } else { console.log( response.data ); } }); }); })( jQuery );
Given the number of comments in the code and assuming you're familiar with writing WordPress plugins and have some experience with Ajax, it should be relatively easy to follow.
In short, the code above makes a call to the server-side when the page is loaded and then writes information to the browser's console about the current user.
If a user is logged in, then the information is written out to the console in the form of a JavaScript object since it's being parsed from JSON.
If, on the other hand, the user is not logged in, then another object will be written out displaying an error code along with the message, all of which you will be able to see in the console.
Conclusion
By now, you should have a clear understanding of the APIs WordPress has available for working with Ajax requests for users who are logged in to the site, and for those who are not.
Ultimately, our goal should be to write the cleanest, most maintainable code possible so we have the ability to continue to work with this code as we move into the future. Additionally, we should write code like this so others who may touch our codebase have a clear understanding of what we're trying to do and are also using the best practices given our environment.
In this tutorial, I used a procedural form of programming for all of the code that was shared, demonstrated, and provided via GitHub. As previously mentioned, there's nothing inherently wrong with this, but I do think it's worth seeing what this looks like from an object-oriented perspective.
In the next tutorial, we're going to look at refactoring this code into an object-oriented paradigm that also employs WordPress Coding Standards for further documenting our work, and that uses clear file organization to make our writing as clean and clear as possible.
Remember, you can catch all of my courses and tutorials on my profile page, and you can follow me on my blog and/or Twitter at @tommcfarlin where I talk about software development in the context of WordPress and enjoy conversing with others about the same topics (as well as other things, too).
In the meantime, please don't hesitate to leave any questions or comments in the feed below and I'll aim to respond to each of them.
Subscribe below and we’ll send you a weekly email summary of all new Code tutorials. Never miss out on learning about the next big thing.Update me weekly | https://code.tutsplus.com/tutorials/improved-ajax-techniques-for-wordpress-procedural-programming--cms-24854?ec_unit=translation-info-language | CC-MAIN-2022-05 | refinedweb | 2,793 | 59.74 |
Gantry::Utils::ModelHelper - mixin for model base classes
use Gantry::Utils::ModelHelper qw( db_Main get_listing get_form_selections ); sub get_db_options { return {}; # put your default options here # consider calling __PACKAGE->_default_attributes }
This module provides mixin methods commonly needed by model base classes. Note that you must request the methods you want for the mixin scheme to work. Also note that you can request either db_Main or auth_db_Main, but not both. Whichever one you choose will be exported as db_Main in your package.
This method returns a valid dbh using the scheme described in Gantry::Docs::DBConn. It is compatible with Class::DBI and Gantry::Plugins::DBIxClassConn (the later is a mixin which allows easy access to a DBIx::Schema object for controllers).
This method is exported as db_Main and works with the scheme described in Gantry::Docs::DBConn. It too is compatible with Class::DBI and Gantry::Plugins::DBIxClassConn.
I will repeat, if you ask for this method in your use statement:
use lib/Gantry/Utils/ModelHelper qw( auth_db_Main ... );
it will come into your namespace as db_Main.
This method gives you a selection list for each foriegn key in your table. The lists come to you as a single hash keyed by the table names of the foreign keys. The values in the hash are ready for use by form.tt as options on the field (whose type should be select). Example:
{ status => [ { value => 2, label => 'Billed' }, { value => 1, label => 'In Progress' }, { value => 3, label => 'Paid' }, ], other_table => [ ... ], }
To use this method, your models must implement these class methods:
(Must be implemented by the model on which get_form_selections is called.) Returns a list of the fully qualified package names of the models of this table's foreign keys. Example:
sub get_foreign_tables { return qw( Apps::AppName::Model::users Apps::AppName::Model::other_table ); }
(Must be implemented by all the models of this table's foreign keys.) Returns an array reference whose elements are the names of the columns which will appear on the screen in the selection list. Example:
sub get_foreign_display_fields { return [ qw( last_name first_name ) ]; }
Replacement for retrieve_all_for_main_listing.
Returns a list of row objects (one for each row in the table). The ORDER BY clause is either the same as the foreign_display columns or chosen by you. If you want to supply the order do it like this:
my @rows = $MODEL->get_listing ( { order_by => 'last, first' } );
Note that your order_by will be used AS IS, so it must be a valid SQL ORDER BY clause, but feel free to include DESC or anything else you and SQL like.
DEPRECATED use get_listing instead
Returns a list of row objects (one for each row in the table) in order by their foreign_display columns.. | http://search.cpan.org/dist/Gantry/lib/Gantry/Utils/ModelHelper.pm | CC-MAIN-2015-11 | refinedweb | 444 | 53.92 |
LGAMMA(3) BSD Programmer's Manual LGAMMA(3)
lgamma, lgammaf, lgamma_r, lgammaf_r, gamma, gammaf, gamma_r, gammaf_r - log gamma function
libm
#include <math.h> extern int signgam; double lgamma(double x); float lgammaf(float x); double lgamma_r(double x, int *sign); float lgammaf_r(float x, int *sign); double gamma(double x); float gammaf(float x); double gamma_r(double x, int *sign); float gammaf_r(float x, int *sign);
lgamma(x) returns ln|I̅(x)|. The external integer signgam returns the sign of I̅(x). lgamma_r() is a reentrant interface that performs identically to lgam- ma(), differing in that the sign of I̅(x) is stored in the location point- ed to by the sign argument and signgam is not modified.
Do not use the expression "signgam*exp(lgamma(x))" to compute g := I̅(x). Instead use a program like this (in C): lg = lgamma(x); g = signgam*exp(lg); Only after lgamma() has returned can signgam be correct.
lgamma() returns appropriate values unless an argument is out of range. Overflow will occur for sufficiently large positive values, and non- positive integers. On the VAX, the reserved operator is returned, and errno is set to ERANGE.
math(3)
The lgamma function appeared in 4.3BSD. MirOS BSD #10-current December 3, 1992. | http://www.mirbsd.org/htman/i386/man3/gammaf_r.htm | CC-MAIN-2019-18 | refinedweb | 209 | 54.73 |
Testing your code brings a wide variety of benefits. It increases your confidence that the code behaves as you expect and ensures that changes to your code won’t cause regressions. Writing and maintaining tests is hard work, so you should leverage all the tools at your disposal to make it as painless as possible.
pytest is one of the best tools you can use to boost your testing productivity.
In this tutorial, you’ll learn:
- What benefits
pytestoffers
- How to ensure your tests are stateless
- How to make repetitious tests more comprehensible
- How to run subsets of tests by name or custom groups
- How to create and maintain reusable testing utilities
Free Bonus: 5 Thoughts On Python Mastery, a free course for Python developers that shows you the roadmap and the mindset you’ll need to take your Python skills to the next level.
How to Install
pytest
To follow along with some of the examples in this tutorial, you’ll need to install
pytest. As with most Python packages, you can install
pytest in a virtual environment from PyPI using
pip:
$ python -m pip install pytest
The
pytest command will now be available in your installation environment.
What Makes
pytest So Useful?
If you’ve written unit tests for your Python code before, then you may have used Python’s built-in
unittest module.
unittest provides a solid base on which to build your test suite, but it has a few shortcomings.
A number of third-party testing frameworks attempt to address some of the issues with
unittest, and
pytest has proven to be one of the most popular.
pytest is a feature-rich, plugin-based ecosystem for testing your Python code.
If you haven’t had the pleasure of using
pytest yet, then you’re in for a treat! Its philosophy and features will make your testing experience more productive and enjoyable. With
pytest, common tasks require less code and advanced tasks can be achieved through a variety of time-saving commands and plugins. It will even run your existing tests out of the box, including those written with
unittest.
As with most frameworks, some development patterns that make sense when you first start using
pytest can start causing pains as your test suite grows. This tutorial will help you understand some of the tools
pytest provides to keep your testing efficient and effective even as it scales.
Less Boilerplate
Most functional tests follow the Arrange-Act-Assert model:
- Arrange, or set up, the conditions for the test
- Act by calling some function or method
- Assert that some end condition is true
Testing frameworks typically hook into your test’s assertions so that they can provide information when an assertion fails.
unittest, for example, provides a number of helpful assertion utilities out of the box. However, even a small set of tests requires a fair amount of boilerplate code.
Imagine you’d like to write a test suite just to make sure
unittest is working properly in your project. You might want to write one test that always passes and one that always fails:
# test_with_unittest.py from unittest import TestCase class TryTesting(TestCase): def test_always_passes(self): self.assertTrue(True) def test_always_fails(self): self.assertTrue(False)
You can then run those tests from the command line using the
discover option of
unittest:
$)
As expected, one test passed and one failed. You’ve proven that
unittest is working, but look at what you had to do:
- Import the
TestCaseclass from
unittest
- Create
TryTesting, a subclass of
TestCase
- Write a method in
TryTestingfor each test
- Use one of the
self.assert*methods from
unittest.TestCaseto make assertions
That’s a significant amount of code to write, and because it’s the minimum you need for any test, you’d end up writing the same code over and over.
pytest simplifies this workflow by allowing you to use Python’s
assert keyword directly:
# test_with_pytest.py def test_always_passes(): assert True def test_always_fails(): assert False
That’s it. You don’t have to deal with any imports or classes. Because you can use the
assert keyword, you don’t need to learn or remember all the different
self.assert* methods in
unittest, either. If you can write an expression that you expect to evaluate to
True, then
pytest will test it for you. You can run it using the
pytest command:
$ pytest ================== test session starts ============================= platform darwin -- Python 3.7.3, pytest-5.3.0, py-1.8.0, pluggy-0.13.0 rootdir: /.../effective-python-testing-with-pytest collected 2 items test_with_pytest.py .F [100%] ======================== FAILURES ================================== ___________________ test_always_fails ______________________________ def test_always_fails(): > assert False E assert False test_with_pytest.py:5: AssertionError ============== 1 failed, 1 passed in 0.07s =========================
pytest presents the test results differently than
unittest. The report shows:
- The system state, including which versions of Python,
pytest, and any plugins you have installed
- The
rootdir, or the directory to search under for configuration and tests
- The number of tests the runner discovered
The output then indicates the status of each test using a syntax similar to
unittest:
- A dot (
.) means that the test passed.
- An
Fmeans that the test has failed.
- An
Emeans that the test raised an unexpected exception.
For tests that fail, the report gives a detailed breakdown of the failure. In the example above, the test failed because
assert False always fails. Finally, the report gives an overall status report of the test suite.
Here are a few more quick assertion examples:
def test_uppercase(): assert "loud noises".upper() == "LOUD NOISES" def test_reversed(): assert list(reversed([1, 2, 3, 4])) == [4, 3, 2, 1] def test_some_primes(): assert 37 in { num for num in range(1, 50) if num != 1 and not any([num % div == 0 for div in range(2, num)]) }
The learning curve for
pytest is shallower than it is for
unittest because you don’t need to learn new constructs for most tests. Also, the use of
assert, which you may have used before in your implementation code, makes your tests more understandable.
State and Dependency Management
Your tests will often depend on pieces of data or test doubles for some of the objects in your code. In
unittest, you might extract these dependencies into
setUp() and
tearDown() methods so each test in the class can make use of them. But in doing so, you may inadvertently make the test’s dependence on a particular piece of data or object entirely implicit.
Over time, implicit dependencies can lead to a complex tangle of code that you have to unwind to make sense of your tests. Tests should help you make your code more understandable. If the tests themselves are difficult to understand, then you may be in trouble!
pytest takes a different approach. It leads you toward explicit dependency declarations that are still reusable thanks to the availability of fixtures.
pytest fixtures are functions that create data or test doubles or initialize some system state for the test suite. Any test that wants to use a fixture must explicitly accept it as an argument, so dependencies are always stated up front.
Fixtures can also make use of other fixtures, again by declaring them explicitly as dependencies. That means that, over time, your fixtures can become bulky and modular. Although the ability to insert fixtures into other fixtures provides enormous flexibility, it can also make managing dependencies more challenging as your test suite grows. Later in this tutorial, you’ll learn more about fixtures and try a few techniques for handling these challenges.
Test Filtering
As your test suite grows, you may find that you want to run just a few tests on a feature and save the full suite for later.
pytest provides a few ways of doing this:
- Name-based filtering: You can limit
pytestto running only those tests whose fully qualified names match a particular expression. You can do this with the
-kparameter.
- Directory scoping: By default,
pytestwill run only those tests that are in or under the current directory.
- Test categorization:
pytestcan include or exclude tests from particular categories that you define. You can do this with the
-mparameter.
Test categorization in particular is a subtly powerful tool.
pytest enables you to create marks, or custom labels, for any test you like. A test may have multiple labels, and you can use them for granular control over which tests to run. Later in this tutorial, you’ll see an example of how
pytest marks work and learn how to make use of them in a large test suite.
Test Parametrization
When you’re testing functions that process data or perform generic transformations, you’ll find yourself writing many similar tests. They may differ only in the input or output of the code being tested. This requires duplicating test code, and doing so can sometimes obscure the behavior you’re trying to test.
unittest offers a way of collecting several tests into one, but they don’t show up as individual tests in result reports. If one test fails and the rest pass, then the entire group will still return a single failing result.
pytest offers its own solution in which each test can pass or fail independently. You’ll see how to parametrize tests with
pytest later in this tutorial.
Plugin-Based Architecture
One of the most beautiful features of
pytest is its openness to customization and new features. Almost every piece of the program can be cracked open and changed. As a result,
pytest users have developed a rich ecosystem of helpful plugins.
Although some
pytest plugins focus on specific frameworks like Django, others are applicable to most test suites. You’ll see details on some specific plugins later in this tutorial.
Fixtures: Managing State and Dependencies
pytest fixtures are a way of providing data, test doubles, or state setup to your tests. Fixtures are functions that can return a wide range of values. Each test that depends on a fixture must explicitly accept that fixture as an argument.
When to Create Fixtures
Imagine you’re writing a function,
format_data_for_display(), to process the data returned by an API endpoint. The data represents a list of people, each with a given name, family name, and job title. The function should output a list of strings that include each person’s full name (their
given_name followed by their
family_name), a colon, and their
title. To test this, you might write the following code:
def format_data_for_display(people): ... # Implement this! def test_format_data_for_display(): people = [ { "given_name": "Alfonsa", "family_name": "Ruiz", "title": "Senior Software Engineer", }, { "given_name": "Sayid", "family_name": "Khan", "title": "Project Manager", }, ] assert format_data_for_display(people) == [ "Alfonsa Ruiz: Senior Software Engineer", "Sayid Khan: Project Manager", ]
Now suppose you need to write another function to transform the data into comma-separated values for use in Excel. The test would look awfully similar:
def format_data_for_excel(people): ... # Implement this! def test_format_data_for_excel(): people = [ { "given_name": "Alfonsa", "family_name": "Ruiz", "title": "Senior Software Engineer", }, { "given_name": "Sayid", "family_name": "Khan", "title": "Project Manager", }, ] assert format_data_for_excel(people) == """given,family,title Alfonsa,Ruiz,Senior Software Engineer Sayid,Khan,Project Manager """
If you find yourself writing several tests that all make use of the same underlying test data, then a fixture may be in your future. You can pull the repeated data into a single function decorated with
@pytest.fixture to indicate that the function is a
pytest fixture:
import pytest @pytest.fixture def example_people_data(): return [ { "given_name": "Alfonsa", "family_name": "Ruiz", "title": "Senior Software Engineer", }, { "given_name": "Sayid", "family_name": "Khan", "title": "Project Manager", }, ]
You can use the fixture by adding it as an argument to your tests. Its value will be the return value of the fixture function:
def test_format_data_for_display(example_people_data): assert format_data_for_display(example_people_data) == [ "Alfonsa Ruiz: Senior Software Engineer", "Sayid Khan: Project Manager", ] def test_format_data_for_excel(example_people_data): assert format_data_for_excel(example_people_data) == """given,family,title Alfonsa,Ruiz,Senior Software Engineer Sayid,Khan,Project Manager """
Each test is now notably shorter but still has a clear path back to the data it depends on. Be sure to name your fixture something specific. That way, you can quickly determine if you want to use it when writing new tests in the future!
When to Avoid Fixtures
Fixtures are great for extracting data or objects that you use across multiple tests. They aren’t always as good for tests that require slight variations in the data. Littering your test suite with fixtures is no better than littering it with plain data or objects. It might even be worse because of the added layer of indirection.
As with most abstractions, it takes some practice and thought to find the right level of fixture use.
Fixtures at Scale
As you extract more fixtures from your tests, you might see that some fixtures could benefit from further extraction. Fixtures are modular, so they can depend on other fixtures. You may find that fixtures in two separate test modules share a common dependency. What can you do in this case?
You can move fixtures from test modules into more general fixture-related modules. That way, you can import them back into any test modules that need them. This is a good approach when you find yourself using a fixture repeatedly throughout your project.
pytest looks for
conftest.py modules throughout the directory structure. Each
conftest.py provides configuration for the file tree
pytest finds it in. You can use any fixtures that are defined in a particular
conftest.py throughout the file’s parent directory and in any subdirectories. This is a great place to put your most widely used fixtures.
Another interesting use case for fixtures is in guarding access to resources. Imagine that you’ve written a test suite for code that deals with API calls. You want to ensure that the test suite doesn’t make any real network calls, even if a test accidentally executes the real network call code.
pytest provides a
monkeypatch fixture to replace values and behaviors, which you can use to great effect:
# conftest.py import pytest import requests @pytest.fixture(autouse=True) def disable_network_calls(monkeypatch): def stunted_get(): raise RuntimeError("Network access not allowed during testing!") monkeypatch.setattr(requests, "get", lambda *args, **kwargs: stunted_get())
By placing
disable_network_calls() in
conftest.py and adding the
autouse=True option, you ensure that network calls will be disabled in every test across the suite. Any test that executes code calling
requests.get() will raise a
RuntimeError indicating that an unexpected network call would have occurred.
Marks: Categorizing Tests
In any large test suite, some of the tests will inevitably be slow. They might test timeout behavior, for example, or they might exercise a broad area of the code. Whatever the reason, it would be nice to avoid running all the slow tests when you’re trying to iterate quickly on a new feature.
pytest enables you to define categories for your tests and provides options for including or excluding categories when you run your suite. You can mark a test with any number of categories.
Marking tests is useful for categorizing tests by subsystem or dependencies. If some of your tests require access to a database, for example, then you could create a
@pytest.mark.database_access mark for them.
Pro tip: Because you can give your marks any name you want, it can be easy to mistype or misremember the name of a mark.
pytest will warn you about marks that it doesn’t recognize.
The
--strict-markers flag to the
pytest command ensures that all marks in your tests are registered in your
pytest configuration. It will prevent you from running your tests until you register any unknown marks.
For more information on registering marks, check out the
pytest documentation.
When the time comes to run your tests, you can still run them all by default with the
pytest command. If you’d like to run only those tests that require database access, then you can use
pytest -m database_access. To run all tests except those that require database access, you can use
pytest -m "not database_access". You can even use an
autouse fixture to limit database access to those tests marked with
database_access.
Some plugins expand on the functionality of marks by guarding access to resources. The
pytest-django plugin provides a
django_db mark. Any tests without this mark that try to access the database will fail. The first test that tries to access the database will trigger the creation of Django’s test database.
The requirement that you add the
django_db mark nudges you toward stating your dependencies explicitly. That’s the
pytest philosophy, after all! It also means that you can run tests that don’t rely on the database much more quickly, because
pytest -m "not django_db" will prevent the test from triggering database creation. The time savings really add up, especially if you’re diligent about running your tests frequently.
pytest provides a few marks out of the box:
skipskips a test unconditionally.
skipifskips a test if the expression passed to it evaluates to
True.
xfailindicates that a test is expected to fail, so if the test does fail, the overall suite can still result in a passing status.
parametrize(note the spelling) creates multiple variants of a test with different values as arguments. You’ll learn more about this mark shortly.
You can see a list of all the marks
pytest knows about by running
pytest --markers.
Parametrization: Combining Tests
You saw earlier in this tutorial how
pytest fixtures can be used to reduce code duplication by extracting common dependencies. Fixtures aren’t quite as useful when you have several tests with slightly different inputs and expected outputs. In these cases, you can parametrize a single test definition, and
pytest will create variants of the test for you with the parameters you specify.
Imagine you’ve written a function to tell if a string is a palindrome. An initial set of tests could look like this:
def test_is_palindrome_empty_string(): assert is_palindrome("") def test_is_palindrome_single_character(): assert is_palindrome("a") def test_is_palindrome_mixed_casing(): assert is_palindrome("Bob") def test_is_palindrome_with_spaces(): assert is_palindrome("Never odd or even") def test_is_palindrome_with_punctuation(): assert is_palindrome("Do geese see God?") def test_is_palindrome_not_palindrome(): assert not is_palindrome("abc") def test_is_palindrome_not_quite(): assert not is_palindrome("abab")
All of these tests except the last two have the same shape:
def test_is_palindrome_<in some situation>(): assert is_palindrome("<some string>")
You can use
@pytest.mark.parametrize() to fill in this shape with different values, reducing your test code significantly:
@pytest.mark.parametrize("palindrome", [ "", "a", "Bob", "Never odd or even", "Do geese see God?", ]) def test_is_palindrome(palindrome): assert is_palindrome(palindrome) @pytest.mark.parametrize("non_palindrome", [ "abc", "abab", ]) def test_is_palindrome_not_palindrome(non_palindrome): assert not is_palindrome(non_palindrome)
The first argument to
parametrize() is a comma-delimited string of parameter names. The second argument is a list of either tuples or single values that represent the parameter value(s). You could take your parametrization a step further to combine all your tests into one:
@pytest.mark.parametrize("maybe_palindrome, expected_result", [ ("", True), ("a", True), ("Bob", True), ("Never odd or even", True), ("Do geese see God?", True), ("abc", False), ("abab", False), ]) def test_is_palindrome(maybe_palindrome, expected_result): assert is_palindrome(maybe_palindrome) == expected_result
Even though this shortened your code, it’s important to note that in this case, it didn’t do much to clarify your test code. Use parametrization to separate the test data from the test behavior so that it’s clear what the test is testing!
Durations Reports: Fighting Slow Tests
Each time you switch contexts from implementation code to test code, you incur some overhead. If your tests are slow to begin with, then overhead can cause friction and frustration.
You read earlier about using marks to filter out slow tests when you run your suite. If you want to improve the speed of your tests, then it’s useful to know which tests might offer the biggest improvements.
pytest can automatically record test durations for you and report the top offenders.
Use the
--durations option to the
pytest command to include a duration report in your test results.
--durations expects an integer value
n and will report the slowest
n number of tests. The output will follow your test results:
$ pytest --durations=3 3.03s call test_code.py::test_request_read_timeout 1.07s call test_code.py::test_request_connection_timeout 0.57s call test_code.py::test_database_read ======================== 7 passed in 10.06s ==============================
Each test that shows up in the durations report is a good candidate to speed up because it takes an above-average amount of the total testing time.
Be aware that some tests may have an invisible setup overhead. You read earlier about how the first test marked with
django_db will trigger the creation of the Django test database. The
durations report reflects the time it takes to set up the database in the test that triggered the database creation, which can be misleading.
Useful
pytest Plugins
You learned about a few valuable
pytest plugins earlier in this tutorial. You can explore those and a few others in more depth below.
pytest-randomly
pytest-randomly does something seemingly simple but with valuable effect: It forces your tests to run in a random order.
pytest always collects all the tests it can find before running them, so
pytest-randomly shuffles that list of tests just before execution.
This is a great way to uncover tests that depend on running in a specific order, which means they have a stateful dependency on some other test. If you built your test suite from scratch in
pytest, then this isn’t very likely. It’s more likely to happen in test suites that you migrate to
pytest.
The plugin will print a seed value in the configuration description. You can use that value to run the tests in the same order as you try to fix the issue.
pytest-cov
If you measure how well your tests cover your implementation code, you likely use the coverage package.
pytest-cov integrates coverage, so you can run
pytest --cov to see the test coverage report.
pytest-django
pytest-django provides a handful of useful fixtures and marks for dealing with Django tests. You saw the
django_db mark earlier in this tutorial, and the
rf fixture provides direct access to an instance of Django’s
RequestFactory. The
settings fixture provides a quick way to set or override Django settings. This is a great boost to your Django testing productivity!
If you’re interested in learning more about using
pytest with Django, then check out How to Provide Test Fixtures for Django Models in Pytest.
pytest-bdd
pytest can be used to run tests that fall outside the traditional scope of unit testing. Behavior-driven development (BDD) encourages writing plain-language descriptions of likely user actions and expectations, which you can then use to determine whether to implement a given feature. pytest-bdd helps you use Gherkin to write feature tests for your code.
You can see which other plugins are available for
pytest with this extensive list of third-party plugins.
Conclusion
pytest offers a core set of productivity features to filter and optimize your tests along with a flexible plugin system that extends its value even further. Whether you have a huge legacy
unittest suite or you’re starting a new project from scratch,
pytest has something to offer you.
In this tutorial, you learned how to use:
- Fixtures for handling test dependencies, state, and reusable functionality
- Marks for categorizing tests and limiting access to external resources
- Parametrization for reducing duplicated code between tests
- Durations to identify your slowest tests
- Plugins for integrating with other frameworks and testing tools
Install
pytest and give it a try. You’ll be glad you did. Happy testing! | https://realpython.com/pytest-python-testing/ | CC-MAIN-2021-43 | refinedweb | 3,919 | 62.48 |
On 05/07/2011 04:24 AM, Eric W. Biederman wrote:> With the networking stack today there is demand to handle> multiple network stacks at a time. Not in the context> of containers but in the context of people doing interesting> things with routing.>> There is also demand in the context of containers to have> an efficient way to execute some code in the container itself.> If nothing else it is very useful ad a debugging technique.>> Both problems can be solved by starting some form of login> daemon in the namespaces people want access to, or you> can play games by ptracing a process and getting the> traced process to do things you want it to do. However> it turns out that a login daemon or a ptrace puppet> controller are more code, they are more prone to> failure, and generally they are less efficient than> simply changing the namespace of a process to a> specified one.>> Pieces of this puzzle can also be solved by instead of> coming up with a general purpose system call coming up> with targed system calls perhaps socketat that solve> a subset of the larger problem. Overall that appears> to be more work for less reward.>> int setns(int fd, int nstype);>> The fd argument is a file descriptor referring to a proc> file of the namespace you want to switch the process to.>> In the setns system call the nstype is 0 or specifies> an clone flag of the namespace you intend to change> to prevent changing a namespace unintentionally.>>>> Signed-off-by: Eric W. Biederman<ebiederm@xmission.com>> ---Acked-by: Daniel Lezcano <daniel.lezcano@free.fr> | http://lkml.org/lkml/2011/5/7/168 | CC-MAIN-2016-36 | refinedweb | 275 | 67.89 |
29 December 2008 16:03 [Source: ICIS news]
By Heidi Finch
LONDON (ICIS news)--The solvents industry can expect a slow start to the year and it was difficult to predict when demand would return, market players said.
“It will probably be a slow start to 2009 and we anticipate that growth will be flat in ?xml:namespace>
The hope for many suppliers is that consumers “will run dry and start to buy again”, but it was difficult to anticipate the timing of when demand would return and was likely to differ according to product.
An integrated producer of glycol ethers and propylene glycol ethers said: “It is a tough call to say when demand returns, but the supply chain is empty.”
For methyl ethyl ketone (MEK) and isopropanol (IPA), European producers were still quite optimistic about the first quarter, saying that the broad range of end-user applications was more likely to minimise any negative economic effects on demand.
“We expect some slight downturn, but not a considerable one,” said one manufacturer.
The slowdown in early 2009 was expected to be more pronounced in the European methyl isobutyl ketone (MIBK) market, added the same seller, noting that one of the main outlets was the automotive industry which had been severely affected by the economic slump.
There was a similar situation in the ethyl acetate sector. “Until we see an improvement in construction and automotive industries, we are going to have to take it day by day”, said a producer.
Extended Christmas plant closures due to the softer market conditions were likely to make the start to 2009 a sluggish one, said other industry participants.
“January will probably be a difficult month, with several manufacturing units not expected to restart before mid-January,” said a reseller.
“Destocking and production cutbacks are likely to balance out during the first quarter 2009 and provided demand returns, there will hopefully be some light at the end of the tunnel by quarter two,” added the same source.
“January will be an important month psychologically, then there could be the disruption of the Chinese New Year in February, meaning it will be the end of quarter one before we get an idea of the true direction for 2009,” added another solvents player.
Aside from concerns about demand, falling upstream costs were also likely to put further downward pressure on solvent prices in the first quarter, stressed buyers.
This was particularly in view of the anticipated ‘historic decreases’ in the olefins sector for the first quarter, along with the recent downward slide in crude and naphtha pricing.
Many market players found it difficult to commit to any kind of forecast for the first quarter, let alone for the rest of the year.
“We are still in the dark, there is a lot of uncertainty and nervousness about 2009 [due to the economy],” said one reseller.
“It is always difficult to predict in a ‘normal’ environment, let alone the unprecedented one we are in now,” said a manufacturer.
“We try to stay positive,” said another seller.
Aside from the economy, players were also keen to monitor the impact of changes to production, following the recent closure of Shell’s
Added to this, was speculation about the possible closure of LyondellBasell’s solvents production at Berre, France, in 2009, although the company declined to comment about this, as well as Sasol’s MIBK expansion plans in South Africa, which were due to be completed in the second half of 2009.
“We expect MIBK [demand] to normalise during the course of 2009 [provided the economy improves] and with the changing structures we expect to see a new balance only by the end of 2009,” said one manufacturer.
Additional reporting by Jane Massingham | http://www.icis.com/Articles/2008/12/29/9179945/outlook-09-europe-solvents-face-sluggish-start-to-the-year.html | CC-MAIN-2015-14 | refinedweb | 623 | 51.52 |
This page contains an archived post to the Design Forum (formerly called the Flexible Java Forum) made prior to February 25, 2002.
If you wish to participate in discussions, please visit the new
Artima Forums.
Yup, can be confusing
Posted by Bill Venners on 03 Jun 1998, 1:58 PM
> I am reading your April article in JavaWorld.
> You write that :> "References to static final variables initialized to a compile-time constant > are resolved at compile-time to a local copy of the constant value".
> So, apparently, the static initializer is not called when a final> static member is used. The sample code below illustrates that.> Don't you think it might be confusing ?
> Sample code :> public class FinalTest> {> public static void main(String argv[]) { > System.out.println("final = "+Loaded.x);> // The static initializer of Loaded in the following line :> System.out.println("non-final = "+Loaded.y);> }> }> class Loaded> {> static {> System.out.println("\tInitialization of Loaded");> }> public static final String x = "final";> public static String y = "non-final";> }
You're right on both counts. You're right that the use of astatic final field (constant) of a class or interface doesn'tqualify as an active use of that class or interface, whichmeans it won't trigger the initialization of that class orinterface. And you're right that it can be confusing.
But I think the greatest risk of confusion lies in the factthat you can change the value of a final static variable inclass Mouse, for example, and if you recompile Mouse, but don'trecompile Cat (which uses the Mouse constant), Cat will stillexecute with the old final value. That's going to confuse peoplefrom time to time. Since Cat gets its own local copy ofMouse's constants, you must recompile Cat if you change thevalues of Mouse's constants before Cat will pick up thechanges.
bv | https://www.artima.com/legacy/design/fieldsmethods/messages/30.html | CC-MAIN-2018-09 | refinedweb | 307 | 53.71 |
This article contains a modular InnoSetup install script that downloads (if setup files don't exist locally) and installs various dependencies like .NET Framework 1.1/2.0/3.5/4.0/4.5 and being structured like this:
#include "scripts\products\dotnetfx11.iss"
main
[Code]
dotnetfx11();
[CustomMessages]
[Files]
Most of the time you need to tweak the setup.iss because of different Windows version / service pack version checks depending thank goes to Ted Ehrich who created the .NET Framework 1.1 script. I am sure that this script will serve me in the future very well and I hope you may like it too.
I also wanted to thank the community for sharing many fixes and improvments. Thanks guys, please keep it up! You can now also easily fork and send pull requests at the official Github repository.
. | http://www.codeproject.com/Articles/20868/NET-Framework-1-1-2-0-3-5-Installer-for-InnoSetup?fid=471622&df=90&mpp=10&sort=Position&spc=None&tid=4430984&PageFlow=FixedWidth | CC-MAIN-2014-52 | refinedweb | 139 | 67.35 |
Notes for Lariat 2-18-14 meeting¶
In order to start a Lariat repository, the following steps can be taken:
- Follow the instructions found in Installing and building the demo, but use the argument "--tag=experiments" when running the quick-start.sh script
- Run the following:
./artdaq-demo/tools/rename.rb <new_package_name> <new_namespace_name>
where <new_package_name> is the name to replace "artdaq-demo", and <new_namespace_name> replaces the "demo::" namespace (though omit the double colon, unlike here)
- Source the new setup<dirname> file, where dirname will be in all caps
- Perform a clean build, and make sure it works
buildtool -c
- Strip the artdaq-demo git history
cd <new_package_name> ; rm -rf .git/
- Edit the ups/product_deps file to reflect the version you want your package to start out at (i.e., replace artdaq-demo's vxx_yy_zz with your own version)
- Re-initialize this directory as a git repository.
git init
- Get all files trackable by git
git add .
- And create a commit
git commit | https://cdcvs.fnal.gov/redmine/projects/artdaq-demo/wiki/Notes_for_Lariat_21814_meeting | CC-MAIN-2021-04 | refinedweb | 162 | 50.46 |
Modern browsers must run sophisticated applications while staying responsive to user actions. Doing so means choosing which of its many tasks to prioritize and which to delay until later—tasks like JavaScript callbacks, user input, and rendering. Moreover, browser work must be split across multiple threads, with different threads running events in parallel to maximize responsiveness.
So far, most of the work our browser’s been doing has come from user actions like scrolling, pressing buttons, and clicking on links. But as the web applications our browser runs get more and more sophisticated, they begin querying remote servers, showing animations, and prefetching information for later. And while users are slow and deliberative, leaving long gaps between actions for the browser to catch up, applications can be very demanding. This requires a change in perspective: the browser now has a never-ending queue of tasks to do.
Modern browsers adapt to this reality by multitasking, prioritizing,
and deduplicating work. Every bit of work the browser might do—loading
pages, running scripts, and responding to user actions—is turned into a
task, which can be executed later, where a task is just a
function (plus its arguments) that can be executed:By writing
*args
as an argument to
Task, we indicate that a
Task can be constructed with any number of arguments, which
are then available as the list
args. Then, calling a
function with
*args unpacks the list back into multiple
arguments.
class Task: def __init__(self, task_code, *args): self.task_code = task_code self.args = args self.__name__ = "task" def run(self): self.task_code(*self.args) self.task_code = None self.args = None
The point of a task is that it can be created at one point in time, and then run at some later time by a task runner of some kind, according to a scheduling algorithm.The event loops we discussed in Chapter 2 and Chapter 11 are task runners, where the tasks to run are provided by the operating system. In our browser, the task runner will store tasks in a first-in first-out queue:
class TaskRunner: def __init__(self): self.tasks = [] def schedule_task(self, task): self.tasks.append(task)
When the time comes to run a task, our task runner can just remove the first task from the queue and run it:First-in-first-out is a simplistic way to choose which task to run next, and real browsers have sophisticated schedulers which consider many different factors.
class TaskRunner: def run(self): if len(self.tasks) > 0): = self.tasks.pop(0) task task.run()
To run those tasks, we need to call the
run method on
our
TaskRunner, which we can do in the main event loop:
class Tab: def __init__(self): self.task_runner = TaskRunner() if __name__ == "__main__": while True: # ... browser.tabs[browser.active_tab].task_runner.run()
Here I’ve chosen to only run tasks on the active tab, which means background tabs can’t slow our browser down.
With this simple task runner, we can now queue up tasks and execute them later. For example, right now, when loading a web page, our browser will download and run all scripts before doing its rendering steps. That makes pages slower to load. We can fix this by creating tasks for running scripts:
class Tab: def run_script(self, url, body): try: print("Script returned: ", self.js.run(body)) except dukpy.JSRuntimeError as e: print("Script", url, "crashed", e) def load(self): for script in scripts: # ... = request(script_url, url) header, body = Task(self.run_script, script_url, body) task self.task_runner.schedule_task(task)
Now our browser will not run scripts until after
load
has completed and the event loop comes around again.
JavaScript is also structured around a task-based event loop, even when it’s not embedded in a browser. It allows messages to be passed to event loops, uses run-to-completion semantics, and generally speaking uses a lot of asynchronous callbacks and events. JavaScript’s programming model is another important reason to architect a browser in the same way.
Tasks are also a natural way to support several JavaScript
APIs that ask for a function to be run at some point in the future. For
example,
setTimeout
lets you run a JavaScript function some number of milliseconds from now.
This code prints “Callback” to the console one second from now:
function callback() { console.log('Callback'); } setTimeout(callback, 1000);
We can implement
setTimeout using the
Timer
class in Python’s
threading
module. You use the class like this:An alternative approach would be to record when each
Task is supposed to occur, and compare against the current
time in the event loop. This is called polling, and is what,
for example, the SDL event loop does to look for events and tasks.
However, that can mean wasting CPU cycles in a loop until the task is
ready, so I expect the
Timer to be more
efficient.
import threading 1, callback).start()threading.Timer(
This runs
callback one second from now on a new Python
thread. Simple! But it’s going to be a little tricky to use
Timer to implement
setTimeout because multiple
threads will be involved.
As with
addEventListener in Chapter 9, the call to
setTimeout will save the callback in a JavaScript variable
and create a handle by which the Python-side code can call it:
= {} SET_TIMEOUT_REQUESTS function setTimeout(callback, time_delta) { var handle = Object.keys(SET_TIMEOUT_REQUESTS).length; = callback; SET_TIMEOUT_REQUESTS[handle] call_python("setTimeout", handle, time_delta) }
The exported
setTimeout function will create a timer,
wait for the requested time period, and then ask the JavaScript runtime
to run the callback. That last part will happen via
__runSetTimeout:Note that we never remove
callback from the
SET_TIMEOUT_REQUESTS dictionary. This could lead to a
memory leak, if the callback it holding on to the last reference to some
large data structure. We saw a similar issue in Chapter 9. In general, avoiding memory leaks
when you have data structures shared between the browser and the browser
application takes a lot of care.
function __runSetTimeout(handle) { var callback = SET_TIMEOUT_REQUESTS[handle] callback(); }
The Python side, however, is quite a bit more complex, because
threading.Timer executes its callback on a new Python
thread. That thread can’t just call
evaljs directly:
we’ll end up with JavaScript running on two Python threads at the same
time, which is not ok.JavaScript is not a multi-threaded programming language.
It’s possible on the web to create workers
of various kinds, but they all run independently and communicate only
via special message-passing APIs. Instead, the timer will
have to merely add a new
Task to the task queue for our
primary thread will execute later:This code has a very subtle bug, wherein a page
might create a
setTimeout, an then have that timer trigger
later, when a user is visiting another web page. In our browser, that
would allow one page to run JavaScript that modifies a different page—a
huge security vulnerability! I think you can avoid this by
resetting
self.js.tab when you navigate to a new page, but
ideally you’d do something more careful, like keeping track of all the
child threads spawned by a
JSContext and ending all of them
before navigating. As our browser gets more complex, our bugs, and their
associated fixes, get more complex too!
= "__runSetTimeout(dukpy.handle)" SETTIMEOUT_CODE class JSContext: def __init__(self, tab): # ... self.interp.export_function("setTimeout", self.setTimeout) def dispatch_settimeout(self, handle): self.interp.evaljs(SETTIMEOUT_CODE, handle=handle) def setTimeout(self, handle, time): def run_callback(): = Task(self.dispatch_settimeout, handle) task self.tab.task_runner.schedule_task(task) / 1000.0, run_callback).start() threading.Timer(time
This way it’s ultimately the primary thread that calls
evaljs. That’s good, but now we have two threads accessing
the
task_runner: the primary thread, to run tasks, and the
timer thread, to add them. This is a race condition
that can cause all sorts of bad things to happen, so we need to make
sure only one thread accesses the
task_runner at a
time.
To do so we use a
Condition
object, which can only held by one thread at a time. Each thread will
try to acquire
condition before reading or writing to the
task_runner, avoiding simultaneous access:The
blocking
parameter to
acquire indicates whether the thread should
wait for the lock to be available before continuing; in this chapter
you’ll always set it to
True. (When the thread is waiting,
it’s said to be blocked.)
The
Condition class is actually a
Lock,
plus functionality to be able to wait until a state condition
occurs. If you have no more work to do right now, acquire
condition and then call
wait. This will cause
the thread to stop at that line of code. When more work comes in to do,
such as in
schedule_task, a call to
notify_all
will wake up the thread that called
wait.
It’s important to call
wait at the end of the
run loop if there is nothing left to do. Otherwise that
thread will tend to use up a lot of the CPU, plus constantly be
acquiring and releasing
condition. This busywork not only
slows down the computer, but also causes the callbacks from the
Timer to happen at erratic times, because the two threads
are competing for the lock.Try removing this code and observe. The timers will become
quite erratic.
class TaskRunner: def __init__(self): # ... self.condition = threading.Condition() def schedule_task(self, task): self.condition.acquire(blocking=True) self.tasks.add_task(task) self.condition.release() def run(self): self.condition.acquire(blocking=True) = None task if len(self.tasks) > 0: = self.tasks.pop(0) task self.condition.release() if task: task.run() self.condition.acquire(blocking=True) if len(self.tasks) == 0: self.condition.wait() self.condition.release()
When using locks, it’s super important to remember to release the
lock eventually and to hold it for the shortest time possible. The code
above, for example, releases the lock before running the
task. That’s because after the task has been removed from
the queue, it can’t be accessed by another thread, so the lock does not
need to be held while the task is running.
Unfortunately, Python currently has a global interpreter lock (GIL), so Python threads don’t truly run in parallel. This is an unfortunate limitation of Python that doesn’t affect real browsers, so in this chapter just try to pretend the GIL isn’t there. Despite the global interpreter lock, we still need locks. Each Python thread can yield between bytecode operations, so you can still get concurrent accesses to shared variables, and race conditions are still possible. And in fact, while debugging the code for this chapter, I often encountered this kind of race condition when I forgot to add a lock; try removing some of the locks from your browser to see for yourself!
Threads can also be used to add browser multitasking. For example, in
Chapter 10 we
implemented the
XMLHttpRequest class, which lets scripts
make requests to the server. But in our implementation, the whole
browser would seize up while waiting for the request to finish. That’s
obviously bad.For this
reason, the synchronous version of the API that we implemented in
Chapter 10 is not very useful and a huge performance footgun. Some
browsers are now moving to deprecate synchronous
XMLHttpRequest.
Threads let us do better. In Python, the code
threading.Thread(target=callback).start()
creates a new thread that runs the
callback function.
Importantly, this code returns right away, and
callback
runs in parallel with any other code. We’ll implement asynchronous
XMLHttpRequest calls using threads. Specifically, we’ll
have the browser start a thread, do the request and parse the response
on that thread, and then schedule a
Task to send the
response back to the script.
Like with
setTimeout, we’ll store the callback on the
JavaScript side and refer to it with a handle:
= {} XHR_REQUESTS function XMLHttpRequest() { this.handle = Object.keys(XHR_REQUESTS).length; this.handle] = this; XHR_REQUESTS[}
When a script calls the
open method on an
XMLHttpRequest object, we’ll now allow the
is_async flag to be true:In browsers, the default for
is_async is
true, which the code below does not
implement.
XMLHttpRequest.prototype.open = function(method, url, is_async) { this.is_async = is_async this.method = method; this.url = url; }
The
send method will need to send over the
is_async flag and the handle:
XMLHttpRequest.prototype.send = function(body) { this.responseText = call_python("XMLHttpRequest_send", this.method, this.url, this.body, this.is_async, this.handle); }
On the browser side, the
XMLHttpRequest_send handler
will have three parts. The first part will resolve the URL and do
security checks:
class JSContext: def XMLHttpRequest_send(self, method, url, body, isasync, handle): = resolve_url(url, self.tab.url) full_url if not self.tab.allowed_request(full_url): raise Exception("Cross-origin XHR blocked by CSP") if url_origin(full_url) != url_origin(self.tab.url): raise Exception( "Cross-origin XHR request not allowed")
Then, we’ll define a function that makes the request and enqueues a task for running callbacks:
class JSContext: def XMLHttpRequest_send(self, method, url, body, isasync, handle): # ... def run_load(): = request( headers, response self.tab.url, payload=body) full_url, = Task(self.dispatch_xhr_onload, response, handle) task self.tab.task_runner.schedule_task(task) if not isasync: return response
Note that the task runs
dispatch_xhr_onload, which we’ll
define in just a moment.
Finally, depending on the
is_async flag the browser will
either call this function right away, or in a new thread:
class JSContext: def XMLHttpRequest_send(self, method, url, body, isasync, handle): # ... if not isasync: return run_load() else: =run_load).start() threading.Thread(target
Note that in the async case, the
XMLHttpRequest_send
method starts a thread and then immediately returns. That thread will
run in parallel to the browser’s main work until the request is
done.
To communicate the result back to JavaScript, we’ll call a
__runXHROnload function from
dispatch_xhr_onload:
= "__runXHROnload(dukpy.out, dukpy.handle)" XHR_ONLOAD_CODE class JSContext: def dispatch_xhr_onload(self, out, handle): = self.interp.evaljs( do_default =out, handle=handle) XHR_ONLOAD_CODE, out
The
__runXHROnload method just pulls the relevant object
from
XHR_REQUESTS and calls its
onload
function:
function __runXHROnload(body, handle) { var obj = XHR_REQUESTS[handle]; var evt = new Event('load'); .responseText = body; objif (obj.onload) .onload(evt); obj}
As you can see, tasks allow not only the browser but also applications running in the browser to delay tasks until later.
XMLHttpRequest played a key role in helping the web
evolve. In the 90s, clicking on a link or submitting a form required
XMLHttpRequest web pages were
able to act a whole lot more like a dynamic application; GMail was one
famous early example.GMail dates from April 2004, soon
after enough browsers finished adding support for the API. The first
application to use
XMLHttpRequest was Outlook Web
Access, in 1999, but it took a while for the API to make it into
other browsers. Nowadays, a web application that uses DOM
mutations instead of page loads to update its state is called a single-page
app. Single-page apps enabled more interactive and complex web apps,
which in turn made browser speed and responsiveness more important.
There’s more to tasks than just implementing some JavaScript APIs.
Once something is a
Task, the task runner controls when it
runs: perhaps now, perhaps later, or maybe at most once a second, or
even at different rates for active and inactive pages, or according to
its priority. A browser could even have multiple task runners, optimized
for different use cases.
Now, it might be hard to see how the browser can prioritize which JavaScript callback to run, or why it might want to execute JavaScript tasks at a fixed cadence. But besides JavaScript the browser also has to render the page, and as you may recall from Chapter 2, we’d like the browser to render the page exactly as fast as the display hardware can refresh. On most computers, this is 60 times per second, or 16ms per frame.
Let’s establish 16ms our ideal refresh rate:16 milliseconds isn’t that precise, since it’s 60 times 16.66666…ms that is just about equal to 1 second. But it’s a toy browser!
= 0.016 # 16msREFRESH_RATE_SEC
Now, there’s some complexity here, because we have multiple tabs. We
don’t need each tab redrawing itself every 16ms, because the
user only sees one tab at a time. We just need the active tab
redrawing itself. Therefore, it’s the
Browser that should
control when we update the display, not individual
Tabs.
Let’s make that happen. First, let’s write a
schedule_animation_frame methodIt’s called an “animation
frame” because sequential rendering of different pixels is an animation,
and each time you render it’s one “frame”—like a drawing in a picture
frame. on
Browser that schedules a
render task to run the
Tab half of the
rendering pipeline:
class Browser: def schedule_animation_frame(self): def callback(): = self.tabs[self.active_tab] active_tab = Task(active_tab.render) task active_tab.task_runner.schedule_task(task) threading.Timer(REFRESH_RATE_SEC, callback).start()
Note how every time a frame is scheduled, we set up a timer to schedule the next one. We can kick off the process when we start the Browser:
if __name__ == "__main__": # ... = Browser() browser # ...
Next, let’s put the rastering and drawing tasks that the
Browser does into their own method:
class Browser: def raster_and_draw(self): self.raster_chrome() self.raster_tab() self.draw()
In the top-level loop, after running a task on the active tab the browser will need to raster-and-draw, in case that task was a rendering task:
if __name__ == "__main__": while True: # ... browser.tabs[browser.active_tab].task_runner.run() browser.raster_and_draw() browser.schedule_animation_frame()
Now we’re scheduling a new rendering task every 16 milliseconds, just as we wanted to.
There’s nothing special about 60 frames per second. Some displays refresh 72 times per second, and displays that refresh even more often are becoming more common. Movies are often shot in 24 frames per second (though some directors advocate 48) while television shows traditionally use 30 frames per second. Consistency is often more important than the actual frame rate: a consistant 24 frames per second can look a lot smoother than a varying framerate between 60 and 24.
If you run this on your computer, there’s a good chance your CPU
usage will spike and your batteries will start draining. That’s because
we’re calling
render every frame, which means our browser
is now constantly styling elements, building layout trees, and painting
display lists. Most of that work is wasted, because on most frames, the
web page will not have changed at all, so the old styles, layout trees,
and display lists would have worked just as well as the new ones.
Let’s fix this using a dirty bit, a piece of state that
tells us if some complex data structure is up to date. Since we want to
know if we need to run
render, let’s call our dirty bit
needs_render:
class Tab: def __init__(self, browser): # ... self.needs_render = False def set_needs_render(self): self.needs_render = True def render(self): if not self.needs_render: return # ... self.needs_render = False
One advantage of this flag is that we can now set
needs_render when the HTML has changed instead of calling
render directly. The
render will still happen,
but later. This makes scripts faster, especially if they modify the page
multiple times. Make this change in
innerHTML_set,
load,
click, and
keypress. For
example, in
load, do this:
class Tab: def load(self, url, body=None): # ... self.set_needs_render()
And in
innerHTML_set, do this:
class JSContext: def innerHTML_set(self, handle, s): # ... self.tab.set_needs_render()
There are more calls to
render; you should find and fix
all of them.
Another problem with our implementation is that the browser is now
doing
raster_and_draw every time the active tab runs a
task. But sometimes that task is just running JavaScript that doesn’t
touch the web page, and the
raster_and_draw call is a
waste.
We can avoid this using another dirty bit, which I’ll call
needs_raster_and_draw:The
needs_raster_and_draw dirty bit doesn’t
just make the browser a bit more efficient. Later in this chapter, we’ll
add multiple browser threads, and at that point this dirty bit is
necessary to avoid erratic behavior when animating. Try removing it
later and see for yourself!
class Browser: def __init__(self): self.needs_raster_and_draw = False def set_needs_raster_and_draw(self): self.needs_raster_and_draw = True def raster_and_draw(self): if not self.needs_raster_and_draw: return # ... self.needs_raster_and_draw = False
We will need to call
set_needs_raster_and_draw every
time either the
Browser changes something about the browser
chrome, or any time the
Tab changes its rendering. The
browser chrome is changed by event handlers:
class Browser: def handle_click(self, e): if e.y < CHROME_PX: # ... self.set_needs_raster_and_draw() def handle_key(self, char): if self.focus == "address bar": # ... self.set_needs_raster_and_draw() def handle_enter(self): if self.focus == "address bar": # ... self.set_needs_raster_and_draw()
And the
Tab should also set this bit after running
render:
class Tab: def __init__(self, browser): # ... self.browser = browser def render(self): # ... self.browser.set_needs_raster_and_draw()
You’ll need to pass in the
browser parameter when a
Tab is constructed:
class Browser: def load(self, url): = Tab(self) new_tab # ...
Now the rendering pipeline is only run if necessary, and the browser should have acceptable performance again.
It was not until the second decade of the 2000s that all modern browsers finished adopting a scheduled, task-based approach to rendering. Once the need became apparent due to the emergence of complex interactive web applications, it still took years of effort to safely refactor all of the complex existing browser codebases. In fact, in some ways it is only very recently–for Chromium at least–that this process can perhaps be said to have completed. Though since software can always be improved, in some sense the work is never done.
One big reason for a steady rendering cadence is so that animations
run smoothly. Web pages can set up such animations using the
requestAnimationFrame
API. This API allows scripts to run code right before the browser runs
its rendering pipeline, making the animation maximally smooth. It works
like this:
function callback() { /* Modify DOM */ } requestAnimationFrame(callback);
By calling
requestAnimationFrame, this code is doing two
things: scheduling a rendering task, and asking that the browser call
callback at the beginning of that rendering task,
before any browser rendering code. This lets web page authors change the
page and be confident that it will be rendered right away.
The implementation of this JavaScript API is straightforward. We store the callbacks on the JavaScript side:
= []; RAF_LISTENERS function requestAnimationFrame(fn) { .push(fn); RAF_LISTENERScall_python("requestAnimationFrame"); }
In
JSContext, when that method is called, we need to
schedule a new rendering task:
class JSContext: def __init__(self, tab): # ... self.interp.export_function("requestAnimationFrame", self.requestAnimationFrame) def requestAnimationFrame(self): = Task(self.tab.render) task self.tab.task_runner.schedule_task(task)
Then, when
render is actually called, we need to call
back into JavaScript, like this:
class Tab: def render(self): if not self.needs_render: return self.js.interp.evaljs("__runRAFHandlers()") # ...
This
__runRAFHandlers function is a little tricky:
function __runRAFHandlers() { var handlers_copy = RAF_LISTENERS; = []; RAF_LISTENERS for (var i = 0; i < handlers_copy.length; i++) { ; handlers_copy[i]() }}
Note that
__runRAFHandlers needs to reset
RAF_LISTENERS to the empty array before it runs any of the
callbacks. That’s because one of the callbacks could itself call
requestAnimationFrame. If this happens during such a
callback, the spec says that a second animation frame should be
scheduled. That means we need to make sure to store the callbacks for
the current frame separately from the callbacks for the
next frame.
This situation may seem like a corner case, but it’s actually very important, as this is how pages can run an animation: by iteratively scheduling one frame after another. For example, here’s a simple counter “animation”:
var count = 0; function callback() { var output = document.querySelectorAll("div")[1]; .innerHTML = "count: " + (count++); outputif (count < 100) requestAnimationFrame(callback); }requestAnimationFrame(callback);
This script will cause 100 animation frame tasks to run on the rendering event loop. During that time, our browser will display an animated count from 0 to 99. Serve this example web page from our HTTP server:
def do_request(session, method, url, headers, body): elif method == "GET" and url == "/count": return "200 OK", show_count() # ... def show_count(): = "<!doctype html>" out += "<div>"; out += " Let's count up to 99!" out += "</div>"; out += "<div>Output</div>" out += "<script src=/eventloop.js></script>" out return out
Load this up and observe an animation from 0 to 99.
One flaw with our implementation so far is that an inattentive coder
might call
requestAnimationFrame multiple times and thereby
schedule more animation frames than expected. If other JavaScript tasks
appear later, they might end up delayed by many, many frames.
Luckily, rendering is special in that it never makes sense to have
two rendering tasks in a row, since the page wouldn’t have changed in
between. To avoid having two rendering tasks we’ll add a dirty bit
called
needs_animation_frame to the
Browser
which indicates whether a rendering task actually needs to be
scheduled:
class Browser: def __init__(self): self.animation_timer = None # ... self.needs_animation_frame = True def schedule_animation_frame(self): def callback(): ...self.animation_timer = None # ... if self.needs_animation_frame and not self.animation_timer: self.animation_timer = \ threading.Timer(REFRESH_RATE_SEC, callback)self.animation_timer.start()
Note how I also checked for not having an animation timer object; this avoids running two at once.
A tab will set the
needs_animation_frame flag when an
animation frame is requested:
class JSContext: def requestAnimationFrame(self): self.tab.browser.set_needs_animation_frame(self.tab) class Tab: def set_needs_render(self): # ... self.browser.set_needs_animation_frame(self) class Browser: def set_needs_animation_frame(self, tab): if tab == self.tabs[self.active_tab]: self.needs_animation_frame = True
Note that
set_needs_animation_frame will only actually
set the dirty bit if called from the active tab. This guarantees that
inactive tabs can’t interfere with active tabs. Besides preventing
scripts from scheduling too many animation frames, this system also
makes sure that if our browser consistently runs slower than 60 frames
per second, we won’t end up with an ever-growing queue of rendering
tasks.
Before
requestAnimationFrame API, developers abused
setTimeout to do something similar:
function callback() { // Modify DOM setTimeout(callback, 16); }setTimeout(callback, 16);
This sort of worked, but there was no guarantee that the callbacks
would cohere with the speed or timing of rendering. For example,
sometimes two callbacks in a row could happen without any rendering
between, which doubles the script work for rendering for no benefit. It
was also possible for other tasks to run between the callback and
rendering, forcing the app to re-do its DOM mutations to respond to the
click. Additionally,
requestAnimationFrame lets the browser
turn off rendering work when a web page tab or window is backgrounded,
minimized or otherwise throttled, while still allowing other background
work like saving your work so it’s not lost.
We now have a system for scheduling a rendering task every 16ms. But what if rendering takes longer than 16ms to finish? Before we answer this question, let’s instrument the browser and measure how much time is really being spent rendering. It’s important to always measure before optimizing, because the result is often surprising.
Let’s implement some simple instrumentation to measure time. We’ll want to average across multiple raster-and-draw cycles:
class MeasureTime: def __init__(self, name): self.name = name self.start_time = None self.total_s = 0 self.count = 0 def text(self): if self.count == 0: return "" = self.total_s / self.count avg return "Time in {} on average: {:>.0f}ms".format( self.name, avg * 1000)
We’ll measure the time for something like raster and draw by just
calling
start and
stop methods on one of these
MeasureTime objects:
class MeasureTime: def start(self): self.start_time = time.time() def stop(self): self.total_s += time.time() - self.start_time self.count += 1 self.start_time = None
Let’s measure the total time for render:
class Tab: # ... self.measure_render = MeasureTime("render") def render(self): if not self.needs_render: return self.measure_render.start() # ... self.measure_render.stop()
And also raster-and-draw:
class Browser: def __init__(self): self.measure_raster_and_draw = MeasureTime("raster-and-draw") def raster_and_draw(self): if not self.needs_raster_and_draw: return self.measure_raster_and_draw.start() # ... self.measure_raster_and_draw.stop()
We can print out the timing measures when we quit:
class Tab: def handle_quit(self): print(self.tab.measure_render.text()) class Browser: def handle_quit(self): print(self.measure_raster_and_draw.text())
(Naturally you’ll need to call these methods before quitting, from the main event loop, so it has a chance to print its timing data.)
Fire up the server, open our timer script, wait for it to finish counting, and then exit the browser. You should see it output timing data. On my computer, it looks like this:
Time in raster-and-draw on average: 66ms Time in render on average: 20ms
On every animation frame, my browser spent about 20ms in
render and about 66ms in
raster_and_draw. That
clearly blows through our 16ms budget. So, what can we do?
Well, one option, of course, is optimizing raster-and-draw, or even render. And if we can, that’s the right choice.See the go further at the end of this section for some ideas on how to do this. But another option—complex, but worthwhile and done by every major browser—is to do the render step in parallel with the raster-and-draw step by adopting a multi-threaded architecture.
Our toy browser spends a lot of time copying pixels. That’s why optimizing
surfaces is important! It’ll be faster by at least 30% if you’ve
done the interest region exercise from Chapter 11; making
tab_surface smaller also helps a lot. Modern browsers go a
step further and perform raster and draw on the
GPU, where a lot more parallelism is available. Even so, on complex
pages raster and draw really do sometimes take a lot of time. I’ll dig
into this more in Chapter 13.
Running rendering in parallel would allow us to produce a new frame every 66ms, instead of every 88ms. That’s good, but there’s more. Since there’s no point to running render more often than raster-and-draw, after the 20ms spent rendering the rendering thread would 46ms left over, which could be used for running JavaScript. And that in turn means many tasks could be handled with a delay of no more than 20ms (and the other thread 66ms), which makes the browser much more responsive. That’s reason enough to add a second thread.
Let’s call our two threads the browser threadIn modern browsers the
analogous thread is often called the compositor
thread, though modern browsers have lots of threads and the
correspondence isn’t exact. and the main
thread.Here I’m
going with the name real browsers often use. A better name might be the
“JavaScript” or “DOM” thread (since JavaScript can sometimes run on other
threads). The browser thread corresponds to the
Browser class and will handle raster and draw. It’ll also
handle interactions with the browser chrome. The main thread, on the
other hand, corresponds to a
Tab and will handle running
scripts, loading resources, and rendering, along with associated tasks
like running event handlers and callbacks. If you’ve got more than one
tab open, you’ll have multiple main threads (one per tab) but only one
browser thread.
Now, multi-threaded architectures are tricky, so let’s do a little planning.
To start, the one thread that exists already—the one that runs when you start the browser—will be the browser thread. We’ll make a main thread every time we create a tab. These two threads will need to communicate to handle events and draw to the screen.
When the browser thread needs to communicate with the main thread, to
inform it of events, it’ll place tasks on the main thread’s
TaskRunner. The main thread will need to communicate with
the browser thread to request animation frames and to send it a display
list to raster and draw, and the main thread will do that via two
methods on
browser:
set_needs_animation_frame
to request an animation frame and
commit to send it a
display list.
The overall control flow for rendering a frame will therefore be:
set_needs_animation_frame, perhaps in response to an event handler or due to
requestAnimationFrame.
TaskRunner.
browser.commit.
Let’s implement this design. To start, we’ll add a
Thread to each
TaskRunner, which will be the
tab’s main thread. This thread will need to run in a loop, pulling tasks
from the task queue and running them. We’ll put that loop inside the
TaskRunner’s
run method.
class TaskRunner: def __init__(self, tab): # ... self.main_thread = threading.Thread(target=self.run) def start(self): self.main_thread.start() def run(self): while True: # ...
Remove the call to
run from the top-level
while True loop, since that loop is now going to be running
in the browser thread. And
run will have its own loop:
class TaskRunner: def run(self): while True: # ...
Because this loop runs forever, the main thread will live on indefinitely.Or until the browser quits, at which point it should ask the main thread to quit as well.
The
Browser should no longer call any methods on the
Tab. Instead, to handle events, it should schedule tasks on
the main thread. For example, here is loading:
class Browser: def schedule_load(self, url, body=None): = self.tabs[self.active_tab] active_tab = Task(active_tab.load, url, body) task active_tab.task_runner.schedule_task(task) def handle_enter(self): if self.focus == "address bar": self.schedule_load(self.address_bar) # ... def load(self, url): # ... self.schedule_load(url)
Event handlers are mostly similar, except that we need to be careful
to distinguish events that affect the browser chrome from those that
affect the tab. For example, consider
handle_click. If the
user clicked on the browser chrome (meaning
e.y < CHROME_PX), we can handle it right there in the
browser thread. But if the user clicked on the web page, we must
schedule a task on the main thread:
class Browser: def handle_click(self, e): if e.y < CHROME_PX: # ... else: # ... = self.tabs[self.active_tab] active_tab = Task(active_tab.click, e.x, e.y - CHROME_PX) task active_tab.task_runner.schedule_task(task)
The same logic holds for
keypress:
class Browser: def handle_key(self, char): if not (0x20 <= ord(char) < 0x7f): return if self.focus == "address bar": # ... elif self.focus == "content": = self.tabs[self.active_tab] active_tab = Task(active_tab.keypress, char) task active_tab.task_runner.schedule_task(task)
Do the same with any other calls from the
Browser to the
Tab.
So now we have the browser thread telling the main thread what to do Communication in the other direction is a little subtler.
Originally, threads were a mechanism for improving responsiveness via pre-emptive multitasking, not throughput (frames per second). Nowadays, though, even phones have several cores plus a highly parallel GPU, and threads are much more powerful. It’s therefore useful to distinguish between conceptual events; event queues and dependencies between them; and their implementation on a computer architecture. This way, the browser implementer (you!) has maximum flexibility to use more or less hardware parallelism as appropriate to the situation. For example, some devices have more CPU cores than others, or are more sensitive to battery power usage, or there system processes such as listening to the wireless radio may limit the actual parallelism available to the browser.
We already have a
set_needs_animation_frame method, but
we also need a
commit method that a
Tab can
call when it’s finished creating a display list. And if you look
carefully at our raster-and-draw code, you’ll see that to draw a display
list we also need to know the URL (to update the browser chrome), the
document height (to allocate a surface of the right size), and the
scroll position (to draw the right part of the surface).
Let’s make a simple class for storing this data:
class CommitForRaster: def __init__(self, url, scroll, height, display_list): self.url = url self.scroll = scroll self.height = height self.display_list = display_list
When running an animation frame, the
Tab should
construct one of these objects and pass it to
commit. To
keep
render from getting too confusing, let’s put this in a
new
run_animation_frame method, and move
__runRAFHandlers there too:
class Tab: def __init__(self, browser): # ... self.browser = browser def run_animation_frame(self): self.js.interp.evaljs("__runRAFHandlers()") self.render() = CommitForRaster( commit_data =self.url, url=self.scroll, scroll=document_height, height=self.display_list, display_list )self.display_list = None self.browser.commit(self, commit_data)
Think of the
CommitForRaster object as being sent from
the main thread to browser thread. That means the main thread shouldn’t
access it any more, and for this reason I’m resetting the
display_list field. The
Browser should now
schedule
run_animation_frame:
class Browser: def schedule_animation_frame(self): def callback(): # ... = Task(active_tab.run_animation_frame) task # ...
On the
Browser side, the new
commit method
needs to read out all of the data it was sent and call
set_needs_raster_and_draw as needed. Because this call will
come from another thread, we’ll need to acquire a lock. Another
important step is to not clear the
animation_timer object
until after the next commit occurs. Otherwise multiple
rendering tasks could be queued at the same time.
class Browser: def __init__(self): self.lock = threading.Lock() self.url = None self.scroll = 0 self.active_tab_height = 0 self.active_tab_display_list = None def commit(self, tab, data): self.lock.acquire(blocking=True) if tab == self.tabs[self.active_tab]: self.url = data.url self.scroll = data.scroll self.active_tab_height = data.height if data.display_list: self.active_tab_display_list = data.display_list self.animation_timer = None self.set_needs_raster_and_draw() self.lock.release()
Note that
commit is called on the main thread, but
acquires the browser thread lock. As a result,
commit is a
critical time when both threads are both “stopped” simultaneously.For this reason commit needs
to be as fast as possible, to maximize parallelism and responsiveness.
In modern browsers, optimizing commit is quite challenging, because
their method of caching and sending data between threads is much more
sophisticated. Also note that, it’s possible for the
browser thread to get a
commit from an inactive tab,That’s because even inactive
tabs are still running their main threads and responding to callbacks
from
setTimeout or
XMLHttpRequest, and might
be processing one last animation frame. so the
tab parameter is compared with the active tab before
copying over any committed data.
Now that we have a browser lock, we also need to acquire the lock any
time the browser thread accesses any of its variables. For example, in
set_needs_animation_frame, do this:
class Browser: def set_needs_animation_frame(self, tab): self.lock.acquire(blocking=True) # ... self.lock.release()
In
schedule_animation_frame you’ll need to do it both
inside and outside the callback:
class Browser: def schedule_animation_frame(self): def callback(): self.lock.acquire(blocking=True) # ... self.lock.release() # ... self.lock.acquire(blocking=True) # ... self.lock.release()
Add locks to
raster_and_draw,
handle_down,
handle_click,
handle_key, and
handle_enter as well.
We also don’t want the main thread doing rendering faster than the browser thread can raster and draw. So we should only schedule animation frames once raster and draw are done.The technique of controlling the speed of the front of a pipeline by means of the speed of its end is called back pressure. Luckily, that’s exactly what we’re doing:
if __name__ == "__main__": while True: # ... browser.raster_and_draw() browser.schedule_animation_frame()
And that’s it: we should now be doing render on one thread and raster and draw on another!
Due to the Python GIL, threading in Python therefore doesn’t increase throughput, but it can increase responsiveness by, say, running JavaScript tasks on the main thread while the browser does raster and draw. It’s also possible to turn off the global interpreter lock while running foreign C/C++ code linked into a Python library; Skia is thread-safe, but DukPy and SDL may not be, and don’t seem to release the GIL. If they did, then JavaScript or raster-and-draw truly could run in parallel with the rest of the browser, and performance would improve as well.
Splitting the main thread from the browser thread means that the main thread can run a lot of JavaScript without slowing down the browser much. But it’s still possible for really slow JavaScript to slow the browser down. For example, imagine our counter adds the following artificial slowdown:
function callback() { for (var i = 0; i < 5e6; i++); // ... }
Now, every tick of the counter has an artificial pause during which the main thread is stuck running JavaScript. This means it can’t respond to any events; for example, if you hold down the down key, the scrolling will be janky and annoying. I encourage you to try this and witness how annoying it is, because modern browsers usually don’t have this kind of jank.Adjust the loop bound to make it pause for about a second or so on your computer.
To fix this, we need to the browser thread to handle scrolling, not
the main thread. This is harder than it might seem, because the scroll
offset can be affected by both the browser (when the user scrolls) and
the main thread (when loading a new page or changing the height of the
document via
innerHTML). Now that the browser thread and
the main thread run in parallel, they can disagree about the scroll
offset.
What should we do? The best we can do is to use the browser thread’s scroll offset until the main thread tells us otherwise, because the scroll offset is incompatible with the web page (by, say, exceeding the document height). To do this, we’ll need the browser thread to inform the main thread about the current scroll offset, and then give the main thread the opportunity to override that scroll offset or to leave it unchanged.
Let’s implement that. To start, we’ll need to store a
scroll variable on the
Browser, and update it
when the user scrolls:
def clamp_scroll(scroll, tab_height): return max(0, min(scroll, tab_height - (HEIGHT - CHROME_PX))) class Browser: def __init__(self): # ... self.scroll = 0 def handle_down(self): self.lock.acquire(blocking=True) if not self.active_tab_height: self.lock.release() return = clamp_scroll( scroll self.scroll + SCROLL_STEP, self.active_tab_height) self.scroll = scroll self.set_needs_raster_and_draw() self.lock.release()
This code sets
needs_raster_and_draw to apply the new
scroll offset.
The scroll offset also needs to change when the user switches tabs,
but in this case we don’t know the right scroll offset yet. We need the
main thread to run in order to commit a new display list for the other
tab, and at that point we will have a new scroll offset as well. Move
tab switching (in
load and
handle_click) to a
new method
set_active_tab that simply schedules a new
animation frame:
class Browser: def set_active_tab(self, index): self.active_tab = index self.scroll = 0 self.url = None self.needs_animation_frame = True
So far, this is only updating the scroll offset on the browser
thread. But the main thread eventually needs to know about the scroll
offset, so it can pass it back to
commit. So, when the
Browser creates a rendering task for
run_animation_frame, it should pass in the scroll offset.
The
run_animation_frame function can then store the scroll
offset before doing anything else. Add a
scroll parameter
to
run_animation_frame:
class Browser: def schedule_animation_frame(self): # ... def callback(): self.lock.acquire(blocking=True) = self.scroll scroll = self.tabs[self.active_tab] active_tab self.needs_animation_frame = False = Task(active_tab.run_animation_frame, scroll) task active_tab.task_runner.schedule_task(task)self.lock.release() # ...
But the main thread also needs to be able to modify the scroll
offset. We’ll add a
scroll_changed_in_tab flag that tracks
whether it’s done so, and only store the browser thread’s scroll offset
if
scroll_changed_in_tab is not already true.Two-threaded scroll has a lot
of edge cases, including some I didn’t anticipate when writing this
chapter. For example, it’s pretty clear that a load should force scroll
to 0 (unless the browser implements scroll
restoration for back-navigations!), but what about a scroll clamp
followed by a browser scroll that brings it back to within the clamped
region? By splitting the browser into two threads, we’ve brought in all
of the challenges of concurrency and distributed
state.
class Tab: def __init__(self, browser): # ... self.scroll_changed_in_tab = False def run_animation_frame(self, scroll): if not self.scroll_changed_in_tab: self.scroll = scroll # ...
We’ll set
scroll_changed_in_tab when loading a new page
or when the browser thread’s scroll offset of past the bottom of the
page:
class Tab: def load(self, url, body=None): self.scroll = 0 self.scroll_changed_in_tab = True def run_animation_frame(self, scroll): # ... = math.ceil(self.document.height) document_height = clamp_scroll(self.scroll, document_height) clamped_scroll if clamped_scroll != self.scroll: self.scroll_changed_in_tab = True self.scroll = clamped_scroll # ... self.scroll_changed_in_tab = False
If the main thread hasn’t overridden the browser’s scroll
offset, we’ll set the scroll offset to
None in the commit
data:
class Tab: def run_animation_frame(self, scroll): # ... = None scroll if self.scroll_changed_in_tab: = self.scroll scroll = CommitForRaster( commit_data =self.url, url=scroll, scroll=document_height, height=self.display_list, display_list )# ...
The browser thread can ignore the scroll offset in this case:
class Browser: def commit(self, tab, data): if tab == self.tabs[self.active_tab]: # ... if data.scroll != None: self.scroll = data.scroll
That’s it! If you try the counting demo now, you’ll be able to scroll even during the artificial pauses. As you’ve seen, moving tasks to the browser thread can be challenging, but can also lead to a much more responsive browser. These same trade-offs are present in real browsers, at a much greater level of complexity.
Scrolling in real browsers goes way beyond what we’ve
implemented here. For example, in a real browser JavaScript can listen
to a
scroll
event and call
preventDefault to cancel scrolling. And some
rendering features like
background-attachment: fixed
are hard to implement on the browser thread.Our browser doesn’t support
any of these features, so it doesn’t run into these difficulties. That’s
also a strategy. For example, until 2020, Chromium-based browsers on
Android did not support
background-attachment: fixed. For this
reason, most real browsers implement both threaded and non-threaded
scrolling, and fall back to non-threaded scrolling when these advanced
features are used.Actually, a real browser only falls back to non-threaded
scrolling when necessary. For example, it might disable threaded
scrolling only if a
scroll event listener calls
preventDefault. Concerns like this also drive
new
JavaScript APIs.
Now that we have separate browser and main threads, and now that some operations are performed on the browser thread, our browser’s thread architecture has started to resemble that of a real browser.Note that many browsers now run some parts of the browser thread and main thread in different processes, which has some advantages for security and error handling. But why not move even more browser components into even more threads? Wouldn’t that make the browser even faster?
In a word, yes. Modern browsers have dozens of threads, which together serve to make the browser even faster and more responsive. For example, raster-and-draw often runs on its own thread so that the browser thread can handle events even while a new frame is being prepared. Likewise, modern browsers typically have a collection of network or IO threads, which move all interaction with the network or the file system off of the main thread.
On the other hand, some parts of the browser can’t be easily threaded. For example, consider the earlier part of the rendering pipeline: style, layout and paint. In our browser, these run on the main thread. But could they move to their own thread?
In principle, yes. The only thing browsers have to do is
implement all the web API specifications correctly, and draw to the
screen after scripts and
requestAnimationFrame callbacks
have completed. The specification spells this out in detail in what it
calls the update-the-rendering
steps. The specification doesn’t mention style or layout at all—because
style and layout, just like paint and draw, are implementation details
of a browser. The specification’s update-the-rendering steps are the
JavaScript-observable things that have to happen before drawing
to the screen.
Nevertheless, in practice, no current modern browser runs style or
layout on off the main thread.The Servo
rendering engine uses multiple threads to take advantage of parallelism
in style and layout, but those steps still block, for example,
JavaScript execution on the main thread. The reason is
simple: there are many JavaScript APIs that can query style or layout
state. For example,
getComputedStyle
requires first computing style, and
getBoundingClientRect
requires first doing layout.There is no JavaScript API that allows reading back state
from anything later in the rendering pipeline than layout. This made it
relatively easy for us to move raster and draw to the browser
thread. If a web page calls one of these APIs, and style
or layout is not up-to-date, then it has to be computed then and there.
These computations are called forced style or forced
layout: style or layout are “forced” to happen right away, as
opposed to possibly 16ms in the future, if they’re not already computed.
Because of these forced style and layout situations, browsers have to be
able to layout and style on the main thread.Or the main thread could force
the compositor thread to do that work, but that’s even worse, because
forcing work on the compositor thread will make scrolling janky unless
you do even more work to avoid that somehow.
One possible way to resolve these tensions is to optimistically move
style and layout off the main thread, similar to optimistically doing
threaded scrolling if a web page doesn’t
preventDefault a
scroll. Is that a good idea? Maybe, but forced style and layout aren’t
just caused by JavaScript execution. One example is our implementation
of
click, which causes a forced render before hit
testing:
class Tab: def click(self, x, y): self.render() # ...
It’s possible (but very hard) to move hit testing off the main thread or to do hit testing against an older version of the layout tree, or to come up with some other technological fix. Thus it’s not impossible to move style and layout off the main thread “optimistically”, but it is challenging. That said, browser developers are always looking for ways to make things faster, and I expect that at some point in the future style and layout will be moved to their own thread. Maybe you’ll be the one to do it?
Browser rendering pipelines are strongly influenced by graphics and games. Many high-performance games are driven by event loops, update a scene graph on each event, convert the scene graph into a display list, and then convert the display list into pixels. But in a game, the programmer knows in advance what scene graphs will be provided, and can tune the graphics pipeline for those graphs. Games can upload hyper-optimized code and pre-rendered data to the CPU and GPU memory when they start. Browsers, on the other hand, need to handle arbitrary web pages, and can’t spend much time optimizing anything. This makes for a very different set of tradeoffs, and is why browsers often feel less fancy and smooth than games.
This chapter explained in some detail the two-thread rendering system at the core of modern browsers. The main points to remember are:
commit, which synchronizes the two threads.
Additionally, you’ve seen how hard it is to move tasks between the two threads, such as the challenges involved in scrolling on the browser thread, or how forced style and layout makes it hard to fully isolate the rendering pipeline from JavaScript.)
EVENT_DISPATCH_CODE
def url_origin(url)
COOKIE_JAR
def request(url, top_level_url, payload)
def parse_color(color)
class DrawLine:
def __init__(x1, y1, x2, y2)
def execute(canvas)
def draw_line(canvas, x1, y1, x2, y2)
def draw_text(canvas, x, y, text, font, color)
def draw_rect(canvas, l, t, r, b, fill, width)
class DocumentLayout:
def __init__(node)
def layout()
def paint(display_list)
def __repr__()
class InputLayout:
def __init__(node, parent, previous)
def layout()
def paint(display_list)
def __repr__()
SCROLL_STEP
CHROME_PX
class MeasureTime:
def __init__(name)
def start()
def stop()
def text()
SETTIMEOUT_CODE
XHR_ONLOAD_CODE
class JSContext:
def __init__(tab)
def run(script, code)
def dispatch_event(type, elt)
def get_handle(elt)
def querySelectorAll(selector_text)
def getAttribute(handle, attr)
def innerHTML_set(handle, s)
def dispatch_settimeout(handle)
def setTimeout(handle, time)
def dispatch_xhr_onload(out, handle)
def XMLHttpRequest_send(method, url, body, isasync, handle)
def now()
def requestAnimationFrame()
USE_BROWSER_THREAD
def raster(display_list, canvas)
def clamp_scroll(scroll, tab_height)
class Tab:
def __init__(browser)
def allowed_request(url)
def script_run_wrapper(script, script_text)
def load(url, body)
def set_needs_render()
def request_animation_frame_callback()
def run_animation_frame(scroll)
def render()
def click(x, y)
def submit_form(elt)
def keypress(char)
def go_back()
WIDTH, HEIGHT
HSTEP, VSTEP
class Task:
def __init__(task_code)
def run()
class SingleThreadedTaskRunner:
def __init__(tab)
def schedule_task(callback)
def clear_pending_tasks()
def start()
def set_needs_quit()
def run()
class CommitForRaster:
def __init__(url, scroll, height, display_list)
class TaskRunner:
def __init__(tab)
def schedule_task(task)
def set_needs_quit()
def clear_pending_tasks()
def start()
def run()
def handle_quit()
REFRESH_RATE_SEC
class Browser:
def __init__()
def render()
def commit(tab, data)
def set_needs_animation_frame(tab)
def set_needs_raster_and_draw()
def raster_and_draw()
def schedule_animation_frame()
def handle_down()
def set_active_tab(index)
def handle_click(e)
def handle_key(char)
def schedule_load(url, body)
def handle_enter()
def load(url)
def raster_tab()
def raster_chrome()
def draw()
def handle_quit()
if __name__ == "__main__"
setInterval:
setInterval
is similar to
setTimeout but runs repeatedly at a given
cadence until
clearInterval
is called. Implement these. Make sure to test
setInterval
with various cadences in a page that also uses
requestAnimationFrame with some expensive rendering
pipeline work to do. Record the actual timing of
setInterval tasks; how consistent is the cadence?
Clock-based frame timing: Right now our browser schedules
the next animation frame to happen exactly 16ms later than the first
time
set_needs_animation_frame is called. However, this
actually leads to a slower animation frame rate cadence than 16ms, for
example if
render takes say 10ms to run. Can you see why?
Fix this in our browser by using the absolute time to schedule animation
frames, instead of a fixed delay between frames. You will need to choose
a slower cadence than 16ms so that the frames don’t overlap.
Scheduling: As more types of complex tasks end up on the
event queue, there comes a greater need to carefully schedule them to
ensure the rendering cadence is as close to 16ms as possible, and also
to avoid task starvation. Implement a task scheduler with a priority
system that balances these two needs. Test it out on a web page that
taxes the system with a lot of
setTimeout-based tasks.
Threaded loading: When loading a page, our browser currently
waits for each style sheet or script resource to load in turn. This is
unnecessarily slow, especially on a bad network. Instead, make your
browser sending off all the network requests in parallel. It may be
convenient to use the
join method on a
Thread,
which will block the thread calling
join until the other
thread completes. This way your
load method can block until
all network requests are complete.
Networking thread: Real browsers usually have a separate thread for networking (and other I/O). Tasks are added to this thread in a similar fashion to the main thread. Implement a third networking thread and put all networking tasks on it.
Fine-grained dirty bits: at the moment, the browser always re-runs the entire rendering pipeline if anything changed. For example, it re-rasters the browser chrome every time (which chapter 11 didn’t do). Add separate dirty bits for raster and draw stages.You can also try adding dirty bits for whether layout needs to be run, but be careful to think very carefully about all the ways this dirty bit might need to end up being set.
Optimized scheduling: On a complicated web page, the browser
may not be able to keep up with the desired cadence. Instead of
constantly pegging the CPU in a futile attempt to keep up, implement a
frame time estimator that estimates the true cadence of the
browser based on previous frames, and adjust
schedule_animation_frame to match. This way complicated
pages get consistently slower, instead of having random slowdowns.
Raster-and-draw thread: Right now, if an input event arrives while the browser thread is rastering or drawing, that input event won’t be handled immediately. This is especially a problem because raster and draw are slow. Fix this by adding a separate raster-and-draw thread controlled by the browser thread. While the raster-and-draw thread is doing its work, the browser thread should be available to handle input events. Be careful: SDL is not thread-safe, so all of the steps that directly use SDL still need to happen on the browser thread.
Did you find this chapter useful? | https://browser.engineering/scheduling.html | CC-MAIN-2022-33 | refinedweb | 9,536 | 63.7 |
generate a unique number
rob morkos
Greenhorn
Joined: Nov 30, 2002
Posts: 1
posted
Nov 30, 2002 00:56:00
0
I want to create a unique number in
java
, because I need the unique Id before, so that I can insert in many tables within the database simultaneous without making any problems with my tables relations with each other. Is it possible and I would really appreciate any comments or code example. I would of liked to let my database generate it by making my field auto number, but the requirements was that I have the unique number before. Thanks in advance.
Maulin Vasavada
Ranch Hand
Joined: Nov 04, 2001
Posts: 1871
posted
Nov 30, 2002 16:14:00
0
hi Rob,
well, the generation of Unique ID depends a lot upon your application, you know. what kind of fields you have, what kind of other constraints you have. how you are going to use the Unique ID in your application etc....
but as far as i remember there isn't a direct way you can generate like GUID using some standard Java Class (please let me know if you don't know what GUID means) EXCEPT one RMI utility which uses IP address and an object reference unique across that IP address (across the JVM running on that machine).
look at,
java.rmi.server.ObjId
for details.
i am not sure if this is useful to you because this depends upon IP address and in RMI the server is usually having Unique IP (please post more questions on RMI at Remote Objects forum on Javaranch as i 'm not at all a wizard of RMI. i just know little bit) but in your case it might not be applicable you know.
just my 2 cents.
maulin
Greg Brouelette
Ranch Hand
Joined: Jan 23, 2002
Posts: 144
posted
Dec 02, 2002 14:10:00
0
The getTime() method of the Date class returns the number of milliseconds since Jan 1st 1970. You could always just construct a date object and ask for it's time to get a unique number (it's a long). As long as you don't have so many users that they're asking for ID's faster than once a millisecond you should be fine.
For a good Prime, call:<br />29819592777931214269172453467810429868925511217482600306406141434158089
Christopher Farnham
Greenhorn
Joined: Sep 18, 2002
Posts: 12
posted
Dec 02, 2002 17:11:00
0
Here is a class that I wrote a while ago... I have used it for several projects.... use it at your own risk.
I have a GlobalUniqueObject interface so that you can use it via inheritance or composition.... if you see any problems with it, i'd appreciate it if you let me know....
Chris
package com.cfe.core.util; import java.net.InetAddress; import java.security.SecureRandom; /** * <b>Created Thu May 02 15:02:54 2002</b> * <p> * Comments * </p> * @author cfarnham * @version 1.0 * <p> * This GUID algorithm was taken from an article on <a href="." target="_blank" rel="nofollow">.</a> * See the article * <a href=">here</a>. * <p> * The specification that defines the format of UUIDs can be found * <a href="">here</a>. * <P> * This object creates a 36-digit alphanumeric (including hyphens) of the format * xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. This String is unique to time, instance, and * geography without the use of a Singleton. The mechanism is detailed below. * <p> * 1) (1-8 hex characters) use the low 32 bits of System.currentTimeMillis(). We could * use the recommended date format by adding 12219292800000L to the * system time long before grabbing the low 32 bits but * there doesn't seem much point. This gives us a * uniqueness of a millisecond - therefore any clashing object will have * to be generated within the same millisecond. * <p> * But this does not give us a uniqueness in space or complete uniqueness * in time. * <p> * 2) (9-16 hex characters) the IP address * of the machine as a hex representation of the 32 * bit integer underlying IP - gives us a spatial uniqueness to * a single machine - guarantees that these characters will be different * for machines in a cluster or on a LAN. * <p> * We now have machine uniqueness per millisecond - but this does not * account for multiple objects on a machine, clock sequence being * reset or the same object producing multiple GUIDs per millisecond. * <p> * 3) (17-24 hex characters) the hex value of the * Stateless Session bean object's hashCode (a 32 bit int) * - in the Java language spec - the hashcode value of Object * is defined as - ((As much as is reasonably practical, the * hashCode method defined by class object does return distinct integers * for distinct objects. (This is typically implemented by converting the * internal address of the object into an integer, but this * implementation technique is not required by the Java programming language.)) * <p> * This removes the need for a singleton object as the * Stateless bean uses its own hashCode as part of the * GUID - so even if two objects create a value at * the same millisecond on the same machine these characters will * be different. Remember the hashCode is not over-ridden here * so the implementation will be the one for Object. Note * - on machines with low RAM the most significant characters will * always be 00 in the hashcode sequence. * <p> * So we now have a number that is unique to the millisecond, the * IP address and the object creating it. There is still * the possibility that the same object can produce many GUIDs * within the same millisecond or the clock may be reset. * <p> * 4) (25-32 hex characters) a random 32 bit integer * generated for each method invocation from the SecureRandom java class * using SecureRandom.nextInt(). This method produces a cryptographically strong pseudo * -random integer. The Java lang defines this as - * ((Returns a pseudo-random, uniformly distributed int value drawn from this random * number generator's sequence. The general contract of nextInt is * that one int value in the specified range is pseudorandomly * generated and returned. All n possible int values are produced * with (approximately) equal probability.)) * <p> * By adding a random int to * the GUID for each new request we now have a * GUID that has a combination of the following four properties * <p> * 1) is unique to the millisecond <br> * 2) is unique to the machine <br> * 3) is unique to the object creating it<br> * 4) is unique to the method call for the same object <br> * **/ public class GlobalUniqueObjectImpl implements GlobalUniqueObject { //************************** // Private static variables //************************** //GUID stuff private static String HEX_INET_ADDRESS; //32 bits //initialize the secure random instance private static SecureRandom SEEDER = new SecureRandom(); //************************** // Instance variables //************************** //the guid string private String _guid; //init to super.hashcode() which becomes //part of the guid private int _hashCode = super.hashCode(); //************************** // Constructors //************************** public GlobalUniqueObjectImpl() throws GlobalObjectCreationException { this._guid = createGUID(this); _hashCode = this.getGUID().hashCode(); } //************************** // Public methods //************************** /** * Return the GUID */ public final String getGUID() { return this._guid; } public void setGUID(String guid) { this._guid = guid; } public boolean equals(Object o) { boolean returnBoolean = false; if (o instanceof GlobalUniqueObjectImpl) { GlobalUniqueObjectImpl guid = (GlobalUniqueObjectImpl) o; returnBoolean = this.getGUID().equals(guid.getGUID()); } return returnBoolean; } public final int hashCode() { return _hashCode; } public String toString() { return _guid; } /** * Creates a guid for the given object **/ public static final String createGUID(Object o) throws GlobalObjectCreationException { String midValue = initGUID(o.hashCode()); long timeNow = System.currentTimeMillis(); int timeLow = (int) timeNow & 0xFFFFFFFF; //32 bits int node = SEEDER.nextInt(); //32 bits String strTimeLow = intToHexString(timeLow, 8); String strNode = intToHexString(node, 8); StringBuffer buff = new StringBuffer(strTimeLow).append(midValue).append(strNode); return buff.toString().toUpperCase(); } //************************** // Private methods //************************** /** * Creates the objects that are reused from * instance to instance **/ private static final String initGUID(int hashCode) throws GlobalObjectCreationException { String returnString; try { // get the inet address InetAddress inet = InetAddress.getLocalHost(); byte[] bytes = inet.getAddress(); HEX_INET_ADDRESS = intToHexString(getInt(bytes), 8); //get the hashcode as hexvalue at least 8 chars long String thisHashCode = intToHexString(hashCode, 8); //set up a cached midValue as this is the same per method //call as is object specific and is the mid part //of the sequence StringBuffer buff = new StringBuffer(); buff.append("-"); buff.append(HEX_INET_ADDRESS.substring(0, 4)); buff.append("-"); buff.append(HEX_INET_ADDRESS.substring(4)); buff.append("-"); buff.append(thisHashCode.substring(0, 4)); buff.append("-"); buff.append(thisHashCode.substring(4)); returnString = buff.toString(); //load up the randomizer first value int node = SEEDER.nextInt(); } catch (Exception e) { e.printStackTrace(); throw new GlobalObjectCreationException(e, "Error creating guid "); } return returnString; } /** * Converts an int to a HexString of a specific length. * it pads a string with 0's or snips it as appropriate. * @param int n the int that you want converted * @param int length the length of the string you want returned **/ private static String intToHexString(int n, int length) { char[] hexArray = Integer.toHexString(n).toCharArray(); char[] returnArray = new char[length]; int lDiff = returnArray.length - hexArray.length; for (int i = 0; i < returnArray.length; i++) { if (i < lDiff) { returnArray[i] = '0'; } else { //index needs to start from the back returnArray[i] = hexArray[i - lDiff]; } } return new String(returnArray); } /** * Converts a byte array to an int. **/ private static int getInt(byte[] array) throws GlobalObjectCreationException { int returnInt = 0; StringBuffer buff = new StringBuffer(); for (int i = 0; i < array.length; i++) { int n = array[i] & 0xFF; buff.append(Integer.toString(n)); } //cut the string off at 9 digits as any more would be too big //and throw a NumberFormatException //System.out.println( buff.toString() ); if (buff.length() > 9) { returnInt = Integer.parseInt(buff.toString().substring(0, 10)); } else { returnInt = Integer.parseInt(buff.toString()); } return returnInt; } } /** * GlobalUniqueObjectImpl ends here **/
Christopher Farnham<br />Boston, MA<p>"Perfect is the Enemy of Good"
I agree. Here's the link:
subject: how to generate a unique number
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Paul Wheaton | http://www.coderanch.com/t/370149/java/java/generate-unique-number | CC-MAIN-2014-15 | refinedweb | 1,645 | 53.21 |
Hello I have problem with streaming video in the newest allegro 5.
I have:
#include <allegro5/allegro_audio.h>#include <allegro5/allegro_acodec.h>#include <allegro5/allegro_video.h>
int main(){
al_install_audio(); al_init_acodec_addon(); al_init_video_addon();
ALLEGRO_VIDEO *splash_vid = al_open_video("vid.ogv"); ALLEGRO_MIXER *mixer = al_create_mixer(44100, ALLEGRO_AUDIO_DEPTH_FLOAT32, ALLEGRO_CHANNEL_CONF_2);
al_start_video(splash_vid, mixer);
al_close_video(splash_vid); al_destroy_mixer(mixer);return 0;}
but after launch I have only black screen which can't be closed.Can u help me solve this problem?
You have to monitor video events and then display a frame when you get an ALLEGRO_EVENT_VIDEO_FRAME_SHOW event. You then get the bitmap to draw with al_get_video_frame. You need to register the video event source with an ALLEGRO_EVENT_QUEUE to receive video events.
Read the video section of the manual for details :
You have a black screen that can't be closed because you didn't create a.
Now I have something like that and I created display earlier, in main fucntion:
void splash_screen(void){ ALLEGRO_VIDEO *splash_vid = al_open_video("vid.ogv"); ALLEGRO_MIXER *mixer = al_create_mixer(44100, ALLEGRO_AUDIO_DEPTH_FLOAT32, ALLEGRO_CHANNEL_CONF_2);
al_set_new_bitmap_flags(ALLEGRO_VIDEO_BITMAP); ALLEGRO_BITMAP *bitmap = al_create_bitmap(al_get_video_scaled_width(splash_vid), al_get_video_scaled_height(splash_vid));
std::cout << al_is_video_playing(splash_vid);
ALLEGRO_EVENT_QUEUE *vid_event_queue = al_create_event_queue();
al_register_event_source(vid_event_queue, al_get_video_event_source(splash_vid));
bool done = false; while (!done) { ALLEGRO_EVENT vid_ev; al_wait_for_event(vid_event_queue, &vid_ev); switch (vid_ev.type) { case ALLEGRO_EVENT_VIDEO_FRAME_SHOW: bitmap = al_get_video_frame(splash_vid); al_draw_bitmap(bitmap, 0, 0, 0); al_flip_display(); //std::cout << _LINE_ << ' ' << _FILE_ << std::endl; al_clear_to_color(al_map_rgb(0, 0, 0)); break; case ALLEGRO_EVENT_VIDEO_FINISHED: done = true; break; } }
al_destroy_event_queue(vid_event_queue); al_close_video(splash_vid); al_destroy_mixer(mixer);}
and still I have black screen.
Set the drawing target to the backbuffer before drawing your bitmap and flipping the display.
Also, you don't need to create a bitmap. al_get_video_frame maintains one for you.
Still it doesn't work :/I can't event gets this events because this lines not executes
Still it doesn't work :/I can't event gets this events because this lines not executes
That's pretty vague. We need more details.
Post full code of a Minimum, Complete, Verifiable Example (MCVE) that fails to play video or fails to compile correctly and then we can help you.
If you video is under 10MB, post it as an attachment as well. Or upload it somewhere else so we can test it.
Ok, so this is my main function:
#include "All_headers.h"
ALLEGRO_TIMER *fps_timer = NULL; ALLEGRO_DISPLAY *display = NULL;int width = 640;int height = 480;int fps = 60;
int main(void){ //allegro variables if (!al_init()) // test allegro al_show_native_message_box(display, "Arcade Jump", "Error", "Error", "Error with allegro", ALLEGRO_MESSAGEBOX_WARN);
al_set_new_display_flags(ALLEGRO_WINDOWED | ALLEGRO_RESIZABLE); display = al_create_display(width, height); al_set_window_title(display, "Arcade Jump"); al_hide_mouse_cursor(display);
if (!display) //test display al_show_native_message_box(display, "Arcade Jump", "Error", "Error", "Error with display", ALLEGRO_MESSAGEBOX_WARN);
fps_timer = al_create_timer(1.0 / fps); al_start_timer(fps_timer);
//addon init al_install_audio(); al_init_acodec_addon(); al_init_video_addon(); al_install_keyboard(); al_init_primitives_addon(); al_init_image_addon();
splash_screen(); menu();
// destroying globall variables al_destroy_display(display); al_destroy_timer(fps_timer); return EXIT_SUCCESS;}
Splash function:
al_set_new_bitmap_flags(ALLEGRO_VIDEO_BITMAP); ALLEGRO_BITMAP *bitmap;
bool done = false; while (!done) { ALLEGRO_EVENT vid_ev; al_wait_for_event(vid_event_queue, &vid_ev); if (vid_ev.type == ALLEGRO_EVENT_VIDEO_FRAME_SHOW) { bitmap = al_get_video_frame(splash_vid); al_draw_bitmap(bitmap, 0, 0, 0); al_flip_display(); std::cout << _LINE_ << ' ' << _FILE_ << std::endl; al_clear_to_color(al_map_rgb(0, 0, 0)); } else if (vid_ev.type == ALLEGRO_EVENT_VIDEO_FINISHED) { done = true; break; } std::cout << _LINE_ << ' ' << _FILE_ << std::endl; }
and headers:
#pragma once// allegro extensions#include <allegro5\allegro.h>#include <allegro5\allegro_native_dialog.h>#include <allegro5\allegro_image.h>#include <allegro5\allegro_audio.h>#include <allegro5\allegro_acodec.h>#include <allegro5\allegro_video.h>#include <iostream>
// splash screenvoid splash_screen(void);
// global variablesextern ALLEGRO_TIMER *fps_timer;extern ALLEGRO_DISPLAY *display;extern int width;extern int height;extern int fps;
video file:
You can include code in <code>code goes here...</code> tags for easier reading and formatting.
Your video is only 1.41 MB. Please upload it as an attachment. I will not be using ZippyShare to install AdWare. Thanks.
EDITYou still haven't set the drawing target to the backbuffer before drawing the video frame and flipping the display.
Still no working, I can't figure why.My event queue is all the time empty.
It's not playing because you're never receiving an ALLEGRO_EVENT_VIDEO_FRAME_SHOWN event. Looks like a bug in Allegro. Could be due to an unsupported video format. .ogv is just a container for different video files.
EDITI've been having problems with DirectX and when I try to close my example program to play your .ogv file it deadlocks in al_close_video.
However, try ex_video to play your .ogv file. There doesn't appear to be anything wrong with the video file. VLC Media Player can play it just fine, and when I run "ex_video.exe vid.ogv" it plays fine. There may be something wrong with my build. I've been having other problems with DirectX.
What version of Allegro are you using? Are you using binaries? If so, what version?
So if you know, could you tell me which video format I can use ?
See my edit.
I have Allegro 5.2.1.1 and I downloaded it from NuGet packages using Visual Studio 2015 Enterprise
EDIT
How can I use ex_video?
Nuget doesn't come with the examples. You have to download the sources and compile ex_video yourself.
Still don't know how to play video but I solved my problem. I rendered my video frame by frame in images and I am drawing them sequentially. Thanks for help and have a nice day
You should post your solution. Are you parsing the video yourself?
Yes.
Like I said, ex_video works, where our example programs do not. They must be doing something different. Look at the source of ex_video.c for clues. You can compile it yourself like any other normal allegro program now that you have Allegro from Nuget installed. | https://www.allegro.cc/forums/thread/616637/1026906 | CC-MAIN-2017-47 | refinedweb | 920 | 50.84 |
Objective
In this article , I will show how to work with Silver Light Navigation framework.
Create a Silver Light Application by selecting Silver Light application from project template. And follow below steps.
Step 1
Adding references
Add below references to Silver Light application.
System.Windows.Control
System.Windos.Control.Data
System.Windows.Control.Navigation
Step2
Adding namespaces
Open MainPage.Xaml and add the namespace. Give name of the namespace as Navigation and add System.Windows.Control.Navigation. See the image below.
Step 3
Creating Silver Light Page for navigation
Now I am constructing the pages to navigate. Right click on silver light project and add a new folder. You can give any name to folder of your choice. I am giving name here View. Add two silver light pages inside this folder. To add right click on folder and add new Item then select Silver Light page. Page I am adding is
- Image.Xaml
- Me.Xaml
Me.Xaml
- Title of the page can be amending in Title tag. See the tag in bold.
- New added Silver Light page is navigation page.
- I have added a simple text block with some static text on the page for the demo purpose.
Image.Xaml
- Title of the page can be amending in Title tag. See the tag in bold.
- New added Silver Light page is navigation page.
- One image is added for the demo purpose.
Step 4
Designing for navigation
Now it is time to design main page for navigation.
- I am adding two HyperLinkButtons. On clicking of buttons, we will navigate to other pages.
- There is TAG property of hyperlink, which says where hyperlink will navigate. Views are folder we added and Me.Xaml is silver light page to navigate.
Tag=”/Views/Me.Xaml”
- Add either a frame or page to where navigated page will be open. There are two options either Page or Frame. Navigation is the name of the namespace we added.
- Navigation framework can have many properties. I am setting few of them. See below.
<Navigation:Frame x:Name=”MyFrame” HorizontalAlignment=”Stretch” VerticalAlignment=”Stretch” Margin=”20″ />
Step 5
Writing code behind to navigate
- Add click event to hyperlinkbuttons.
btnAbt.Click += new RoutedEventHandler(NavigateToLink)
btnImg.Click +=new RoutedEventHandler(NavigateToLink);
- Handle the click event
void NavigateToLink(object sender, RoutedEventArgs e)
{
HyperlinkButton buttonToNavigate = sender as
HyperlinkButton;
string urlToNavigate = buttonToNavigate.Tag.ToString();
this.MyFrame.Navigate(new Uri(urlToNavigate, UriKind.Relative));}
Step 6
Run the application.
You can see while clicking on the hyperlinks, we are able to navigate in the frame. So, we are able to navigate through pages using navigation framework.
Conclusion
We saw how to work with navigation framework in this article. Thanks for reading | https://debugmode.net/2009/12/11/introduction-to-silver-light-3-0-navigation/ | CC-MAIN-2022-05 | refinedweb | 444 | 53.47 |
- .6.)
In this MT application, we execute three separate recursive functions—first in a single-threaded fashion, followed by the alternative with multiple threads.
1 #!/usr/bin/env python 2 3 from myThread import MyThread 4 from time import ctime, sleep 5 6 def fib(x): 7 sleep(0.005) 8 if x < 2: return 1 9 return (fib(x-2) + fib(x-1)) 10 11 def fac(x): 12 sleep(0.1) 13 if x < 2: return 1 14 return (x * fac(x-1)) 15 16 def sum(x): 17 sleep(0.1) 18 if x < 2: return 1 19 return (x + sum(x-1)) 20 21 funcs = [fib, fac, sum] 22 n = 12 23 24 def main(): 25 nfuncs = range(len(funcs)) 26 27 print '*** SINGLE THREAD' 28 for i in nfuncs: 29 print 'starting', funcs[i].__name__, 'at:', 30 ctime() 31 print funcs[i](n) 32 print funcs[i].__name__, 'finished at:', 33 ctime() 34 35 print '\n*** MULTIPLE THREADS' 36 threads = [] 37 for i in nfuncs: 38 t = MyThread(funcs[i], (n,), 39 funcs[i].__name__) 40 threads.append(t) 41 42 for i in nfuncs: 43 threads[i].start() 44 45 for i in nfuncs: 46 threads[i].join() 47 print threads[i].getResult() 48 49 print 'all DONE' 50 51 if __name__ == '__main__': 52 781600 78 all DONE | http://www.informit.com/articles/article.aspx?p=1850445&seqNum=6 | CC-MAIN-2019-30 | refinedweb | 224 | 81.33 |
Don't underestimate super.
Here at Exec, I've been working for a bit now into having a system to allow us to log whatever happens in the system;
Either a modification is made by an admins through the admin's dashboard, or a user directly throught the website, we wanted to be able to track everything and easily access the history of a job, a user's info, etc.
For that purpose, I created an Audit model, which, through polymorphism, can be used no matter who 'generates' that audit, and for which model it is;
create_table "audits" do t.text "notes" t.string "author_type" t.integer "author_id" t.string "thing_type" t.integer "thing_id" t.datetime "created_at" t.datetime "updated_at" end class Audit < ActiveRecord::Base belongs_to :thing, polymorphic: true belongs_to :author, polymorphic: true end
Basic enough class to be able to create a helper method in ApplicationController;
class ApplicationController < ActionController::Base def audit(args) Audit.create! args end end
Pretty basic class, but since it is (twice!) polymorphic, you can't have a simple ApplicationController method that allows you to create an Audit without having to set everything all the time.
audit author_type: 'Admin', author_id: @admin.id, thing_type: 'Job', thing_id: @job.id, notes: "Changed job #{job.id}'s date."
Not so convenient to always have to write all that…
A first step would be to extract, for example, the thing data by redefining audit inside of the Thing Controller and using super.
def update @job.date = new_date audit author_type: 'Admin', author_id: @admin.id, notes: "Changed date." end def audit(args) super(args.merge(thing_type: 'Job', thing_id: @job.id)) end
As you can see here, I don't have to set the thing type and id anymore, because I added a new audit helper method in my Job controller, that accepts the still needed arguments and calls super with those arguments and the thing data.
But I still have to set my author, since the job's audit could be generated by either an admin or a user.
The difference here is that, if the user is doing the modification, the update action will be called by a different controller than if it was my admin doing the same modification on the same job. Why? Because my admin uses our internal admin's dashboard, when my user is using his own dashboard.
Hence I have 2 JobsControllers, one inheriting from AdminsController and another one inheriting from WebController.
So when audit is called in my JobsController, super looks first into the related inheriting controller for an audit method, before grabing the audit method inside ApplicationController.
So let's go inside my AdminsController.
class AdminsController < ApplicationController def audit(args) super(args.merge(author_type: 'Admin', author_id: @admin.id)) end end
I'm inside my AdminsController, so I know the action is always triggered by my admin here. Same thing if I was in my web controller with the author being user.
So now, when I call audit inside my JobsController, I don't have to set the author data anymore either, and just have to set what matters there, the notes field. Let's have a last look at my inheritance here;
class JobController < AdminsController def update @job.date = new_date audit notes: "Changed date to #{new_date}." end private def audit(args) super(args.merge(thing_type: 'Job', thing_id: @job.id)) end end # super then travels to AdminsController class AdminsController < ApplicationController def audit(args) super(args.merge(author_type: 'Admin', author_id: @admin.id)) end end # super then again, travels to the parent, ApplicationController # where the audit is actually being created! class ApplicationController < ActionController::Base def audit(args) Audit.create! args end end | http://www.jypepin.com/don-t-underestimate-super | CC-MAIN-2019-09 | refinedweb | 605 | 58.18 |
A Stack?
A Stack is using the principle first-in-last-out.
It is like a stack of plates. The last one you put on the top is the first one you take.
How can you implement them in Python? Well, we are in luck, you can use a Stack, and if done correctly, you will have the same performance as an actual Stack implementation will have.
But first, how can you do it wrong?
Well, you might think that the first element of the list is the top of your stack, hence in you will insert the elements on the first position, and, hence, remove them from the first position as well.
# Create a list as a stack s = [] # Insert into the first position. element = 7 s.insert(0, element) # Remove from the first position. s.pop(0)
Sounds about right?
Let’s test that and compare it with a different approach. To add the newest element to the end of the list, and, hence, remove them from the end of the list.
# Create a list and use it as stack s = [] # Insert element in last postion element = 7 s.append(element) # Remove from the last position s.pop()
Let’s check the performance of those two approaches.
Comparing the performance of the two approaches
How do you compare. You can use cProfile library. It is easy to use and informative results
See the sample code below, which compares the two approaches by create a stack each and inserting n elements to it and removing them afterwards.
import cProfile def profile_list_as_queue_wrong(n): s = [] for i in range(n): s.insert(0, i) while len(s) > 0: s.pop(0) def profile_list_as_queue_correct(n): s = [] for i in range(n): s.append(i) while len(s) > 0: s.pop() def profile(n): profile_list_as_queue_wrong(n) profile_list_as_queue_correct(n) cProfile.run("profile(100000)")
The results are given here.
Ordered by: standard name ncalls tottime percall cumtime percall filename:lineno(function) 1 0.000 0.000 5.842 5.842 <string>:1(<module>) 1 0.078 0.078 0.107 0.107 Stack.py:12(profile_list_as_queue_correct) 1 0.000 0.000 5.842 5.842 Stack.py:20(profile) 1 0.225 0.225 5.735 5.735 Stack.py:4(profile_list_as_queue_wrong) 200002 0.017 0.000 0.017 0.000 {len} 100000 0.007 0.000 0.007 0.000 {method 'append' of 'list' objects} 1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects} 100000 3.547 0.000 3.547 0.000 {method 'insert' of 'list' objects} 200000 1.954 0.000 1.954 0.000 {method 'pop' of 'list' objects} 2 0.014 0.007 0.014 0.007 {range}
Observe that the “wrong” implementation takes over 5 seconds and the “correct” takes approximately 0.1 second. Over a factor 50 in difference.
Looking into the details
If we look at the complexities given by Python, it explains it all.
The Python lists amortised complexities are given on this page.
And you notice that the append and pop (last element) are O(1), which means constant time. Constant time, means that the operations are independent on the size of the lists. That means the correct implementation gives O(n) time complexity.
On the other hand, the insert and pop(0) have linear performance. That basically means that we with the wrong implementation end up with O(n^2) time complexity. | https://www.learnpythonwithrune.org/comparing-performance-of-python-list-as-a-stack-how-a-wrong-implementation-can-ruin-performance/ | CC-MAIN-2021-25 | refinedweb | 574 | 77.53 |
Part 1 Modify your program from Learning Journal Unit 7 to read...
Part 1
Modify your program from Learning Journal Unit 7 to read dictionary items from a file and write the inverted dictionary to a file. You will need to decide on the following:
- How.
Part 2
Copy your program from Part 1 and modify it to do the following:
- Read the output file from Part 1 and create a dictionary from it (the inverted dictionary from Part 1).
- Invert that dictionary.
- Write the re-inverted dictionary to an output file.
It will be interesting to see if your original dictionary is reversible. If you invert it twice, do you get the original dictionary back?
Include the following in your Learning Journal submission:
- The input file for your original dictionary (with at least six items).
- The Python program for Part 1.
- The output file for your inverted dictionary, which is also the input file for Part 2.
- The Python program for Part 2.
- The output file for your twice-inverted dictionary.
- A description of any differences between your program for Part 1 and your program for Part 2.
- A description of any differences between the original input file and the final twice-inverted output file.
Reference:
Learning Journal Unit 7
Create a Python dictionary where the value is a list. The key can be whatever type you want.
Design the dictionary so that it could be useful for something meaningful to you. Create at least three different items in it. Invent the dictionary yourself. Do not copy the design or items from some other source.
Next consider the invert_dict function from Section 11.5 of your textbook.
# From Section 11.5 of:
# Downey, A. (2015). Think Python: How to think like a computer scientist. Needham, Massachusetts: Green Tree Press.
def invert_dict(d):
inverse = dict()
for key in d:
val = d[key]
if val not in inverse:
inverse[val] = [key]
else:
inverse[val].append(key)
return inverse
Modify this function so that it can invert your dictionary. In particular, the function will need to turn each of the list items into separate keys in the inverted dictionary.
Run your modified invert_dict function on your dictionary. Print the original dictionary and the inverted one.
Include your Python program and the output in your Learning Journal submission.
Describe what is useful about your dictionary. Then describe whether the inverted dictionary is useful or meaningful, and why.
I'm able to pull out the text file but I'm having trouble doing the assingment:
import os
cwd = os.getcwd()
fin = open('words.txt')
for line in fin:
word = line.strip()
print(word)
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a. Fusce dui lac,,amet, consexuscuscictrices ac magna. Fuipsum dolor sit amet, consectetur adipiscing elit. Nam lacinia pulvinar torat, ultrices ac marisus,ac,ec facicitur laoreet. Nam risus ante, dapibus a molestie consequat, ultricnec facilisis. P0ultricesfsus antuscegrisus,aciuscrem irisus ante, dapibus a molestie consequarem isumrem i,fficitur laoreet. Namongue verem i,icitur laoreet. Nam risu, consectet vita | https://www.coursehero.com/tutors-problems/Computer-Science/16352696-Part-1-Modify-your-program-from-Learning-Journal-Unit-7-to-read-dictio/ | CC-MAIN-2022-33 | refinedweb | 557 | 60.72 |
Re: Global subroutines
From: tshad (tscheiderich_at_ftsolutions.com)
Date: 02/03/05
- ]
Date: Thu, 3 Feb 2005 08:26:45 -0800
"fd123456" <fd123456@hotmail.com> wrote in message
news:c8d02ef8.0502030448.7b1b5a90@posting.google.com...
> Hi Tom !
>
> Sorry about the messy quoting, Google is playing tricks on me at the
> moment.
>
>> Global.asax is where you normally have the Global Application
>> and Session variables and code to manipulate them. It starts
>> and ends with <script></script> tags.
>>
>> Yours looks like a compiled version of it.
>>
>> It is just like any ASP.net page. If you use code-inside, you
>> surround the code with the script tags. To make the code into
>> a code-behind file, you move the code to a new file and leave
>> out the script tags.
>
> I had never thought of it that way. I'm not saying you're wrong, to be
> honest I'm not at all sure, but :
> 1) I've searched hi and lo and can't find anything resembling script
> tags in Global.asax.
> 2) There has to be a Global shared (static) class, because that's
> where the variables are held.
> 3) In VS, contrarily to plain aspx pages, you don't have access to
> HTML code for Global.asax (usually, an aspx combo has three different
> views : the html view and the design view, which are two tabs on the
> same window, and the code-behind file which sits in another window.
> There's no design or html tab in Global.asax.
> 4) As far as I know, aspx stands for Active Server Page eXtended(?),
> asax stands for Active Server Application eXtended(?). It's supposed
> to be an app, not an page as such. You cannot, for instance, drop a
> html table on Global.asax, but mind you, you can drop Windows Forms
> controls on it !!
>
> So, I do believe it's not an aspx but a proper app, contained in a
> class, and not enclosed in a script block. Again, I could be wrong. I
> wish some guru would help us there.
You may be correct.
I know the Global.asax has script tags (only because that was the way the
example program I used a while ago had it set up). In the books I have,
such as "ASP.net: Tips, Tutorials and Code" - it shows it with the script
Maybe it doesn't matter. Maybe .net just throws it away. I assume that if
you don't have script tags in yours and I do in mine, it isn't an issue with
.net.
>
>> To have a class, I think you would need to compile the file, as you said
>> and you would have to have the codebehind/inherits on all my pages. I am
>> trying to get around this.
>
> You definitely need to compile the file in any case. Compiling it
> creates a dll in a bin directory, without which no aspx page can be
> served (plain html can, though, but that's IIS working under the
> scene). You don't have to inherit it on any page, because the
> structure is as follows :
>
> Global.asax inherits from the System.Web.HttpApplication class and is
> inside the namespace that's named after your project. As it is shared,
> it can be used from any other object that is inside that namespace, so
> any page inside that namespace can refer to Global.asax simply by
> using, for instance, "Global.SomeMethod" (provided that method is
> public, obviously).
> Pages inherit from System.Web.Ui class. They don't need to inherit
> from the application itself (read : they musn't).
> Each page has an associated code-behind file, and the aspx file
> inherits from the class that lies in the code-behind file. With VS,
> all this is totally transparent and taken care for you by the
> Framework.
>
So if I compile it, would I end up with Global.dll?
With a regular code behind, I would compile it like so:
vbc /t:library something.vb
This would give me something.dll.
Would I compile the Global.asax something like:
vbc /t:library Global.asax
To get get Global.dll
Or would I need to name it Global.asax.vb and do:
vbc /t:library Global.dll
>> The other problem is - how would I handle 2 codebehind files. Each
>> aspx page would have it's own code behind and then you have the
>> Global one. How would you set that up in your ASP pages (you would
>> need 2 inherits and 2 codebehind statements).
>
> You don't. Again, I think your misconception comes from the fact that
> you think the app is not compiled. Think of it this way : the app
> contains many classes, some being pages, some being code-behind files,
> and one being the Global object. All these classes can (theoretically)
> talk to each other, and that's why, to return to the beginning of your
> question, you can include shared methods in the Global class and use
> them from other classes (code-behind files).
>
>> I did that last night, as you suggested, and just have to wait for the
>> CD.
>
> Well, that's very good news for you, because I'm positive that it'll
> all become clear very quickly, and I'm also quite sure that you'll
> have tremendous fun. VS is the best toy I ever dreamed of, it's fast,
> deep, smart, coherent and has the most impressive optimisations. In a
> month and a half, I've developped a program that used to cost around
> 100.000 $ five years ago. I'm in no way affiliated blah blah,
> obviously.
>
Should be here soon.
Thanks,
Tom
> So, have fun with it !
>
> Michel
- ] | http://www.tech-archive.net/Archive/DotNet/microsoft.public.dotnet.framework.aspnet/2005-02/2230.html | crawl-002 | refinedweb | 947 | 83.66 |
Saving Image with different ColorProfile
Hello,
I am stuck with a problem where I try to open an image in
ImageObject()apply a
.dotScreenfilter on it and save it again.
Now I always end up with an image saved with RGB profile but I would like to generate an image just black and white — no color information.
I looked into the documentation and first I thought it has something to do with
colorSpace()but I guess that is not the case.
So I ended up by the saving options and I think that
imageColorSyncProfileDatais actually what I am looking for. But I do not understand how to work with it.
For further interest I would be keen to know if there is a way to convert images into different profiles. Especially thinking about print production where I maybe need certain ICC-Profiles.
I am happy for any help or information for a solution.
Thank you.
I think conversions between color modes and color profiles are better handled with PIL/Pillow.
here’s a small script to convert a
.pngimage!
Hey @gferreira,
thank you for you reply! I will have a more detailed look into the PIL-Library but I think that's it for the moment.
Still, if you have some further information or any idea where to find something about the
imageColorSyncProfileDataand how to use it that would be great! Always happy to learn something new.
Have a great day.
you need color profile data:
like this one ICC Profiles (end-user)/RGB/AppleRGB.icc
import AppKit fill(1, 0, 0) rect(20, 20, width()-40, height()-40) data = AppKit.NSData.dataWithContentsOfFile_('path/to/AppleRGB.icc') saveImage("test.tiff", imageColorSyncProfileData=data)
good luck!!
see futher discussion
Hey ataneeds.
Anyway, thanks again for your help. | https://forum.drawbot.com/topic/226/saving-image-with-different-colorprofile/2 | CC-MAIN-2020-05 | refinedweb | 295 | 66.84 |
Ok, I am really stuck, and need major help. Ths assignment i am working on is as follows:
Its american idol. Design a function getJudgeData that asks the user for a judge's score, stores it in a reference parameter variable, and validates it. This function should be called by your function main() once for each of the 5 judges.
I have my class built i am just working on the main.cpp file...
I would REALLY appiciated ANY help. I am having trouble passing it by reference by using the Class Stat. I cant get the getJudgeData to put the data and store it into the class. Does anybody have ANY suggestions PLEASE? I can post the class if you need to see it I want to take the s.getNum(); and store the scores into there.
Code:#include <iostream> #include "Stat.h" using namespace std; void getJudgeData(int &); double calcScore(); int main() { int score1 = 0, score2 = 0, score3=0, score4=0, score5=0; Stat s; cout << "This program assignment number 4 was created by Jeremy Rice" << endl; cout<< "The Next American Idol!!!"<<endl; cout<< "Please enter your scores below!"<<endl; cout<<"Judge #1 what is your score"<<endl; getJudgeData(score1); cout<<"Judge #2 what is your score"<<endl; getJudgeData(score2); cout<<"Judge #3 what is your score"<<endl; getJudgeData(score3); cout<<"Judge #4 what is your score"<<endl; getJudgeData(score4); cout<<"Judge #5 what is your score"<<endl; getJudgeData(score5); system("pause"); return 0; } void getJudgeData(int &score) { Stat s; s.getNum(""); } // The average is the min and max subtracted // the remaining three numbers are calculated for average /*double calcScore() { Stat s; int average = 0; average(s.getSum - s.getMin - s.getMax)/3; } */ | http://cboard.cprogramming.com/cplusplus-programming/95192-pass-reference.html | CC-MAIN-2014-42 | refinedweb | 285 | 64 |
July 27, 2018
Back to Tips and Tricks Table of Contents
The end goal is of this tutorial is to release C++ code developed in Ubuntu – and currently on Github – in Docker images, with all of the required libraries, such that others can run, evaluate, and use it. To get there, well, that took a while.
This guide is assembled from my own notes as I was learning Docker. I most frequently program in C++ on Ubuntu, with OpenCV, OpenMP, Eigen, and other libraries. I give the information from the tutorial in the text, and you can also get the examples as directories from Github, here, or
git clone
First, of all, I’m using
Docker version 18.06.0-ce, build 0ffa825
Good resources are available from the Docker website, my personal favorites being Getting started and Build the app. The remainder of this document assumes that you have read and tried the examples on these two pages. Oh! And that you have a version of Docker installed. After a half-hearted attempt to install the latest from Github, I installed Docker CE for Ubuntu – painless on Ubuntu 16.04 (2x).
Later, the best practices page can be useful. Vladislav’s site is also good, though I discovered it too late in this particular quest.
To break this task into smaller sections, this tutorial has the following structure:
First, I’ll mention some notes that turned out to be useful deugging tools. If you haven’t touched Docker yet, though, you are safe to skip them at the present time.
This section contains some items I wished that I had known earlier. However, it might be confusing if you’re only first starting to use Docker – hence the title.
This tutorial is offered exclusively from the Dockerfile perspective, because that is needed for automated builds (more on that later). However, for debugging purposes, I have found it sometimes useful to work out all the kinks by running an image:
docker run -it ubuntu bash
And then you’re in
bash in ubuntu, or whatever other image you have selected (could be your own!). Then execute your commands using the command line. To save as a new image, you can commit (Note, you need to open a new bash shell to get the image id).
If you have a slow internet connection or large images,
docker pull,
push, and
build (which includes
pull) will stall out. You may get some unhelpful hints from the docker command about how fix that – but to be clear, first you need to kill the Docker daemon
dockerd. If you installed Docker from the method above and haven’t restarted, you didn’t start this deamon yourself, so you’ll have to find it the usual way:
$ ps aux | grep dockerd atabb 1537 0.0 0.0 15948 932 pts/27 R+ 09:34 0:00 grep --color=auto dockerd root 38974 0.0 0.0 75396 2172 pts/18 S+ Jul26 0:00 sudo dockerd root 38975 0.5 0.0 3302072 102404 pts/18 Sl+ Jul26 5:59 dockerd
(
dockerd is the Docker daemon). I’m including all the steps for all the different levels of users.
Grab the id of the
dockerd,
sudo kill 38975.
Then restart the daemon with some parameters that will work better for your setting ( Docker daemon doc. ). For instance:
$ dockerd --max-concurrent-downloads 1 --max-concurrent-uploads 1
would change the layers downloaded and uploaded at a time from 5 (default) to 1. This still doesn’t solve all problems for big images – that’s handled to some extent on Page 3, but it may solve some.
Finally, pulling images and building lots of images can take a lot of hard drive space. Some tips for dealing with that are here, appropriately titled “Keeping the whale happy …”.
First, we’ll start with the goal of getting a C++ program to compile and run in Docker. To do so, we’ll use the familiar `Hello World’ template, but then gradually add complexity that will mirror that of the final goal application: passing arguments, assessing the host file system, and writing data to the host file system.
Navigate to
DockerHelloWorldProject0 in the command line from the Github repository I mentioned above, which contains file
Dockerfile and folder
HelloWorld.
The Dockerfile looks like this:
FROM amytabb/docker_ubuntu16_essentials COPY HelloWorld /HelloWorld WORKDIR /HelloWorld/ RUN g++ -o HelloWorld helloworld.cpp CMD ["./HelloWorld"]
The C++ file,
helloworld.cpp is straightforward:
#include <iostream> using namespace std; int main() { cout << "Hello world 0!" << endl; return 0; }
FROMcreates a layer from the
amytabb/docker_ubuntu16_essentialsimage.
COPYadds the local folder HelloWorld to the Docker image’s directory structure
WORKDIRchanges the directory to
/HelloWorld/.
RUN cd HelloWorlddoes not work, not only because I have tried it, but because at every
RUN, you are adding a new layer, which happens at the
/level of the image. More info here. I also have a dedicated page about
WORKDIR.
RUN ...compiles the .cpp file into an executable.
CMDruns/executes the new executible only when we use docker to run an image, when building, it sets up this expected behavior.
The standard order of operations is to then try to build. On certain connections, the download of the larger layers will time out during the build. I get around this problem by pulling them first:
docker pull amytabb/docker_ubuntu16_essentials
And then, in the directory
DockerHelloWorldProject0, try to build with Docker:
$ docker build -t hello0 .
By the way, for this example we could substitute
gcc:4.9 for my docker container
amytabb/docker_ubuntu16_essentials; but we’ll use the latter container in the other examples. Once it has been pulled to the local machine, docker will use it throughout the session, so we don’t need to download it again. My result looks like:
$ sudo docker build -t hello0 . Sending build context to Docker daemon 5.632kB Step 1/5 : FROM amytabb/docker_ubuntu16_essentials ---> 8c0f518d0b72 Step 2/5 : COPY HelloWorld /HelloWorld ---> Using cache ---> 8af16ac6ec94 Step 3/5 : WORKDIR /HelloWorld/ ---> Running in bc718f92ef92 Removing intermediate container bc718f92ef92 ---> d60afcf83759 Step 4/5 : RUN g++ -o HelloWorld helloworld.cpp ---> Running in 849f5b06d8c7 Removing intermediate container 849f5b06d8c7 ---> 74ddc7fb4a2a Step 5/5 : CMD ["./HelloWorld"] ---> Running in 33a0ebe24e99 Removing intermediate container 33a0ebe24e99 ---> 14fe6de84535 Successfully built 14fe6de84535 Successfully tagged hello0:latest
Then, the moment of truth! Try to run:
$ docker run -it hello0 Hello world 0!
Next challenge: Sending arguments to our simple hello world program. I’ll use the environment variable method sent through explicit
-e flags, described in detail here. There are alternate methods, that work better for lots of variables.
Navigating to the next folder in the directory,
DockerHelloWorldProject1, we have a Dockerfile, shell script, and a folder with the .cpp file in it.
First, the Dockerfile:
FROM amytabb/docker_ubuntu16_essentials ENV NAME VAR1 ENV NAME VAR2 ENV NAME VAR3 COPY run_hello1.sh /run_hello1.sh COPY HelloWorld /HelloWorld WORKDIR /HelloWorld/ RUN g++ -o HelloWorld1 helloworld1.cpp WORKDIR / CMD ["/bin/sh", "/run_hello1.sh"]
FROMcreates a layer from the
amytabb/docker_ubuntu16_essentialsimage.
ENV NAMEspecifies the environment variables that may be passed from the command line when the container is run. In this example, we have three arguments maximum. If the arguments are not specified, they are not passed to the C++ program, but more on that later.
COPYcopies files from the host to the image; syntax is host -> image. Unless we specifically place it in the image, it will not magically get there.
WORKDIRchanges the directory to
/HelloWorld/in the image.
RUN ...compiles the .cpp file into an executable.
CMDruns/executes the new executible using a shell script, which interprets the environment varibles and sends them to the C++ program as arguments.
Pretty simple: we’re just packaging everything together so that the C++ program can receive it. To make things easier, we wouldn’t have navigated into and out of the HelloWorld directory. However, I did so since the final goal application will require doing so, and I would rather fail early on the easy stuff.
#!/bin/sh ./HelloWorld/HelloWorld1 $VAR1 $VAR2 $VAR3
#include <iostream> #include <string> using namespace std; int main(int argc, char **argv) { cout << "Hello world 1, with arguments!" << endl; string val; for (int i = 1; i < argc; i++){ val = argv[i]; cout << "Argument " << i << " " << val << endl; } return 0; }
Choose a different tag, and build:
docker build -t hello1 .
Then, it is time to run and play around with arguments:
$ docker run -it -e VAR1='23' hello1 Hello world 1, with arguments! Argument 1 23
If we send no arguments, that’s no problem either:
$ docker run -it hello1 Hello world 1, with arguments!
What about arguments we didn’t specify in the Dockerfile, in other words, the user messes up?
$ docker run -it -e VAR1='23' -e VAR2='12' -e VAR3='10000' -e MYSTERY='blah' hello1 Hello world 1, with arguments! Argument 1 23 Argument 2 12 Argument 3 10000
I chose to bindmount a folder on the host to a folder in the image. From the way I have written the Dockerfile, the container’s folder HAS to be
/write_directory. The source folder on the host is where the data will be read and written. While in my own programs I remove and create folders of results with system calls – otherwise, there’s just too much accumulated junk in the development/debugging stage when I am working on algorithms – for releases I do not in case a user doesn’t read the fine print. Details of bindmounting and other types of mounting are here.
First, the Dockerfile:
FROM amytabb/docker_ubuntu16_essentials ENV NAME VAR1 ENV NAME VAR2 ENV NAME VAR3 RUN mkdir /write_directory ARG DIRECTORY=/write_directory ENV VAR_DIR=$DIRECTORY COPY run_hello2.sh /run_hello2.sh COPY HelloWorld /HelloWorld WORKDIR /HelloWorld/ RUN g++ -o HelloWorld2 helloworld2.cpp WORKDIR / CMD ["/bin/sh", "/run_hello2.sh"]
Many things are similar from the previous two sections, so I will only cover the new sections.
ARGis a way to specify build-type variables, which you can then copy over to environment varibles. Thanks to vsupalov’s site – here and here specifically – go there for more details.
In this case, the first argument for the program is the directory of the Docker container. I have chosen this order because I want it to be that way, not for any other reason.
#!/bin/sh ./HelloWorld/HelloWorld2 $VAR_DIR $VAR1 $VAR2 $VAR3
This program is similar to the others, except that we want some evidence that the bindmounting worked – or didn’t. So this program opens a new file in the directory – in the Docker image, which is bound to the directory on the host – and writes some text, and then closes the file.
#include <iostream> #include <string> #include <fstream> using namespace std; int main(int argc, char **argv) { cout << "Hello world 2, with a directory and arguments!" << endl; ofstream out; string val; if (argc >= 2){ val = argv[1]; cout << "Directory is : " << val << endl; string filename = val + "/test_write.txt"; out.open(filename.c_str()); out << "HELLO WORLD FROM A BINDMOUNT!" << endl; for (int i = 2; i < argc; i++){ val = argv[i]; cout << "Argument " << i << " " << val << endl; out << "Argument " << i << " " << val << endl; } out.close(); } else return 0; }
By now, you know the drill. Within the directory, build.
$ docker build -t hello2 .
Now, we’ll try bindmounting! Remember, the image’s folder HAS to be
/write_directory, so I’ll try
docker run -it -v /home/atabb/docker/HelloWorldMount:/write_directory -e VAR1=15 hello2 Hello world 2, with a directory and arguments! Directory is : /write_directory Argument 2 15
And the contents of my host folder has
HelloWorldMount]$ ls -l total 4 -rw-r--r-- 1 root root 44 test_write.txt
So the file’s there, and it has the expected text:
HELLO WORLD FROM A BINDMOUNT! Argument 2 15
Notice, that the owner of
test_write.txt is
root – or else the docker group if you have configured docker that way.
What if we run without any directory specified, or the user forgets? The Docker container doesn’t die, a win, but no data is written to the host folder.
$ docker run -it -e VAR1=15 hello2 Hello world 2, with a directory and arguments! Directory is : /write_directory Argument 2 15
Another variation, what if the user binds to the wrong folder?
$ docker run -it -v /home/atabb/docker/HelloWorldMount:/write_dir -e VAR1=25 hello2
Here, the user selected
write_dir instead of
write_directory. The host folder
HelloWorldMount was bound to a non-existent
write_dir, and so no data was written. In this toy example, nothing broke. However, depending on the application, you should be sure to test whether the files you need to read are in the directory, and exit the C++ code gracefully, which of course you do anyway. In my test, if
HelloWorldMount does not exist, it is created when running
docker run ..... Of course, it will be empty and be owned by
root (or someone else, depending on how you set up Docker).
My favorite for testing whether files are present in C++:
ifstream in; string filename = read_directory + "number_cameras.txt"; in.open(filename.c_str()); if (!in.good()){ cout << "Input file is bad for number cameras -- abort." << filename << endl; exit(1); }
Back to Tips and Tricks Table of Contents
© Amy Tabb 2018-2021. All rights reserved. The contents of this site reflect my personal perspectives and not those of any other entity. | https://amytabb.com/ts/2018_07_28/ | CC-MAIN-2021-21 | refinedweb | 2,219 | 63.19 |
RationalWiki:Saloon bar/Archive32
Contents
- 1 Drunken editing
- 2 Working toward a post-CP RW
- 3 freethoughtpedia
- 4 TK in my pub...
- 5 District 9
- 6 Questions for the mob
- 7 Important
- 8 Funny Stuff....
- 9 Fail.
- 10 Maus
- 11 Awesome film
- 12 Usain Bolt
- 13 Media termns
- 14 WTF
- 15 Pornographie!
- 16 Cinema/Movies
- 17 That health care bill sure would be nice right about now....
- 18 Spam?
- 19 "When Zombies Attack!: Mathematical Modelling of an Outbreak of Zombie Infection"
- 20 Math question
- 21 US ‘may take military action’ to liberate Britain from the NHS
- 22 Here, have a bag of LOLs
- 23 Fucking crickets!
- 24 UFOs
- 25 Master of the Internet!
- 26 Bible translation
Drunken editing[edit]
I just got in from a friend's party (1am now here in the
USSR UK) and of the approximately sixty odd people there only about five of them got sick. Three of them in my mate's kitchen though. HA! Poor guy. Anyway, I saw my ex-girlfriend there and we shared an awkward moment talking about the past. I'm actually surprised how off guard it caught me as I have no real outlet and have simply tried avoiding her for the last two months. Not that I reacted outwardly but I felt a weird twinge. Then "I have a sudden need for another cigarette!" I can't wait until I'm scarpering to uni a month or so to get away from this. SJ Debaser 00:16, 15 August 2009 (UTC)
- You didn't suggest a quick and temporary reunion in the closet toilet? CrundyTalk nerdy to me 14:24, 16 August 2009 (UTC)
Working toward a post-CP RW[edit]
Alright, Armondikov and I were talking last night about removing CP references from mainspace articles, and I've been doing a lot of editing toward the goal of making the mainspace CP-free. That may piss a few folks off, but I think it would be good for the project to make it even less CP-centric. My prolonged boycott idea didn't really get off the ground, and that's disappointing. We're smart and funny. The world is full of nonsense. That should be enough to keep us busy--who needs to pick on a loser like Andy?
For now, I'm not removing the "CP has an article on this too...." template. But should we? Thoughts? TheoryOfPractice (talk) 14:34, 15 August 2009 (UTC)
- I'd suggest linking to more sites, not fewer. Linking to Creation Wiki, WikiSynergy and aSK as well as CP would allow a wider range of wingnuttery to be exposed. If, at some point in the future, CP finally disappears, just take it out of a common template. SuspectedReplicant (talk) 14:50, 15 August 2009 (UTC)
- Good idea--I'll start making the relevant templates this evening. TheoryOfPractice (talk) 14:53, 15 August 2009 (UTC)
- I've been working on a few new-age medical woo items and there are certainly some good WTF sites out there. It takes a bit more work than just watching the CP ant-farm but it's getting like the Last of the Mohicans over there. Генгисpillaging 15:12, 15 August 2009 (UTC)
- Linking out to them and using the examples is great, WND (although they have gone a bit birtherific) for example. I'd encourage using CP as evidence as CP is certainly, as our article on them suggests, a manifestation of how such people think. So indeed it's a great first stop. But the random "kendoll" references and "some people" links things need to go or at least be integrated in properly as in chaning "some dicks think" to "a neo-conservative perspective thinks... as evidenced by Conservapedia". narchist 15:18, 15 August 2009 (UTC)
- Ann Coulter, Rush Limbaugh and other stalwarts of the American right wing could provide ample amusement and discussion. EddyP (talk) 15:20, 15 August 2009 (UTC)
- Where CP has a particularly funny history, there's no reason why RW couldn't host a separate article to preserve teh lulz but keep the mainspace articles CP-free. In fact, since so many diffs have been TKed, it would be a good excuse to give things a thorough house cleaning. SuspectedReplicant (talk) 15:24, 15 August 2009 (UTC)
- That's why we have the CP space--I'm not talking about getting rid of that. Just, as A-kov says, lame links to CP material in the mainspace....TheoryOfPractice (talk) 15:26, 15 August 2009 (UTC)
- Sorry... yes, that's what I meant. I just forgot to mention the actual namespace. SuspectedReplicant (talk) 15:40, 15 August 2009 (UTC)
- While most of us know about Coulter, Limbaugh, Hannity et al, we don't get the same exposure to them outside North America. It was the online presence of CP which allowed the rest of the world to follow their antics. Генгисpillaging 15:46, 15 August 2009 (UTC)
- To comment on the initial point, I think that raking CP out of mainspace is a great idea. I would have suggested that it should be discussed a bit more generally first, but as I agree with the idea wholeheartedly I'm not going to mention it.--BobNot Jim 16:52, 15 August 2009 (UTC)
- Bob, you're right, I should have brought it up for discussion before going on a tear, but I
was drunkfigured presenting as a fait accompli would get things moving quicker and generate discussion should there be any protest....TheoryOfPractice (talk) 16:59, 15 August 2009 (UTC)
-
- The only objection I would have to this mainspace scrubbing is that we lose a large number of diff-links to lunacy on Conservapedia. ListenerXTalkerX 17:06, 15 August 2009 (UTC)
Most of what I've removed has been internal links to Andy articles or other sysop articles, a few uses of the Andy picture and links to CP stories that aren't difflinks/permalinks. AFAIK, no difflinks have been removed.TheoryOfPractice (talk) 17:12, 15 August 2009 (UTC)
- Exactly. The working difflinks are preserved but we have an opportunity to scrub broken ones. We don't lose anything by removing a link that doesn't work. SuspectedReplicant (talk) 17:32, 15 August 2009 (UTC)
- We wouldn't lose much by removing working ones that just weren't relevent. But in most cases, they usually are relevent enough. As ToP and I have pointed out, it's mostly the internal in-jokes that have really run their course. narchist 17:59, 15 August 2009 (UTC)
- I approve of this conversation and its apparent conclusions. It also would not bother me if the CP-article and no-CP-article boxes slowly went to the great template graveyard in the sea. ħuman 20:40, 15 August 2009 (UTC)
- Perhaps we should replace the cp template with a more generic one that links to other places as well (ask, creationwiki, etc.), e.g. {{others|cp=article|ask=other article}}, which would then produce a similar box ("For those living in an alternate reality, here are some "articles" about pagename:" and a list of links). -- Nx / talk 20:46, 15 August 2009 (UTC)
- I can only see CP disappearing under the following scenario: 'a shooter, white male, goes and kills gays, Muslims, feminists etc. After being apprehended/his suicide, a check on his computer shows various segments of CP bookmarked. The government investigates if CP does not close for bad coverage after deleting what he has bookmarked. CP is accused of hate speech or something. Fox News martyrs CP and Andy. CP is told to close, which it complies but promises it's readers it will fight it'. ANYWAY, I think that we can always broaden the site. I do not care about CP more than the occasional laugh. I like going after cult leaders and organizations that spring up during moral panics, so I will focus on them and anything else I feel worthy.--Tabris (talk) 20:53, 15 August 2009 (UTC)
-
- Are you kidding, Tabris? Getting the EVIL FASCIST LIBRUL GUBMINT to persecute him would be like pure crack to Andy. He's be getting wingnut welfare funds for the defense faster than you can say "Rush Limbaugh". --Gulik (talk) 18:40, 16 August 2009 (UTC)
I like the idea of de-CP-ing; I don't like adding ask templates nor Wikisynergy templates. ASK and Wikisynergy are tiny, tiny and not worth the effort. Sterile Toyota 22:36, 15 August 2009 (UTC)
- To be honest, I like the cp template as it can quickly link to a first hand account of what the "opposition" supposedly think. The wp one is also massively useful. But I do like the idea of the "super external link" better, perhaps CreationWiki's articles on evolution etc. are more relevant and give better examples than the corresponding CP ones - which are usually just less coherent rehashes of other creationist stuff. narchist 16:33, 16 August 2009 (UTC)
freethoughtpedia[edit]
Does anyone know anything about these guys? They seem kinda small (really small), but a lot like us. Sterile Toyota 22:32, 15 August 2009 (UTC)
- On the recent changes list there seem to be a grand total of 6 edits in the last week. It looks way too anti-religion for me... SJ Debaser 22:45, 15 August 2009 (UTC)
Fuck, I'll bite--in what ways can one be sufficiently racist and homophobic? TheoryOfPractice (talk) 23:14, 15 August 2009 (UTC)
- I don't think you can apply the same criteria of anti-religion to anti-racism and homophobia. Sure, they may incorporate the latter two into religion, but I still think anti-religion can go too far. As for homophobia and racism... unacceptable. SJ Debaser 23:21, 15 August 2009 (UTC)
- PC hasn't even edited there for weeks. Talk about your wiki graveyards... ħuman 04:58, 16 August 2009 (UTC)
- I don't think she likes me any more after I basically left Liberapedia. SJ Debaser 10:54, 16 August 2009 (UTC)
- I just had a quick look and it appears that they plagiarised our Poe's Law article. It still has redlinks where ours are blue and they even retained one of our templates, which, of course, is borked. Lily Inspirate me. 14:07, 16 August 2009 (UTC)
The freethinkers have always struck me as being so rantingly anti-religion that "free-thought" doesn't come into it - it's just a kneejerk. They're the kind of people who accuse you of shoving religion down their throats when you mention the bible. Free of religion they may be, but free thinkers they are not. Totnesmartin (talk) 12:22, 16 August 2009 (UTC)
It's certainly possible to be too anti-religious. Forcing people to publicly repent isn't healthy behavior for ANY cause,
even ESPECIALLY one that claims to be the "good guys". And as the USSR found out, nothing strengthens religious fervor like the sweet, sweet feeling of persecution. --Gulik (talk) 18:45, 16 August 2009 (UTC)
- I suppose it's possible to be "too" anything. Too generous, too handsome, too rich. Sadly I suffer from all of these. --BobNot Jim 20:50, 16 August 2009 (UTC)
- You can be too anti-racist and anti-homophobic; its the people who interpret any criticism towards a member of a certain group as being motivated by hatred for that group. For example: a black guy is not doing his job well. Boss: 'You're not doing your job well'. Anti-racist:'Racist!' EddyP (talk) 21:27, 16 August 2009 (UTC)
- Is that along the lines of the recent trend of considering any and every criticism of Israel to be "anti-semetic"? Although I suspect that's more of a deliberate, cynical overreaction than being honestly overzealous in some cases. --Kels (talk) 21:32, 16 August 2009 (UTC)
- Anti-Semite!!!!!1111!1!111oneone!! --The Emperor Kneel before Zod! 21:39, 16 August 2009 (UTC)
TK in my pub...[edit]
I was in a pub last week and noticed an unusual spot of graffiti upon the bathroom window...
The Super Secret Police of Conservapedia are watching us! SJ Debaser 11:09, 16 August 2009 (UTC)
- Would it be disingenuous of me to say that a men's bathroom is exactly the kind of place I'd expect to find TK lurking? --Psy - C20H25N3OYou know you want to 12:02, 16 August 2009 (UTC)
- Just obvious. - π 12:03, 16 August 2009 (UTC)
- But worthy of lulz, surely. SJ Debaser 12:15, 16 August 2009 (UTC)
- We shold block him for being a member of a vandal site. Totnesmartin (talk) 12:55, 16 August 2009 (UTC)
Again[edit]
I was in the same pub again last night! Man, it's creepy now... SJ Debaser 10:41, 19 August 2009 (UTC)
District 9[edit]
Anybody seen this yet? Know we don't normally talk films, but when a $30m sci-fi flick, shot in and around Jo'burg with no big name actors, kicks Michael Bey off the top of the US box office, it must be kinda special. Alas, hasn't opened here yet - typical. --Psy - C20H25N3OYou know you want to 13:50, 16 August 2009 (UTC)
- I'm going to check it out tonight, it looks like it has potential.--الملعب الاسود العقل In my prime like Optimus 16:13, 16 August 2009 (UTC)
- The Spill guys all gave it the Better than Sex rating. I'm interested. ENorman (talk) 20:53, 16 August 2009 (UTC)
- Its fucking awesome, Peter Jackson produced it and its gold. Ace McWickedModel 500 09:37, 17 August 2009 (UTC)
Questions for the mob[edit]
Resurrected from RationalWiki:Saloon_bar/Archive26#Discussion_regarding_hiding_revisions I'll try to keep this simple
- Should bureaucrats be able to hide a revision with the show/hide button in such a way that only another bureaucrat can see it and restore it?
- Currently, if you hide a revision, any sysop can view it. Since basically every user is a sysop, the point is somewhat lost. With this option privacy violations could be hidden so that sysops can't see them.
- Which users should be able to see a log of bureaucrats hiding revisions from sysops: bureaucrats only, sysops too, registered users, or everyone including BONs?
- I'm only asking this question because there is an option, though I believe most people will say open the log to everyone.
-- Nx / talk 14:29, 16 August 2009 (UTC)
- I assume this came up because of something that happened in the dim and distant past. Can somebody give me a link or a quick precis? SuspectedReplicant (talk) 16:26, 16 August 2009 (UTC)
- No comment on the first matter. However, EVERYONE should be able to see what happened, BON's included. --The Emperor Kneel before Zod! 19:16, 16 August 2009 (UTC)
- Well no argument on everyone being able to see the log. Is the hiding really necessary though? I'm sure that, at the time, people will be able to find the hidden edit, but if I wanted to locate that stuff now I wouldn't know where to look. Besides, given the stupidly large number of 'crats this site has, you aren't really hiding anything all that securely. SuspectedReplicant (talk) 19:34, 16 August 2009 (UTC)
- I say leave that option for sysops and 'crats only. Or at least limit it as far as autoconfirmed users goes. Given some of the problems here, and considering issues of privacy, do we really want cyberstalking to be possible through us?Lord of the Goons (talk) 19:38, 16 August 2009 (UTC)
- Here's an example of the log. It's basically the same as what you get when you use the interface as a sysop, only it goes into a different log (I have no idea why they made it that way, the deleted revision is still visible in the article history, so this isn't like oversight where it vanishes without a trace). As for the first option, all it does is add an extra checkbox on the show/hide page titled "Apply these restrictions to administrators and lock this interface". -- Nx / talk 20:07, 16 August 2009 (UTC)
- Suggestion: Any implementation should be done after Trent is back so Just in case someone screw things up with newly powers (for them anyways) it would be less of a panic.
- I am personally indifferent who can supress revisions as long as sysops can view it (it's mostly violation of community standards, so presumably those who follows the rules won't do much with the extra information, and it's easier to see what happened) ThiehWhat is going on? 23:24, 16 August 2009 (UTC)
- It should be possible for revisions to be deleted such that sysops cannot see them, but the log should note, for all to see, that revisions were removed. The information that is being deleted may indeed be harmful, but I see no reason to hide from anyone that something was deleted. Fedhaji (talk) 07:48, 17 August 2009 (UTC)
Important[edit]
I am going away for a few weeks on Tuesday. I will not have physical access to the servers for two weeks. More than ever, it is important for people to make sure they are aware of rationalwiki.blogspot.com. This will be always be my primary form of communication if the site is inaccessible. If anyone has any ideas about how to spread the word more effectively about the existence of the blog please feel free to do so. tmtoulouse 19:05, 16 August 2009 (UTC)
- Aaaarrgh! Doomed! We're all doomed! Lily Inspirate me. 19:14, 16 August 2009 (UTC)
- Maybe it's time to have another whip round and buy him a watchdog timer board for Christmas so he can go away without too much worry. --JeevesMkII The gentleman's gentleman at the other site 19:59, 16 August 2009 (UTC)
Funny Stuff....[edit]
If only because there are not a lot of rap songs that name-check Margaret Sanger. TheoryOfPractice (talk) 20:24, 16 August 2009 (UTC)
- "I Would Never (Have Sex with You)" should be required watching for all teenage males. Would prevent alotta disappointment to be sure! - Clepper
Fail.[edit]
with a goat. That is all. ĵ₳¥ášÇ♠ʘ secret trainer of boars! 20:48, 16 August 2009 (UTC)
- "Dunno source" - the source is the evil Cult of Jerboa and their photoshopping lies. Totnesmartin (talk) 21:32, 16 August 2009 (UTC)
Maus[edit]
#2 cat has just presented me with a (dead) mouse & is noisily eating it as I type. I am eating & honeychat 01:56, 17 August 2009 (UTC)
- Thought we were about to talk comic books. TheoryOfPractice (talk) 01:59, 17 August 2009 (UTC)
- Naw! Just nature RED in tooth & claw. I am eating & honeychat 02:03, 17 August 2009 (UTC)
- That's one of my favorite things about owning a cat. I've never actually seen a mouse here, but on several occasions he's managed to kill a bird. He never fails to present it right in front of my lounge chair.--الملعب الاسود العقل How strange it is to be anything at all 02:13, 17 August 2009 (UTC)
- All that's left is a smear of blood and what looks like a mouse sized liver. #1 cat used to bring loads of mice, but didn't kill 'em, just chased 'em around until they died of terror or hid under the fridge. I am eating & honeychat 02:26, 17 August 2009 (UTC)
- My old cat used to kill the occasional mice that managed to make it into the house, and then just sort of leave it where it lay. I doubt she ever tried to eat one. --Kels (talk) 02:35, 17 August 2009 (UTC)
- Sometimes the "what to do after you torture it to death" part is bred out, but the "torture" part is still there. Sometimes they eat all but the best bits and bring them to their pet human to make mouse liver omelettes with. One I had caught a bird and slowly devoured it a yard from where I now sit, when she was done all that was left were some feather tips. She was then the most contented cat for about 24 hours. Live food is good food for carnivores. ħuman 03:01, 17 August 2009 (UTC)
- Evolution at work. Lily Inspirate me. 07:57, 17 August 2009 (UTC)
- Well, actually it's artificial selection. But there isn't much of a difference, since "we" are the modern domestic cat's environment. ħuman 08:14, 17 August 2009 (UTC)
- Evolution either way, methinks. - Clepper
- It is also improving the mouse population, the better mice survive. Генгисpillaging 09:37, 17 August 2009 (UTC)
- Ah, but do you people not see that this is evidence for the existence of God? Cats instinctively know to leave offerings to their deity: you, the human being. They practice religion the way they know, bringing an offering of a mouse now and then to leave in front of the altar (your easy chair). NEED VICODIN NOW (talk) 21:29, 17 August 2009 (UTC)
- One of my kitty cats seems to be almost actively vegetarian. He won't eat any sort of raw or cooked meat, but does eat catfood that allegedly is made of meat, but mostly just eats dry food. However, he still has the hunting instinct and will catch all sorts of small furry animals or even birds. He just doesn't really know what to do with them after he's killed them. He's never managed something so daring as a former kitty cat I had years ago who caught a large rabbit and managed to drag it in, headless, and hide it under the sideboard. --JeevesMkII The gentleman's gentleman at the other site 11:08, 18 August 2009 (UTC)
- I had to rescue yet another mouse from my youngest (and most psychopathic) kitteh in the middle of the night. Seriously, if there is an afterlife then when I die I expect all the mice I've saved to have chipped in and bought me a nice watch or something. CrundyTalk nerdy to me 10:56, 19 August 2009 (UTC)
Awesome film[edit]
District 9. damn good. You'll see. End Transmission. Ace McWickedModel 500 09:33, 17 August 2009 (UTC)
- I saw a trailer for that the other day. Looks most unusul. SJ Debaser 10:13, 17 August 2009 (UTC)
- What's it about? --Gulik (talk) 01:02, 18 August 2009 (UTC)
- Check out the District 9 tralier on youtube. It one of the best films I have seen in recent memory. Ace McWickedModel 500 01:41, 18 August 2009 (UTC)
- Wangled an invite to the première here tomorrow night (so will be on best behaviour) - looking forward to it. @Gulik - aliens arrive in Johannesburg, turns out they're refugees and are placed in a refugee camp. Later on, humans get fed up with them and go all apartheid on them. (Ok, that's a brief, bad summary). --Psy - C20H25N3OYou know you want to 16:08, 18 August 2009 (UTC)
Usain Bolt[edit]
I was just watching Usain Bolt on Youtube, and one of the commenters put this little gem: right.. now he's obviously the fastest person alive...anyone half man/half cheetah hiding around here? c'mon, itd be awesome to beat him ;) - Where is that boy when you need him? Totnesmartin (talk) 10:28, 17 August 2009 (UTC)
- I caught the race last night on the telly - it was beautiful to watch - I felt kinda sorry for Gay, he runs a superb race, breaks the US national record and still he's a metre behind Bolt. Bob Soles (talk) 10:37, 17 August 2009 (UTC)
- And the guy was pretty quick around the Top Gear track too. narchist 13:45, 17 August 2009 (UTC)
- Absolutely ridiculous, human beings aren't supposed to be able to run that fast. I always end up wondering what track stars would do in other sports. If he can catch a football someone needs to sign him, he'd make young Randy Moss look slow.--الملعب الاسود العقل Your ballroom days are over, baby 14:53, 17 August 2009 (UTC)
- Half man/half cheetah? Does Aimee Mullins count? --Kels (talk) 15:24, 17 August 2009 (UTC)
- That must be CUR's favourite pin-up - all his dreams come true at once! Bob Soles (talk) 15:32, 17 August 2009 (UTC)
- I ran into a talk she gave at TED (which led to finding another, older one) and she's awesome. It's funny, the cheetah legs she wore for the photo shoot were totally impractical for walking, so she had all sorts of trouble getting around on the shoot. Great result, though. --Kels (talk) 15:41, 17 August 2009 (UTC)
Media termns[edit]
Some funny stuff. Some terms may even be worth stealing and expanding on as articles. I quite like "PR-reviewed", as in contrast to peer-reviewed. Ben Goldacre brought it up on a very recent blog entry too. I definitely reckon it has something to it. narchist 16:03, 17 August 2009 (UTC)
WTF[edit]
Just...wtf Totnesmartin (talk) 17:18, 17 August 2009 (UTC)
- Worrying is the "Ex Transexual" part... is it physically possible to have an operation to become a woman and then have it a second time to become a man again? And "Ex HIV Positive"? Isn't that just HIV in remission or is that not one of "those diseases"... SJ Debaser 17:32, 17 August 2009 (UTC)
- I reckon that's worth stealing and using as an article illustration. I just can't think what. narchist 17:49, 17 August 2009 (UTC)
- Bullshit? Faith Healing? ENorman (talk) 20:29, 17 August 2009 (UTC)
- It's not physically impossible to reverse the SRS.. it's just really expensive and you won't really be the same. The reason why doctors sell Sexual Reassignment Surgery as permanent is because you technically won't be able "function" down there again after a reverse surgery.
- Vaginoplasty takes the penis and morphs it into a penis.. magically--because I was too scared to look at the case studies of it. Same with a vagina (Labiaplasty), they take the labia and "such" (didn't research that part too much) and bippity-boppity-boo.. a penis!
- Financially speaking, changing a penis into a vagina costs about $50,000 (for the best), then back again would cost around $75,000 (for the best). Penis transformed into a vagina is easier because there's more to "work with". Silly Mr. Cat 20:41, 17 August 2009 (UTC)
- First of all a transexual does not necessarily have to have had reassignment surgery, just a change of mind. He's also married "with a woman who has no uterus" not to a woman who has no uterus. And I think it would be theoretically possible for a woman without a uterus to still donate eggs which could be fertilised and implanted in a surrogate. Also, judging by some message-board comments this should have happened last year, yet there doesn't appear to be any other record of it on the ineternet (OK I didn't bother clicking on the second Google search page) apart from the picture. Генгисpillaging 20:49, 17 August 2009 (UTC)
- @Skittlebucket. It's not just the penis, they usually remove the testes as well. Генгисpillaging 20:53, 17 August 2009 (UTC)
- Actually it says "married with a woman who had no uterus". Does that mean she's got one now? Генгисpillaging 21:02, 17 August 2009 (UTC)
- From what I know of it, the common practice is to skin the penis like a banana, toss away most of the insides, invert it into the body to make the vagina, toss the testes away, turn the scrotum into labia, and re-route the nerves. Tends to be very good results. The other direction, that ain't so easy. The more "traditional" is to take a skin graft from the arm or leg, make a tube out of that and graft it to where the now-closed vagina used to be, plus the same re-routing of nerves. Not a great result, overall a bit of a Frankenstein job, no ejaculation of course and usually a pump to get hard. Better results come from another version where the clitoris is released from the hood and anchoring to hang more freely. Re-route the urethera, make a new scrotum out of the labia where possible and insert fake balls, and add some hormone therapy which increases the size of the clitoris, and voila. A smallish and non-ejaculatory penis that gets hard the natural way and generally has better sensitivity, without the huge scarring and suchlike. Either way, nothing a person would go through "on a lark", so I expect this "ex-transsexual" is either lying, or is living a happy life of repression pushed by the church. Either way, I don't expect there was ever any surgery involved. --Kels (talk) 21:06, 17 August 2009 (UTC)
-
- Uh, that is, I think, a lot more than most of us needed to know about that... ListenerXTalkerX 04:10, 18 August 2009 (UTC)
- I didn't make it past "skin the penis like a banana". --الملعب الاسود العقل You pray for rain, I'll pray for blindness 04:20, 18 August 2009 (UTC)
- There is a website but it makes no mention of Prophet Isaac. The site doesn't appear to have been updated much since early 2008. Генгисpillaging 05:13, 18 August 2009 (UTC)
- There is also a USA organisation with the same name but their website is no longer available. However, Google cache gives this gem from their about us page :
- Who We Are - A sinificant [sic] Christian presence in the third world country is strong in the big cities which leaves the rural areas with very minimal or no Christian influence due to the economy and lack of trained leadership.
- We seek to establish and help churches develop a significant Christian witness in the rural community which requires a shift in ministry paradigm appropriate for the rural context.
- Генгисpillaging 05:20, 18 August 2009 (UTC)
(UD) One thing they missed out on the list of Exes is Ex-parrot. He could be dead. Lily Inspirate me. 05:59, 18 August 2009 (UTC)
Pornographie![edit]
And no, it is not just to get your attention.
I have a question for the residential porn experts that bothers me for quite some time now: why does most of the internet assume that German porn is all about pissing and shitting and other disgusting stuff? I`ve been surfing the internet for Porn for about 10 years now, and I don`t see anything especially shitty about our domestic porn. Is it because Germans are said to give a shit about everything? Or do you think we just want to piss of the rest of the world? Nothing but questions...— Unsigned, by: Gmb / talk / contribs
- Hmm. My impression of German porn is either the soft stuff with middle-aged guys in lederhosen and hats with feathers in them rolling in the hay with a blond jungfrau with bunches or overly-serious masked (maybe even gas-masked) swingers with rubber and leather fetishes. But then I haven't seen a lot of it. Генгисpillaging 20:25, 17 August 2009 (UTC)
- I assumed it was Russian. Just like the beastiality stuff. (wandering 4chan does too much to your mind). Ke
klik 20:43, 17 August 2009 (UTC)
- The fact that Germans love pissing and shitting in their fucking is an incontrovertible truism. Denying this is like that denying the beauty of fall foliage reduces the risk of cancer. Are you against school prayer by any chance? Judging by your other, more ludicrous positions on the state of the art of German pornography, I am 97.5% certain you are. — Signed, by: Neveruse513 / Talk / Block 20:45, 17 August 2009 (UTC)
"Anonymous User" (what an absurd user name that is), your determination to deny conservative values is remarkable. I've managed to read your rants and nearly every one of your postings here includes a puerile, sneering remark, so my confidence is over three standard deviations away from the mean that you're almost certainly a liberal who's here to push your misguided ideology rather than genuinely help anyone learn. Like all atheists, you deny that action at a distance helps resist moral decay. As I've said before, it's a myth that were atheists in ancient times. There may not even be true atheists today. Your statement does not explain how a materialist, which most atheists are, can believe in something immaterial like love. Most don't. Try to open your mind in the future.--Aschlafly 09:00, 16 May 2022 (UTC)
oh come on, such a wonderfull lead-in and all you can come up with is quotes from the assfly? show some more creativity Gmb (talk) 21:26, 17 August 2009 (UTC)
- Fuck you bossy bum, you show some more creativity. 75.127.68.98 03:12, 18 August 2009 (UTC)
- Whenever Bill uses Emule to download films and he gets a fake pornographic one it frequently seems to involve Germans involved in fairly basic acts. On the other hand I've only got his word for this story from start to finish so there may be some doubts about this data.--Hillary Rodham Clinton (talk) 07:13, 18 August 2009 (UTC)
Cinema/Movies[edit]
Just a little query: How often to people go to the movies? The last time I went was in 1962 (Sean Connery/Dr. No). I just haven't got the attention span to sit in one place just watching a film for that length of time. The only films I've seen for ages have been on DVD. Right now I'm flicking between Firefox (3 windows, 17 tabs) and Open Office Writer & the TV is constantly on. My other half is similarly occupied but with a book instead of OOW (she did go to see Titanic!). Am I unusual? I am eating & honeychat 01:24, 18 August 2009 (UTC)
- You're typical (ADD for adults is fun, not a disease!). I actually like settling in and watching a complete film (screw movies, they have commercials, whatever). Last one I saw in a theater was Fargo, IIRC. But I rent and watch things I own, only pausing for pee or food/drink breaks. ħuman 02:39, 18 August 2009 (UTC)
- I see a large number of films in the theater, mostly with no cash outlay, since I am on the mailing-lists for those free preview screenings the film distributors put on. ListenerXTalkerX 04:09, 18 August 2009 (UTC)
- Lucky bastid. ħuman 05:04, 18 August 2009 (UTC)
- I go very very rarely (much to chargrin of Ms McWicked) as you cant smoke, I always need to take a piss and when I was a movie reviewer I had to see 2 - 3 a day weekends on end, it really put me off. Although as I have already stated District 9 - awesome. Ace McWickedModel 500 05:23, 18 August 2009 (UTC)
- That's always been my problem too. About halfway into the movie I start thinking "shit, I need a smoke" and can't fully enjoy the film. I'd say I go once every couple months though.--EcheNegraMente I can't drive straight counting your fake frowns 05:28, 18 August 2009 (UTC)
- Wow. Just how many people on this site smoke? It seems to be way above average. I gave up (counts) two and a half years ago. SuspectedReplicant (talk) 05:32, 18 August 2009 (UTC)
Poll:
ListenerXTalkerX 05:37, 18 August 2009 (UTC)
Further poll for smokers, how many per day?:
Ace McWickedModel 500 05:41, 18 August 2009 (UTC) M
- I am 6 foot 4 in the old money so after about 30 minutes in those seats my ass is numb and I can't wait to get out. Still, the only movie I ever walked out of was Sunshine. Terrible, terrible film (apologies to those that liked it). Rad McCool (talk) 10:17, 18 August 2009 (UTC)
- NZlanders use cockney rhyming slang? Last movie I saw that sucked arse was the Butterfly Effect. I love that bit in Family Guy... "I got the idea to build a panic room after I saw that movie - you know, the Butterfly Effect? I thought 'wow, this is terrible, I wish I could escape to somewhere where this movie could never find me,' and then-" SJ Debaser 10:48, 18 August 2009 (UTC)
So (on a huge sample size) half of RW users have smoked at some point. I'm sure Schlafly could come up with a statistic on that. Worst film? Well obviously Plan 9 from Outer Space, but that's so bad it's funny. You have to go a long way to beat the Blair Witch Project. I thought that was utterly rubbish. SuspectedReplicant (talk) 14:00, 18 August 2009 (UTC)
- Been about three years since I've seen a movie in the theatre (went to see Howl's Moving Castle, totally worth it), but coincidentally I'm going to see Ponyo today. For a while before that I went fairly often to the local rep cinema, saw some great stuff, but it's been rare over the past decade for me to go to a main line cinema. Gonna be fun in October though, I'll be volunteering at the Ottawa Animation Festival. --Kels (talk) 14:04, 18 August 2009 (UTC)
- Me and the wife go to the movies quite frequently, maybe twice a month, not to mention our extensive DVD collection and bitchin home theater. And as far as bad movies go, only two movies need to be considered; American Movie, and the Howling 7. Howling 7 wins though, because at least American Movie tried to have a plot. No, I wouldn't recommend anyone ever seeing either of these. Z3rotalk 15:48, 18 August 2009 (UTC)
- I haven't been since 300. It was OK until the big giant Persian thing walked on and I thought "they have a cave troll." there's one in every film of that type nowadays, going by the trailers. Totnesmartin (talk) 09:50, 19 August 2009 (UTC)
smoking poll[edit]
So, a few people here smoke... but what do you smoke? Totnesmartin (talk) 09:51, 19 August 2009 (UTC)
That health care bill sure would be nice right about now....[edit]
Well, the battle over health care just became a fairly personal one for me. I just found out I have a stage 2-3 case of chronic kidney disease. I'm only 22 so this sucks pretty hard, even if I might've done it to myself. Luckily, I have decent insurance so I'm not totally in the shitter, but things are going to be really tight for a while. A little bit of extra help would go a long way. Hopefully this shit will get sorted out soon, I sure would like to able to afford more than tortillas and velveeta!--PitchBlackMind So analyze me, surprise me, but can't magmatize me 01:31, 18 August 2009 (UTC)
- Fuck dude, sorry to hear that man. Wishing the best though. Ace McWickedModel 500 01:40, 18 August 2009 (UTC)
- EC) That's a bastard, PBM. At 22 y.o. it's specially bad, you expect bits to start breaking down at my age but that sucks. Suggest that you start sounding out blood relatives with working parts ASAP. I am eating & honeychat 01:44, 18 August 2009 (UTC)
- I don't know the details about your condition but it obviously doesn't sound good. Best wishes for successful treatment. Генгисpillaging 02:07, 18 August 2009 (UTC)
- I can't offer anything aside from a "that really sucks man" Javasca₧ A sig not even he can predict! 02:12, 18 August 2009 (UTC)
- Hang in there. Sterile Toyota 02:18, 18 August 2009 (UTC)
- Best of luck, and concentrate on keeping that insurance up-to-date and fully paid. And, oh, yeah, seconding the ghoulish "mine your relatives for organs" comment. ħuman 02:41, 18 August 2009 (UTC)
- That terrible mate. Best of luck, always keep positive about things. - π 02:48, 18 August 2009 (UTC)
Thanks everyone, I really appreciate that. I should've explained more about it when I mentioned it, I wasn't sure what it was when I first heard it either. It's serious, but it's manageable. There's a strong possibility I'll be on dialysis or in need of a transplant when I'm around 55-60. Though that might not happen at all, only time will tell. Either way there should be plenty of time to life a good life. Still, there will be copious amounts of medication and doctor visits in my future, so Uncle Sam picking up the tab here and there would help a great deal.--EcheNegraMente When I look up the sky's all I see 02:54, 18 August 2009 (UTC)
Good luck with this. I know it might not do any good, but apparently, various liberal groups are trying to stir up people to go to these townhall meetings to counteract the screaming rightwing loonies. You might want to consider attending a few, as a good personal story is worth a thousand pages of statistics. (Planning on going to a local one myself tomorrow.) --Gulik (talk) 03:57, 18 August 2009 (UTC)
- It's never nice to find out seomthing nasty about one's health. However, you have apparently still got a long life in front of you before you need major stuff. That's 30+ years of medical research. I'm sure that things will have changed enormously by then, who knows what the options will be? Lily Inspirate me. 06:03, 18 August 2009 (UTC)
- Slightly intrigued by: "even if I might've done it to myself.". I am eating & honeychat 13:54, 18 August 2009 (UTC)
- Okay, I'll bite. I was pretty severely addicted to crystal meth for many years. Being basically pure poison, it's extremely hard on just about every part of your body. It may not be the specific cause, but it's undoubtedly a contributing factor.--PitchBlackMind Midnight wish blow me a kiss 14:34, 18 August 2009 (UTC)
- Aah! Possibly Too Much Information. I am eating & honeychat 14:46, 18 August 2009 (UTC)
- "If my answers frighten you then you should cease asking scary questions." :)--PitchBlackMind So analyze me, surprise me, but can't magmatize me 15:26, 18 August 2009 (UTC)
- So, er, do you watch Breaking Bad? And if so, how "authentic" is it when it's not trying to be hilarious? ħuman 20:50, 18 August 2009 (UTC)
- On the bright side, at least you're off the crystal meth now, right? Lily Inspirate me. 21:21, 18 August 2009 (UTC)
- Yes Lily, I've been off of it for quite some time. Breaking Bad is a fantastic show, Human. It's a remarkably accurate take on the meth world and the people involved with it. Even the funnier stuff is plausible. They must have done some serious research for the show, because everything about it is as close to reality as you can get.--PitchBlackMind A smooth operator operating correctly 23:35, 18 August 2009 (UTC)
Spam?[edit]
I received the following email today:
forumadmin@richarddawkins.net Reply Follow up message The following is an e-mail sent to you by an administrator of "RichardDawkins.net Forum". If this message is spam, contains abusive or other comments you find offensive please contact the webmaster of the board at the following address: forumadmin@richarddawkins.net Include this full e-mail (particularly the headers). Message sent to you follows: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You have been invited to join It is one of the best sites around to get all your free application downloads, latest movies, games of all sorts, and many other great things. Please make an introduction topic there so you can get a warm welcome from your members! -- Thanks, RDF
is it spam or wot? I am eating & honeychat 01:39, 18 August 2009 (UTC)
- "WAREZ" = Piracy! Spam definitely. Генгисpillaging 01:58, 18 August 2009 (UTC)
- Yup, I got two of these. Considering it's from a "forum administrator" I'm guessing old dickie hasn't kept his forum software up to date and some spammers have hijacked an account to send spam. CrundyTalk nerdy to me 09:27, 18 August 2009 (UTC)
"When Zombies Attack!: Mathematical Modelling of an Outbreak of Zombie Infection"[edit]
I'm.... speechless ... about this. Sterile Toyota 02:21, 18 August 2009 (UTC)
- I'll say. There no discussion on previous zombie infection models, I would have asked for a more detailed literature review if I was the editor. - π 02:41, 18 August 2009 (UTC)
Math question[edit]
Maybe a tad technical, but I know we have at least a few mathematicians that frequent these parts. I need some help.
I have a set of discrete points on a Cartesian plane and I need to calculate the area swept out underneath these points. Now if this was a function I know you just integrate under the curve, but these are discrete points. My two best guesses so far on what to do are to calculate some polynomial function with n degrees of freedom that meets some arbitrarily small mean square error between the function and the points. Then use that function to calculate the area.
My second idea was to use some Runge-Kuttaesque method where I do a stepwise integration between two points with some arbitrarily small step size, then sum up the area between all the points.
Would either of these be likely to fail? Is there a better, more accepted way to do this? Thanks much for anyone that happens upon this and can provide some insight. tmtoulouse 04:29, 18 August 2009 (UTC)
- Without really being to sure exactly what you are trying to do, but based on "if this was a function I know you just integrate under the curve, but these are discrete points", I would say you would need to take the Lebesgue integral. 192.43.227.18 04:52, 18 August 2009 (UTC)
US ‘may take military action’ to liberate Britain from the NHS[edit]
Made me laugh. SuspectedReplicant (talk) 05:51, 18 August 2009 (UTC)
- (explanatory links for non-Brits: [1] [2] and [3]) SuspectedReplicant (talk) 05:54, 18 August 2009 (UTC)
- At least the US gave us ER. Casualty was just a pale imitation and they had to get their babies from the US as well. Lily Inspirate me. 06:10, 18 August 2009 (UTC)
- Wait, I thought Casualty had been around for way longer than ER? CrundyTalk nerdy to me 09:30, 18 August 2009 (UTC)
- It has. "Casualty is the longest running emergency medical drama series in the world" according to WP. It started in 1986, compared to 1994 for E.R. SuspectedReplicant (talk) 09:47, 18 August 2009 (UTC)
I demand an equal opportunity to be freed from the tyranny of the Spanish health service Taliban.--BobNot Jim 09:56, 18 August 2009 (UTC)
Bookmarked. That'll go nicely with my daily mash. Totnesmartin (talk) 10:17, 18 August 2009 (UTC)
Obama is believed to have abandoned his plans to adopt the NHS model for American healthcare, even though he has privately commented that the bed-hopping antics of British medics 'sure look like fun'. Class. SJ Debaser 10:56, 18 August 2009 (UTC)
- That's some funny parody, that there is, it is. I like how it actually takes the trouble to be two different jokes wrapped up in one. ħuman 20:54, 18 August 2009 (UTC)
- Ah - I didn't know about the Daily Mash. Now bookmarked. SuspectedReplicant (talk) 06:24, 19 August 2009 (UTC)
- Could be worse. They could have intercepted the transmission of a couple of episodes of Doctors. narchist 11:21, 19 August 2009 (UTC)
Here, have a bag of LOLs[edit]
I'd never heard this before. Have you? --Kels (talk) 15:26, 18 August 2009 (UTC)
- Also this from him. CrundyTalk nerdy to me 08:26, 19 August 2009 (UTC)
Fucking crickets![edit]
OK, I was at Scientific evidence for God's existence and I knew those crickets were digital. But I closed it. Now I still here crickets. Well, hell, it's cricket season. Or is Mike Malloy reading Scientific evidence for God's existence while ranting? I once recorded an early version of a song, and you can hear a cricket chirping on the master in the background at the beginning and the end. Meaning the damn insect is deep in the background of the entire song. Never figured out an "easy" way to make the much later, listenable, version incorporate that delightful feature. Except... oh, shit, it's August! Cricket season! I could turn everything off and mike the "current" cricket on a spare track and mix the bastid in! I wonder if I could do that competently, it's not that late, I've only had a few "soul enriching beverages".... ħuman 02:42, 19 August 2009 (UTC)
- Just think, in but a few short months, they will be gone. Summer really has been going fast. I'm already starting to prepare firewood--Tabris (talk) 02:54, 19 August 2009 (UTC)
Then there's the real cricket. Last Test starts tomorrow (? well, 1000GMT Thursday 20/8). This is serious stuff for us Aussies - revenge for 2005.RagTopGone sailing 11:18, 19 August 2009 (UTC)
UFOs[edit]
Hehehe "One report, from 1995, describes how two children from Bovingdon, in Hertfordshire, were almost lured onto a helicopter-shaped spacecraft by an alien who 'could walk backwards but made it look like he was walking forwards'.
According to the files: "The translucent creature called to them in a melodic falsetto and was only scared off after a local farmer threatened to report him and his pet monkey to the police."" CrundyTalk nerdy to me 08:33, 19 August 2009 (UTC)
Master of the Internet![edit]Totnesmartin (talk) 09:36, 19 August 2009 (UTC)
Bible translation[edit]
Anyone thought about doing a RW re-translation? "Jesus then rebuked the evil spirit, "Shut up, muthafucka..."" narchist 12:27, 19 August 2009 (UTC) | https://rationalwiki.org/wiki/RationalWiki:Saloon_bar/Archive32 | CC-MAIN-2022-21 | refinedweb | 8,465 | 71.24 |
state, and
props. If you already know React, you still need to learn some React-Native-specific stuff, like the native components. This tutorial is aimed at all audiences, whether you have React experience or not.
import React, { Component } from 'react'; import { Text, View } from 'react-native'; export default class HelloWorldApp extends Component { render() { return ( <View style={{ flex: 1, justifyContent: 'center', alignItems: 'center' }}> <Text>Hello, world!</Text> </View> ); } }
App.jsfile to create a real app on your local machine.
import,
from,
class, and
extendsin the example above are all ES2015 features. If you aren't familiar with ES2015, you can probably pick it up by reading through sample code like this tutorial has. If you want, this page has a good overview of ES2015 features.
displays some text and
Viewis like the
<div>or
<span>.
HelloWorldApp, a new
Component. When you're building a React Native app, you'll be making new components a lot. Anything you see on the screen is some sort of component. A component can be pretty basic - the only thing that's required is a
renderfunction which returns some JSX to render. | https://docs.expo.io/versions/v36.0.0/react-native/tutorial/ | CC-MAIN-2020-16 | refinedweb | 187 | 58.69 |
An Intro to the Model-View-Controller in MonoTouch
In our first article we created an application using MonoTouch on the iPhone. We used outlets and actions, got to know the basic application structure, and made a simple user interface. In this article we’re going to make another simple application, but this time we’re going to explore using Views and View Controllers to make an application with more than one screen. Specifically, we’ll use the UINavigationController to navigate to two different pages/screen in our application.
Before we begin building our application, let’s briefly touch on an important pattern that iPhone applications use.
Model-View-Controller (MVC) Pattern
Cocoa Touch uses a modified version of the Model-View-Controller (MVC) pattern to handle the display of their GUI. The MVC pattern has been around for a long time (since 1979) and it is intended to separate the burden of tasks necessary to display a user interface, and handle user interaction.
As the name implies, the MVC has three main parts, the Model, the View, and the Controller:
- Model – The model is a domain specific representation of data. For instance, let’s say we were making a task-list application. You might have a collection of Task objects, say List<Task>. You might store these in a DB, an XML file, or even pull them from a web service, but the MVC isn’t specifically interested in where/how they’re persisted (or even if they are). Rather, it deals specifically with how they’re displayed and users interact with them.
- View – The view represents how the data is actually displayed. In our hypothetical task application, we might display these tasks on a web page (in HTML), or a WPF page (in XAML), or in a UITableView on an iPhone application. If a user clicks on a specific task, say to delete it, then typically, the view raises an event, or makes a callback to our Controller.
- Controller – The controller is the glue between the Model and the View. It’s the Controller’s job to take the data in the model and tell the View to display it. It is also the Controller’s job to listen to the View when our user clicks on the task to delete it, and then either delete that task from the Model, or tell the Model to delete the task itself.
By separating the responsibilities of displaying data, persisting data, and handling user interaction, the MVC pattern tends to create code that is easily understood. Furthermore, it encourages the decoupling of the View and the Model, so that the Model can be re-used. For example, if in your app, you had both a web based interface, and a WPF interface, you could still use the same code for your Model for both.
So that’s how it’s supposed to work, and in many MVC frameworks, it works exactly like that. In Cocoa (and Cocoa Touch), however, it works a little differently, and largely, Apple uses the MVC in name, employing Views, View Controllers, and Models, however, they’re inconsistent between different controls on how they actually implement it. We’ll explore this in more detail when building our sample application.
Views and View Controllers in MonoTouch
I mentioned briefly before, that in an iPhone application, you only ever have one window. However, you can have lots of screens. To accomplish this, you add a View and a View Controller for each screen you want to have.
The view actually has all the visual elements, such as your labels, buttons, etc., and the View Controller handles the actual user interaction (via events) on the View and allows you to run code when those events are raised. In a rough analogy, this is a slightly similar model to ASP.NET or WPF, where you define your user interface in HTML or XAML, and have a code-behind page that handles events.
When you want to go to another page, you push your View Controller (and associated view) onto the View Controller stack. In the application we’re going to build today, we’ll use a Navigation View Controller (UINavigationController) to handle our different screens, because it gives us a way to navigate between screens very easily by giving you a hierarchal-based navigation bar that allows your user to navigate backwards and forwards through View Controllers.
The UINavigationController is seen in many of the stock iPhone applications. For example, when you’re viewing a list of your text messages, if you click on one, the top bar gets a left arrow tab at the top that takes you back a view to the message list.
Hello World with Multiple Screens
Now that we understand how all that works in concept, let’s actually create an application that does it.
First, create a new MonoTouch iPhone solution in MonoDevelop and name it Example_HelloWorld_2 (refer to the first article if you’ve forgotten how to do this).
Next, let’s add two View Controllers (and their associated views) that will serve as the screens of our application that we’ll navigate to. To do this, right click on your project and choose Add : New File. Then, in the new file dialog, choose iPhone : View Interface Definition with Controller. Name our first new file “HelloWorldScreen”, and the second one “HelloUniverseScreen”:
Open the .xib files up in Interface builder and add a label to the HelloWorldScreen that says “Hello World,” and add a label to the HelloUniverseScreen that says “Hello Universe” as shown in the following screenshot:
Now, let’s add a Navigation Controller to the Main Window. To do this, open the MainWindow.xib file in Interface Builder, and drag a Navigation Controller from the Library Window onto the Document Window:
The Navigation Controller has several parts to it:
- Navigation Controller – This is the main Controller that handles the navigation events and wires it all up together.
- Navigation Bar – This is the bar along the top that allows the user to see where they’re at in the navigation hierarchy, and navigate backwards.
- View Controller – This is the View Controller for the view that it will hold.
- Navigation Item – The navigation item is in the Navigation Bar and is what actually has the button for navigating, as well as the title.
Next, let’s add a Table View to the Navigation Controller, so we can create a list of links of our screens. To do this, drag a UITableView from the library onto the View Controller in the Navigation Controller:
Let’s change the title of the Navigation Bar. Double click on the top-bar in the Navigation Controller and type in “Hello World Home.”:
Do I have to use a Table View to hold my Navigation Items?
No, you can put just about anything into your View Controller. As we’ll see later, when we want to navigate to a new screen, we call NavigationController.PushViewController and pass it our View Controller for the screen we want to go to. We could just as easily do this when a user clicks on a button.
Now that we have our Navigation Controller we need to make both it, and it’s associated Table View available to our code-behind. We need to make the Navigation Controller available so that we can push our View Controllers onto it, and we need the Table View available so that we can populate it with the names of the screens we can navigate to.
To do this, lets create Outlets for them as we did in Part 1. Let’s call them mainNavigationController for the Navigation Controller, and mainNavTableView for the Table View. Make sure to create them on your AppDelegate. When you’re done, your Connection Inspector should look like the following:
Next, we need to set our Navigation Controller to show up when we start the app. Remember the commented out Window.AddSubview in Main.cs from before? Well, this is where we’ll use it. Let’s change that line to the following:
// If you have defined a view, add it here: window.AddSubview (this.mainNavigationController.View);
AddSubView is a lot like AddControl in WPF, ASP.NET, etc. By passing it the View property of our mainNavigationController, we’re telling the window to display the Navigation Controller interface.
Let’s run the application now, we should see the following:
Our Navigation Controller shows up, but there are no links yet to our other screens. In order to get links, we have to populate the Table View with Data. In order to do this we have to create a UITableViewDataSource and bind it to the DataSource property of our Table View. In traditional .NET programming, you would bind anything that implements IEnumerable to the DataSource property, specify some of the data binding parameters (such as what fields to use), and it would magically data bind. In Cocoa it works a little differently, as we’ll see, the DataSource itself is called whenever the object that it’s bound to needs to build out a new item, and the DataSource is responsible for actually creating the item.
Before we implement our DataSource though, let’s create the actual item that our DataSource we’ll use. Create a new class called NavItem. To do this right-click on your project and choose Add : New File, select General : Empty Class, and name it “NavItem”:
Now, put the following code in there:
using System; using MonoTouch.UIKit; namespace Example_HelloWorld_2 { //======================================================================== /// <summary> /// /// </summary> public class NavItem { //============================================================= #region -= declarations =- /// <summary> /// The name of the nav item, shows up as the label /// </summary> public string Name { get { return this._name; } set { this._name = value; } } protected string _name; /// <summary> /// The UIViewController that the nav item opens. Use this property if you /// wanted to early instantiate the controller when the nav table is built out, /// otherwise just set the Type property and it will lazy-instantiate when the /// nav item is clicked on. /// </summary> public UIViewController Controller { get { return this._controller; } set { this._controller = value; } } protected UIViewController _controller; /// <summary> /// The Type of the UIViewController. Set this to the type and leave the Controller /// property empty to lazy-instantiate the ViewController when the nav item is /// clicked. /// </summary> public Type ControllerType { get { return this._controllerType; } set { this._controllerType = value; } } protected Type _controllerType; /// <summary> /// a list of the constructor args (if neccesary) for the controller. use this in /// conjunction with ControllerType if lazy-creating controllers. /// </summary> public object[] ControllerConstructorArgs { get { return this._controllerConstructorArgs; } set { this._controllerConstructorArgs = value; this._controllerConstructorTypes = new Type[this._controllerConstructorArgs.Length]; for (int i = 0; i < this._controllerConstructorArgs.Length; i++) { this._controllerConstructorTypes[i] = this._controllerConstructorArgs[i].GetType (); } } } protected object[] _controllerConstructorArgs = new object[] { }; /// <summary> /// The types of constructor args. /// </summary> public Type[] ControllerConstructorTypes { get { return this._controllerConstructorTypes; } } protected Type[] _controllerConstructorTypes = Type.EmptyTypes; #endregion //======================================================================== //======================================================================== #region -= constructors =- public NavItem () { } public NavItem (string name) : this() { this._name = name; } public NavItem (string name, UIViewController controller) : this(name) { this._controller = controller; } public NavItem (string name, Type controllerType) : this(name) { this._controllerType = controllerType; } public NavItem (string name, Type controllerType, object[] controllerConstructorArgs) : this(name, controllerType) { this.ControllerConstructorArgs = controllerConstructorArgs; } #endregion //=============================================================== } }
This class is fairly simple. Let’s first explore the properties:
- Name – The Name of the screen as we want to see it in our Navigation Table.
- Controller – The actual UIViewController of our screen.
- ControllerType – This is the type of the UIVeiwController of our screen, we can use this to late-instantiate the UIViewController by simply storing the type of the controller and creating it only when necessary.
- ControllerConstructorArgs – If your UIViewController has any constructor arguments that you want to pass, this is where you put them. In our example, we won’t need this, so we can ignore it for now, but I left it in here because it’s a handy class to build on later.
- ControllerConstructorTypes – This is a read-only property that pulls the types from the ControllerConstructorArgs, it’s used for instantiating the control.
The rest of the class is just some basic constructors.
Now that we have NavItem, let’s create a DataSource for our Navigation Table View that actually uses it. Create a new class called NavTableViewDataSource. Do this just as you created NavItem.
Now, put the following code in there:
using System; using System.Collections.Generic; using MonoTouch.UIKit; using MonoTouch.Foundation; namespace Example_HelloWorld_2 { //======================================================================== // // The data source for our Navigation TableView // public class NavTableViewDataSource : UITableViewDataSource { /// <summary> /// The collection of Navigation Items that we bind to our Navigation Table /// </summary> public List<NavItem> NavItems { get { return this._navItems; } set { this._navItems = value; } } protected List<NavItem> _navItems; /// <summary> /// Constructor /// </summary> public NavTableViewDataSource (List<NavItem> navItems) { this._navItems = navItems; } /// <summary> /// Called by the TableView to determine how man cells to create for that particular section. /// </summary> public override int RowsInSection (UITableView tableView, int section) { return this._navItems.Count; } /// <summary> /// Called by the TableView to actually build each cell. /// </summary> public override UITableViewCell GetCell (UITableView tableView, NSIndexPath indexPath) { //---- declare vars string cellIdentifier = "SimpleCellTemplate"; //---- try to grab a cell object from the internal queue var cell = tableView.DequeueReusableCell (cellIdentifier); //---- if there wasn't any available, just create a new one if (cell == null) { cell = new UITableViewCell (UITableViewCellStyle.Default, cellIdentifier); } //---- set the cell properties cell.TextLabel.Text = this._navItems[indexPath.Row].Name; cell.Accessory = UITableViewCellAccessory.DisclosureIndicator; //---- return the cell return cell; } } //==================================================================== }
Let’s take at look at this. The first part is our List<NavItem> collection. This is just a collection of our NavItem objects. We then have a basic constructor that forces you to initialize the NavTableViewDataSource with your NavItems.
We then override RowsInSection. Table Views can have multiple sections with items in each section. RowsInSection should return the number of items in whatever section it passes in via the section parameter. In our case, we only have one section, so we return the Count property of our NavItem collection.
The last method GetCell is actually where the interesting bits of the data binding happen. This method is called by the UITableView for each row it needs to build. You can use this method to build out each row of your Table to look like whatever you want.
The first thing we do here is try to get a UITableViewCell object from the TableView via the DequeueReusableCell method. The TableView keeps an internal pool of UITableViewCell objects, based on CellIdentifiers. This allows you to create a custom template for a UITableViewCell one time, and then reuse that object, instead of each time GetCell is called and can increase performance. The first time that we call DequeueReusableCell, this should return nothing, so we create a new UITableViewCell. Every time after, the UITableViewCell should already exist, so we can just reuse it.
We’re using the Default cell style, which gives us just a few options for customization, so the next thing we do is set the TextLabel.Text property to be the Name of our NavItem. Next, we set the Accessory property to use the DisclosureIndicator, which is just a simple arrow that shows up on the right side of our Navigation Item.
Now that we have our UITableViewDataSource created, it’s time to put it to use. Open up Main.cs in MonoDevelop and add the following line to our AppDelegate class:
protected List<NavItem> _navItems = new List<NavItem> ();
This will hold our NavItem objects.
Next, add the following code to the FinishedLaunching method, right after);
All we’re doing here is creating two NavItem objects, and adding them to our _navItems collection. Then, we create a NavTableViewDataSource and bind it to our Navigation Table View.
Our AppDelegate class should now look like this, after we’ve put the preceding code); return true; } // This method is required in iPhoneOS 3.0 public override void OnActivated (UIApplication application) { } }
If you run your application now, you should see something like the following:
We now have our Navigation Items being built out, but nothing happens when we click on them. When you click on an item, the UITableView raises an event, but it needs us to give it a special class, called a UITableViewDelegate to actually listen to those events. To do this, create a new class in your project called “NavTableDelegate” and put in the following code:
using MonoTouch.Foundation; using MonoTouch.UIKit; using System; using System.Collections.Generic; using System.Reflection; namespace Example_HelloWorld_2 { //======================================================================== // // This class receives notifications that happen on the UITableView // public class NavTableDelegate : UITableViewDelegate { //---- declare vars UINavigationController _navigationController; List<NavItem> _navItems; //======================================================================== /// <summary> /// Constructor /// </summary> public NavTableDelegate (UINavigationController navigationController, List<NavItem> navItems) { this._navigationController = navigationController; this._navItems = navItems; } //======================================================================== //======================================================================== /// <summary> /// Is called when a row is selected /// </summary> public override void RowSelected (UITableView tableView, NSIndexPath indexPath) { //---- get a reference to the nav item NavItem navItem = this._navItems[indexPath.Row]; //---- if the nav item has a proper controller, push it on to the NavigationController // NOTE: we could also raise an event here, to loosely couple this, but isn't neccessary, // because we'll only ever use this this way if (navItem.Controller != null) { this._navigationController.PushViewController (navItem.Controller, true); //---- show the nav bar (we don't show it on the home page) this._navigationController.NavigationBarHidden = false; } else { if (navItem.ControllerType != null) { //---- ConstructorInfo ctor = null; //---- if the nav item has constructor aguments if (navItem.ControllerConstructorArgs.Length > 0) { //---- look for the constructor ctor = navItem.ControllerType.GetConstructor (navItem.ControllerConstructorTypes); } else { //---- search for the default constructor ctor = navItem.ControllerType.GetConstructor (System.Type.EmptyTypes); } //---- if we found the constructor if (ctor != null) { //---- UIViewController instance = null; if (navItem.ControllerConstructorArgs.Length > 0) { //---- instance the view controller instance = ctor.Invoke (navItem.ControllerConstructorArgs) as UIViewController; } else { //---- instance the view controller instance = ctor.Invoke (null) as UIViewController; } if (instance != null) { //---- save the object navItem.Controller = instance; //---- push the view controller onto the stack this._navigationController.PushViewController (navItem.Controller, true); } else { Console.WriteLine ("instance of view controller not created"); } } else { Console.WriteLine ("constructor not found"); } } } } //================================================================== } //======================================================================== }
The first part of this class is a couple of declarations for a UINavigationController and a Collection of NavItem objects, and then a constructor that requires them. We’ll see why we need these in the next method, RowSelected.
RowSelected is called by our UITableView when a user clicks on a row, and it gives us a reference to the UITableView that it’s from, as well as the NSIndexPath (index of section and row) that the user clicked on. The first thing we do is look up the NavItem based on that NSIndexPath. Next, we push the UIViewController of that NavItem onto our NavigationController. If the Controller is null, then we try to instantiate it based on the type.
These last two operations are why we need a reference to both the NavItem collection and the NavigationController.
Now that we have our UITableViewDelegate, let’s wire it up. Go back over to Main.cs, and add the following line right after we set our DataSource property in our AppDelegate class:
this.mainNavTableView.Delegate = new NavTableDelegate (this.mainNavigationController, this._navItems);
This creates a new NavTableDelegate class, with a reference to our Navigation Controller and our collection of NavItems, and tells our mainNavTable to use it to handle events.
Our AppDelegate class in Main.cs should now look something like); this.mainNavTableView.Delegate = new NavTableDelegate (this.mainNavigationController, this._navItems); return true; } // This method is required in iPhoneOS 3.0 public override void OnActivated (UIApplication application) { } }
Let’s run our application now and see what happens, click on “Hello World” and you should see:
Notice that we automatically get a “Hello World Home” button at the top that allows us to go back to our home screen. Clicking on “Hello Universe” should get you:
Congratulations! You should now understand the basic concept of how to work with multiple screens in a MonoTouch iPhone application, as well as have a basic understanding of how the UINavigationController works!
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FWIW, the evaluation version of Monotouch is free (as are Mono, MonoDevelop and XCode), which are all you need to create iPhone apps, up until the point where you are ready to sell stuff on iTunes Appstore anyway.
If you are simply looking to write apps for Mac/Windows/Linux, then Mono/MonoDevelop are of course, free.
If you already program in Obj-C and like it, then I see no reason to switch to MonoTouch, but for .NET developers who want to break into iPhone apps, this is a dream come true, even with the licensing fee.
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What if you wanted to go from a Menu to a submenu to a screen?
Would you need to create another Nav table view? | http://www.infoq.com/articles/monotouch-mvc | CC-MAIN-2016-07 | refinedweb | 3,546 | 55.24 |
rules for setting up null and alternative hypotheses:
- The H_0 is true before you collect any data.
- The H_0 usually states there is no effect or that two groups are equal.
- The H_0 and H_1 are competing, non-overlapping hypotheses.
- H_1 is what we would like to prove to be true.
- H_0 contains an equal sign of some kind – either =, \leq, or \geq.
- H_1 contains the opposition of the null – either \neq, >, or <.
You saw that the statement, “Innocent until proven guilty” is one that suggests the following hypotheses are true:
H_0: Innocent
H_1: Guilty
We can relate this to the idea that “innocent” is true before we collect any data. Then the alternative must be a competing, non-overlapping hypothesis. Hence, the alternative hypothesis is that an individual is guilty.
Because we wanted to test if a new page was better than an existing page, we set that up in the alternative. Two indicators are that the null should hold the equality, and the statement we would like to be true should be in the alternative. Therefore, it would look like this:
H_0: \mu_1 \leq \mu_2
H_1: \mu_1 > \mu_2
Here \mu_1 represents the population mean return from the new page. Similarly, \mu_2 represents the population mean return from the old page.
Depending on your question of interest, you would change your null and alternative hypotheses to match.
Type I Errors
Type I errors have the following features:
- You should set up your null and alternative hypotheses, so that the worse of your errors is the type I error.
- They are denoted by the symbol \alpha.
- The definition of a type I error is: Deciding the alternative (H_1) is true, when actually (H_0) is true.
- Type I errors are often called false positives.
Type II Errors
- They are denoted by the symbol \beta.
- The definition of a type II error is: Deciding the null (H_0) is true, when actually (H_1) is true.
- Type II errors are often called false negatives.
In the most extreme case, we can always choose one hypothesis (say always choosing the null) to ensure that a particular error never occurs (never a type I error assuming we always choose the null). However, more generally, there is a relationship where with a single set of data decreasing your chance of one type of error, increases the chance of the other error occurring.
Parachute Example
This example let you see one of the most extreme cases of errors that might be committed in hypothesis testing. In a type I error an individual died. In a type II error, you lost 30 dollars.
In the hypothesis tests you build in the upcoming lessons, you will be able to choose a type I error threshold, and your hypothesis tests will be created to minimize the type II errors after ensuring the type I error rate is met.
You are always performing hypothesis tests on population parameters, never on statistics. Statistics are values that you already have from the data, so it does not make sense to perform hypothesis tests on these values.
Common hypothesis tests include:
- Testing a population mean (One sample t-test).
- Testing the difference in means (Two sample t-test)
- Testing the difference before and after some treatment on the same individual (Paired t-test)
- Testing a population proportion (One sample z-test)
- Testing the difference between population proportions (Two sample z-test)
You can use one of these sites to provide a t-table or z-table to support one of the above approaches: t-table, t-table or z-table
There are literally 100s of different hypothesis tests! However, instead of memorizing how to perform all of these tests, you can find the statistic(s) that best estimates the parameter(s) you want to estimate, you can bootstrap to simulate the sampling distribution. Then you can use your sampling distribution to assist in choosing the appropriate hypothesis.
low, high = np.percentilre(means, 2.5), np.percentile(means, 97.5)
plt.axvline(x=low, color=’r’, linewidth=2)
plt.axvline(x=high, color=’r’, linewidth=2)
Simulating From the Null Hypothesis
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
%matplotlib inline
np.random.seed(42)
full_data = pd.read_csv(‘../data/coffee_dataset.csv’)
sample_data = full_data.sample(200)
1. If you were interested in if the average height for coffee drinkers is the same as for non-coffee drinkers, what would the null and alternative be? Place them in the cell below, and use your answer to answer the first quiz question below.
Since there is no directional component associated with this statement, a not equal to seems most reasonable.
μcoffμcoff and μnoμno are the population mean values for coffee drinkers and non-coffee drinkers, respectivley.
2. If you were interested in if the average height for coffee drinkers is less than non-coffee drinkers, what would the null and alternative be? Place them in the cell below, and use your answer to answer the second quiz question below.
μcoffμcoff and μnoμno are the population mean values for coffee drinkers and non-coffee drinkers, respectivley.
3. For 10,000 iterations: bootstrap the sample data, calculate the mean height for coffee drinkers and non-coffee drinkers, and calculate the difference in means for each sample. You will want to have three arrays at the end of the iterations – one for each mean and one for the difference in means. Use the results of your sampling distribution, to answer the third quiz question below.
nocoff_means, coff_means, diffs = [], [], []
for _ in range(10000):
bootsamp = sample_data.sample(200, replace = True)
coff_mean = bootsamp[bootsamp[‘drinks_coffee’] == True][‘height’].mean()
nocoff_mean = bootsamp[bootsamp[‘drinks_coffee’] == False][‘height’].mean()
# append the info
coff_means.append(coff_mean)
nocoff_means.append(nocoff_mean)
diffs.append(coff_mean – nocoff_mean)
np.std(nocoff_means) # the standard deviation of the sampling distribution for nocoff
np.std(coff_means) # the standard deviation of the sampling distribution for coff
np.std(diffs) # the standard deviation for the sampling distribution for difference in means
plt.hist(nocoff_means, alpha = 0.5);
plt.hist(coff_means, alpha = 0.5); # They look pretty normal to me!
plt.hist(diffs, alpha = 0.5); # again normal – this is by the central limit theorem
4. Now, use your sampling distribution for the difference in means and the docs to simulate what you would expect if your sampling distribution were centered on zero. Also, calculate the observed sample mean difference in
sample_data. Use your solutions to answer the last questions in the quiz below.
null_vals = np.random.normal(0, np.std(diffs), 10000) # Here are 10000 draws from the sampling distribution under the null
plt.hist(null_vals); #Here is the sampling distribution of the difference under the null
Nice job! That’s right. Notice the standard deviation with the difference in means is larger than either of the individual. It turns out that this value for the standard deviation of the difference is actually the square root of the sum of the variance of each of the individual sampling distributions. And the mean has a standard deviation of the original draws divided by the square root of the sample size taken. More on this here and here.
What Is A P-value Anyway?
The definition of a p-value is the probability of observing your statistic (or one more extreme in favor of the alternative) if the null hypothesis is true.
In this video, you learned exactly how to calculate this value. The more extreme in favor of the alternative portion of this statement determines the shading associated with your p-value.
Therefore, you have the following cases:
If your parameter is greater than some value in the alternative hypothesis, your shading would look like this to obtain your p-value:
If your parameter is less than some value in the alternative hypothesis, your shading would look like this to obtain your p-value:
If your parameter is not equal to some value in the alternative hypothesis, your shading would look like this to obtain your p-value:
You could integrate the sampling distribution to obtain the area for each of these p-values. Alternatively, you will be simulating to obtain these proportions in the next concepts.
sample+mean = sample.df.height.mean()
(null_vals > sample_mean).mean()
(null_vals < sample_mean).mean()
null_mean = 70
(null_vals < sample_mean).mean() + (null_vals > null_mean + (null_mean – sample_mean)).mean()
low = sample_mean
high = null_mean + (null_mean – sample_mean)
plt.hist(null_vals);
plt.axvline(x=low, color=’r’, linewidth=2)
plt.axvline(x=high, color=’r’, linewidth=2)
There are a lot of moving parts in these videos. Let’s highlight the process:
- Simulate the values of your statistic that are possible from the null.
- Calculate the value of the statistic you actually obtained in your data.
- Compare your statistic to the values from the null.
- Calculate the proportion of null values that are considered extreme based on your alternative.
The p-value is the probability of getting our statistic or a more extreme value if the null is true.
Therefore, small p-values suggest our null is not true. Rather, our statistic is likely to have come from a different distribution than the null.
When the p-value is large, we have evidence that our statistic was likely to come from the null hypothesis. Therefore, we do not have evidence to reject the null.
By comparing our p-value to our type I error threshold (\alpha), we can make our decision about which hypothesis we will choose.
pval \leq \alpha \Rightarrow Reject H_0
pval > \alpha \Rightarrow Fail to Reject H_0
The word accept is one that is avoided when making statements regarding the null and alternative. You are not stating that one of the hypotheses is true. Rather, you are making a decision based on the likelihood of your data coming from the null hypothesis with regard to your type I error threshold.
Therefore, the wording used in conclusions of hypothesis testing includes: We reject the null hypothesisor We fail to reject the null hypothesis. This lends itself to the idea that you start with the null hypothesis true by default, and “choosing” the null at the end of the test would have been the choice even if no data were collected.
Drawing Conclusions – Calculating Errors
import numpy as np
import pandas as pd
jud_data = pd.read_csv(‘../data/judicial_dataset_predictions.csv’)
par_data = pd.read_csv(‘../data/parachute_dataset.csv’)
jud_data.head()
par_data.head()
1. Above, you can see the actual and predicted columns for each of the datasets. Using the jud_data, find the proportion of errors for the dataset, and furthermore, the percentage of errors of each type. Use the results to answer the questions in quiz 1 below.
Hint for quiz: an error is any time the prediction doesn’t match an actual value. Additionally, there are Type I and Type II errors to think about. We also know we can minimize one type of error by maximizing the other type of error. If we predict all individuals as innocent, how many of the guilty are incorrectly labeled? Similarly, if we predict all individuals as guilty, how many of the innocent are incorrectly labeled?
jud_data[jud_data[‘actual’] != jud_data[‘predicted’]].shape[0]/jud_data.shape[0] # Number of errros
jud_data.query(“actual == ‘innocent’ and predicted == ‘guilty'”).count()[0]/jud_data.shape[0] # Type 1
jud_data.query(“actual == ‘guilty’ and predicted == ‘innocent'”).count()[0]/jud_data.shape[0] # Type 2
2. Above, you can see the actual and predicted columns for each of the datasets. Using the par_data, find the proportion of errors for the dataset, and furthermore, the percentage of errors of each type. Use the results to answer the questions in quiz 2 below.
par_data[par_data[‘actual’] != par_data[‘predicted’]].shape[0]/par_data.shape[0] # Number of errros
par_data.query(“actual == ‘fails’ and predicted == ‘opens'”).count()[0]/par_data.shape[0] # Type 1
par_data.query(“actual == ‘opens’ and predicted == ‘fails'”).count()[0]/par_data.shape[0] # Type 2
One of the most important aspects of interpreting any statistical results (and one that is frequently overlooked) is assuring that your sample is truly representative of your population of interest.
Particularly in the way that data is collected today in the age of computers, response bias is so important to keep in mind. In the 2016 U.S election, polls conducted by many news media suggested a staggering difference from the reality of poll results. You can read about how response bias played a role here.
Hypothesis Testing vs. Machine Learning
With large sample sizes, hypothesis testing leads to even the smallest of findings as statistically significant. However, these findings might not be practically significant at all.
For example, Imagine you find that statistically more people prefer beverage 1 to beverage 2 on a study of more than one million people. Based on this you decide to open a shop to sell beverage 1. You then find out that beverage 1 is only more popular than beverage 2 by 0.0002% (but a statistically significant amount with your large sample size). Practically, maybe you should have opened a store that sold both.
Hypothesis testing takes an aggregate approach towards the conclusions made based on data, as these tests are aimed at understanding population parameters (which are aggregate population values).
Alternatively, machine learning techniques take an individual approach towards making conclusions, as they attempt to predict an outcome for each specific data point.
In the final lessons of this class, you will learn about two of the most fundamental machine learning approaches used in practice: linear and logistic regression.
When performing more than one hypothesis test, your type I error compounds. In order to correct for this, a common technique is called the Bonferroni correction. This correction is very conservative, but says that your new type I error rate should be the error rate you actually want divided by the number of tests you are performing.
Therefore, if you would like to hold a type I error rate of 1% for each of 20 hypothesis tests, the Bonferronicorrected rate would be 0.01/20 = 0.0005. This would be the new rate you should use as your comparison to the p-value for each of the 20 tests to make your decision.
Other Techniques
Additional techniques to protect against compounding type I errors include:
A two-sided hypothesis test (that is a test involving a \neq in the alternative) is the same in terms of the conclusions made as a confidence interval as long as:
1 – CI = \alpha
For example, a 95% confidence interval will draw the same conclusions as a hypothesis test with a type I error rate of 0.05 in terms of which hypothesis to choose, because:
1 – 0.95 = 0.05
assuming that the alternative hypothesis is a two sided test.
Video on effect size here.
The Impact of Large Sample Sizes
When we increase our sample size, even the smallest of differences may seem significant.
To illustrate this point, work through this notebook and the quiz questions that follow below.
Start by reading in the libraries and data.
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
%matplotlib inline
np.random.seed(42)
full_data = pd.read_csv(‘coffee_dataset.csv’)
1. In this case, imagine we are interested in testing if the mean height of all individuals in
full_data is equal to 67.60 inches. First, use quiz 1 below to identify the null and alternative hypotheses for these cases.
$$H_0: \mu = 67.60$$
$$H_1: \mu \neq 67.60$$
2. What is the population mean height? What is the standard deviation of the population heights? Create a sample set of data using the code below. What is the sample mean height? Simulate the sampling distribution for the mean of five values to see the shape and plot a histogram. What is the standard deviation of the sampling distribution of the mean of five draws? Use quiz 2 below to assure your answers are correct.
# population height mean and standard deviation
full_data.height.mean(), full_data.height.std()
sample1 = full_data.sample(5)
sample1.height.mean()
sampling_dist_mean5 = []
for _ in range(10000):
bootstrap_sample = sample1.sample(5, replace=True)
bootstrap_mean = bootstrap_sample.height.mean()
sampling_dist_mean5.append(bootstrap_mean)
plt.hist(sampling_dist_mean5);
std_sampling_dist = np.std(sampling_dist_mean5)
std_sampling_dist
null_mean = 67.60 # this is another way to compute the standard deviation of the sampling distribution theoretically std_sampling_dist = full_data.height.std()/np.sqrt(5) num_sims = 10000 null_sims = np.random.normal(null_mean, std_sampling_dist, num_sims) low_ext = (null_mean - (sample1.height.mean() - null_mean)) high_ext = sample1.height.mean() (null_sims > high_ext).mean() + (null_sims < low_ext).mean()
3. Using the null and alternative set up in question 1 and the results of your sampling distribution in question 2, simulate the mean values you would expect from the null hypothesis. Use these simulated values to determine a p-value to make a decision about your null and alternative hypotheses. Check your solution using quiz 3 and quiz 4 below.
Hint: Use the numpy documentation here to assist with your solution.
null_mean = 67.60
null_vals = np.random.normal(null_mean, std_sampling_dist, 10000)
plt.hist(null_vals);
# where our sample mean falls on null distribution
plt.axvline(x=sample1.height.mean(), color = ‘red’);
# for a two sided hypothesis, we want to look at anything
# more extreme from the null in both directions
obs_mean = sample1.height.mean()
prob_more_extreme_high = (null_vals > obs_mean).mean()
prob_more_extreme_low = (null_vals < null_mean – (obs_mean – null_mean)).mean()
pval = prob_more_extreme_low + prob_more_extreme_high
pval
# let’s see where our sample mean falls on the null distribution
lower_bound = null_mean – (obs_mean – null_mean)
upper_bound = obs_mean
plt.hist(null_vals);
plt.axvline(x=lower_bound, color = ‘red’);
plt.axvline(x=upper_bound, color = ‘red’);
4. Now, imagine you received the same sample mean you calculated from the sample in question 2 above, but with a sample of 1000. What would the new standard deviation be for your sampling distribution for the mean of 1000 values? Additionally, what would your new p-value be for choosing between the null and alternative hypotheses you set up? Simulate the sampling distribution for the mean of five values to see the shape and plot a histogram. Use your solutions here to answer the second to last quiz question below.
# get standard deviation for a sample size of 1000
sample2 = full_data.sample(1000)
sampling_dist_mean1000 = []
for _ in range(10000):
bootstrap_sample = sample2.sample(1000, replace=True)
bootstrap_mean = bootstrap_sample.height.mean()
sampling_dist_mean1000.append(bootstrap_mean)
std_sampling_dist1000 = np.std(sampling_dist_mean1000)
std_sampling_dist1000
null_vals = np.random.normal(null_mean, std_sampling_dist1000, 10000)
plt.hist(null_vals);
plt.axvline(x=lower_bound, color = ‘red’);
plt.axvline(x=upper_bound, color = ‘red’);
# for a two sided hypothesis, we want to look at anything
# more extreme from the null in both directions
prob_more_extreme_low = (null_vals < lower_bound).mean()
prob_more_extreme_high = (upper_bound < null_vals).mean()
pval = prob_more_extreme_low + prob_more_extreme_high
pval
Multiple Tests
In this notebook, you will work with a similar dataset to the judicial dataset you were working with before. However, instead of working with decisions already being provided, you are provided with a p-value associated with each individual.
Use the questions in the notebook and the dataset to answer the questions at the bottom of this page.
Here is a glimpse of the data you will be working with:
import numpy as np
import pandas as pd
df = pd.read_csv(‘judicial_dataset_pvalues.csv’)
df.head()
1. Remember back to the null and alternative hypotheses for this example. Use that information to determine the answer for Quiz 1 and Quiz 2 below.
A pvalue is the probability of observing your data or more extreme data, if the null is true. Type I errors are when you choose the alternative when the null is true, and vice-versa for Type II. Therefore, deciding an individual is guilty when they are actually innocent is a Type I error. The alpha level is a threshold for the percent of the time you are willing to commit a Type I error.
2. If we consider each individual as a single hypothesis test, find the conservative Bonferroni corrected alpha level we should use to maintain a 5% type I error rate.
bonf_alpha = 0.05/df.shape[0]
bonf_alpha
3. What is the proportion of type I errors made if the correction isn’t used? How about if it is used?
Use your answers to find the solution to Quiz 3 below.
df.query(“actual == ‘innocent’ and pvalue < 0.05”).count()[0]/df.shape[0] # If not used
df.query(“actual == ‘innocent’ and pvalue < @bonf_alpha”).count()[0]/df.shape[0] # If used
4. Think about how hypothesis tests can be used, and why this example wouldn’t exactly work in terms of being able to use hypothesis testing in this way. Check your answer with Quiz 4 below.
This is looking at individuals, and that is more of the aim for machine learning techniques. Hypothesis testing and confidence intervals are for population parameters. Therefore, they are not meant to tell us about individual cases, and we wouldn’t obtain pvalues for individuals in this way. We could get probabilities, but that isn’t the same as the probabilities associated with the relationship to sampling distributions as you have seen in these lessons.
Recap
Wow! That was a ton. You learned:
- How to set up hypothesis tests. You learned the null hypothesis is what we assume to be true before we collect any data, and the alternative is usually what we want to try and prove to be true.
- You learned about Type I and Type II errors. You learned that Type I errors are the worst type of errors, and these are associated with choosing the alternative when the null hypothesis is actually true.
- You learned that p-values are the probability of observing your data or something more extreme in favor of the alternative given the null hypothesis is true. You learned that using a confidence interval from the bootstrapping samples, you can essentially make the same decisions as in hypothesis testing (without all of the confusion of p-values).
- You learned how to make decisions based on p-values. That is, if the p-value is less than your Type I error threshold, then you have evidence to reject the null and choose the alternative. Otherwise, you fail to reject the null hypothesis.
- You learned that when sample sizes are really large, everything appears statistically significant (that is you end up rejecting essentially every null), but these results may not be practically significant.
- You learned that when performing multiple hypothesis tests, your errors will compound. Therefore, using some sort of correction to maintain your true Type I error rate is important. A simple, but very conservative approach is to use what is known as a Bonferroni correction, which says you should just divide your \alpha level (or Type I error threshold) by the number of tests performed. | http://tomreads.com/2018/03/10/hypothesis-testing/ | CC-MAIN-2019-04 | refinedweb | 3,763 | 56.96 |
[thousands of words long text, stay up late to update, original is not easy, a lot of support, thank you]
preface
Hello, guys, hello. In the previous article, we have implemented the submission function of the questionnaire. After completing the questionnaire and clicking submit, the questionnaire results will be displayed in the console. However, this form is obviously unfriendly to users. Some users even don't know how to open the console. It gives the impression that there is no response when they click the submit button, they can't see the submission results, and they don't know whether they have submitted successfully. In this sharing, we will continue to go deeper along the previous article. With the help of Vue router, after clicking the submit button, the carrier's questionnaire results will jump to a new "questionnaire results" page and show the results to users.
Install and configure routing
Because this sharing will involve page Jump, we will introduce Vue router to realize page Jump with the help of routing control.
- First, install the latest version of Vue router (NPM install Vue)- router@4 ), if router is checked when creating the project, it indicates that it has been installed. This step can be omitted
- Create a router directory under the src directory of the project to store routing related files
- Create a new index.js file in the router directory created above
- Open index.js and import the two methods in Vue router at the top. createRouter and createWebHashHistory are used to create a route object and a route in hash mode respectively
- Import components that need routing control, such as questionnaire page component (Home.vue) and result page component (result.vue)
- Configure the routing information corresponding to different components
- Call the createRouter method to create a routing object and export it by default
- Finally, you need to import the routing object created above in main.js and apply it to the vue instance
- router/index.js source code display
import { createRouter, createWebHashHistory } from 'vue-router' import Home from '../Home.vue' const routes = [ { path:'/', name: "Home", component: Home }, { path: '/result', name: 'Result', component: () => import(/*webChunkName: "Result"*/ '../result.vue') } ] const router = createRouter({ history:createWebHashHistory(),//Routing with hash mode routes }) export default router;
- main.js modification
//Add code import router from './router' //Modify code createApp(App).use(router).mount('#app')
Modify App.vue component
Because we will control the display and jump of the page through the route, we need to transform the App.vue component:
- Delete the original Home component in App.vue
- Add two new routing labels to the template:
- Router link: hyperlink label used to control route jump
- Router view: used to display the page content corresponding to the route
The modified source code is as follows:
<template> <router-linkquestionnaire</router-link> <router-view /> </template>
export default { setup(){} }
Modify the Home.vue component
There are not many changes to the Home.vue component. There are mainly two steps: add a title "Questionnaire" to the template, realize route jump in the submit button, and carry the results as parameters
- Modify the template of the component and add an h1 tag at the top of the page to display the title: "Questionnaire"
- Import the useRouter method of the route in JavaScript code. (since vue instances cannot be accessed through this in vue 3.0, routing information cannot be obtained through this. $route and this. $route, but the corresponding vue route provides us with two corresponding methods, useRoute and useRoute, to replace them.)
- In the setup method, we call the useRouter method to get the router object.
- In the submit method of the submit button, the route jump is realized through the push method of the router object, and the questionnaire result is passed to the questionnaire result page as a parameter. (Note: in the previous article, we saved the questionnaire results into an object. Since the object cannot be directly passed as a parameter, we need to convert the results into JSON string with the help of JSON.stringify method, and then pass them.)
<template> <!--...ellipsis--> <div class="main"> <div style="text-align:center"> <h1>questionnaire investigation</h1> </div> <!--...ellipsis--> </div> </template>
//... omitted import {useRouter} from 'vue-router' setup(){ //... omitted const router = useRouter(); const submit = ()=>{ router.push({ name:'Result', //Route name configured in route query:{ result:JSON.stringify(result) } }) } //... omitted }
Create a new questionnaire result page result.vue
Add a new result.vue page to display the questionnaire results. This page is relatively simple. You only need to get the questionnaire results from the routing parameters and display them on the page. In order to make the page not too ugly, we need to simply add some styles
- Add two div tags in the template to display the title of the questionnaire results and the specific contents of the questionnaire results respectively
- The second div tag needs to output the questionnaire results circularly with the help of the v-for instruction
- The useRoute method of importing route in script is used to obtain the current route information. (note that useRoute is used instead of useRouter. The former obtains the current route and the latter obtains the entire route object)
- In the setup method, the useRoute method is called to get the current route and to store it in the route variable.
- Get the parameters passed from the questionnaire page in the current route through route.query, that is, the questionnaire results (it needs to be converted into the form of objects with the help of JOSN.parse)
- Expose the questionnaire results to the template through return
- Finally, simply set the page style
<template> <div style="text-align:center;"> <h1>Questionnaire results</h1> </div> <div class="item" v-{{item}}</div> </template>
import {useRoute} from 'vue-router' export default { setup(){ const route = useRoute(); const result = JSON.parse(route.query.result); return { result } } }
.item{ width:100%; padding: 5px; box-sizing: border-box; border: 1px solid lightblue; border-radius: 5px; margin-top:10px; }
Effect display
summary
At this point, a questionnaire survey with route jump and result display function are completed. The main function point of this sharing is Vue router routing. In this paper, I introduced Vue router and made a simple configuration. Click the submit button to jump to the questionnaire result page. At the same time, the filled results are passed to the result page as parameters and displayed.
That's all for this sharing. Your favorite friends are welcome to comment and pay attention! | https://programmer.help/blogs/619ee47e90b0e.html | CC-MAIN-2021-49 | refinedweb | 1,075 | 54.83 |
In this python tutorial, we will discuss python threading and multithreading. We will also check:
- What is a thread?
- What is threading?
- Python thread creating using class
- Python threading lock
- Threads using queue
- Python Multi-thread creating using functions
- Synchronization in Multithreading
- Python thread pool
- Multithreading vs Multiprocessing
- Thread vs Multithread
What is a thread?
A thread is the smallest unit that is scheduled in an operating system, which can perform multitask simultaneously. When the task requires some time for execution python threads are used in this scenario.
Introduction to Python threading
- Threading is a process of running multiple threads at the same time.
- The threading module includes a simple way to implement a locking mechanism that is used to synchronize the threads.
In this example, I have imported a module called threading and time. Also, we will define a function Evennum as def Evennum(). We have used for loop and range() function and also sleep() is used to wait for executing the current thread for given seconds of time.
Example:
import threading import time def Evennum(): for i in range(2, 10, 2): time.sleep(1) print(i) threading.Thread(target=Evennum).start()
Below screenshot shows the evennumbers from the range 2 to10.
Read How to Put Screen in Specific Spot in Python Pygame
Python thread creating using class
Here, we can see how to create thread using class in python.
Syntax to create thread class:
Thread(group=None, target=None, name=None, args=(), kwargs={})
To create a thread using class in python there are some class methods:
- run() – This method calls the target function that is passed to the object constructor.
- start() – Thread activity is started by calling the start()method, when we call start() It internally invokes the run method and executes the target object.
-.
- isAlive() – This method returns that the thread is alive or not. The thread is alive at the time when the start() is invoked and lasts until the run() terminates.
- setDaemon(Daemonic) – This method is used to set the daemon flag to Boolean value daemonic. this should be called before the start().
- isDaemon() – This method returns the value of the thread’s daemon flag.
- In this example, I have imported a module called thread from threading and defined a function as a threaded function and an argument is passed.
- The value of __name__ attribute is set to “__main__”. When the module is run as a program. __name__ is the inbuilt variable that determines the name for a current module.
- If the module is running directly from the command line then “__name__” is set to “__main__”.
Example:
from threading import Thread def threaded_function(arg): for i in range(arg): print("python guides") if __name__ == "__main__": thread = Thread(target = threaded_function, args = (3, )) thread.start() thread.join() print("Thread Exiting...")
You can see in the below screenshot that python guides printed three times as mentioned in the range().
Python threading lock
The threading module has a synchronization tool called lock. A lock class has two methods:
- acquire(): This method locks the Lock and blocks the execution until it is released.
- release(): This method is used to release the lock. This method is only called in the locked state.
- In this example, I have imported called Lock from threading, lock = Lock() used to declare a lock, and defined function to multiply the value as def multiply_one().
- lock.acquire() is used to lock when the state is unlocked and return immediately.
- lock.release() is used to unlock the state this is only called when the state is locked.
- Threads.append(Thread(target=func)) used to instantiate it with a target function.
- threads[-1].start() used to call start, print(a)gives the final value.
Example:
from threading import Lock, Thread lock = Lock() a = 1 def multiply_one(): global a lock.acquire() a *= 4 lock.release() def multiply_two(): global a lock.acquire() a *= 6 lock.release() threads = [] for func in [multiply_one, multiply_two]: threads.append(Thread(target=func)) threads[-1].start() for thread in threads: thread.join() print(a)
You can refer the below screenshot to see the multiplied value .
Threads using queue
- In this example, I have imported modules called queue and threading. The function employee is used as a def employee().
- Infinite loop(while True) is called to make threads ready to accept all the tasks.
- Then define queue as project = q.get() .
- task_done() tells the queue that the processing on task is completed. When the project is put in the queue task_done is called.
- threading.Thread(target=employee, daemon=True).start() is used to start the employee thread.
- for a time in range(5)means 5 tasks are sent to the employee.
- q.join blocks till all the tasks are completed.
Example:
import threading, queue q = queue.Queue() def employee(): while True: project = q.get() print(f'working on {project}') print(f'done{project}') q.task_done() threading.Thread(target=employee, daemon=True).start() for project in range(5): q.put(project) print('project requests sent\n', end='') q.join() print('projects completed')
You can refer the below screenshot to see output of all the 5 tasks.
What is Multithreading in Python?
A process of executing multiple threads parallelly. Multi-threads use maximum utilization of CPU by multitasking. Web Browser and Web Server are the applications of multithreading.
Python Multithread creating using functions
- In this example, I have imported threading and defined a function, and performed arithmetic operations.
- The format() returns a formatted string. t1.start() to start the thread. t1.join() performs the main thread to wait until the other thread to finish.
- The value of __name__ attribute is set to “__main__”. When the module is run as a program. __name__ is the inbuilt variable that determines the name for a current module.
- If the module is running directly from the command line then “__name__” is set to “__main__”.
Example:
import threading def multiplication(num): print("Multiplication: {}".format(num * num)) def addition(num): print("Addition: {}".format(num + num)) def division(num): print("Division: {}".format(num / num)) def substraction(num): print("substraction: {}".format(num - num)) if __name__ == "__main__": t1 = threading.Thread(target=multiplication, args=(20,)) t2 = threading.Thread(target=addition, args=(5,)) t3 = threading.Thread(target=division, args=(100,)) t4 = threading.Thread(target=substraction, args=(3,)) t1.start() t2.start() t3.start() t4.start() t1.join() t2.join() t3.join() t4.join()
You can refer the below screenshot to check the arithmetic operation.
Synchronization in Multithreading
Shared resource is protected by thread synchronization by ensuring that one thread is accessed at a time. It also protects from race conditions.
What is race condition?
The shared resource is accessed by multiple threads at a time. All threads racing to complete the task and finally, it will end up with inconsistent data. To over this race condition synchronization method is used.
- Here, we have to create a shared resource. shared resource generates a multiplication table for any given number.
- In this example, I have imported a module called threading and defined class Multiplication and defined a function Mul as def Mul.
- Then I have used for the loop in the range(1,6) and then used print(num, ‘X’ ,i, ‘=’ ,num*i). Here num is the number whichever you give and ‘X’ is the multiplication symbol, i is the range given.
- Then defined another class as MyThread and defined a constructor as def__init__(self,tableobj,num). and in the constructor, I have defined a superclass constructor.
- To include the shared resource in this thread we need an object and used tableobj as a parameter and another parameter as num is used.
- Again defined a run function using def run(self).
- Thread lock is created using threadlock=Lock().
- This lock should be created before accessing the shared resource and after accessing the shared resource, we have to release using threadlock.release().
- To get the output self.tableobj.Mul(self.num) is used.
- Shared resource object is created using tableobj=Multiplication().
- Create two threads using t1=MyThread(tableobj,2)and then pass parameter tableobj and a number.
- After that, we have to start the thread using t1.start().
Example:
from threading import * class Multiplication: def Mul(self,num): for i in range(1,6): print(num,'X',i,'=',num*i) class MyThread(Thread): def __init__(self,tableobj,num): Thread.__init__(self) self.tableobj=tableobj self.num=num def run(self): threadlock.acquire() self.tableobj.Mul(self.num) threadlock.release() threadlock=Lock() tableobj=Multiplication() t1=MyThread(tableobj,2) t2=MyThread(tableobj,3) t1.start() t2.start()
Here, In the below screenshot we can see the multiplication tables of number 2 and 3.
You can refer the below screenshot for improper arrangement of data.
- In this output, we can see the improper arrangement of data. This is due to a race condition. To overcome the race condition synchronization is used.
- Sometimes we may get proper data but many times we will be getting improper data arrangement.
- So, it is better to use the synchronization method (lock class).
Python thread pool
- Thread pool is a group of worker threads waiting for the job.
- In a thread pool, a group of a fixed size of threads is created.
- A service provider pulls the thread from the thread pool and assigns the task to the thread.
- After finishing the task a thread is returned into the thread pool.
- The advantage of the thread pool is thread pool reuses the threads to perform the task, after completion of a task the thread is not destroyed. It is returned back into the thread pool.
- Threadpool is having better performance because there is no need to create a thread.
- In this example, I have imported a module called concurrent.futures this module provides an interface for processing the tasks using pools of thread.
- The NumPy module is also imported which is used to work with the array.
- Time modules handle various functions related to time.
- ThreadPoolExecutor is an executor subclass that uses thread pools to execute the call. By using ThreadPoolExecutor 2 threads have been created.
- Then the task is given by the function in the form of an argument as a number and wait for 2 sec to execute the function and display the results.
- When the task is completed the done() returns a True value.
- submit() method is a subinterface of executor. The submit() accepts both runnable and callable tasks.
Example:
import concurrent.futures import numpy as np from time import sleep numbers = [1,2,3,] def number(numbers): sleep(2) print(numbers) with concurrent.futures.ThreadPoolExecutor(max_workers = 2) as executor: thread1 = executor.submit(number, (numbers)) print("Thread 1 executed ? :",thread1.done())
In this below screenshot, we can see that done() returns the true value after finishing the task.
Multithreading vs Multiprocessing
Thread vs Multithread
You may like the following Python tutorials:
- How to convert Python degrees to radians
- Python Comparison Operators
- Python Tkinter Frame
- How to make a matrix in Python
- Linked Lists in Python
- How to display a calendar in Python
- How to make a calculator in Python
- Escape sequence in Python
- Introduction to Python Interface
In this Python tutorial, we have learned about Python threading and multithreading. Also, We covered these below topics:
- What is Threading?
- What is Multithreading?
- Python thread creating using class
- Python threading lock
- Threads using queue
- Python Multi-thread creating using functions
- Synchronization in Multithreading
- Python thread pool
- Multithreading vs Multiprocessing
- Thread vs Multithread
Entrepreneur, Founder, Author, Blogger, Trainer, and more. Check out my profile. | https://pythonguides.com/python-threading-and-multithreading/ | CC-MAIN-2022-21 | refinedweb | 1,903 | 59.19 |
In today’s Programming Praxis exercise, our goal is to implement a unix checksum utility. Let’s get started, shall we?
Some imports:
import Data.Char import System.Environment
I made two changes in the checksum algorithm compared to the Scheme version. I included to conversion to a string to remove some duplication and I used a simpler method of dividing and rounding up.
checksum :: String -> String checksum = (\(s,b) -> show s ++ " " ++ show (div (b + 511) 512)) . foldl (\(s,b) c -> (mod (s + ord c) 65535, b + 1)) (0,0)
Depending on whether or not the program was called with any arguments, the checksum is calculated for either the stdin input or the files provided.
main :: IO () main = getArgs >>= \args -> case args of [] -> interact checksum fs -> mapM_ (\f -> putStrLn . (++ ' ':f) . checksum =<< readFile f) fs
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Tags: bonsai, checksum, code, Haskell, kata, praxis, programming, sum, unix | https://bonsaicode.wordpress.com/2011/03/25/programming-praxis-sum/ | CC-MAIN-2017-30 | refinedweb | 145 | 65.93 |
Opened 5 years ago
Closed 4 years ago
#18114 closed Bug (duplicate)
makemessages does not care about context in trans templatetag
Description (last modified by )
We are working with translations and we have done the following
- we have 2 templates: template1.html and template2.html
- in template1 we have the following:
{% trans 'contact' as trans_contact %}
- in template2 we have the following:
{% trans 'contact' context 'suggesttive' as trans_contact %}
- when we makemessages -a we get the following in the django.po file:
#: web/templates/web/template1.html:35 #: web/templates/web/template2.html:21 msgid "contact" msgstr ""
- what we expect instead (in django.po) is actually:
#: web/templates/web/template1.html:35 msgid "contact" msgstr "" #: web/templates/web/template2.html:21 msgctxt "suggesttive" msgid "contact" msgstr ""
So it seems that the "django-admin.py makemessages -a" does not take into account context in the trans templatetag (but it does process both trans tag as can be seen in the comment)
If we write (anywhere in the code) the following:
from django.utils.translation import pgettext test = pgettext('suggesttive', 'contact')
then the django.po content is as expected and if we translate the strings (in django.po) and then render the template, the context is taken into account and the translation on the webpage (produced from the template) is as it should be, so the trans templatetag works as expected, just the makemessages does not.
If this is a "feature" I apologize in advance.
Attachments (2)
Change History (12)
comment:1 Changed 5 years ago by
comment:2 Changed 5 years ago by
Thanks for the report, however I cannot reproduce your issue (see the attached test case). Are you able to provide a test case for Django that highlights the problem?
Changed 5 years ago by
Changed 5 years ago by
Same patch but with .diff extension
comment:3 Changed 5 years ago by
comment:4 Changed 5 years ago by
comment:5 follow-up: 7 Changed 4 years ago by
We just hit the same problem. In our case it seems to be related to single quote versus double quote. If we set the context keyword in single quotes makemessages ignores the context and sets the translation to have no context. If we change to double quote it then considers the context keyword.
Example:
Works:
{% trans 'Active' context "plural" %}
Doesn't work:
{% trans 'Active' context 'plural' %}
comment:6 Changed 4 years ago by
comment:7 Changed 4 years ago by
comment:8 Changed 4 years ago by
Django 1.4(.0)
sorry, there is a typo in my report: in my code it is not:
but it is:
{% trasn ...
}}}
so this is definitely not the problem. | https://code.djangoproject.com/ticket/18114 | CC-MAIN-2017-26 | refinedweb | 445 | 62.17 |
- not really a math geek (been years) but I think that a friend and I came up with a decent formula, but not sure how to express it :) after that, we realized that all squares are open lockers, so our "solution" became more a proof of why squares are open lockers
We initial figured that a locker "toggles" when a factor of the number is encountered. Then figured that an odd number of factors would leave the locker open. The formula is something like the sum of all instance from 1 to x (where in this case x is 100) where the number of factors of x is odd. So starting off: 1 has 1 (1 - odd) 2 has 2 (1 2 - even) 3 has 2 (1 3 - even) 4 has 3 (1 2 4 - odd) 5 has 2 (1 5 - even) ... and so on. Further down the locker line... 48 has 10 (1 2 3 4 6 8 12 16 24 48 - even) 49 has 3 (1 7 49 - odd) 50 has 6 (1 2 5 10 25 50 - even) 51 has 4 (1 3 17 51 - even)
Looking at this, we realize that squares are odd because we only count it's square factor once, when it multiplies itself.
As far as least toggled locker, locker #1 only once :) next in line, all prime number are toggled twice (1 and itself), naturally all being closed lockers
Sam
Admin
I just saw the 8 pages of comments, and realized that it's been solved already :( oh well, my last post stands, I figured it out while drinking beers :)
Admin
comparable cpu effort for 10^4 to 10^9 lockers (at least as reported)
Admin
MATLAB code:
n = 100;
L = zeros(1,n); mask = 1:n; toggle = zeros(n);
for i=1:n toggle(i,:) = mod(mask,i)==0; L = L + toggle(i,:); L(find(L>1)) = 0; end L t = sum(toggle); least = find(t==min(t)) most = find(t==max(t))
Admin
def least_toggled(n): return 1
Admin
Make that toggle = zeros(1, n); or even just toggle = L;
(zeros(n) is an n x n matrix)
Admin
It's easy. 11 = 1 22 = 4 33 = 9 44 = 16 55 = 25 66 = 36 77 = 49 88 = 64 99 = 81 1010=100
done.
Admin
matlab? pfft. ;)
You're still brutin' it.
Admin
Without looking at previous comments:
Open: Even powers of primes (1,4,9,16,25,49,64,81) Closed: Everything else.
Most toggled: Whatever has the most prime factors (too lazy to figure it out, so I'm going to guess 60)
Least toggled: 1 (duh) and in second place, all primes.
Admin
Yeah I got it wrong. All squares have an odd number of factors, not just even powers of primes. Oh well.
Admin
Simple: each locker with an index that is a prime number will be closed. All of these will be toggled just twice. For the rest they will be either open or closed depending on the number of unique dividers. For example 12 has 5 unique dividers 1, 2, 3, 4 and 6. It will be open.
Admin
ooops forgot 12 is also a divider. It will actually be closed :)
Admin
I meant "perfect square" of course, not "perfect prime".
Admin
Locker 1 and all primes are toggled least (twice).
Admin
Admin
For extra points, do not assume English; support at least all languages spoken in the EU.
Seriously, Mrs MeChokemchild suggested a harder problem:
It doesn't say "after performing toggles for i=1..n on n lockers", it doesn't even say "after toggling every mth locker for m=1..n". It says "after toggling n lockers" where one toggling is defined as "changing the state of one door".
Admittedly the simulator takes the number of lockers as input, not the number of togglings, but then the simulation was 'To Get Started' only.
Captcha: capio - I got it! (?)
Admin
Uh... Maurits's "follow-up question" is much too easy: No mater how many lockers you have, locker #1 is only ever touched once.
Admin
Meh, generic C#...
using System; using System.Collections.Generic; using System.Linq; using System.Text;
namespace ConsoleApplication1 { class Program {
}
Admin
locker #1 is toggled only once. The prime number ones are toggled exactly twice, by one and the prime they represent.
Admin
Hmmmm... wonder if anyone has tried a Texas Instruments calculator version. Would like to see it run on my crappy TI-83 Plus!
Admin
Obviously, locker 1 is toggled only once. Lockers with prime numbers are toggled twice: once on the first iteration, and once for itself. For others, find the factors of the locker number. The number of factors equals the number of times it's toggled.
Admin
The 1 followed by the primes are toggled the least. The number of toggles is based upon the number of factors.
1: 1 toggle Primes: 2 toggles Perfect Squares: Odd number of toggles, hence open Other: Even number of toggles, hence closed
Admin
Prime numbered ones. They're toggled twice, one at the first step, and once at their own.
As a general rule, each locker is toggled a number of times equal to the number of possible unique groupings of its prime factors that are <= the number of lockers. So for example, take the 20th locker, with factors 2,2,5. It gets toggled:
On the 1st step. On the 2nd step. On the (22)th[4th] step. On the 5th step. On the (25)th[10th] step. And of course on its own (20th) step.
If the number of swaps n is odd (that is, n mod 2 = 1), that locker is open, and if that number is even (n mod 2 = 0), the locker is closed. Thus, locker 20, with six toggles, is closed.
Admin
Easy. Locker number 1 (once), followed by any prime numbers (twice). From there, it's whatever numbers have exactly 3 factors (incl. themselves).
I'm fairly sure that 96 is the locker that would be toggled the most incidentally.
Admin
Locker one is toggled once. Otherwise, consider that factors ordinarily come in pairs, except in the case of perfect squares, where the squareroot lacks a partner (being its own).
Admin
Prime numbers.
Admin
The objective is to beat the jocks with the right answer, not how that answer is obtained, right?
In a lazy 7 minutes all I did was program what the jocks were doing.
DOS batch:
setlocal enabledelayedexpansion
for /l %%x in (1,1,100) do ( set locker%%x=0 for /l %%y in (1,1,100) do ( set /a remainder=%%x%%%%y if !remainder!==0 if !locker%%x!==0 (set locker%%x=1) else set locker%%x=0 ) echo locker%%x: !locker%%x! )
Admin
K, I didn't read the no brute force part. Whatever.
Admin
The first locker is toggled exactly once. Prime-numbered lockers are toggled twice.
Admin
Link exchange is nothing else but it is just placing the other persons weblog link on your page at proper place and other person will also do similar in support of you. fkkgfgcbbcebcgdb | https://thedailywtf.com/articles/comments/Nerds,-Jocks,-and-Lockers/9 | CC-MAIN-2018-05 | refinedweb | 1,188 | 72.16 |
The following walkthrough describes the process for accessing an XML Web service from an application created using C++.
During the course of this walkthrough, you will accomplish the following activities:
Create a client application using the CLR Console Application project template.
Add a Web reference for an XML Web service.
Write code to access the XML Web service.
Run the client application in debug mode.
To complete the walkthrough, you must provide the following:
A machine meeting3 XML Web service, which was the name given to the XML Web service created in Walkthrough: Creating an XML Web Service Using C++ and the CLR.
To access a different implementation of the temperature conversion XML Web service, simply substitute the appropriate names where the TempConvert3 name appears throughout this walkthrough.
On the File menu, point to New, and then click Project to open the New Project dialog box.
Expand the Visual C++ node, and select CLR.
Click the CLR Console Application icon.
Change the name of the project to TempConvertClient3.
Click OK to create the project. How to: Generate an XML Web Service Proxy.
From Solution Explorer, select the TempConvert3Client project node. How to: Add and Remove.
In Solution Explorer, locate TempConvertClient3.cpp in the Source Files folder and open this file for editing.
Replace the contents of this file with the following:
#include "stdafx.h"
#include "WebService.h"
using namespace System;
int main(void)
{
while (true)
{
try
{
ConvertSvc::TempConvert3Class^ proxy =
gcnew ConvertSvc::TempConvert3Class();: {0}", e->Message);
break;
}
}
return 0;
}
The name of the XML Web service class generated when adding a Web reference may differ from the one shown above as TempConvert3Class.
Save the solution.
On the Build menu, click Build Solution.
When you run the application, it accesses the XML Web service and displays the Celsius equivalent of the entered Fahrenheit temperature.
Visual Studio offers several methods to build and run an application from within the IDE, such as:
Start Debugging
Start without Debugging
As a Visual Studio project, this application has separate configurations for Release and Debug versions. Because you created this project using the CLR Console Application project template, Visual Studio automatically created these configurations and set the appropriate default options and other settings. For more information, see How to: Set Debug and Release Configurations.
In this walkthrough, you will place a breakpoint in the application and use the Start Debugging method.
Prior to debugging, verify your debug settings. For more information, see Debugging Preparation: Console Projects.
In the Code Editor, place the cursor on the line of code that calls the proxy function:
double dCelsius = proxy->ConvertTemperature(dFahrenheit);
Press F9 to place a breakpoint on this line of code.
— Or —
Click to the left of that line of code in the indicator margin.
For more information, see How to: Debug Code in the Editor.
On the Debug menu, click Start Debugging.
This command instructs Visual Studio to run the application in the debugger. Visual Studio builds the project and launches the application.
In the console window, type the number 212 and press Enter.
When processing reaches the breakpoint, processing stops. The Visual Studio debugger highlights the line containing the breakpoint and while halted, you can perform a variety of tasks. For more information, see Debugger Roadmap and Viewing Data in the Debugger. Delete All Breakpoints. | http://msdn.microsoft.com/en-us/library/14hykb68(VS.80).aspx | crawl-002 | refinedweb | 548 | 57.77 |
Input for Agenda Planning for the Technical Architecture Group
This is the view of actions grouped by issues ordered by due dates; see also the view of issues groups by products.
Open issues with open and pending review action items
- Grouped by issues
- Mechanisms for obtaining information about the meaning of a given URI (ISSUE-57 HttpRedirections-57)
ACTION-201 on Jonathan Rees: Report on status of AWWSW discussions - due 2012-10-02 - open
- "appear[s] to definitely require discussion" per Noah's ftf planning msg Connolly, 19 May 2010, 18:18:43
ACTION-749 on Jonathan Rees: With help from HT and JT to draft the TAG's response to the ISSUE-57 change proposal process initiated on 29 February 2012, based on and F2F minutes of 8 October 2012. - due 2013-07-01 - open
- URIs, URNs, "location independent" naming systems and associated registries for naming on the Web (ISSUE-50 URNsAndRegistries-50)
ACTION-478 on Jonathan Rees: Prepare a second draft of a finding on persistence of references, to be based on decision tree from Oct. 2010 F2F - due 2012-10-06 - open
ACTION-33 on Henry Thompson: revise naming challenges story in response to Dec 2008 F2F discussion - due 2013-01-01 - open
ACTION-121 on Henry Thompson: HT to draft TAG input to review of draft ARK RFC - due 2013-01-01 - open
- What should a "namespace document" look like? (ISSUE-8 namespaceDocument-8)
ACTION-23 on Henry Thompson: track progress of #int bug 1974 in the XML Schema namespace document in the XML Schema WG - due 2012-11-06 - open
- Metadata Architecture for the Web (ISSUE-63 metadataArchitecture-63)
ACTION-282 on Jonathan Rees: Draft a finding on metadata architecture. - due 2013-04-01 - open
- See discussion of 16 September 2010 regarding scope of this action.Noah Mendelsohn, 16 Sep 2010, 17:35:01
- Weekly Teleconference (ISSUE-64 weekly)
ACTION-213 on Noah Mendelsohn: Prepare 18 April 2013 Telcon Agenda - due 2013-04-16 - pending review
Action Items Pending Review
There are 6 pending review actions.
Overdue action items
There are 96 overdue actions.
Action items due next week
There are 0 upcoming actions.
Issues discussed over the last week
There are 0 recently discussed issues listed in the system.
Raised Issues
There is 1 raised issue listed in the system.
Pending Review Issues
The following issues are candidate for closing.
There are 8 pending review issues listed in the system. | https://www.w3.org/2001/tag/group/track/agenda | CC-MAIN-2018-47 | refinedweb | 406 | 51.52 |
Substratum provides a baseline configuration for your Node.js projects, primarily via a set of common gulp tasks.
To get started:
npm install substratum --save
and create a
gulpfile.js:
var gulp = ;gulp;
Substratum will assume a standard project layout, with sources under
src/,
tests under
test/, etc.
You can override these values (and many more), by passing options via the
second argument to
configureTasks.
See
Context for a full reference.
Substratum defines many gulp tasks for you in a cascade. Tasks are grouped into
namespaces, and a namespace tasks will run all tasks under them. I.e.
gulp test will run all tasks that begin with
test:.
For a full reference, just run
gulp -T.
watch
This should be your bread and butter. Leave
gulp watch running in the
background, and it will continually run tests against any file that changes as
you edit it. Any issues will trigger a notification for you.
test:style:jshint
Runs jshint configured for a modern world against your project's sources.
test:style:jscs
Runs jshint configured for a modern world against your project's sources. | https://www.npmjs.com/package/substratum | CC-MAIN-2017-22 | refinedweb | 184 | 76.52 |
This program is supposed to give me the average, largest, smallest, sum, and number of entries from a group of integers.
The results I'm getting are impossibly wrong. I suspect that the "while (cin >> x) " has something to do with it, but I may be wrong. What I'm trying to do there is say "if you're still getting input, keep at it".
The other thought I had is that it is taking end of file (ctrl+Z) as a value. Anyway, this is the code (I know it's not pretty, I'm new at this!):
And this is what I get for results, irregardless of the entries:And this is what I get for results, irregardless of the entries:Code:// entering a list of integers and finding the number of entries, the smallest/largest entry, // the average of the entries, and their sum. (that's the theory, anyway : ) ) #include <iostream> #include <iomanip> #include <cstdlib> using namespace std; int get_data (int); int count_integers (int,int); int sum_int (int , int); int large_num (int, int); int small_num (int, int); int avg_total (int ,int , int, int); int results (int ,int, int, int, int); int main () { int x; int count; int sum; int largest; int smallest; int avg; get_data (x); count_integers (x,count); sum_int (sum, x); large_num (x, largest); small_num (x, smallest); avg_total (x, count, sum, avg); results (count, sum, avg, largest, smallest); system ("pause"); return 0; } int get_data (int x) //getting input from keyboard { cout<<"Please enter a list of integers,([Ctrl]+Z to end):"<<endl; cin>>x; return x; } int count_integers (int x, int count) // counting the # of entries { while (cin>>x) { count++; } return count; } int sum_int (int sum, int x) // getting the sum of the entries { while (cin>>x) { sum = sum + x; } return sum; } int large_num (int x, int largest) //finding the largest entry { while (cin>>x) { if (x >= largest) { largest = x; } } return largest; } int small_num (int x, int smallest) //finding the smallest entry { while (cin>>x) { if (x<=smallest) { smallest = x; } } return smallest; } int avg_total (int x,int count, int sum,int avg) // finding the average of the ehtries { while (cin>>x) { avg = count/sum; } return avg; } int results (int count, int sum, int avg,int smallest, int largest) //print results { cout<<"You entered "<<count<<" integers."<<endl; cout<<"the sum of the integers is "<<sum<<"."<<endl; cout<<"The average of the integers is "<<avg<<"."<<endl; cout<<"The largest integer entered was "<<largest<<"."<<endl; cout<<"The smallest integer entered was "<<smallest<<"."<<endl; }
Any ideas? I know, it's something glaringly obvious. I think I just need that one hint that'll make me say "Oooohh, ok.."Any ideas? I know, it's something glaringly obvious. I think I just need that one hint that'll make me say "Oooohh, ok.."Please enter a list of integers,([Ctrl]+Z to end):
12
2
22
55
^Z
You entered 4370432 integers.
the sum of the integers is 4198592.
The average of the integers is 2293600.
The largest integer entered was 2009196833.
The smallest integer entered was 2293664.
Press any key to continue . . .
If there is a good tutorial or page that might help to clarify things, please clue me in. I am still woefully lacking in decent reference texts, so for now I'm using the web. | https://cboard.cprogramming.com/cplusplus-programming/52578-strange-numbers-while-loops-questionable.html | CC-MAIN-2017-51 | refinedweb | 547 | 68.1 |
Pre-render routes with react-snap
Not server-side rendering but still want to speed up the performance of your React site? Try pre-rendering!
react-snap is a third-party
library that pre-renders pages on your site into static HTML files. This can
improve
First Paint
times in your application.
Here's a comparison of the same application with and without pre-rendering loaded on a simulated 3G connection and mobile device:
react-snap is not the only library that can pre-render static HTML content
for your React application.
react-snapshot
is another alternative.
Why is this useful?
The main performance problem with large single-page applications is that the user needs to wait for the JavaScript bundle(s) that make up the site to finish downloading before they can see any real content. The larger the bundles, the longer the user will have to wait.
To solve this, many developers take the approach of rendering the application on the server instead of only booting it up on the browser. With each page/route transition, the complete HTML is generated on the server and sent to the browser, which reduces First Paint times but comes at the cost of a slower Time to First Byte.
Pre-rendering is a separate technique that is less complex than server rendering, but also provides a way to improve First Paint times in your application. A headless browser, or a browser without a user interface, is used to generate static HTML files of every route during build time. These files can then be shipped along with the JavaScript bundles that are needed for the application.
react-snap
react-snap uses Puppeteer to
create pre-rendered HTML files of different routes in your application. To
begin, install it as a development dependency:
npm install --save-dev react-snap
Then add a
postbuild script in your
package.json:
"scripts": {
//...
"postbuild": "react-snap"
}
This would automatically run the
react-snap command everytime a new build of
the applications made (
npm build).
npm supports pre and post commands for main and arbitrary scripts which
will always run directly before or after the original script respectively. You
can learn more in the
npm documentation.
The last thing you will need to do is change how the application is booted.
Change the
src/index.js file to the following:
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
ReactDOM.render(<App />, document.getElementById('root'));
Instead of only using
ReactDOM.render to render the root React element
directly into the DOM, this checks to see if any child nodes are already present
to determine whether HTML contents were pre-rendered (or rendered on the
server). If that's the case,
ReactDOM.hydrate is used instead to attach event
listeners to the already created HTML instead of creating it anew.
Building the application will now generate static HTML files as payloads for each route that is crawled. You can take a look at what the HTML payload looks like by clicking the URL of the HTML request and then clicking the Previews tab within Chrome DevTools.
react-snap can be used for other frameworks than React! This includes Vue
and Preact. More instructions about this can be found in the
react-snap README.
Flash of unstyled content
Although static HTML is now rendered almost immediately, it still remains unstyled by default which may cause the issue of showing a "flash of unstyled content" (FOUC). This can be especially noticeable if you are using a CSS-in-JS library to generate selectors since the JavaScript bundle will have to finish executing before any styles can be applied.
To help prevent this, the critical CSS, or the minimum amount of CSS that is
needed for the initial page to render, can be inlined directly to the
<head>
of the HTML document.
react-snap uses another third-party library under the
hood,
minimalcss, to extract any
critical CSS for different routes. You can enable this by specifying the
following in your
package.json file:
"reactSnap": {
"inlineCss": true
}
Taking a look at the response preview in Chrome DevTools will now show the styled page with critical CSS inlined.
Caution:
The
inlineCSS option is still experimental. It is worth double-checking to
make sure styles are being applied correctly for your routes.
Conclusion
If you are not server-side rendering routes in your application, use
react-snap to pre-render static HTML to your users.
- Install it as a development dependency and begin with just the default settings.
- Use the experimental
inlineCssoption to inline critical CSS if it works for your site.
- If you are code-splitting on a component level within any routes, be careful to not pre-render a loading state to your users. The
react-snapREADME covers this in more. | https://web.dev/prerender-with-react-snap | CC-MAIN-2019-22 | refinedweb | 806 | 54.02 |
Remove unused code
npm makes adding code to your project a breeze. But are you really using all those extra bytes?
Registries like npm have transformed the JavaScript world for the better by allowing anyone to easily download and use over half a million public packages. But we often include libraries we're not fully utilizing. To fix this issue, analyze your bundle to detect unused code. Then remove unused and unneeded libraries.
Analyze your bundle
The simplest way to see the size of all network requests is to open the
Network panel in DevTools, check
Disable Cache, and reload the page.
The Coverage tab in DevTools will also tell you how much CSS and JS code in your application is unused.
By specifying a full Lighthouse configuration through its Node CLI, an "Unused JavaScript" audit can also be used to trace how much unused code is being shipped with your application.
If you happen to be using webpack as your bundler, Webpack Bundle Analyzer will help you investigate what makes up the bundle. Include the plugin in your webpack configurations file like any other plugin:
module.exports = {
//...
plugins: [
//...
new BundleAnalyzerPlugin()
]
}
Although webpack is commonly used to build single-page applications, other bundlers, such as Parcel and Rollup, also have visualization tools that you can use to analyze your bundle.
Reloading the application with this plugin included shows a zoomable treemap of your entire bundle.
Using this visualization allows you to inspect which parts of your bundle are larger than others, as well as get a better idea of all the libraries that you're importing. This can help identify if you are using any unused or unnecessary libraries.
Remove unused libraries
In the previous treemap image, there are quite a few packages within a single
@firebase domain. If your website only needs the firebase database component,
update the imports to fetch that library:
import firebase from 'firebase';
It is important to emphasize that this process is significantly more complex for larger applications.
For the mysterious looking package that you're quite sure is not being used anywhere, take a step back and see which of your top-level dependencies are using it. Try to find a way to only import the components that you need from it. If you aren't using a library, remove it. If the library isn't required for the initial page load, consider if it can be lazy loaded.
Try it! Remove unused code.
Remove unneeded libraries
Not all libraries can be easily broken down into parts and selectively imported. In these scenarios, consider if the library could be removed entirely. Building a custom solution or leveraging a lighter alternative should always be options worth considering. However, it is important to weigh the complexity and effort required for either of these efforts before removing a library entirely from an. | https://web.dev/remove-unused-code | CC-MAIN-2019-22 | refinedweb | 475 | 53.21 |
Python realization of LiveJournal (LJ) API.Checkout for more info
Project DescriptionRelease History Download Files
Feel free to make pull requests!
A python realization of LiveJournal (LJ) API
A full description of the protocol can be found at:
Installation
Just type (pip integration is work in progress):
pip install lj
You can also find Python LJ on Github
Usage example
from lj import lj as _lj lj = _lj.LJServer("Python-Blog3/1.0", "; i@daniil-r.ru") lj.login("yourusername", "yourpassword") lj.postevent("Awesome post", "Awesome subject", props={"taglist": "github,livejournal"})
Download Files
Download the file for your platform. If you're not sure which to choose, learn more about installing packages. | https://pypi.org/project/lj/ | CC-MAIN-2018-05 | refinedweb | 112 | 55.24 |
Hi,
I have created an application which uses OpenCV API for Hand Gesture Recognition.It recognizes the hand movement and the event is handled as per hand gestures.I wish to know whether it is feasible for Kinect Sensor to act as an alternative for Hand Gesture
Recognition in my project.Please note that my application is a windows desktop application which runs on WPF using C#.net.
There is no relation between my application with Xbox.I wish to know whether kinect is applicable only for Xbox apps/games or it can be applied to normal windows applications which uses windows forms or WPF?
View Complete Post
Hello,
I'm currently developing a small app in WPF that requires gesture recognition, so I ended up using the InkCanvas. Everything works just fine on my desktop and laptop (running windows 7) but the app must run in another computer (an Asus Eee Top running windows
XP). I've read that I had to install the Tablet PC SDK and the Tablet PC Recognition Pack, but I'm unable to install the Recognition pack because it complains about an unsuported OS: apparently it only suports XP up to Service pack 2, and I'm running SP3.
Are there any other alternatives?
Thanks
I'm working in a wpf app that is binding controls to a class that implements INotifyPropertyChanged. I'm trying to track when there are changes to the underlying object by setting a flag whenever a property is changed. To do so, I wired up an event handler
to the PropertyChanged event of the class like so:
_facilityLogic.PropertyChanged += new System.ComponentModel.PropertyChangedEventHandler(facilityLogic_PropertyChanged);
...
public void facilityLogic_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
SetIsChanged();
}
When a request is submitted and the response is recieved and before the page loads with the response, is there a way to control the user to press any key board buttons?
Hi all,
how to add a Event Handling In Share Point for particular document library or list.
actually i saw one article for restrict the deletion i tried that article,
i created one class library in that i added one class and two xml files(elements.xml and feature.xml).
Code are give Below.
class file
using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.SharePoint;
namespace EventHandlerExample1
{
public class CancelAnnouncementDeleteHandler : SPItemEventReceiver
{
public override void ItemDeleting(SPItemEventProperties properties)
{
string HandledMessage = ("Announcements can not be deleted from this list");
properties.ErrorMessage = HandledMessage;
properties.Cancel = true;
}
}
}
Elements.xml
<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="">
<ListTemplate
Name="announce"
Type="104"
BaseType="0"
OnQuickLaunch="TRUE"
SecurityBits="11"
Sequence="320"
DisplayName="$Resources:core,announceList;"
D
Is it possible to handle the same event in more than one client without using Remoting or WCF? In my test example I have 2 console apps and a class library all in the same solution. The event lives in a Singleton class in the class library and
both console apps have a reference to the dll and have handlers for the event. I have the 2 console apps set as multiple startup projects; however the event appears to only be firing to the one that is "active". If I could get confirmation on whether
what I'm trying is not possible (or whether I'm going about it the wrong way) it would be much appreciated.
Thanks,
-Dave)?
How do i handle 404 page not found?
Hall of Fame Twitter Terms of Service Privacy Policy Contact Us Archives Tell A Friend | http://www.dotnetspark.com/links/62744-hand-gesture-recognition-and-event-handling.aspx | CC-MAIN-2016-44 | refinedweb | 584 | 54.93 |
/* Utilities to execute a program in a subprocess (possibly linked by pipes with other subprocesses), and wait for it. OS/2 specialization. Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2003. */ #include "pex-common.h" #ifdef HAVE_UNISTD_H #include <unistd.h> #endif #ifdef HAVE_STDLIB_H #include <stdlib.h> #endif #ifdef HAVE_SYS_WAIT_H #include <sys/wait.h> #endif /* ??? Does OS2 have process.h? */ extern int spawnv (); extern int spawnvp (); int pexecute (program, argv, this_pname, temp_base, errmsg_fmt, errmsg_arg, flags) const char *program; char * const *argv; const char *this_pname; const char *temp_base; char **errmsg_fmt, **errmsg_arg; int flags; { int pid; if ((flags & PEXECUTE_ONE) != PEXECUTE_ONE) abort (); /* ??? Presumably 1 == _P_NOWAIT. */ pid = (flags & PEXECUTE_SEARCH ? spawnvp : spawnv) (1, program, argv); if (pid == -1) { *errmsg_fmt = install_error_msg; *errmsg_arg = program; return -1; } return pid; } int pwait (pid, status, flags) int pid; int *status; int flags; { /* ??? Here's an opportunity to canonicalize the values in STATUS. Needed? */ int pid = wait (status); return pid; } | http://opensource.apple.com//source/gcc_os_35/gcc_os_35-3506/libiberty/pex-os2.c | CC-MAIN-2016-44 | refinedweb | 148 | 59.7 |
Announcing Scala.js 0.5.0
We!
- Tutorial, for newcomers to Scala.js
- Upgrading from Scala.js 0.4.x
- Try Scala.js right in your browser with Scala.jsFiddle (currently using Scala.js 0.4.4)
New features in the 0.5.x series
Scala.js 0.5.0 introduces new features, improvements and bug fixes in many areas, ranging from compiler correctness to usability to emitted code size and speed.
Language changes
- Scala semantics for integer and character types (i.e., wrapping semantics)
Int,
Byte,
Short, and
Charnow behave the same way as on the JVM with respect to wrapping around their range, e.g.,
Intis truly a signed 32-bit integer.
- Exception: division by 0 is still unspecified.
Longcontinues to behave as a proper signed 64-bit integer, as it did for a long time
Floatstill behaves just like
Double, as it always did.
- Full details
- Improved interoperability with JavaScript
- Normal Scala primitive types can be used instead of
js.Number,
js.Boolean,
js.Stringand
js.Undefinedfor interoperability with JavaScript, because they are guaranteed to always be represented as primitive JavaScript values (
Charand
Longare still opaque to JavaScript, because they do not have a corresponding type in JavaScript). See the documentation on type correspondance for more details.
- Introduced the type
js.UndefOr[+A](API), which represents a value of type
Aor
undefined, and offers an
Option-like interface where
undefinedtakes the role of
None.
Improvements to the generated code
- Smaller. For a non-trivial application, we have
- ~1.3 MB for fast-optimized code (for iterative development)
- ~180 KB for full-optimized code (for production)
- Faster.
- Values of primitive types, excluding
Char, are not boxed anymore when assigned to
Anyor generic types
- We don't have precise benchmarks, but we received reports of noticeable improvements.
sbt plugin changes
preoptimizeJSand
optimizeJShave been renamed
fastOptJSand
fullOptJS, respectively, to better represent their intent.
fastOptJSis really fast (less than 1/2 second in addition to the normal
compileof scalac), and is now the recommended default for iterative development.
- Running and testing with Node.js and PhantomJS
- With
fastOptStage::runor
fastOptStage::test, run your code using a native-speed interpreter on the result of fast-optimization.
- By default, Node.js is used, unless the setting
requiresDOM := trueis set, in which case PhantomJS is used
- Replace
fastOptStageby
fullOptStageto execute the full-optimized version of your code.
- Node.js and/or PhantomJS must be installed separately for this to work. The basic
runand
teststill use Rhino and work out-of-the-box.
- Auto-discovery of objects extending the
js.JSApptrait (API)
- Can be run directly with the
runtask
- With
persistLauncher := true, sbt will emit a tiny JavaScript entry point that calls the
mainmethod.
- To support this the best we could, we have dropped auto-discovery of objects defining a
def main(args: Array[String])method.
- More information in the tutorial
Binary compatibility and dependency management
- Backward binary compatibility across minor releases
- Similarly to Scala, except it is only backward.
- For example, libraries compiled with Scala.js 0.5.0 will be usable with Scala.js 0.5.1, but not (necessarily) the other way around.
- The sbt plugin encodes the Scala.js binary version in artifact names in addition to the Scala binary version. For example, the artifacts for a library "foo" compiled with Scala 2.11.1 and Scala.js 0.5.0 will be named
foo_sjs0.5_2.11.
- To depend on the doubly-cross compiled version of a Scala.js library, use
%%%instead of
%%in your
libraryDependencies. For example,
"org.scala-lang.modules.scalajs" %%% "scalajs-dom" % "0.6"
- Managing your dependencies on JavaScript libraries
- In addition to depending on other Scala.js libraries, Scala.js now supports depending on JavaScript libraries through WebJars, that will be resolved automatically.
- You can ask the sbt plugin to package all your JavaScript dependencies in a single
.jsfile if you so wish, but this is not mandatory.
- See the tutorial for more information.
Command line interface (CLI)
- Following a request by some of our users, we added a stand-alone distribution that allows to use Scala.js without sbt (but with Scala).
scalajscis a front-end to
scalacsetting up correctly the Scala.js compiler plugin and library on the classpath
scalajsldperforms linking and optimizations (the equivalent of
fastOptJSand
fullOptJSin sbt)
scalajspprints the content of
.sjsirfiles (the intermediate files produced by
scalajscand consumed by
scalajsld) in a human-readable form.
Upgrading from Scala.js 0.4.x
Source code written for Scala.js 0.4.x should mostly compile without change
for Scala.js 0.5.0. Due to the ability to type JavaScript APIs more precisely,
in particular using
scala.Ints and
js.UndefOr, it is possible that code
interacting with, for example, the statically typed DOM API will need some
minor changes.
However, build files and HTML files surrounding Scala.js source code will need important adaptations. The easiest is to reproduce the changes of this commit of the bootstrapping skeleton.
You may also wish to take advantage of the new
persistLauncher setting to
automatically generate a launcher script based on the discovered
JSApp, in
which case you can also apply the changes of
this other commit.
Known issues
This release suffers from a few known issues, which we decided to postpone to a later (binary-compatible) release. The most important ones are:
- #727 - Source mapping does not work with our Rhino interpreter (with
runand
test)
- Prefer
fastOptStage::runand
fastOptStage::testto run with Node.js: it is faster and you will get stack traces from your
.scalasource files.
- #608 - Ordering issues with the test reporter, which can mix results of tests ran in parallel.
- When a test fails, consider using
fastOptStage::testQuickor
fastOptStage::testOnlyto rerun only the failing test, which will mitigate this issue.
- #706 - JS libraries that act "too" smartly in Node.js.
- Work around: force usage of PhantomJS instead of Node.js, on which this issue does not seem to manifest.
You can find the complete list of known issues (and report new issues) on GitHub. | http://www.scala-js.org/news/2014/06/13/announcing-scalajs-0.5.0/ | CC-MAIN-2015-18 | refinedweb | 1,003 | 50.94 |
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