55.3 kB

	"""
	The legend module defines the Legend class, which is responsible for
	drawing legends associated with Axes and/or figures.

	.. important::

	It is unlikely that you would ever create a Legend instance manually.
	Most users would normally create a legend via the `~.Axes.legend`
	function. For more details on legends there is also a :ref:`legend guide
	<legend_guide>`.

	The `Legend` class is a container of legend handles and legend texts.

	The legend handler map specifies how to create legend handles from artists
	(lines, patches, etc.) in the Axes or figures. Default legend handlers are
	defined in the :mod:`~matplotlib.legend_handler` module. While not all artist
	types are covered by the default legend handlers, custom legend handlers can be
	defined to support arbitrary objects.

	See the :ref`<legend_guide>` for more
	information.
	"""

	import itertools
	import logging
	import numbers
	import time

	import numpy as np

	import matplotlib as mpl
	from matplotlib import _api, _docstring, cbook, colors, offsetbox
	from matplotlib.artist import Artist, allow_rasterization
	from matplotlib.cbook import silent_list
	from matplotlib.font_manager import FontProperties
	from matplotlib.lines import Line2D
	from matplotlib.patches import (Patch, Rectangle, Shadow, FancyBboxPatch,
	StepPatch)
	from matplotlib.collections import (
	Collection, CircleCollection, LineCollection, PathCollection,
	PolyCollection, RegularPolyCollection)
	from matplotlib.text import Text
	from matplotlib.transforms import Bbox, BboxBase, TransformedBbox
	from matplotlib.transforms import BboxTransformTo, BboxTransformFrom
	from matplotlib.offsetbox import (
	AnchoredOffsetbox, DraggableOffsetBox,
	HPacker, VPacker,
	DrawingArea, TextArea,
	)
	from matplotlib.container import ErrorbarContainer, BarContainer, StemContainer
	from . import legend_handler


	class DraggableLegend(DraggableOffsetBox):
	def __init__(self, legend, use_blit=False, update="loc"):
	"""
	Wrapper around a `.Legend` to support mouse dragging.

	Parameters
	----------
	legend : `.Legend`
	The `.Legend` instance to wrap.
	use_blit : bool, optional
	Use blitting for faster image composition. For details see
	:ref:`func-animation`.
	update : {'loc', 'bbox'}, optional
	If "loc", update the loc parameter of the legend upon finalizing.
	If "bbox", update the bbox_to_anchor parameter.
	"""
	self.legend = legend

	_api.check_in_list(["loc", "bbox"], update=update)
	self._update = update

	super().__init__(legend, legend._legend_box, use_blit=use_blit)

	def finalize_offset(self):
	if self._update == "loc":
	self._update_loc(self.get_loc_in_canvas())
	elif self._update == "bbox":
	self._update_bbox_to_anchor(self.get_loc_in_canvas())

	def _update_loc(self, loc_in_canvas):
	bbox = self.legend.get_bbox_to_anchor()
	# if bbox has zero width or height, the transformation is
	# ill-defined. Fall back to the default bbox_to_anchor.
	if bbox.width == 0 or bbox.height == 0:
	self.legend.set_bbox_to_anchor(None)
	bbox = self.legend.get_bbox_to_anchor()
	_bbox_transform = BboxTransformFrom(bbox)
	self.legend._loc = tuple(_bbox_transform.transform(loc_in_canvas))

	def _update_bbox_to_anchor(self, loc_in_canvas):
	loc_in_bbox = self.legend.axes.transAxes.transform(loc_in_canvas)
	self.legend.set_bbox_to_anchor(loc_in_bbox)


	_legend_kw_doc_base = """
	bbox_to_anchor : `.BboxBase`, 2-tuple, or 4-tuple of floats
	Box that is used to position the legend in conjunction with loc.
	Defaults to ``axes.bbox`` (if called as a method to `.Axes.legend`) or
	``figure.bbox`` (if ``figure.legend``). This argument allows arbitrary
	placement of the legend.

	Bbox coordinates are interpreted in the coordinate system given by
	bbox_transform, with the default transform
	Axes or Figure coordinates, depending on which ``legend`` is called.

	If a 4-tuple or `.BboxBase` is given, then it specifies the bbox
	``(x, y, width, height)`` that the legend is placed in.
	To put the legend in the best location in the bottom right
	quadrant of the Axes (or figure)::

	loc='best', bbox_to_anchor=(0.5, 0., 0.5, 0.5)

	A 2-tuple ``(x, y)`` places the corner of the legend specified by loc at
	x, y. For example, to put the legend's upper right-hand corner in the
	center of the Axes (or figure) the following keywords can be used::

	loc='upper right', bbox_to_anchor=(0.5, 0.5)

	ncols : int, default: 1
	The number of columns that the legend has.

	For backward compatibility, the spelling ncol is also supported
	but it is discouraged. If both are given, ncols takes precedence.

	prop : None or `~matplotlib.font_manager.FontProperties` or dict
	The font properties of the legend. If None (default), the current
	:data:`matplotlib.rcParams` will be used.

	fontsize : int or {'xx-small', 'x-small', 'small', 'medium', 'large', \
	'x-large', 'xx-large'}
	The font size of the legend. If the value is numeric the size will be the
	absolute font size in points. String values are relative to the current
	default font size. This argument is only used if prop is not specified.

	labelcolor : str or list, default: :rc:`legend.labelcolor`
	The color of the text in the legend. Either a valid color string
	(for example, 'red'), or a list of color strings. The labelcolor can
	also be made to match the color of the line or marker using 'linecolor',
	'markerfacecolor' (or 'mfc'), or 'markeredgecolor' (or 'mec').

	Labelcolor can be set globally using :rc:`legend.labelcolor`. If None,
	use :rc:`text.color`.

	numpoints : int, default: :rc:`legend.numpoints`
	The number of marker points in the legend when creating a legend
	entry for a `.Line2D` (line).

	scatterpoints : int, default: :rc:`legend.scatterpoints`
	The number of marker points in the legend when creating
	a legend entry for a `.PathCollection` (scatter plot).

	scatteryoffsets : iterable of floats, default: ``[0.375, 0.5, 0.3125]``
	The vertical offset (relative to the font size) for the markers
	created for a scatter plot legend entry. 0.0 is at the base the
	legend text, and 1.0 is at the top. To draw all markers at the
	same height, set to ``[0.5]``.

	markerscale : float, default: :rc:`legend.markerscale`
	The relative size of legend markers compared to the originally drawn ones.

	markerfirst : bool, default: True
	If True, legend marker is placed to the left of the legend label.
	If False, legend marker is placed to the right of the legend label.

	reverse : bool, default: False
	If True, the legend labels are displayed in reverse order from the input.
	If False, the legend labels are displayed in the same order as the input.

	.. versionadded:: 3.7

	frameon : bool, default: :rc:`legend.frameon`
	Whether the legend should be drawn on a patch (frame).

	fancybox : bool, default: :rc:`legend.fancybox`
	Whether round edges should be enabled around the `.FancyBboxPatch` which
	makes up the legend's background.

	shadow : None, bool or dict, default: :rc:`legend.shadow`
	Whether to draw a shadow behind the legend.
	The shadow can be configured using `.Patch` keywords.
	Customization via :rc:`legend.shadow` is currently not supported.

	framealpha : float, default: :rc:`legend.framealpha`
	The alpha transparency of the legend's background.
	If shadow is activated and framealpha is ``None``, the default value is
	ignored.

	facecolor : "inherit" or color, default: :rc:`legend.facecolor`
	The legend's background color.
	If ``"inherit"``, use :rc:`axes.facecolor`.

	edgecolor : "inherit" or color, default: :rc:`legend.edgecolor`
	The legend's background patch edge color.
	If ``"inherit"``, use :rc:`axes.edgecolor`.

	mode : {"expand", None}
	If mode is set to ``"expand"`` the legend will be horizontally
	expanded to fill the Axes area (or bbox_to_anchor if defines
	the legend's size).

	bbox_transform : None or `~matplotlib.transforms.Transform`
	The transform for the bounding box (bbox_to_anchor). For a value
	of ``None`` (default) the Axes'
	:data:`~matplotlib.axes.Axes.transAxes` transform will be used.

	title : str or None
	The legend's title. Default is no title (``None``).

	title_fontproperties : None or `~matplotlib.font_manager.FontProperties` or dict
	The font properties of the legend's title. If None (default), the
	title_fontsize argument will be used if present; if title_fontsize is
	also None, the current :rc:`legend.title_fontsize` will be used.

	title_fontsize : int or {'xx-small', 'x-small', 'small', 'medium', 'large', \
	'x-large', 'xx-large'}, default: :rc:`legend.title_fontsize`
	The font size of the legend's title.
	Note: This cannot be combined with title_fontproperties. If you want
	to set the fontsize alongside other font properties, use the size
	parameter in title_fontproperties.

	alignment : {'center', 'left', 'right'}, default: 'center'
	The alignment of the legend title and the box of entries. The entries
	are aligned as a single block, so that markers always lined up.

	borderpad : float, default: :rc:`legend.borderpad`
	The fractional whitespace inside the legend border, in font-size units.

	labelspacing : float, default: :rc:`legend.labelspacing`
	The vertical space between the legend entries, in font-size units.

	handlelength : float, default: :rc:`legend.handlelength`
	The length of the legend handles, in font-size units.

	handleheight : float, default: :rc:`legend.handleheight`
	The height of the legend handles, in font-size units.

	handletextpad : float, default: :rc:`legend.handletextpad`
	The pad between the legend handle and text, in font-size units.

	borderaxespad : float, default: :rc:`legend.borderaxespad`
	The pad between the Axes and legend border, in font-size units.

	columnspacing : float, default: :rc:`legend.columnspacing`
	The spacing between columns, in font-size units.

	handler_map : dict or None
	The custom dictionary mapping instances or types to a legend
	handler. This handler_map updates the default handler map
	found at `matplotlib.legend.Legend.get_legend_handler_map`.

	draggable : bool, default: False
	Whether the legend can be dragged with the mouse.
	"""

	_loc_doc_base = """
	loc : str or pair of floats, default: {default}
	The location of the legend.

	The strings ``'upper left'``, ``'upper right'``, ``'lower left'``,
	``'lower right'`` place the legend at the corresponding corner of the
	{parent}.

	The strings ``'upper center'``, ``'lower center'``, ``'center left'``,
	``'center right'`` place the legend at the center of the corresponding edge
	of the {parent}.

	The string ``'center'`` places the legend at the center of the {parent}.
	{best}
	The location can also be a 2-tuple giving the coordinates of the lower-left
	corner of the legend in {parent} coordinates (in which case bbox_to_anchor
	will be ignored).

	For back-compatibility, ``'center right'`` (but no other location) can also
	be spelled ``'right'``, and each "string" location can also be given as a
	numeric value:

	================== =============
	Location String Location Code
	================== =============
	'best' (Axes only) 0
	'upper right' 1
	'upper left' 2
	'lower left' 3
	'lower right' 4
	'right' 5
	'center left' 6
	'center right' 7
	'lower center' 8
	'upper center' 9
	'center' 10
	================== =============
	{outside}"""

	_loc_doc_best = """
	The string ``'best'`` places the legend at the location, among the nine
	locations defined so far, with the minimum overlap with other drawn
	artists. This option can be quite slow for plots with large amounts of
	data; your plotting speed may benefit from providing a specific location.
	"""

	_legend_kw_axes_st = (
	_loc_doc_base.format(parent='axes', default=':rc:`legend.loc`',
	best=_loc_doc_best, outside='') +
	_legend_kw_doc_base)
	_docstring.interpd.register(_legend_kw_axes=_legend_kw_axes_st)

	_outside_doc = """
	If a figure is using the constrained layout manager, the string codes
	of the loc keyword argument can get better layout behaviour using the
	prefix 'outside'. There is ambiguity at the corners, so 'outside
	upper right' will make space for the legend above the rest of the
	axes in the layout, and 'outside right upper' will make space on the
	right side of the layout. In addition to the values of loc
	listed above, we have 'outside right upper', 'outside right lower',
	'outside left upper', and 'outside left lower'. See
	:ref:`legend_guide` for more details.
	"""

	_legend_kw_figure_st = (
	_loc_doc_base.format(parent='figure', default="'upper right'",
	best='', outside=_outside_doc) +
	_legend_kw_doc_base)
	_docstring.interpd.register(_legend_kw_figure=_legend_kw_figure_st)

	_legend_kw_both_st = (
	_loc_doc_base.format(parent='axes/figure',
	default=":rc:`legend.loc` for Axes, 'upper right' for Figure",
	best=_loc_doc_best, outside=_outside_doc) +
	_legend_kw_doc_base)
	_docstring.interpd.register(_legend_kw_doc=_legend_kw_both_st)

	_legend_kw_set_loc_st = (
	_loc_doc_base.format(parent='axes/figure',
	default=":rc:`legend.loc` for Axes, 'upper right' for Figure",
	best=_loc_doc_best, outside=_outside_doc))
	_docstring.interpd.register(_legend_kw_set_loc_doc=_legend_kw_set_loc_st)


	class Legend(Artist):
	"""
	Place a legend on the figure/axes.
	"""

	# 'best' is only implemented for Axes legends
	codes = {'best': 0, **AnchoredOffsetbox.codes}
	zorder = 5

	def __str__(self):
	return "Legend"

	@_docstring.interpd
	def __init__(
	self, parent, handles, labels,
	*,
	loc=None,
	numpoints=None, # number of points in the legend line
	markerscale=None, # relative size of legend markers vs. original
	markerfirst=True, # left/right ordering of legend marker and label
	reverse=False, # reverse ordering of legend marker and label
	scatterpoints=None, # number of scatter points
	scatteryoffsets=None,
	prop=None, # properties for the legend texts
	fontsize=None, # keyword to set font size directly
	labelcolor=None, # keyword to set the text color

	# spacing & pad defined as a fraction of the font-size
	borderpad=None, # whitespace inside the legend border
	labelspacing=None, # vertical space between the legend entries
	handlelength=None, # length of the legend handles
	handleheight=None, # height of the legend handles
	handletextpad=None, # pad between the legend handle and text
	borderaxespad=None, # pad between the Axes and legend border
	columnspacing=None, # spacing between columns

	ncols=1, # number of columns
	mode=None, # horizontal distribution of columns: None or "expand"

	fancybox=None, # True: fancy box, False: rounded box, None: rcParam
	shadow=None,
	title=None, # legend title
	title_fontsize=None, # legend title font size
	framealpha=None, # set frame alpha
	edgecolor=None, # frame patch edgecolor
	facecolor=None, # frame patch facecolor

	bbox_to_anchor=None, # bbox to which the legend will be anchored
	bbox_transform=None, # transform for the bbox
	frameon=None, # draw frame
	handler_map=None,
	title_fontproperties=None, # properties for the legend title
	alignment="center", # control the alignment within the legend box
	ncol=1, # synonym for ncols (backward compatibility)
	draggable=False # whether the legend can be dragged with the mouse
	):
	"""
	Parameters
	----------
	parent : `~matplotlib.axes.Axes` or `.Figure`
	The artist that contains the legend.

	handles : list of (`.Artist` or tuple of `.Artist`)
	A list of Artists (lines, patches) to be added to the legend.

	labels : list of str
	A list of labels to show next to the artists. The length of handles
	and labels should be the same. If they are not, they are truncated
	to the length of the shorter list.

	Other Parameters
	----------------
	%(_legend_kw_doc)s

	Attributes
	----------
	legend_handles
	List of `.Artist` objects added as legend entries.

	.. versionadded:: 3.7
	"""
	# local import only to avoid circularity
	from matplotlib.axes import Axes
	from matplotlib.figure import FigureBase

	super().__init__()

	if prop is None:
	self.prop = FontProperties(size=mpl._val_or_rc(fontsize, "legend.fontsize"))
	else:
	self.prop = FontProperties._from_any(prop)
	if isinstance(prop, dict) and "size" not in prop:
	self.prop.set_size(mpl.rcParams["legend.fontsize"])

	self._fontsize = self.prop.get_size_in_points()

	self.texts = []
	self.legend_handles = []
	self._legend_title_box = None

	#: A dictionary with the extra handler mappings for this Legend
	#: instance.
	self._custom_handler_map = handler_map

	self.numpoints = mpl._val_or_rc(numpoints, 'legend.numpoints')
	self.markerscale = mpl._val_or_rc(markerscale, 'legend.markerscale')
	self.scatterpoints = mpl._val_or_rc(scatterpoints, 'legend.scatterpoints')
	self.borderpad = mpl._val_or_rc(borderpad, 'legend.borderpad')
	self.labelspacing = mpl._val_or_rc(labelspacing, 'legend.labelspacing')
	self.handlelength = mpl._val_or_rc(handlelength, 'legend.handlelength')
	self.handleheight = mpl._val_or_rc(handleheight, 'legend.handleheight')
	self.handletextpad = mpl._val_or_rc(handletextpad, 'legend.handletextpad')
	self.borderaxespad = mpl._val_or_rc(borderaxespad, 'legend.borderaxespad')
	self.columnspacing = mpl._val_or_rc(columnspacing, 'legend.columnspacing')
	self.shadow = mpl._val_or_rc(shadow, 'legend.shadow')

	if reverse:
	labels = [*reversed(labels)]
	handles = [*reversed(handles)]

	handles = list(handles)
	if len(handles) < 2:
	ncols = 1
	self._ncols = ncols if ncols != 1 else ncol

	if self.numpoints <= 0:
	raise ValueError("numpoints must be > 0; it was %d" % numpoints)

	# introduce y-offset for handles of the scatter plot
	if scatteryoffsets is None:
	self._scatteryoffsets = np.array([3. / 8., 4. / 8., 2.5 / 8.])
	else:
	self._scatteryoffsets = np.asarray(scatteryoffsets)
	reps = self.scatterpoints // len(self._scatteryoffsets) + 1
	self._scatteryoffsets = np.tile(self._scatteryoffsets,
	reps)[:self.scatterpoints]

	# _legend_box is a VPacker instance that contains all
	# legend items and will be initialized from _init_legend_box()
	# method.
	self._legend_box = None

	if isinstance(parent, Axes):
	self.isaxes = True
	self.axes = parent
	self.set_figure(parent.get_figure(root=False))
	elif isinstance(parent, FigureBase):
	self.isaxes = False
	self.set_figure(parent)
	else:
	raise TypeError(
	"Legend needs either Axes or FigureBase as parent"
	)
	self.parent = parent

	self._mode = mode
	self.set_bbox_to_anchor(bbox_to_anchor, bbox_transform)

	# Figure out if self.shadow is valid
	# If shadow was None, rcParams loads False
	# So it shouldn't be None here

	self._shadow_props = {'ox': 2, 'oy': -2} # default location offsets
	if isinstance(self.shadow, dict):
	self._shadow_props.update(self.shadow)
	self.shadow = True
	elif self.shadow in (0, 1, True, False):
	self.shadow = bool(self.shadow)
	else:
	raise ValueError(
	'Legend shadow must be a dict or bool, not '
	f'{self.shadow!r} of type {type(self.shadow)}.'
	)

	# We use FancyBboxPatch to draw a legend frame. The location
	# and size of the box will be updated during the drawing time.

	facecolor = mpl._val_or_rc(facecolor, "legend.facecolor")
	if facecolor == 'inherit':
	facecolor = mpl.rcParams["axes.facecolor"]

	edgecolor = mpl._val_or_rc(edgecolor, "legend.edgecolor")
	if edgecolor == 'inherit':
	edgecolor = mpl.rcParams["axes.edgecolor"]

	fancybox = mpl._val_or_rc(fancybox, "legend.fancybox")

	self.legendPatch = FancyBboxPatch(
	xy=(0, 0), width=1, height=1,
	facecolor=facecolor, edgecolor=edgecolor,
	# If shadow is used, default to alpha=1 (#8943).
	alpha=(framealpha if framealpha is not None
	else 1 if shadow
	else mpl.rcParams["legend.framealpha"]),
	# The width and height of the legendPatch will be set (in draw())
	# to the length that includes the padding. Thus we set pad=0 here.
	boxstyle=("round,pad=0,rounding_size=0.2" if fancybox
	else "square,pad=0"),
	mutation_scale=self._fontsize,
	snap=True,
	visible=mpl._val_or_rc(frameon, "legend.frameon")
	)
	self._set_artist_props(self.legendPatch)

	_api.check_in_list(["center", "left", "right"], alignment=alignment)
	self._alignment = alignment

	# init with null renderer
	self._init_legend_box(handles, labels, markerfirst)

	# Set legend location
	self.set_loc(loc)

	# figure out title font properties:
	if title_fontsize is not None and title_fontproperties is not None:
	raise ValueError(
	"title_fontsize and title_fontproperties can't be specified "
	"at the same time. Only use one of them. ")
	title_prop_fp = FontProperties._from_any(title_fontproperties)
	if isinstance(title_fontproperties, dict):
	if "size" not in title_fontproperties:
	title_fontsize = mpl.rcParams["legend.title_fontsize"]
	title_prop_fp.set_size(title_fontsize)
	elif title_fontsize is not None:
	title_prop_fp.set_size(title_fontsize)
	elif not isinstance(title_fontproperties, FontProperties):
	title_fontsize = mpl.rcParams["legend.title_fontsize"]
	title_prop_fp.set_size(title_fontsize)

	self.set_title(title, prop=title_prop_fp)

	self._draggable = None
	self.set_draggable(state=draggable)

	# set the text color

	color_getters = { # getter function depends on line or patch
	'linecolor': ['get_color', 'get_facecolor'],
	'markerfacecolor': ['get_markerfacecolor', 'get_facecolor'],
	'mfc': ['get_markerfacecolor', 'get_facecolor'],
	'markeredgecolor': ['get_markeredgecolor', 'get_edgecolor'],
	'mec': ['get_markeredgecolor', 'get_edgecolor'],
	}
	labelcolor = mpl._val_or_rc(labelcolor, 'legend.labelcolor')
	if labelcolor is None:
	labelcolor = mpl.rcParams['text.color']
	if isinstance(labelcolor, str) and labelcolor in color_getters:
	getter_names = color_getters[labelcolor]
	for handle, text in zip(self.legend_handles, self.texts):
	try:
	if handle.get_array() is not None:
	continue
	except AttributeError:
	pass
	for getter_name in getter_names:
	try:
	color = getattr(handle, getter_name)()
	if isinstance(color, np.ndarray):
	if (
	color.shape[0] == 1
	or np.isclose(color, color[0]).all()
	):
	text.set_color(color[0])
	else:
	pass
	else:
	text.set_color(color)
	break
	except AttributeError:
	pass
	elif cbook._str_equal(labelcolor, 'none'):
	for text in self.texts:
	text.set_color(labelcolor)
	elif np.iterable(labelcolor):
	for text, color in zip(self.texts,
	itertools.cycle(
	colors.to_rgba_array(labelcolor))):
	text.set_color(color)
	else:
	raise ValueError(f"Invalid labelcolor: {labelcolor!r}")

	def _set_artist_props(self, a):
	"""
	Set the boilerplate props for artists added to Axes.
	"""
	a.set_figure(self.get_figure(root=False))
	if self.isaxes:
	a.axes = self.axes

	a.set_transform(self.get_transform())

	@_docstring.interpd
	def set_loc(self, loc=None):
	"""
	Set the location of the legend.

	.. versionadded:: 3.8

	Parameters
	----------
	%(_legend_kw_set_loc_doc)s
	"""
	loc0 = loc
	self._loc_used_default = loc is None
	if loc is None:
	loc = mpl.rcParams["legend.loc"]
	if not self.isaxes and loc in [0, 'best']:
	loc = 'upper right'

	type_err_message = ("loc must be string, coordinate tuple, or"
	f" an integer 0-10, not {loc!r}")

	# handle outside legends:
	self._outside_loc = None
	if isinstance(loc, str):
	if loc.split()[0] == 'outside':
	# strip outside:
	loc = loc.split('outside ')[1]
	# strip "center" at the beginning
	self._outside_loc = loc.replace('center ', '')
	# strip first
	self._outside_loc = self._outside_loc.split()[0]
	locs = loc.split()
	if len(locs) > 1 and locs[0] in ('right', 'left'):
	# locs doesn't accept "left upper", etc, so swap
	if locs[0] != 'center':
	locs = locs[::-1]
	loc = locs[0] + ' ' + locs[1]
	# check that loc is in acceptable strings
	loc = _api.check_getitem(self.codes, loc=loc)
	elif np.iterable(loc):
	# coerce iterable into tuple
	loc = tuple(loc)
	# validate the tuple represents Real coordinates
	if len(loc) != 2 or not all(isinstance(e, numbers.Real) for e in loc):
	raise ValueError(type_err_message)
	elif isinstance(loc, int):
	# validate the integer represents a string numeric value
	if loc < 0 or loc > 10:
	raise ValueError(type_err_message)
	else:
	# all other cases are invalid values of loc
	raise ValueError(type_err_message)

	if self.isaxes and self._outside_loc:
	raise ValueError(
	f"'outside' option for loc='{loc0}' keyword argument only "
	"works for figure legends")

	if not self.isaxes and loc == 0:
	raise ValueError(
	"Automatic legend placement (loc='best') not implemented for "
	"figure legend")

	tmp = self._loc_used_default
	self._set_loc(loc)
	self._loc_used_default = tmp # ignore changes done by _set_loc

	def _set_loc(self, loc):
	# find_offset function will be provided to _legend_box and
	# _legend_box will draw itself at the location of the return
	# value of the find_offset.
	self._loc_used_default = False
	self._loc_real = loc
	self.stale = True
	self._legend_box.set_offset(self._findoffset)

	def set_ncols(self, ncols):
	"""Set the number of columns."""
	self._ncols = ncols

	def _get_loc(self):
	return self._loc_real

	_loc = property(_get_loc, _set_loc)

	def _findoffset(self, width, height, xdescent, ydescent, renderer):
	"""Helper function to locate the legend."""

	if self._loc == 0: # "best".
	x, y = self._find_best_position(width, height, renderer)
	elif self._loc in Legend.codes.values(): # Fixed location.
	bbox = Bbox.from_bounds(0, 0, width, height)
	x, y = self._get_anchored_bbox(self._loc, bbox,
	self.get_bbox_to_anchor(),
	renderer)
	else: # Axes or figure coordinates.
	fx, fy = self._loc
	bbox = self.get_bbox_to_anchor()
	x, y = bbox.x0 + bbox.width * fx, bbox.y0 + bbox.height * fy

	return x + xdescent, y + ydescent

	@allow_rasterization
	def draw(self, renderer):
	# docstring inherited
	if not self.get_visible():
	return

	renderer.open_group('legend', gid=self.get_gid())

	fontsize = renderer.points_to_pixels(self._fontsize)

	# if mode == fill, set the width of the legend_box to the
	# width of the parent (minus pads)
	if self._mode in ["expand"]:
	pad = 2 * (self.borderaxespad + self.borderpad) * fontsize
	self._legend_box.set_width(self.get_bbox_to_anchor().width - pad)

	# update the location and size of the legend. This needs to
	# be done in any case to clip the figure right.
	bbox = self._legend_box.get_window_extent(renderer)
	self.legendPatch.set_bounds(bbox.bounds)
	self.legendPatch.set_mutation_scale(fontsize)

	# self.shadow is validated in __init__
	# So by here it is a bool and self._shadow_props contains any configs

	if self.shadow:
	Shadow(self.legendPatch, **self._shadow_props).draw(renderer)

	self.legendPatch.draw(renderer)
	self._legend_box.draw(renderer)

	renderer.close_group('legend')
	self.stale = False

	# _default_handler_map defines the default mapping between plot
	# elements and the legend handlers.

	_default_handler_map = {
	StemContainer: legend_handler.HandlerStem(),
	ErrorbarContainer: legend_handler.HandlerErrorbar(),
	Line2D: legend_handler.HandlerLine2D(),
	Patch: legend_handler.HandlerPatch(),
	StepPatch: legend_handler.HandlerStepPatch(),
	LineCollection: legend_handler.HandlerLineCollection(),
	RegularPolyCollection: legend_handler.HandlerRegularPolyCollection(),
	CircleCollection: legend_handler.HandlerCircleCollection(),
	BarContainer: legend_handler.HandlerPatch(
	update_func=legend_handler.update_from_first_child),
	tuple: legend_handler.HandlerTuple(),
	PathCollection: legend_handler.HandlerPathCollection(),
	PolyCollection: legend_handler.HandlerPolyCollection()
	}

	# (get\|set\|update)_default_handler_maps are public interfaces to
	# modify the default handler map.

	@classmethod
	def get_default_handler_map(cls):
	"""Return the global default handler map, shared by all legends."""
	return cls._default_handler_map

	@classmethod
	def set_default_handler_map(cls, handler_map):
	"""Set the global default handler map, shared by all legends."""
	cls._default_handler_map = handler_map

	@classmethod
	def update_default_handler_map(cls, handler_map):
	"""Update the global default handler map, shared by all legends."""
	cls._default_handler_map.update(handler_map)

	def get_legend_handler_map(self):
	"""Return this legend instance's handler map."""
	default_handler_map = self.get_default_handler_map()
	return ({default_handler_map, self._custom_handler_map}
	if self._custom_handler_map else default_handler_map)

	@staticmethod
	def get_legend_handler(legend_handler_map, orig_handle):
	"""
	Return a legend handler from legend_handler_map that
	corresponds to orig_handler.

	legend_handler_map should be a dictionary object (that is
	returned by the get_legend_handler_map method).

	It first checks if the orig_handle itself is a key in the
	legend_handler_map and return the associated value.
	Otherwise, it checks for each of the classes in its
	method-resolution-order. If no matching key is found, it
	returns ``None``.
	"""
	try:
	return legend_handler_map[orig_handle]
	except (TypeError, KeyError): # TypeError if unhashable.
	pass
	for handle_type in type(orig_handle).mro():
	try:
	return legend_handler_map[handle_type]
	except KeyError:
	pass
	return None

	def _init_legend_box(self, handles, labels, markerfirst=True):
	"""
	Initialize the legend_box. The legend_box is an instance of
	the OffsetBox, which is packed with legend handles and
	texts. Once packed, their location is calculated during the
	drawing time.
	"""

	fontsize = self._fontsize

	# legend_box is a HPacker, horizontally packed with columns.
	# Each column is a VPacker, vertically packed with legend items.
	# Each legend item is a HPacker packed with:
	# - handlebox: a DrawingArea which contains the legend handle.
	# - labelbox: a TextArea which contains the legend text.

	text_list = [] # the list of text instances
	handle_list = [] # the list of handle instances
	handles_and_labels = []

	# The approximate height and descent of text. These values are
	# only used for plotting the legend handle.
	descent = 0.35 * fontsize * (self.handleheight - 0.7) # heuristic.
	height = fontsize * self.handleheight - descent
	# each handle needs to be drawn inside a box of (x, y, w, h) =
	# (0, -descent, width, height). And their coordinates should
	# be given in the display coordinates.

	# The transformation of each handle will be automatically set
	# to self.get_transform(). If the artist does not use its
	# default transform (e.g., Collections), you need to
	# manually set their transform to the self.get_transform().
	legend_handler_map = self.get_legend_handler_map()

	for orig_handle, label in zip(handles, labels):
	handler = self.get_legend_handler(legend_handler_map, orig_handle)
	if handler is None:
	_api.warn_external(
	"Legend does not support handles for "
	f"{type(orig_handle).__name__} "
	"instances.\nA proxy artist may be used "
	"instead.\nSee: https://matplotlib.org/"
	"stable/users/explain/axes/legend_guide.html"
	"#controlling-the-legend-entries")
	# No handle for this artist, so we just defer to None.
	handle_list.append(None)
	else:
	textbox = TextArea(label, multilinebaseline=True,
	textprops=dict(
	verticalalignment='baseline',
	horizontalalignment='left',
	fontproperties=self.prop))
	handlebox = DrawingArea(width=self.handlelength * fontsize,
	height=height,
	xdescent=0., ydescent=descent)

	text_list.append(textbox._text)
	# Create the artist for the legend which represents the
	# original artist/handle.
	handle_list.append(handler.legend_artist(self, orig_handle,
	fontsize, handlebox))
	handles_and_labels.append((handlebox, textbox))

	columnbox = []
	# array_split splits n handles_and_labels into ncols columns, with the
	# first n%ncols columns having an extra entry. filter(len, ...)
	# handles the case where n < ncols: the last ncols-n columns are empty
	# and get filtered out.
	for handles_and_labels_column in filter(
	len, np.array_split(handles_and_labels, self._ncols)):
	# pack handlebox and labelbox into itembox
	itemboxes = [HPacker(pad=0,
	sep=self.handletextpad * fontsize,
	children=[h, t] if markerfirst else [t, h],
	align="baseline")
	for h, t in handles_and_labels_column]
	# pack columnbox
	alignment = "baseline" if markerfirst else "right"
	columnbox.append(VPacker(pad=0,
	sep=self.labelspacing * fontsize,
	align=alignment,
	children=itemboxes))

	mode = "expand" if self._mode == "expand" else "fixed"
	sep = self.columnspacing * fontsize
	self._legend_handle_box = HPacker(pad=0,
	sep=sep, align="baseline",
	mode=mode,
	children=columnbox)
	self._legend_title_box = TextArea("")
	self._legend_box = VPacker(pad=self.borderpad * fontsize,
	sep=self.labelspacing * fontsize,
	align=self._alignment,
	children=[self._legend_title_box,
	self._legend_handle_box])
	self._legend_box.set_figure(self.get_figure(root=False))
	self._legend_box.axes = self.axes
	self.texts = text_list
	self.legend_handles = handle_list

	def _auto_legend_data(self, renderer):
	"""
	Return display coordinates for hit testing for "best" positioning.

	Returns
	-------
	bboxes
	List of bounding boxes of all patches.
	lines
	List of `.Path` corresponding to each line.
	offsets
	List of (x, y) offsets of all collection.
	"""
	assert self.isaxes # always holds, as this is only called internally
	bboxes = []
	lines = []
	offsets = []
	for artist in self.parent._children:
	if isinstance(artist, Line2D):
	lines.append(
	artist.get_transform().transform_path(artist.get_path()))
	elif isinstance(artist, Rectangle):
	bboxes.append(
	artist.get_bbox().transformed(artist.get_data_transform()))
	elif isinstance(artist, Patch):
	lines.append(
	artist.get_transform().transform_path(artist.get_path()))
	elif isinstance(artist, PolyCollection):
	lines.extend(artist.get_transform().transform_path(path)
	for path in artist.get_paths())
	elif isinstance(artist, Collection):
	transform, transOffset, hoffsets, _ = artist._prepare_points()
	if len(hoffsets):
	offsets.extend(transOffset.transform(hoffsets))
	elif isinstance(artist, Text):
	bboxes.append(artist.get_window_extent(renderer))

	return bboxes, lines, offsets

	def get_children(self):
	# docstring inherited
	return [self._legend_box, self.get_frame()]

	def get_frame(self):
	"""Return the `~.patches.Rectangle` used to frame the legend."""
	return self.legendPatch

	def get_lines(self):
	r"""Return the list of `~.lines.Line2D`\s in the legend."""
	return [h for h in self.legend_handles if isinstance(h, Line2D)]

	def get_patches(self):
	r"""Return the list of `~.patches.Patch`\s in the legend."""
	return silent_list('Patch',
	[h for h in self.legend_handles
	if isinstance(h, Patch)])

	def get_texts(self):
	r"""Return the list of `~.text.Text`\s in the legend."""
	return silent_list('Text', self.texts)

	def set_alignment(self, alignment):
	"""
	Set the alignment of the legend title and the box of entries.

	The entries are aligned as a single block, so that markers always
	lined up.

	Parameters
	----------
	alignment : {'center', 'left', 'right'}.

	"""
	_api.check_in_list(["center", "left", "right"], alignment=alignment)
	self._alignment = alignment
	self._legend_box.align = alignment

	def get_alignment(self):
	"""Get the alignment value of the legend box"""
	return self._legend_box.align

	def set_title(self, title, prop=None):
	"""
	Set legend title and title style.

	Parameters
	----------
	title : str
	The legend title.

	prop : `.font_manager.FontProperties` or `str` or `pathlib.Path`
	The font properties of the legend title.
	If a `str`, it is interpreted as a fontconfig pattern parsed by
	`.FontProperties`. If a `pathlib.Path`, it is interpreted as the
	absolute path to a font file.

	"""
	self._legend_title_box._text.set_text(title)
	if title:
	self._legend_title_box._text.set_visible(True)
	self._legend_title_box.set_visible(True)
	else:
	self._legend_title_box._text.set_visible(False)
	self._legend_title_box.set_visible(False)

	if prop is not None:
	self._legend_title_box._text.set_fontproperties(prop)

	self.stale = True

	def get_title(self):
	"""Return the `.Text` instance for the legend title."""
	return self._legend_title_box._text

	def get_window_extent(self, renderer=None):
	# docstring inherited
	if renderer is None:
	renderer = self.get_figure(root=True)._get_renderer()
	return self._legend_box.get_window_extent(renderer=renderer)

	def get_tightbbox(self, renderer=None):
	# docstring inherited
	return self._legend_box.get_window_extent(renderer)

	def get_frame_on(self):
	"""Get whether the legend box patch is drawn."""
	return self.legendPatch.get_visible()

	def set_frame_on(self, b):
	"""
	Set whether the legend box patch is drawn.

	Parameters
	----------
	b : bool
	"""
	self.legendPatch.set_visible(b)
	self.stale = True

	draw_frame = set_frame_on # Backcompat alias.

	def get_bbox_to_anchor(self):
	"""Return the bbox that the legend will be anchored to."""
	if self._bbox_to_anchor is None:
	return self.parent.bbox
	else:
	return self._bbox_to_anchor

	def set_bbox_to_anchor(self, bbox, transform=None):
	"""
	Set the bbox that the legend will be anchored to.

	Parameters
	----------
	bbox : `~matplotlib.transforms.BboxBase` or tuple
	The bounding box can be specified in the following ways:

	- A `.BboxBase` instance
	- A tuple of ``(left, bottom, width, height)`` in the given
	transform (normalized axes coordinate if None)
	- A tuple of ``(left, bottom)`` where the width and height will be
	assumed to be zero.
	- None, to remove the bbox anchoring, and use the parent bbox.

	transform : `~matplotlib.transforms.Transform`, optional
	A transform to apply to the bounding box. If not specified, this
	will use a transform to the bounding box of the parent.
	"""
	if bbox is None:
	self._bbox_to_anchor = None
	return
	elif isinstance(bbox, BboxBase):
	self._bbox_to_anchor = bbox
	else:
	try:
	l = len(bbox)
	except TypeError as err:
	raise ValueError(f"Invalid bbox: {bbox}") from err

	if l == 2:
	bbox = [bbox[0], bbox[1], 0, 0]

	self._bbox_to_anchor = Bbox.from_bounds(*bbox)

	if transform is None:
	transform = BboxTransformTo(self.parent.bbox)

	self._bbox_to_anchor = TransformedBbox(self._bbox_to_anchor,
	transform)
	self.stale = True

	def _get_anchored_bbox(self, loc, bbox, parentbbox, renderer):
	"""
	Place the bbox inside the parentbbox according to a given
	location code. Return the (x, y) coordinate of the bbox.

	Parameters
	----------
	loc : int
	A location code in range(1, 11). This corresponds to the possible
	values for ``self._loc``, excluding "best".
	bbox : `~matplotlib.transforms.Bbox`
	bbox to be placed, in display coordinates.
	parentbbox : `~matplotlib.transforms.Bbox`
	A parent box which will contain the bbox, in display coordinates.
	"""
	return offsetbox._get_anchored_bbox(
	loc, bbox, parentbbox,
	self.borderaxespad * renderer.points_to_pixels(self._fontsize))

	def _find_best_position(self, width, height, renderer):
	"""Determine the best location to place the legend."""
	assert self.isaxes # always holds, as this is only called internally

	start_time = time.perf_counter()

	bboxes, lines, offsets = self._auto_legend_data(renderer)

	bbox = Bbox.from_bounds(0, 0, width, height)

	candidates = []
	for idx in range(1, len(self.codes)):
	l, b = self._get_anchored_bbox(idx, bbox,
	self.get_bbox_to_anchor(),
	renderer)
	legendBox = Bbox.from_bounds(l, b, width, height)
	# XXX TODO: If markers are present, it would be good to take them
	# into account when checking vertex overlaps in the next line.
	badness = (sum(legendBox.count_contains(line.vertices)
	for line in lines)
	+ legendBox.count_contains(offsets)
	+ legendBox.count_overlaps(bboxes)
	+ sum(line.intersects_bbox(legendBox, filled=False)
	for line in lines))
	# Include the index to favor lower codes in case of a tie.
	candidates.append((badness, idx, (l, b)))
	if badness == 0:
	break

	_, _, (l, b) = min(candidates)

	if self._loc_used_default and time.perf_counter() - start_time > 1:
	_api.warn_external(
	'Creating legend with loc="best" can be slow with large '
	'amounts of data.')

	return l, b

	def contains(self, mouseevent):
	return self.legendPatch.contains(mouseevent)

	def set_draggable(self, state, use_blit=False, update='loc'):
	"""
	Enable or disable mouse dragging support of the legend.

	Parameters
	----------
	state : bool
	Whether mouse dragging is enabled.
	use_blit : bool, optional
	Use blitting for faster image composition. For details see
	:ref:`func-animation`.
	update : {'loc', 'bbox'}, optional
	The legend parameter to be changed when dragged:

	- 'loc': update the loc parameter of the legend
	- 'bbox': update the bbox_to_anchor parameter of the legend

	Returns
	-------
	`.DraggableLegend` or None
	If state is ``True`` this returns the `.DraggableLegend` helper
	instance. Otherwise this returns None.
	"""
	if state:
	if self._draggable is None:
	self._draggable = DraggableLegend(self,
	use_blit,
	update=update)
	else:
	if self._draggable is not None:
	self._draggable.disconnect()
	self._draggable = None
	return self._draggable

	def get_draggable(self):
	"""Return ``True`` if the legend is draggable, ``False`` otherwise."""
	return self._draggable is not None


	# Helper functions to parse legend arguments for both `figure.legend` and
	# `axes.legend`:
	def _get_legend_handles(axs, legend_handler_map=None):
	"""Yield artists that can be used as handles in a legend."""
	handles_original = []
	for ax in axs:
	handles_original += [
	*(a for a in ax._children
	if isinstance(a, (Line2D, Patch, Collection, Text))),
	*ax.containers]
	# support parasite Axes:
	if hasattr(ax, 'parasites'):
	for axx in ax.parasites:
	handles_original += [
	*(a for a in axx._children
	if isinstance(a, (Line2D, Patch, Collection, Text))),
	*axx.containers]

	handler_map = {**Legend.get_default_handler_map(),
	**(legend_handler_map or {})}
	has_handler = Legend.get_legend_handler
	for handle in handles_original:
	label = handle.get_label()
	if label != '_nolegend_' and has_handler(handler_map, handle):
	yield handle
	elif (label and not label.startswith('_') and
	not has_handler(handler_map, handle)):
	_api.warn_external(
	"Legend does not support handles for "
	f"{type(handle).__name__} "
	"instances.\nSee: https://matplotlib.org/stable/"
	"tutorials/intermediate/legend_guide.html"
	"#implementing-a-custom-legend-handler")
	continue


	def _get_legend_handles_labels(axs, legend_handler_map=None):
	"""Return handles and labels for legend."""
	handles = []
	labels = []
	for handle in _get_legend_handles(axs, legend_handler_map):
	label = handle.get_label()
	if label and not label.startswith('_'):
	handles.append(handle)
	labels.append(label)
	return handles, labels


	def _parse_legend_args(axs, args, handles=None, labels=None, *kwargs):
	"""
	Get the handles and labels from the calls to either ``figure.legend``
	or ``axes.legend``.

	The parser is a bit involved because we support::

	legend()
	legend(labels)
	legend(handles, labels)
	legend(labels=labels)
	legend(handles=handles)
	legend(handles=handles, labels=labels)

	The behavior for a mixture of positional and keyword handles and labels
	is undefined and issues a warning; it will be an error in the future.

	Parameters
	----------
	axs : list of `.Axes`
	If handles are not given explicitly, the artists in these Axes are
	used as handles.
	*args : tuple
	Positional parameters passed to ``legend()``.
	handles
	The value of the keyword argument ``legend(handles=...)``, or None
	if that keyword argument was not used.
	labels
	The value of the keyword argument ``legend(labels=...)``, or None
	if that keyword argument was not used.
	**kwargs
	All other keyword arguments passed to ``legend()``.

	Returns
	-------
	handles : list of (`.Artist` or tuple of `.Artist`)
	The legend handles.
	labels : list of str
	The legend labels.
	kwargs : dict
	kwargs with keywords handles and labels removed.

	"""
	log = logging.getLogger(__name__)

	handlers = kwargs.get('handler_map')

	if (handles is not None or labels is not None) and args:
	_api.warn_deprecated("3.9", message=(
	"You have mixed positional and keyword arguments, some input may "
	"be discarded. This is deprecated since %(since)s and will "
	"become an error in %(removal)s."))

	if (hasattr(handles, "__len__") and
	hasattr(labels, "__len__") and
	len(handles) != len(labels)):
	_api.warn_external(f"Mismatched number of handles and labels: "
	f"len(handles) = {len(handles)} "
	f"len(labels) = {len(labels)}")
	# if got both handles and labels as kwargs, make same length
	if handles and labels:
	handles, labels = zip(*zip(handles, labels))

	elif handles is not None and labels is None:
	labels = [handle.get_label() for handle in handles]

	elif labels is not None and handles is None:
	# Get as many handles as there are labels.
	handles = [handle for handle, label
	in zip(_get_legend_handles(axs, handlers), labels)]

	elif len(args) == 0: # 0 args: automatically detect labels and handles.
	handles, labels = _get_legend_handles_labels(axs, handlers)
	if not handles:
	_api.warn_external(
	"No artists with labels found to put in legend. Note that "
	"artists whose label start with an underscore are ignored "
	"when legend() is called with no argument.")

	elif len(args) == 1: # 1 arg: user defined labels, automatic handle detection.
	labels, = args
	if any(isinstance(l, Artist) for l in labels):
	raise TypeError("A single argument passed to legend() must be a "
	"list of labels, but found an Artist in there.")

	# Get as many handles as there are labels.
	handles = [handle for handle, label
	in zip(_get_legend_handles(axs, handlers), labels)]

	elif len(args) == 2: # 2 args: user defined handles and labels.
	handles, labels = args[:2]

	else:
	raise _api.nargs_error('legend', '0-2', len(args))

	return handles, labels, kwargs

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