53 kB

	from fontTools.config import OPTIONS
	from fontTools.misc.textTools import Tag, bytesjoin
	from .DefaultTable import DefaultTable
	from enum import IntEnum
	import sys
	import array
	import struct
	import logging
	from functools import lru_cache
	from typing import Iterator, NamedTuple, Optional, Tuple

	log = logging.getLogger(__name__)

	have_uharfbuzz = False
	try:
	import uharfbuzz as hb

	have_uharfbuzz = True
	except ImportError:
	pass

	USE_HARFBUZZ_REPACKER = OPTIONS[f"{__name__}:USE_HARFBUZZ_REPACKER"]


	class OverflowErrorRecord(object):
	def __init__(self, overflowTuple):
	self.tableType = overflowTuple[0]
	self.LookupListIndex = overflowTuple[1]
	self.SubTableIndex = overflowTuple[2]
	self.itemName = overflowTuple[3]
	self.itemIndex = overflowTuple[4]

	def __repr__(self):
	return str(
	(
	self.tableType,
	"LookupIndex:",
	self.LookupListIndex,
	"SubTableIndex:",
	self.SubTableIndex,
	"ItemName:",
	self.itemName,
	"ItemIndex:",
	self.itemIndex,
	)
	)


	class OTLOffsetOverflowError(Exception):
	def __init__(self, overflowErrorRecord):
	self.value = overflowErrorRecord

	def __str__(self):
	return repr(self.value)


	class RepackerState(IntEnum):
	# Repacking control flow is implemnted using a state machine. The state machine table:
	#
	# State \| Packing Success \| Packing Failed \| Exception Raised \|
	# ------------+-----------------+----------------+------------------+
	# PURE_FT \| Return result \| PURE_FT \| Return failure \|
	# HB_FT \| Return result \| HB_FT \| FT_FALLBACK \|
	# FT_FALLBACK \| HB_FT \| FT_FALLBACK \| Return failure \|

	# Pack only with fontTools, don't allow sharing between extensions.
	PURE_FT = 1

	# Attempt to pack with harfbuzz (allowing sharing between extensions)
	# use fontTools to attempt overflow resolution.
	HB_FT = 2

	# Fallback if HB/FT packing gets stuck. Pack only with fontTools, don't allow sharing between
	# extensions.
	FT_FALLBACK = 3


	class BaseTTXConverter(DefaultTable):
	"""Generic base class for TTX table converters. It functions as an
	adapter between the TTX (ttLib actually) table model and the model
	we use for OpenType tables, which is necessarily subtly different.
	"""

	def decompile(self, data, font):
	"""Create an object from the binary data. Called automatically on access."""
	from . import otTables

	reader = OTTableReader(data, tableTag=self.tableTag)
	tableClass = getattr(otTables, self.tableTag)
	self.table = tableClass()
	self.table.decompile(reader, font)

	def compile(self, font):
	"""Compiles the table into binary. Called automatically on save."""

	# General outline:
	# Create a top-level OTTableWriter for the GPOS/GSUB table.
	# Call the compile method for the the table
	# for each 'converter' record in the table converter list
	# call converter's write method for each item in the value.
	# - For simple items, the write method adds a string to the
	# writer's self.items list.
	# - For Struct/Table/Subtable items, it add first adds new writer to the
	# to the writer's self.items, then calls the item's compile method.
	# This creates a tree of writers, rooted at the GUSB/GPOS writer, with
	# each writer representing a table, and the writer.items list containing
	# the child data strings and writers.
	# call the getAllData method
	# call _doneWriting, which removes duplicates
	# call _gatherTables. This traverses the tables, adding unique occurences to a flat list of tables
	# Traverse the flat list of tables, calling getDataLength on each to update their position
	# Traverse the flat list of tables again, calling getData each get the data in the table, now that
	# pos's and offset are known.

	# If a lookup subtable overflows an offset, we have to start all over.
	overflowRecord = None
	# this is 3-state option: default (None) means automatically use hb.repack or
	# silently fall back if it fails; True, use it and raise error if not possible
	# or it errors out; False, don't use it, even if you can.
	use_hb_repack = font.cfg[USE_HARFBUZZ_REPACKER]
	if self.tableTag in ("GSUB", "GPOS"):
	if use_hb_repack is False:
	log.debug(
	"hb.repack disabled, compiling '%s' with pure-python serializer",
	self.tableTag,
	)
	elif not have_uharfbuzz:
	if use_hb_repack is True:
	raise ImportError("No module named 'uharfbuzz'")
	else:
	assert use_hb_repack is None
	log.debug(
	"uharfbuzz not found, compiling '%s' with pure-python serializer",
	self.tableTag,
	)

	if (
	use_hb_repack in (None, True)
	and have_uharfbuzz
	and self.tableTag in ("GSUB", "GPOS")
	):
	state = RepackerState.HB_FT
	else:
	state = RepackerState.PURE_FT

	hb_first_error_logged = False
	lastOverflowRecord = None
	while True:
	try:
	writer = OTTableWriter(tableTag=self.tableTag)
	self.table.compile(writer, font)
	if state == RepackerState.HB_FT:
	return self.tryPackingHarfbuzz(writer, hb_first_error_logged)
	elif state == RepackerState.PURE_FT:
	return self.tryPackingFontTools(writer)
	elif state == RepackerState.FT_FALLBACK:
	# Run packing with FontTools only, but don't return the result as it will
	# not be optimally packed. Once a successful packing has been found, state is
	# changed back to harfbuzz packing to produce the final, optimal, packing.
	self.tryPackingFontTools(writer)
	log.debug(
	"Re-enabling sharing between extensions and switching back to "
	"harfbuzz+fontTools packing."
	)
	state = RepackerState.HB_FT

	except OTLOffsetOverflowError as e:
	hb_first_error_logged = True
	ok = self.tryResolveOverflow(font, e, lastOverflowRecord)
	lastOverflowRecord = e.value

	if ok:
	continue

	if state is RepackerState.HB_FT:
	log.debug(
	"Harfbuzz packing out of resolutions, disabling sharing between extensions and "
	"switching to fontTools only packing."
	)
	state = RepackerState.FT_FALLBACK
	else:
	raise

	def tryPackingHarfbuzz(self, writer, hb_first_error_logged):
	try:
	log.debug("serializing '%s' with hb.repack", self.tableTag)
	return writer.getAllDataUsingHarfbuzz(self.tableTag)
	except (ValueError, MemoryError, hb.RepackerError) as e:
	# Only log hb repacker errors the first time they occur in
	# the offset-overflow resolution loop, they are just noisy.
	# Maybe we can revisit this if/when uharfbuzz actually gives
	# us more info as to why hb.repack failed...
	if not hb_first_error_logged:
	error_msg = f"{type(e).__name__}"
	if str(e) != "":
	error_msg += f": {e}"
	log.warning(
	"hb.repack failed to serialize '%s', attempting fonttools resolutions "
	"; the error message was: %s",
	self.tableTag,
	error_msg,
	)
	hb_first_error_logged = True
	return writer.getAllData(remove_duplicate=False)

	def tryPackingFontTools(self, writer):
	return writer.getAllData()

	def tryResolveOverflow(self, font, e, lastOverflowRecord):
	ok = 0
	if lastOverflowRecord == e.value:
	# Oh well...
	return ok

	overflowRecord = e.value
	log.info("Attempting to fix OTLOffsetOverflowError %s", e)

	if overflowRecord.itemName is None:
	from .otTables import fixLookupOverFlows

	ok = fixLookupOverFlows(font, overflowRecord)
	else:
	from .otTables import fixSubTableOverFlows

	ok = fixSubTableOverFlows(font, overflowRecord)

	if ok:
	return ok

	# Try upgrading lookup to Extension and hope
	# that cross-lookup sharing not happening would
	# fix overflow...
	from .otTables import fixLookupOverFlows

	return fixLookupOverFlows(font, overflowRecord)

	def toXML(self, writer, font):
	self.table.toXML2(writer, font)

	def fromXML(self, name, attrs, content, font):
	from . import otTables

	if not hasattr(self, "table"):
	tableClass = getattr(otTables, self.tableTag)
	self.table = tableClass()
	self.table.fromXML(name, attrs, content, font)
	self.table.populateDefaults()

	def ensureDecompiled(self, recurse=True):
	self.table.ensureDecompiled(recurse=recurse)


	# https://github.com/fonttools/fonttools/pull/2285#issuecomment-834652928
	assert len(struct.pack("i", 0)) == 4
	assert array.array("i").itemsize == 4, "Oops, file a bug against fonttools."


	class OTTableReader(object):
	"""Helper class to retrieve data from an OpenType table."""

	__slots__ = ("data", "offset", "pos", "localState", "tableTag")

	def __init__(self, data, localState=None, offset=0, tableTag=None):
	self.data = data
	self.offset = offset
	self.pos = offset
	self.localState = localState
	self.tableTag = tableTag

	def advance(self, count):
	self.pos += count

	def seek(self, pos):
	self.pos = pos

	def copy(self):
	other = self.__class__(self.data, self.localState, self.offset, self.tableTag)
	other.pos = self.pos
	return other

	def getSubReader(self, offset):
	offset = self.offset + offset
	return self.__class__(self.data, self.localState, offset, self.tableTag)

	def readValue(self, typecode, staticSize):
	pos = self.pos
	newpos = pos + staticSize
	(value,) = struct.unpack(f">{typecode}", self.data[pos:newpos])
	self.pos = newpos
	return value

	def readArray(self, typecode, staticSize, count):
	pos = self.pos
	newpos = pos + count * staticSize
	value = array.array(typecode, self.data[pos:newpos])
	if sys.byteorder != "big":
	value.byteswap()
	self.pos = newpos
	return value.tolist()

	def readInt8(self):
	return self.readValue("b", staticSize=1)

	def readInt8Array(self, count):
	return self.readArray("b", staticSize=1, count=count)

	def readShort(self):
	return self.readValue("h", staticSize=2)

	def readShortArray(self, count):
	return self.readArray("h", staticSize=2, count=count)

	def readLong(self):
	return self.readValue("i", staticSize=4)

	def readLongArray(self, count):
	return self.readArray("i", staticSize=4, count=count)

	def readUInt8(self):
	return self.readValue("B", staticSize=1)

	def readUInt8Array(self, count):
	return self.readArray("B", staticSize=1, count=count)

	def readUShort(self):
	return self.readValue("H", staticSize=2)

	def readUShortArray(self, count):
	return self.readArray("H", staticSize=2, count=count)

	def readULong(self):
	return self.readValue("I", staticSize=4)

	def readULongArray(self, count):
	return self.readArray("I", staticSize=4, count=count)

	def readUInt24(self):
	pos = self.pos
	newpos = pos + 3
	(value,) = struct.unpack(">l", b"\0" + self.data[pos:newpos])
	self.pos = newpos
	return value

	def readUInt24Array(self, count):
	return [self.readUInt24() for _ in range(count)]

	def readTag(self):
	pos = self.pos
	newpos = pos + 4
	value = Tag(self.data[pos:newpos])
	assert len(value) == 4, value
	self.pos = newpos
	return value

	def readData(self, count):
	pos = self.pos
	newpos = pos + count
	value = self.data[pos:newpos]
	self.pos = newpos
	return value

	def __setitem__(self, name, value):
	state = self.localState.copy() if self.localState else dict()
	state[name] = value
	self.localState = state

	def __getitem__(self, name):
	return self.localState and self.localState[name]

	def __contains__(self, name):
	return self.localState and name in self.localState


	class OffsetToWriter(object):
	def __init__(self, subWriter, offsetSize):
	self.subWriter = subWriter
	self.offsetSize = offsetSize

	def __eq__(self, other):
	if type(self) != type(other):
	return NotImplemented
	return self.subWriter == other.subWriter and self.offsetSize == other.offsetSize

	def __hash__(self):
	# only works after self._doneWriting() has been called
	return hash((self.subWriter, self.offsetSize))


	class OTTableWriter(object):
	"""Helper class to gather and assemble data for OpenType tables."""

	def __init__(self, localState=None, tableTag=None):
	self.items = []
	self.pos = None
	self.localState = localState
	self.tableTag = tableTag
	self.parent = None
	self.name = "<none>"

	def __setitem__(self, name, value):
	state = self.localState.copy() if self.localState else dict()
	state[name] = value
	self.localState = state

	def __getitem__(self, name):
	return self.localState[name]

	def __delitem__(self, name):
	del self.localState[name]

	# assembler interface

	def getDataLength(self):
	"""Return the length of this table in bytes, without subtables."""
	l = 0
	for item in self.items:
	if hasattr(item, "getCountData"):
	l += item.size
	elif hasattr(item, "subWriter"):
	l += item.offsetSize
	else:
	l = l + len(item)
	return l

	def getData(self):
	"""Assemble the data for this writer/table, without subtables."""
	items = list(self.items) # make a shallow copy
	pos = self.pos
	numItems = len(items)
	for i in range(numItems):
	item = items[i]

	if hasattr(item, "subWriter"):
	if item.offsetSize == 4:
	items[i] = packULong(item.subWriter.pos - pos)
	elif item.offsetSize == 2:
	try:
	items[i] = packUShort(item.subWriter.pos - pos)
	except struct.error:
	# provide data to fix overflow problem.
	overflowErrorRecord = self.getOverflowErrorRecord(
	item.subWriter
	)

	raise OTLOffsetOverflowError(overflowErrorRecord)
	elif item.offsetSize == 3:
	items[i] = packUInt24(item.subWriter.pos - pos)
	else:
	raise ValueError(item.offsetSize)

	return bytesjoin(items)

	def getDataForHarfbuzz(self):
	"""Assemble the data for this writer/table with all offset field set to 0"""
	items = list(self.items)
	packFuncs = {2: packUShort, 3: packUInt24, 4: packULong}
	for i, item in enumerate(items):
	if hasattr(item, "subWriter"):
	# Offset value is not needed in harfbuzz repacker, so setting offset to 0 to avoid overflow here
	if item.offsetSize in packFuncs:
	items[i] = packFuncs[item.offsetSize](0)
	else:
	raise ValueError(item.offsetSize)

	return bytesjoin(items)

	def __hash__(self):
	# only works after self._doneWriting() has been called
	return hash(self.items)

	def __ne__(self, other):
	result = self.__eq__(other)
	return result if result is NotImplemented else not result

	def __eq__(self, other):
	if type(self) != type(other):
	return NotImplemented
	return self.items == other.items

	def _doneWriting(self, internedTables, shareExtension=False):
	# Convert CountData references to data string items
	# collapse duplicate table references to a unique entry
	# "tables" are OTTableWriter objects.

	# For Extension Lookup types, we can
	# eliminate duplicates only within the tree under the Extension Lookup,
	# as offsets may exceed 64K even between Extension LookupTable subtables.
	isExtension = hasattr(self, "Extension")

	# Certain versions of Uniscribe reject the font if the GSUB/GPOS top-level
	# arrays (ScriptList, FeatureList, LookupList) point to the same, possibly
	# empty, array. So, we don't share those.
	# See: https://github.com/fonttools/fonttools/issues/518
	dontShare = hasattr(self, "DontShare")

	if isExtension and not shareExtension:
	internedTables = {}

	items = self.items
	for i, item in enumerate(items):
	if hasattr(item, "getCountData"):
	items[i] = item.getCountData()
	elif hasattr(item, "subWriter"):
	item.subWriter._doneWriting(
	internedTables, shareExtension=shareExtension
	)
	# At this point, all subwriters are hashable based on their items.
	# (See hash and comparison magic methods above.) So the ``setdefault``
	# call here will return the first writer object we've seen with
	# equal content, or store it in the dictionary if it's not been
	# seen yet. We therefore replace the subwriter object with an equivalent
	# object, which deduplicates the tree.
	if not dontShare:
	items[i].subWriter = internedTables.setdefault(
	item.subWriter, item.subWriter
	)
	self.items = tuple(items)

	def _gatherTables(self, tables, extTables, done):
	# Convert table references in self.items tree to a flat
	# list of tables in depth-first traversal order.
	# "tables" are OTTableWriter objects.
	# We do the traversal in reverse order at each level, in order to
	# resolve duplicate references to be the last reference in the list of tables.
	# For extension lookups, duplicate references can be merged only within the
	# writer tree under the extension lookup.

	done[id(self)] = True

	numItems = len(self.items)
	iRange = list(range(numItems))
	iRange.reverse()

	isExtension = hasattr(self, "Extension")

	selfTables = tables

	if isExtension:
	assert (
	extTables is not None
	), "Program or XML editing error. Extension subtables cannot contain extensions subtables"
	tables, extTables, done = extTables, None, {}

	# add Coverage table if it is sorted last.
	sortCoverageLast = False
	if hasattr(self, "sortCoverageLast"):
	# Find coverage table
	for i in range(numItems):
	item = self.items[i]
	if (
	hasattr(item, "subWriter")
	and getattr(item.subWriter, "name", None) == "Coverage"
	):
	sortCoverageLast = True
	break
	if id(item.subWriter) not in done:
	item.subWriter._gatherTables(tables, extTables, done)
	else:
	# We're a new parent of item
	pass

	for i in iRange:
	item = self.items[i]
	if not hasattr(item, "subWriter"):
	continue

	if (
	sortCoverageLast
	and (i == 1)
	and getattr(item.subWriter, "name", None) == "Coverage"
	):
	# we've already 'gathered' it above
	continue

	if id(item.subWriter) not in done:
	item.subWriter._gatherTables(tables, extTables, done)
	else:
	# Item is already written out by other parent
	pass

	selfTables.append(self)

	def _gatherGraphForHarfbuzz(self, tables, obj_list, done, objidx, virtual_edges):
	real_links = []
	virtual_links = []
	item_idx = objidx

	# Merge virtual_links from parent
	for idx in virtual_edges:
	virtual_links.append((0, 0, idx))

	sortCoverageLast = False
	coverage_idx = 0
	if hasattr(self, "sortCoverageLast"):
	# Find coverage table
	for i, item in enumerate(self.items):
	if getattr(item, "name", None) == "Coverage":
	sortCoverageLast = True
	if id(item) not in done:
	coverage_idx = item_idx = item._gatherGraphForHarfbuzz(
	tables, obj_list, done, item_idx, virtual_edges
	)
	else:
	coverage_idx = done[id(item)]
	virtual_edges.append(coverage_idx)
	break

	child_idx = 0
	offset_pos = 0
	for i, item in enumerate(self.items):
	if hasattr(item, "subWriter"):
	pos = offset_pos
	elif hasattr(item, "getCountData"):
	offset_pos += item.size
	continue
	else:
	offset_pos = offset_pos + len(item)
	continue

	if id(item.subWriter) not in done:
	child_idx = item_idx = item.subWriter._gatherGraphForHarfbuzz(
	tables, obj_list, done, item_idx, virtual_edges
	)
	else:
	child_idx = done[id(item.subWriter)]

	real_edge = (pos, item.offsetSize, child_idx)
	real_links.append(real_edge)
	offset_pos += item.offsetSize

	tables.append(self)
	obj_list.append((real_links, virtual_links))
	item_idx += 1
	done[id(self)] = item_idx
	if sortCoverageLast:
	virtual_edges.pop()

	return item_idx

	def getAllDataUsingHarfbuzz(self, tableTag):
	"""The Whole table is represented as a Graph.
	Assemble graph data and call Harfbuzz repacker to pack the table.
	Harfbuzz repacker is faster and retain as much sub-table sharing as possible, see also:
	https://github.com/harfbuzz/harfbuzz/blob/main/docs/repacker.md
	The input format for hb.repack() method is explained here:
	https://github.com/harfbuzz/uharfbuzz/blob/main/src/uharfbuzz/_harfbuzz.pyx#L1149
	"""
	internedTables = {}
	self._doneWriting(internedTables, shareExtension=True)
	tables = []
	obj_list = []
	done = {}
	objidx = 0
	virtual_edges = []
	self._gatherGraphForHarfbuzz(tables, obj_list, done, objidx, virtual_edges)
	# Gather all data in two passes: the absolute positions of all
	# subtable are needed before the actual data can be assembled.
	pos = 0
	for table in tables:
	table.pos = pos
	pos = pos + table.getDataLength()

	data = []
	for table in tables:
	tableData = table.getDataForHarfbuzz()
	data.append(tableData)

	return hb.serialize_with_tag(str(tableTag), data, obj_list)

	def getAllData(self, remove_duplicate=True):
	"""Assemble all data, including all subtables."""
	if remove_duplicate:
	internedTables = {}
	self._doneWriting(internedTables)
	tables = []
	extTables = []
	done = {}
	self._gatherTables(tables, extTables, done)
	tables.reverse()
	extTables.reverse()
	# Gather all data in two passes: the absolute positions of all
	# subtable are needed before the actual data can be assembled.
	pos = 0
	for table in tables:
	table.pos = pos
	pos = pos + table.getDataLength()

	for table in extTables:
	table.pos = pos
	pos = pos + table.getDataLength()

	data = []
	for table in tables:
	tableData = table.getData()
	data.append(tableData)

	for table in extTables:
	tableData = table.getData()
	data.append(tableData)

	return bytesjoin(data)

	# interface for gathering data, as used by table.compile()

	def getSubWriter(self):
	subwriter = self.__class__(self.localState, self.tableTag)
	subwriter.parent = (
	self # because some subtables have idential values, we discard
	)
	# the duplicates under the getAllData method. Hence some
	# subtable writers can have more than one parent writer.
	# But we just care about first one right now.
	return subwriter

	def writeValue(self, typecode, value):
	self.items.append(struct.pack(f">{typecode}", value))

	def writeArray(self, typecode, values):
	a = array.array(typecode, values)
	if sys.byteorder != "big":
	a.byteswap()
	self.items.append(a.tobytes())

	def writeInt8(self, value):
	assert -128 <= value < 128, value
	self.items.append(struct.pack(">b", value))

	def writeInt8Array(self, values):
	self.writeArray("b", values)

	def writeShort(self, value):
	assert -32768 <= value < 32768, value
	self.items.append(struct.pack(">h", value))

	def writeShortArray(self, values):
	self.writeArray("h", values)

	def writeLong(self, value):
	self.items.append(struct.pack(">i", value))

	def writeLongArray(self, values):
	self.writeArray("i", values)

	def writeUInt8(self, value):
	assert 0 <= value < 256, value
	self.items.append(struct.pack(">B", value))

	def writeUInt8Array(self, values):
	self.writeArray("B", values)

	def writeUShort(self, value):
	assert 0 <= value < 0x10000, value
	self.items.append(struct.pack(">H", value))

	def writeUShortArray(self, values):
	self.writeArray("H", values)

	def writeULong(self, value):
	self.items.append(struct.pack(">I", value))

	def writeULongArray(self, values):
	self.writeArray("I", values)

	def writeUInt24(self, value):
	assert 0 <= value < 0x1000000, value
	b = struct.pack(">L", value)
	self.items.append(b[1:])

	def writeUInt24Array(self, values):
	for value in values:
	self.writeUInt24(value)

	def writeTag(self, tag):
	tag = Tag(tag).tobytes()
	assert len(tag) == 4, tag
	self.items.append(tag)

	def writeSubTable(self, subWriter, offsetSize):
	self.items.append(OffsetToWriter(subWriter, offsetSize))

	def writeCountReference(self, table, name, size=2, value=None):
	ref = CountReference(table, name, size=size, value=value)
	self.items.append(ref)
	return ref

	def writeStruct(self, format, values):
	data = struct.pack(*(format,) + values)
	self.items.append(data)

	def writeData(self, data):
	self.items.append(data)

	def getOverflowErrorRecord(self, item):
	LookupListIndex = SubTableIndex = itemName = itemIndex = None
	if self.name == "LookupList":
	LookupListIndex = item.repeatIndex
	elif self.name == "Lookup":
	LookupListIndex = self.repeatIndex
	SubTableIndex = item.repeatIndex
	else:
	itemName = getattr(item, "name", "<none>")
	if hasattr(item, "repeatIndex"):
	itemIndex = item.repeatIndex
	if self.name == "SubTable":
	LookupListIndex = self.parent.repeatIndex
	SubTableIndex = self.repeatIndex
	elif self.name == "ExtSubTable":
	LookupListIndex = self.parent.parent.repeatIndex
	SubTableIndex = self.parent.repeatIndex
	else: # who knows how far below the SubTable level we are! Climb back up to the nearest subtable.
	itemName = ".".join([self.name, itemName])
	p1 = self.parent
	while p1 and p1.name not in ["ExtSubTable", "SubTable"]:
	itemName = ".".join([p1.name, itemName])
	p1 = p1.parent
	if p1:
	if p1.name == "ExtSubTable":
	LookupListIndex = p1.parent.parent.repeatIndex
	SubTableIndex = p1.parent.repeatIndex
	else:
	LookupListIndex = p1.parent.repeatIndex
	SubTableIndex = p1.repeatIndex

	return OverflowErrorRecord(
	(self.tableTag, LookupListIndex, SubTableIndex, itemName, itemIndex)
	)


	class CountReference(object):
	"""A reference to a Count value, not a count of references."""

	def __init__(self, table, name, size=None, value=None):
	self.table = table
	self.name = name
	self.size = size
	if value is not None:
	self.setValue(value)

	def setValue(self, value):
	table = self.table
	name = self.name
	if table[name] is None:
	table[name] = value
	else:
	assert table[name] == value, (name, table[name], value)

	def getValue(self):
	return self.table[self.name]

	def getCountData(self):
	v = self.table[self.name]
	if v is None:
	v = 0
	return {1: packUInt8, 2: packUShort, 4: packULong}[self.size](v)


	def packUInt8(value):
	return struct.pack(">B", value)


	def packUShort(value):
	return struct.pack(">H", value)


	def packULong(value):
	assert 0 <= value < 0x100000000, value
	return struct.pack(">I", value)


	def packUInt24(value):
	assert 0 <= value < 0x1000000, value
	return struct.pack(">I", value)[1:]


	class BaseTable(object):
	"""Generic base class for all OpenType (sub)tables."""

	def __getattr__(self, attr):
	reader = self.__dict__.get("reader")
	if reader:
	del self.reader
	font = self.font
	del self.font
	self.decompile(reader, font)
	return getattr(self, attr)

	raise AttributeError(attr)

	def ensureDecompiled(self, recurse=False):
	reader = self.__dict__.get("reader")
	if reader:
	del self.reader
	font = self.font
	del self.font
	self.decompile(reader, font)
	if recurse:
	for subtable in self.iterSubTables():
	subtable.value.ensureDecompiled(recurse)

	def __getstate__(self):
	# before copying/pickling 'lazy' objects, make a shallow copy of OTTableReader
	# https://github.com/fonttools/fonttools/issues/2965
	if "reader" in self.__dict__:
	state = self.__dict__.copy()
	state["reader"] = self.__dict__["reader"].copy()
	return state
	return self.__dict__

	@classmethod
	def getRecordSize(cls, reader):
	totalSize = 0
	for conv in cls.converters:
	size = conv.getRecordSize(reader)
	if size is NotImplemented:
	return NotImplemented
	countValue = 1
	if conv.repeat:
	if conv.repeat in reader:
	countValue = reader[conv.repeat] + conv.aux
	else:
	return NotImplemented
	totalSize += size * countValue
	return totalSize

	def getConverters(self):
	return self.converters

	def getConverterByName(self, name):
	return self.convertersByName[name]

	def populateDefaults(self, propagator=None):
	for conv in self.getConverters():
	if conv.repeat:
	if not hasattr(self, conv.name):
	setattr(self, conv.name, [])
	countValue = len(getattr(self, conv.name)) - conv.aux
	try:
	count_conv = self.getConverterByName(conv.repeat)
	setattr(self, conv.repeat, countValue)
	except KeyError:
	# conv.repeat is a propagated count
	if propagator and conv.repeat in propagator:
	propagator[conv.repeat].setValue(countValue)
	else:
	if conv.aux and not eval(conv.aux, None, self.__dict__):
	continue
	if hasattr(self, conv.name):
	continue # Warn if it should NOT be present?!
	if hasattr(conv, "writeNullOffset"):
	setattr(self, conv.name, None) # Warn?
	# elif not conv.isCount:
	# # Warn?
	# pass
	if hasattr(conv, "DEFAULT"):
	# OptionalValue converters (e.g. VarIndex)
	setattr(self, conv.name, conv.DEFAULT)

	def decompile(self, reader, font):
	self.readFormat(reader)
	table = {}
	self.__rawTable = table # for debugging
	for conv in self.getConverters():
	if conv.name == "SubTable":
	conv = conv.getConverter(reader.tableTag, table["LookupType"])
	if conv.name == "ExtSubTable":
	conv = conv.getConverter(reader.tableTag, table["ExtensionLookupType"])
	if conv.name == "FeatureParams":
	conv = conv.getConverter(reader["FeatureTag"])
	if conv.name == "SubStruct":
	conv = conv.getConverter(reader.tableTag, table["MorphType"])
	try:
	if conv.repeat:
	if isinstance(conv.repeat, int):
	countValue = conv.repeat
	elif conv.repeat in table:
	countValue = table[conv.repeat]
	else:
	# conv.repeat is a propagated count
	countValue = reader[conv.repeat]
	countValue += conv.aux
	table[conv.name] = conv.readArray(reader, font, table, countValue)
	else:
	if conv.aux and not eval(conv.aux, None, table):
	continue
	table[conv.name] = conv.read(reader, font, table)
	if conv.isPropagated:
	reader[conv.name] = table[conv.name]
	except Exception as e:
	name = conv.name
	e.args = e.args + (name,)
	raise

	if hasattr(self, "postRead"):
	self.postRead(table, font)
	else:
	self.__dict__.update(table)

	del self.__rawTable # succeeded, get rid of debugging info

	def compile(self, writer, font):
	self.ensureDecompiled()
	# TODO Following hack to be removed by rewriting how FormatSwitching tables
	# are handled.
	# https://github.com/fonttools/fonttools/pull/2238#issuecomment-805192631
	if hasattr(self, "preWrite"):
	deleteFormat = not hasattr(self, "Format")
	table = self.preWrite(font)
	deleteFormat = deleteFormat and hasattr(self, "Format")
	else:
	deleteFormat = False
	table = self.__dict__.copy()

	# some count references may have been initialized in a custom preWrite; we set
	# these in the writer's state beforehand (instead of sequentially) so they will
	# be propagated to all nested subtables even if the count appears in the current
	# table only after the offset to the subtable that it is counting.
	for conv in self.getConverters():
	if conv.isCount and conv.isPropagated:
	value = table.get(conv.name)
	if isinstance(value, CountReference):
	writer[conv.name] = value

	if hasattr(self, "sortCoverageLast"):
	writer.sortCoverageLast = 1

	if hasattr(self, "DontShare"):
	writer.DontShare = True

	if hasattr(self.__class__, "LookupType"):
	writer["LookupType"].setValue(self.__class__.LookupType)

	self.writeFormat(writer)
	for conv in self.getConverters():
	value = table.get(
	conv.name
	) # TODO Handle defaults instead of defaulting to None!
	if conv.repeat:
	if value is None:
	value = []
	countValue = len(value) - conv.aux
	if isinstance(conv.repeat, int):
	assert len(value) == conv.repeat, "expected %d values, got %d" % (
	conv.repeat,
	len(value),
	)
	elif conv.repeat in table:
	CountReference(table, conv.repeat, value=countValue)
	else:
	# conv.repeat is a propagated count
	writer[conv.repeat].setValue(countValue)
	try:
	conv.writeArray(writer, font, table, value)
	except Exception as e:
	e.args = e.args + (conv.name + "[]",)
	raise
	elif conv.isCount:
	# Special-case Count values.
	# Assumption: a Count field will always precede
	# the actual array(s).
	# We need a default value, as it may be set later by a nested
	# table. We will later store it here.
	# We add a reference: by the time the data is assembled
	# the Count value will be filled in.
	# We ignore the current count value since it will be recomputed,
	# unless it's a CountReference that was already initialized in a custom preWrite.
	if isinstance(value, CountReference):
	ref = value
	ref.size = conv.staticSize
	writer.writeData(ref)
	table[conv.name] = ref.getValue()
	else:
	ref = writer.writeCountReference(table, conv.name, conv.staticSize)
	table[conv.name] = None
	if conv.isPropagated:
	writer[conv.name] = ref
	elif conv.isLookupType:
	# We make sure that subtables have the same lookup type,
	# and that the type is the same as the one set on the
	# Lookup object, if any is set.
	if conv.name not in table:
	table[conv.name] = None
	ref = writer.writeCountReference(
	table, conv.name, conv.staticSize, table[conv.name]
	)
	writer["LookupType"] = ref
	else:
	if conv.aux and not eval(conv.aux, None, table):
	continue
	try:
	conv.write(writer, font, table, value)
	except Exception as e:
	name = value.__class__.__name__ if value is not None else conv.name
	e.args = e.args + (name,)
	raise
	if conv.isPropagated:
	writer[conv.name] = value

	if deleteFormat:
	del self.Format

	def readFormat(self, reader):
	pass

	def writeFormat(self, writer):
	pass

	def toXML(self, xmlWriter, font, attrs=None, name=None):
	tableName = name if name else self.__class__.__name__
	if attrs is None:
	attrs = []
	if hasattr(self, "Format"):
	attrs = attrs + [("Format", self.Format)]
	xmlWriter.begintag(tableName, attrs)
	xmlWriter.newline()
	self.toXML2(xmlWriter, font)
	xmlWriter.endtag(tableName)
	xmlWriter.newline()

	def toXML2(self, xmlWriter, font):
	# Simpler variant of toXML, only for the top level tables (like GPOS, GSUB).
	# This is because in TTX our parent writes our main tag, and in otBase.py we
	# do it ourselves. I think I'm getting schizophrenic...
	for conv in self.getConverters():
	if conv.repeat:
	value = getattr(self, conv.name, [])
	for i, item in enumerate(value):
	conv.xmlWrite(xmlWriter, font, item, conv.name, [("index", i)])
	else:
	if conv.aux and not eval(conv.aux, None, vars(self)):
	continue
	value = getattr(
	self, conv.name, None
	) # TODO Handle defaults instead of defaulting to None!
	conv.xmlWrite(xmlWriter, font, value, conv.name, [])

	def fromXML(self, name, attrs, content, font):
	try:
	conv = self.getConverterByName(name)
	except KeyError:
	raise # XXX on KeyError, raise nice error
	value = conv.xmlRead(attrs, content, font)
	# Some manually-written tables have a conv.repeat of ""
	# to represent lists. Hence comparing to None here to
	# allow those lists to be read correctly from XML.
	if conv.repeat is not None:
	seq = getattr(self, conv.name, None)
	if seq is None:
	seq = []
	setattr(self, conv.name, seq)
	seq.append(value)
	else:
	setattr(self, conv.name, value)

	def __ne__(self, other):
	result = self.__eq__(other)
	return result if result is NotImplemented else not result

	def __eq__(self, other):
	if type(self) != type(other):
	return NotImplemented

	self.ensureDecompiled()
	other.ensureDecompiled()

	return self.__dict__ == other.__dict__

	class SubTableEntry(NamedTuple):
	"""See BaseTable.iterSubTables()"""

	name: str
	value: "BaseTable"
	index: Optional[int] = None # index into given array, None for single values

	def iterSubTables(self) -> Iterator[SubTableEntry]:
	"""Yield (name, value, index) namedtuples for all subtables of current table.

	A sub-table is an instance of BaseTable (or subclass thereof) that is a child
	of self, the current parent table.
	The tuples also contain the attribute name (str) of the of parent table to get
	a subtable, and optionally, for lists of subtables (i.e. attributes associated
	with a converter that has a 'repeat'), an index into the list containing the
	given subtable value.
	This method can be useful to traverse trees of otTables.
	"""
	for conv in self.getConverters():
	name = conv.name
	value = getattr(self, name, None)
	if value is None:
	continue
	if isinstance(value, BaseTable):
	yield self.SubTableEntry(name, value)
	elif isinstance(value, list):
	yield from (
	self.SubTableEntry(name, v, index=i)
	for i, v in enumerate(value)
	if isinstance(v, BaseTable)
	)

	# instance (not @class)method for consistency with FormatSwitchingBaseTable
	def getVariableAttrs(self):
	return getVariableAttrs(self.__class__)


	class FormatSwitchingBaseTable(BaseTable):
	"""Minor specialization of BaseTable, for tables that have multiple
	formats, eg. CoverageFormat1 vs. CoverageFormat2."""

	@classmethod
	def getRecordSize(cls, reader):
	return NotImplemented

	def getConverters(self):
	try:
	fmt = self.Format
	except AttributeError:
	# some FormatSwitchingBaseTables (e.g. Coverage) no longer have 'Format'
	# attribute after fully decompiled, only gain one in preWrite before being
	# recompiled. In the decompiled state, these hand-coded classes defined in
	# otTables.py lose their format-specific nature and gain more high-level
	# attributes that are not tied to converters.
	return []
	return self.converters.get(self.Format, [])

	def getConverterByName(self, name):
	return self.convertersByName[self.Format][name]

	def readFormat(self, reader):
	self.Format = reader.readUShort()

	def writeFormat(self, writer):
	writer.writeUShort(self.Format)

	def toXML(self, xmlWriter, font, attrs=None, name=None):
	BaseTable.toXML(self, xmlWriter, font, attrs, name)

	def getVariableAttrs(self):
	return getVariableAttrs(self.__class__, self.Format)


	class UInt8FormatSwitchingBaseTable(FormatSwitchingBaseTable):
	def readFormat(self, reader):
	self.Format = reader.readUInt8()

	def writeFormat(self, writer):
	writer.writeUInt8(self.Format)


	formatSwitchingBaseTables = {
	"uint16": FormatSwitchingBaseTable,
	"uint8": UInt8FormatSwitchingBaseTable,
	}


	def getFormatSwitchingBaseTableClass(formatType):
	try:
	return formatSwitchingBaseTables[formatType]
	except KeyError:
	raise TypeError(f"Unsupported format type: {formatType!r}")


	# memoize since these are parsed from otData.py, thus stay constant
	@lru_cache()
	def getVariableAttrs(cls: BaseTable, fmt: Optional[int] = None) -> Tuple[str]:
	"""Return sequence of variable table field names (can be empty).

	Attributes are deemed "variable" when their otData.py's description contain
	'VarIndexBase + {offset}', e.g. COLRv1 PaintVar* tables.
	"""
	if not issubclass(cls, BaseTable):
	raise TypeError(cls)
	if issubclass(cls, FormatSwitchingBaseTable):
	if fmt is None:
	raise TypeError(f"'fmt' is required for format-switching {cls.__name__}")
	converters = cls.convertersByName[fmt]
	else:
	converters = cls.convertersByName
	# assume if no 'VarIndexBase' field is present, table has no variable fields
	if "VarIndexBase" not in converters:
	return ()
	varAttrs = {}
	for name, conv in converters.items():
	offset = conv.getVarIndexOffset()
	if offset is not None:
	varAttrs[name] = offset
	return tuple(sorted(varAttrs, key=varAttrs.__getitem__))


	#
	# Support for ValueRecords
	#
	# This data type is so different from all other OpenType data types that
	# it requires quite a bit of code for itself. It even has special support
	# in OTTableReader and OTTableWriter...
	#

	valueRecordFormat = [
	# Mask Name isDevice signed
	(0x0001, "XPlacement", 0, 1),
	(0x0002, "YPlacement", 0, 1),
	(0x0004, "XAdvance", 0, 1),
	(0x0008, "YAdvance", 0, 1),
	(0x0010, "XPlaDevice", 1, 0),
	(0x0020, "YPlaDevice", 1, 0),
	(0x0040, "XAdvDevice", 1, 0),
	(0x0080, "YAdvDevice", 1, 0),
	# reserved:
	(0x0100, "Reserved1", 0, 0),
	(0x0200, "Reserved2", 0, 0),
	(0x0400, "Reserved3", 0, 0),
	(0x0800, "Reserved4", 0, 0),
	(0x1000, "Reserved5", 0, 0),
	(0x2000, "Reserved6", 0, 0),
	(0x4000, "Reserved7", 0, 0),
	(0x8000, "Reserved8", 0, 0),
	]


	def _buildDict():
	d = {}
	for mask, name, isDevice, signed in valueRecordFormat:
	d[name] = mask, isDevice, signed
	return d


	valueRecordFormatDict = _buildDict()


	class ValueRecordFactory(object):
	"""Given a format code, this object convert ValueRecords."""

	def __init__(self, valueFormat):
	format = []
	for mask, name, isDevice, signed in valueRecordFormat:
	if valueFormat & mask:
	format.append((name, isDevice, signed))
	self.format = format

	def __len__(self):
	return len(self.format)

	def readValueRecord(self, reader, font):
	format = self.format
	if not format:
	return None
	valueRecord = ValueRecord()
	for name, isDevice, signed in format:
	if signed:
	value = reader.readShort()
	else:
	value = reader.readUShort()
	if isDevice:
	if value:
	from . import otTables

	subReader = reader.getSubReader(value)
	value = getattr(otTables, name)()
	value.decompile(subReader, font)
	else:
	value = None
	setattr(valueRecord, name, value)
	return valueRecord

	def writeValueRecord(self, writer, font, valueRecord):
	for name, isDevice, signed in self.format:
	value = getattr(valueRecord, name, 0)
	if isDevice:
	if value:
	subWriter = writer.getSubWriter()
	writer.writeSubTable(subWriter, offsetSize=2)
	value.compile(subWriter, font)
	else:
	writer.writeUShort(0)
	elif signed:
	writer.writeShort(value)
	else:
	writer.writeUShort(value)


	class ValueRecord(object):
	# see ValueRecordFactory

	def __init__(self, valueFormat=None, src=None):
	if valueFormat is not None:
	for mask, name, isDevice, signed in valueRecordFormat:
	if valueFormat & mask:
	setattr(self, name, None if isDevice else 0)
	if src is not None:
	for key, val in src.__dict__.items():
	if not hasattr(self, key):
	continue
	setattr(self, key, val)
	elif src is not None:
	self.__dict__ = src.__dict__.copy()

	def getFormat(self):
	format = 0
	for name in self.__dict__.keys():
	format = format \| valueRecordFormatDict[name][0]
	return format

	def getEffectiveFormat(self):
	format = 0
	for name, value in self.__dict__.items():
	if value:
	format = format \| valueRecordFormatDict[name][0]
	return format

	def toXML(self, xmlWriter, font, valueName, attrs=None):
	if attrs is None:
	simpleItems = []
	else:
	simpleItems = list(attrs)
	for mask, name, isDevice, format in valueRecordFormat[:4]: # "simple" values
	if hasattr(self, name):
	simpleItems.append((name, getattr(self, name)))
	deviceItems = []
	for mask, name, isDevice, format in valueRecordFormat[4:8]: # device records
	if hasattr(self, name):
	device = getattr(self, name)
	if device is not None:
	deviceItems.append((name, device))
	if deviceItems:
	xmlWriter.begintag(valueName, simpleItems)
	xmlWriter.newline()
	for name, deviceRecord in deviceItems:
	if deviceRecord is not None:
	deviceRecord.toXML(xmlWriter, font, name=name)
	xmlWriter.endtag(valueName)
	xmlWriter.newline()
	else:
	xmlWriter.simpletag(valueName, simpleItems)
	xmlWriter.newline()

	def fromXML(self, name, attrs, content, font):
	from . import otTables

	for k, v in attrs.items():
	setattr(self, k, int(v))
	for element in content:
	if not isinstance(element, tuple):
	continue
	name, attrs, content = element
	value = getattr(otTables, name)()
	for elem2 in content:
	if not isinstance(elem2, tuple):
	continue
	name2, attrs2, content2 = elem2
	value.fromXML(name2, attrs2, content2, font)
	setattr(self, name, value)

	def __ne__(self, other):
	result = self.__eq__(other)
	return result if result is NotImplemented else not result

	def __eq__(self, other):
	if type(self) != type(other):
	return NotImplemented
	return self.__dict__ == other.__dict__

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