"""
Default legend handlers.
.. important::
This is a low-level legend API, which most end users do not need.
We recommend that you are familiar with the :ref:`legend guide
<legend_guide>` before reading this documentation.
Legend handlers are expected to be a callable object with a following
signature::
legend_handler(legend, orig_handle, fontsize, handlebox)
Where *legend* is the legend itself, *orig_handle* is the original
plot, *fontsize* is the fontsize in pixels, and *handlebox* is an
`.OffsetBox` instance. Within the call, you should create relevant
artists (using relevant properties from the *legend* and/or
*orig_handle*) and add them into the *handlebox*. The artists need to
be scaled according to the *fontsize* (note that the size is in pixels,
i.e., this is dpi-scaled value).
This module includes definition of several legend handler classes
derived from the base class (HandlerBase) with the following method::
def legend_artist(self, legend, orig_handle, fontsize, handlebox)
"""
from itertools import cycle
import numpy as np
from matplotlib import cbook
from matplotlib.lines import Line2D
from matplotlib.patches import Rectangle
import matplotlib.collections as mcoll
def update_from_first_child(tgt, src):
first_child = next(iter(src.get_children()), None)
if first_child is not None:
tgt.update_from(first_child)
class HandlerBase:
"""
A base class for default legend handlers.
The derived classes are meant to override *create_artists* method, which
has the following signature::
def create_artists(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize,
trans):
The overridden method needs to create artists of the given
transform that fits in the given dimension (xdescent, ydescent,
width, height) that are scaled by fontsize if necessary.
"""
def __init__(self, xpad=0., ypad=0., update_func=None):
"""
Parameters
----------
xpad : float, optional
Padding in x-direction.
ypad : float, optional
Padding in y-direction.
update_func : callable, optional
Function for updating the legend handler properties from another
legend handler, used by `~HandlerBase.update_prop`.
"""
self._xpad, self._ypad = xpad, ypad
self._update_prop_func = update_func
def _update_prop(self, legend_handle, orig_handle):
if self._update_prop_func is None:
self._default_update_prop(legend_handle, orig_handle)
else:
self._update_prop_func(legend_handle, orig_handle)
def _default_update_prop(self, legend_handle, orig_handle):
legend_handle.update_from(orig_handle)
def update_prop(self, legend_handle, orig_handle, legend):
self._update_prop(legend_handle, orig_handle)
legend._set_artist_props(legend_handle)
legend_handle.set_clip_box(None)
legend_handle.set_clip_path(None)
def adjust_drawing_area(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize,
):
xdescent = xdescent - self._xpad * fontsize
ydescent = ydescent - self._ypad * fontsize
width = width - self._xpad * fontsize
height = height - self._ypad * fontsize
return xdescent, ydescent, width, height
def legend_artist(self, legend, orig_handle,
fontsize, handlebox):
"""
Return the artist that this HandlerBase generates for the given
original artist/handle.
Parameters
----------
legend : `~matplotlib.legend.Legend`
The legend for which these legend artists are being created.
orig_handle : :class:`matplotlib.artist.Artist` or similar
The object for which these legend artists are being created.
fontsize : int
The fontsize in pixels. The artists being created should
be scaled according to the given fontsize.
handlebox : `~matplotlib.offsetbox.OffsetBox`
The box which has been created to hold this legend entry's
artists. Artists created in the `legend_artist` method must
be added to this handlebox inside this method.
"""
xdescent, ydescent, width, height = self.adjust_drawing_area(
legend, orig_handle,
handlebox.xdescent, handlebox.ydescent,
handlebox.width, handlebox.height,
fontsize)
artists = self.create_artists(legend, orig_handle,
xdescent, ydescent, width, height,
fontsize, handlebox.get_transform())
# create_artists will return a list of artists.
for a in artists:
handlebox.add_artist(a)
# we only return the first artist
return artists[0]
def create_artists(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize,
trans):
"""
Return the legend artists generated.
Parameters
----------
legend : `~matplotlib.legend.Legend`
The legend for which these legend artists are being created.
orig_handle : `~matplotlib.artist.Artist` or similar
The object for which these legend artists are being created.
xdescent, ydescent, width, height : int
The rectangle (*xdescent*, *ydescent*, *width*, *height*) that the
legend artists being created should fit within.
fontsize : int
The fontsize in pixels. The legend artists being created should
be scaled according to the given fontsize.
trans : `~matplotlib.transforms.Transform`
The transform that is applied to the legend artists being created.
Typically from unit coordinates in the handler box to screen
coordinates.
"""
raise NotImplementedError('Derived must override')
class HandlerNpoints(HandlerBase):
"""
A legend handler that shows *numpoints* points in the legend entry.
"""
def __init__(self, marker_pad=0.3, numpoints=None, **kwargs):
"""
Parameters
----------
marker_pad : float
Padding between points in legend entry.
numpoints : int
Number of points to show in legend entry.
**kwargs
Keyword arguments forwarded to `.HandlerBase`.
"""
super().__init__(**kwargs)
self._numpoints = numpoints
self._marker_pad = marker_pad
def get_numpoints(self, legend):
if self._numpoints is None:
return legend.numpoints
else:
return self._numpoints
def get_xdata(self, legend, xdescent, ydescent, width, height, fontsize):
numpoints = self.get_numpoints(legend)
if numpoints > 1:
# we put some pad here to compensate the size of the marker
pad = self._marker_pad * fontsize
xdata = np.linspace(-xdescent + pad,
-xdescent + width - pad,
numpoints)
xdata_marker = xdata
else:
xdata = [-xdescent, -xdescent + width]
xdata_marker = [-xdescent + 0.5 * width]
return xdata, xdata_marker
class HandlerNpointsYoffsets(HandlerNpoints):
"""
A legend handler that shows *numpoints* in the legend, and allows them to
be individually offset in the y-direction.
"""
def __init__(self, numpoints=None, yoffsets=None, **kwargs):
"""
Parameters
----------
numpoints : int
Number of points to show in legend entry.
yoffsets : array of floats
Length *numpoints* list of y offsets for each point in
legend entry.
**kwargs
Keyword arguments forwarded to `.HandlerNpoints`.
"""
super().__init__(numpoints=numpoints, **kwargs)
self._yoffsets = yoffsets
def get_ydata(self, legend, xdescent, ydescent, width, height, fontsize):
if self._yoffsets is None:
ydata = height * legend._scatteryoffsets
else:
ydata = height * np.asarray(self._yoffsets)
return ydata
class HandlerLine2DCompound(HandlerNpoints):
"""
Original handler for `.Line2D` instances, that relies on combining
a line-only with a marker-only artist. May be deprecated in the future.
"""
def create_artists(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize,
trans):
# docstring inherited
xdata, xdata_marker = self.get_xdata(legend, xdescent, ydescent,
width, height, fontsize)
ydata = np.full_like(xdata, ((height - ydescent) / 2))
legline = Line2D(xdata, ydata)
self.update_prop(legline, orig_handle, legend)
legline.set_drawstyle('default')
legline.set_marker("")
legline_marker = Line2D(xdata_marker, ydata[:len(xdata_marker)])
self.update_prop(legline_marker, orig_handle, legend)
legline_marker.set_linestyle('None')
if legend.markerscale != 1:
newsz = legline_marker.get_markersize() * legend.markerscale
legline_marker.set_markersize(newsz)
# we don't want to add this to the return list because
# the texts and handles are assumed to be in one-to-one
# correspondence.
legline._legmarker = legline_marker
legline.set_transform(trans)
legline_marker.set_transform(trans)
return [legline, legline_marker]
class HandlerLine2D(HandlerNpoints):
"""
Handler for `.Line2D` instances.
See Also
--------
HandlerLine2DCompound : An earlier handler implementation, which used one
artist for the line and another for the marker(s).
"""
def create_artists(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize,
trans):
# docstring inherited
xdata, xdata_marker = self.get_xdata(legend, xdescent, ydescent,
width, height, fontsize)
markevery = None
if self.get_numpoints(legend) == 1:
# Special case: one wants a single marker in the center
# and a line that extends on both sides. One will use a
# 3 points line, but only mark the #1 (i.e. middle) point.
xdata = np.linspace(xdata[0], xdata[-1], 3)
markevery = [1]
ydata = np.full_like(xdata, (height - ydescent) / 2)
legline = Line2D(xdata, ydata, markevery=markevery)
self.update_prop(legline, orig_handle, legend)
if legend.markerscale != 1:
newsz = legline.get_markersize() * legend.markerscale
legline.set_markersize(newsz)
legline.set_transform(trans)
return [legline]
class HandlerPatch(HandlerBase):
"""
Handler for `.Patch` instances.
"""
def __init__(self, patch_func=None, **kwargs):
"""
Parameters
----------
patch_func : callable, optional
The function that creates the legend key artist.
*patch_func* should have the signature::
def patch_func(legend=legend, orig_handle=orig_handle,
xdescent=xdescent, ydescent=ydescent,
width=width, height=height, fontsize=fontsize)
Subsequently, the created artist will have its ``update_prop``
method called and the appropriate transform will be applied.
**kwargs
Keyword arguments forwarded to `.HandlerBase`.
"""
super().__init__(**kwargs)
self._patch_func = patch_func
def _create_patch(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize):
if self._patch_func is None:
p = Rectangle(xy=(-xdescent, -ydescent),
width=width, height=height)
else:
p = self._patch_func(legend=legend, orig_handle=orig_handle,
xdescent=xdescent, ydescent=ydescent,
width=width, height=height, fontsize=fontsize)
return p
def create_artists(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize, trans):
# docstring inherited
p = self._create_patch(legend, orig_handle,
xdescent, ydescent, width, height, fontsize)
self.update_prop(p, orig_handle, legend)
p.set_transform(trans)
return [p]
class HandlerStepPatch(HandlerBase):
"""
Handler for `~.matplotlib.patches.StepPatch` instances.
"""
@staticmethod
def _create_patch(orig_handle, xdescent, ydescent, width, height):
return Rectangle(xy=(-xdescent, -ydescent), width=width,
height=height, color=orig_handle.get_facecolor())
@staticmethod
def _create_line(orig_handle, width, height):
# Unfilled StepPatch should show as a line
legline = Line2D([0, width], [height/2, height/2],
color=orig_handle.get_edgecolor(),
linestyle=orig_handle.get_linestyle(),
linewidth=orig_handle.get_linewidth(),
)
# Overwrite manually because patch and line properties don't mix
legline.set_drawstyle('default')
legline.set_marker("")
return legline
def create_artists(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize, trans):
# docstring inherited
if orig_handle.get_fill() or (orig_handle.get_hatch() is not None):
p = self._create_patch(orig_handle, xdescent, ydescent, width,
height)
self.update_prop(p, orig_handle, legend)
else:
p = self._create_line(orig_handle, width, height)
p.set_transform(trans)
return [p]
class HandlerLineCollection(HandlerLine2D):
"""
Handler for `.LineCollection` instances.
"""
def get_numpoints(self, legend):
if self._numpoints is None:
return legend.scatterpoints
else:
return self._numpoints
def _default_update_prop(self, legend_handle, orig_handle):
lw = orig_handle.get_linewidths()[0]
dashes = orig_handle._us_linestyles[0]
color = orig_handle.get_colors()[0]
legend_handle.set_color(color)
legend_handle.set_linestyle(dashes)
legend_handle.set_linewidth(lw)
def create_artists(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize, trans):
# docstring inherited
xdata, xdata_marker = self.get_xdata(legend, xdescent, ydescent,
width, height, fontsize)
ydata = np.full_like(xdata, (height - ydescent) / 2)
legline = Line2D(xdata, ydata)
self.update_prop(legline, orig_handle, legend)
legline.set_transform(trans)
return [legline]
class HandlerRegularPolyCollection(HandlerNpointsYoffsets):
r"""Handler for `.RegularPolyCollection`\s."""
def __init__(self, yoffsets=None, sizes=None, **kwargs):
super().__init__(yoffsets=yoffsets, **kwargs)
self._sizes = sizes
def get_numpoints(self, legend):
if self._numpoints is None:
return legend.scatterpoints
else:
return self._numpoints
def get_sizes(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize):
if self._sizes is None:
handle_sizes = orig_handle.get_sizes()
if not len(handle_sizes):
handle_sizes = [1]
size_max = max(handle_sizes) * legend.markerscale ** 2
size_min = min(handle_sizes) * legend.markerscale ** 2
numpoints = self.get_numpoints(legend)
if numpoints < 4:
sizes = [.5 * (size_max + size_min), size_max,
size_min][:numpoints]
else:
rng = (size_max - size_min)
sizes = rng * np.linspace(0, 1, numpoints) + size_min
else:
sizes = self._sizes
return sizes
def update_prop(self, legend_handle, orig_handle, legend):
self._update_prop(legend_handle, orig_handle)
legend_handle.set_figure(legend.figure)
# legend._set_artist_props(legend_handle)
legend_handle.set_clip_box(None)
legend_handle.set_clip_path(None)
def create_collection(self, orig_handle, sizes, offsets, offset_transform):
return type(orig_handle)(
orig_handle.get_numsides(),
rotation=orig_handle.get_rotation(), sizes=sizes,
offsets=offsets, offset_transform=offset_transform,
)
def create_artists(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize,
trans):
# docstring inherited
xdata, xdata_marker = self.get_xdata(legend, xdescent, ydescent,
width, height, fontsize)
ydata = self.get_ydata(legend, xdescent, ydescent,
width, height, fontsize)
sizes = self.get_sizes(legend, orig_handle, xdescent, ydescent,
width, height, fontsize)
p = self.create_collection(
orig_handle, sizes,
offsets=list(zip(xdata_marker, ydata)), offset_transform=trans)
self.update_prop(p, orig_handle, legend)
p.set_offset_transform(trans)
return [p]
class HandlerPathCollection(HandlerRegularPolyCollection):
r"""Handler for `.PathCollection`\s, which are used by `~.Axes.scatter`."""
def create_collection(self, orig_handle, sizes, offsets, offset_transform):
return type(orig_handle)(
[orig_handle.get_paths()[0]], sizes=sizes,
offsets=offsets, offset_transform=offset_transform,
)
class HandlerCircleCollection(HandlerRegularPolyCollection):
r"""Handler for `.CircleCollection`\s."""
def create_collection(self, orig_handle, sizes, offsets, offset_transform):
return type(orig_handle)(
sizes, offsets=offsets, offset_transform=offset_transform)
class HandlerErrorbar(HandlerLine2D):
"""Handler for Errorbars."""
def __init__(self, xerr_size=0.5, yerr_size=None,
marker_pad=0.3, numpoints=None, **kwargs):
self._xerr_size = xerr_size
self._yerr_size = yerr_size
super().__init__(marker_pad=marker_pad, numpoints=numpoints, **kwargs)
def get_err_size(self, legend, xdescent, ydescent,
width, height, fontsize):
xerr_size = self._xerr_size * fontsize
if self._yerr_size is None:
yerr_size = xerr_size
else:
yerr_size = self._yerr_size * fontsize
return xerr_size, yerr_size
def create_artists(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize,
trans):
# docstring inherited
plotlines, caplines, barlinecols = orig_handle
xdata, xdata_marker = self.get_xdata(legend, xdescent, ydescent,
width, height, fontsize)
ydata = np.full_like(xdata, (height - ydescent) / 2)
legline = Line2D(xdata, ydata)
xdata_marker = np.asarray(xdata_marker)
ydata_marker = np.asarray(ydata[:len(xdata_marker)])
xerr_size, yerr_size = self.get_err_size(legend, xdescent, ydescent,
width, height, fontsize)
legline_marker = Line2D(xdata_marker, ydata_marker)
# when plotlines are None (only errorbars are drawn), we just
# make legline invisible.
if plotlines is None:
legline.set_visible(False)
legline_marker.set_visible(False)
else:
self.update_prop(legline, plotlines, legend)
legline.set_drawstyle('default')
legline.set_marker('none')
self.update_prop(legline_marker, plotlines, legend)
legline_marker.set_linestyle('None')
if legend.markerscale != 1:
newsz = legline_marker.get_markersize() * legend.markerscale
legline_marker.set_markersize(newsz)
handle_barlinecols = []
handle_caplines = []
if orig_handle.has_xerr:
verts = [((x - xerr_size, y), (x + xerr_size, y))
for x, y in zip(xdata_marker, ydata_marker)]
coll = mcoll.LineCollection(verts)
self.update_prop(coll, barlinecols[0], legend)
handle_barlinecols.append(coll)
if caplines:
capline_left = Line2D(xdata_marker - xerr_size, ydata_marker)
capline_right = Line2D(xdata_marker + xerr_size, ydata_marker)
self.update_prop(capline_left, caplines[0], legend)
self.update_prop(capline_right, caplines[0], legend)
capline_left.set_marker("|")
capline_right.set_marker("|")
handle_caplines.append(capline_left)
handle_caplines.append(capline_right)
if orig_handle.has_yerr:
verts = [((x, y - yerr_size), (x, y + yerr_size))
for x, y in zip(xdata_marker, ydata_marker)]
coll = mcoll.LineCollection(verts)
self.update_prop(coll, barlinecols[0], legend)
handle_barlinecols.append(coll)
if caplines:
capline_left = Line2D(xdata_marker, ydata_marker - yerr_size)
capline_right = Line2D(xdata_marker, ydata_marker + yerr_size)
self.update_prop(capline_left, caplines[0], legend)
self.update_prop(capline_right, caplines[0], legend)
capline_left.set_marker("_")
capline_right.set_marker("_")
handle_caplines.append(capline_left)
handle_caplines.append(capline_right)
artists = [
*handle_barlinecols, *handle_caplines, legline, legline_marker,
]
for artist in artists:
artist.set_transform(trans)
return artists
class HandlerStem(HandlerNpointsYoffsets):
"""
Handler for plots produced by `~.Axes.stem`.
"""
def __init__(self, marker_pad=0.3, numpoints=None,
bottom=None, yoffsets=None, **kwargs):
"""
Parameters
----------
marker_pad : float, default: 0.3
Padding between points in legend entry.
numpoints : int, optional
Number of points to show in legend entry.
bottom : float, optional
yoffsets : array of floats, optional
Length *numpoints* list of y offsets for each point in
legend entry.
**kwargs
Keyword arguments forwarded to `.HandlerNpointsYoffsets`.
"""
super().__init__(marker_pad=marker_pad, numpoints=numpoints,
yoffsets=yoffsets, **kwargs)
self._bottom = bottom
def get_ydata(self, legend, xdescent, ydescent, width, height, fontsize):
if self._yoffsets is None:
ydata = height * (0.5 * legend._scatteryoffsets + 0.5)
else:
ydata = height * np.asarray(self._yoffsets)
return ydata
def create_artists(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize,
trans):
# docstring inherited
markerline, stemlines, baseline = orig_handle
# Check to see if the stemcontainer is storing lines as a list or a
# LineCollection. Eventually using a list will be removed, and this
# logic can also be removed.
using_linecoll = isinstance(stemlines, mcoll.LineCollection)
xdata, xdata_marker = self.get_xdata(legend, xdescent, ydescent,
width, height, fontsize)
ydata = self.get_ydata(legend, xdescent, ydescent,
width, height, fontsize)
if self._bottom is None:
bottom = 0.
else:
bottom = self._bottom
leg_markerline = Line2D(xdata_marker, ydata[:len(xdata_marker)])
self.update_prop(leg_markerline, markerline, legend)
leg_stemlines = [Line2D([x, x], [bottom, y])
for x, y in zip(xdata_marker, ydata)]
if using_linecoll:
# change the function used by update_prop() from the default
# to one that handles LineCollection
with cbook._setattr_cm(
self, _update_prop_func=self._copy_collection_props):
for line in leg_stemlines:
self.update_prop(line, stemlines, legend)
else:
for lm, m in zip(leg_stemlines, stemlines):
self.update_prop(lm, m, legend)
leg_baseline = Line2D([np.min(xdata), np.max(xdata)],
[bottom, bottom])
self.update_prop(leg_baseline, baseline, legend)
artists = [*leg_stemlines, leg_baseline, leg_markerline]
for artist in artists:
artist.set_transform(trans)
return artists
def _copy_collection_props(self, legend_handle, orig_handle):
"""
Copy properties from the `.LineCollection` *orig_handle* to the
`.Line2D` *legend_handle*.
"""
legend_handle.set_color(orig_handle.get_color()[0])
legend_handle.set_linestyle(orig_handle.get_linestyle()[0])
class HandlerTuple(HandlerBase):
"""
Handler for Tuple.
"""
def __init__(self, ndivide=1, pad=None, **kwargs):
"""
Parameters
----------
ndivide : int or None, default: 1
The number of sections to divide the legend area into. If None,
use the length of the input tuple.
pad : float, default: :rc:`legend.borderpad`
Padding in units of fraction of font size.
**kwargs
Keyword arguments forwarded to `.HandlerBase`.
"""
self._ndivide = ndivide
self._pad = pad
super().__init__(**kwargs)
def create_artists(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize,
trans):
# docstring inherited
handler_map = legend.get_legend_handler_map()
if self._ndivide is None:
ndivide = len(orig_handle)
else:
ndivide = self._ndivide
if self._pad is None:
pad = legend.borderpad * fontsize
else:
pad = self._pad * fontsize
if ndivide > 1:
width = (width - pad * (ndivide - 1)) / ndivide
xds_cycle = cycle(xdescent - (width + pad) * np.arange(ndivide))
a_list = []
for handle1 in orig_handle:
handler = legend.get_legend_handler(handler_map, handle1)
_a_list = handler.create_artists(
legend, handle1,
next(xds_cycle), ydescent, width, height, fontsize, trans)
a_list.extend(_a_list)
return a_list
class HandlerPolyCollection(HandlerBase):
"""
Handler for `.PolyCollection` used in `~.Axes.fill_between` and
`~.Axes.stackplot`.
"""
def _update_prop(self, legend_handle, orig_handle):
def first_color(colors):
if colors.size == 0:
return (0, 0, 0, 0)
return tuple(colors[0])
def get_first(prop_array):
if len(prop_array):
return prop_array[0]
else:
return None
# orig_handle is a PolyCollection and legend_handle is a Patch.
# Directly set Patch color attributes (must be RGBA tuples).
legend_handle._facecolor = first_color(orig_handle.get_facecolor())
legend_handle._edgecolor = first_color(orig_handle.get_edgecolor())
legend_handle._original_facecolor = orig_handle._original_facecolor
legend_handle._original_edgecolor = orig_handle._original_edgecolor
legend_handle._fill = orig_handle.get_fill()
legend_handle._hatch = orig_handle.get_hatch()
# Hatch color is anomalous in having no getters and setters.
legend_handle._hatch_color = orig_handle._hatch_color
# Setters are fine for the remaining attributes.
legend_handle.set_linewidth(get_first(orig_handle.get_linewidths()))
legend_handle.set_linestyle(get_first(orig_handle.get_linestyles()))
legend_handle.set_transform(get_first(orig_handle.get_transforms()))
legend_handle.set_figure(orig_handle.get_figure())
# Alpha is already taken into account by the color attributes.
def create_artists(self, legend, orig_handle,
xdescent, ydescent, width, height, fontsize, trans):
# docstring inherited
p = Rectangle(xy=(-xdescent, -ydescent),
width=width, height=height)
self.update_prop(p, orig_handle, legend)
p.set_transform(trans)
return [p]