legend_handler.py

"""
This module defines default legend handlers.

It is strongly encouraged to have read the :doc:`legend guide
</tutorials/intermediate/legend_guide>` before 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 a
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 needs to
be scaled according to the fontsize (note that the size is in pixel,
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.lines import Line2D
from matplotlib.patches import Rectangle
import matplotlib.collections as mcoll
import matplotlib.colors as mcolors


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 a 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):
        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 : :class:`matplotlib.legend.Legend` instance
            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 : float or int
            The fontsize in pixels. The artists being created should
            be scaled according to the given fontsize.
        handlebox : :class:`matplotlib.offsetbox.OffsetBox` instance
            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):
        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, **kw):
        """
        Parameters
        ----------
        marker_pad : float
            Padding between points in legend entry.

        numpoints : int
            Number of points to show in legend entry.

        Notes
        -----
        Any other keyword arguments are given to `HandlerBase`.
        """
        HandlerBase.__init__(self, **kw)

        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 offest in the y-direction.
    """
    def __init__(self, numpoints=None, yoffsets=None, **kw):
        """
        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.

        Notes
        -----
        Any other keyword arguments are given to `HandlerNpoints`.
        """
        HandlerNpoints.__init__(self, numpoints=numpoints, **kw)
        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 HandlerLine2D(HandlerNpoints):
    """
    Handler for `.Line2D` instances.
    """
    def __init__(self, marker_pad=0.3, numpoints=None, **kw):
        """
        Parameters
        ----------
        marker_pad : float
            Padding between points in legend entry.

        numpoints : int
            Number of points to show in legend entry.

        Notes
        -----
        Any other keyword arguments are given to `HandlerNpoints`.
        """
        HandlerNpoints.__init__(self, marker_pad=marker_pad,
                                numpoints=numpoints, **kw)

    def create_artists(self, legend, orig_handle,
                       xdescent, ydescent, width, height, fontsize,
                       trans):

        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 HandlerPatch(HandlerBase):
    """
    Handler for `.Patch` instances.
    """
    def __init__(self, patch_func=None, **kw):
        """
        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.

        Notes
        -----
        Any other keyword arguments are given to `HandlerBase`.
        """
        HandlerBase.__init__(self, **kw)
        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):
        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 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):

        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):
    """
    Handler for `.RegularPolyCollections`.
    """
    def __init__(self, yoffsets=None, sizes=None, **kw):
        HandlerNpointsYoffsets.__init__(self, yoffsets=yoffsets, **kw)

        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, transOffset):
        p = type(orig_handle)(orig_handle.get_numsides(),
                              rotation=orig_handle.get_rotation(),
                              sizes=sizes,
                              offsets=offsets,
                              transOffset=transOffset,
                              )
        return p

    def create_artists(self, legend, orig_handle,
                       xdescent, ydescent, width, height, fontsize,
                       trans):
        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)),
                                   transOffset=trans)

        self.update_prop(p, orig_handle, legend)
        p._transOffset = trans
        return [p]


class HandlerPathCollection(HandlerRegularPolyCollection):
    """
    Handler for `.PathCollections`, which are used by `~.Axes.scatter`.
    """
    def create_collection(self, orig_handle, sizes, offsets, transOffset):
        p = type(orig_handle)([orig_handle.get_paths()[0]],
                              sizes=sizes,
                              offsets=offsets,
                              transOffset=transOffset,
                              )
        return p


class HandlerCircleCollection(HandlerRegularPolyCollection):
    """
    Handler for `.CircleCollections`.
    """
    def create_collection(self, orig_handle, sizes, offsets, transOffset):
        p = type(orig_handle)(sizes,
                              offsets=offsets,
                              transOffset=transOffset,
                              )
        return p


class HandlerErrorbar(HandlerLine2D):
    """
    Handler for Errorbars.
    """
    def __init__(self, xerr_size=0.5, yerr_size=None,
                 marker_pad=0.3, numpoints=None, **kw):

        self._xerr_size = xerr_size
        self._yerr_size = yerr_size

        HandlerLine2D.__init__(self, marker_pad=marker_pad,
                               numpoints=numpoints, **kw)

    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):

        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, **kw):
        """
        Parameters
        ----------
        marker_pad : float
            Padding between points in legend entry. Default is 0.3.

        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.

        Notes
        -----
        Any other keyword arguments are given to `HandlerNpointsYoffsets`.
        """

        HandlerNpointsYoffsets.__init__(self, marker_pad=marker_pad,
                                        numpoints=numpoints,
                                        yoffsets=yoffsets,
                                        **kw)
        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):
        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
            orig_update_func = self._update_prop_func
            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)

        if using_linecoll:
            self._update_prop_func = orig_update_func

        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):
        """
        Method to copy properties from a LineCollection (orig_handle) to a
        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.

    Additional kwargs are passed through to `HandlerBase`.

    Parameters
    ----------
    ndivide : int, optional
        The number of sections to divide the legend area into. If None,
        use the length of the input tuple. Default is 1.


    pad : float, optional
        If None, fall back to ``legend.borderpad`` as the default.
        In units of fraction of font size. Default is None.
    """
    def __init__(self, ndivide=1, pad=None, **kwargs):

        self._ndivide = ndivide
        self._pad = pad
        HandlerBase.__init__(self, **kwargs)

    def create_artists(self, legend, orig_handle,
                       xdescent, ydescent, width, height, fontsize,
                       trans):

        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 is None:
                return None
            colors = mcolors.to_rgba_array(colors)
            if len(colors):
                return colors[0]
            else:
                return "none"

        def get_first(prop_array):
            if len(prop_array):
                return prop_array[0]
            else:
                return None
        edgecolor = getattr(orig_handle, '_original_edgecolor',
                            orig_handle.get_edgecolor())
        legend_handle.set_edgecolor(first_color(edgecolor))
        facecolor = getattr(orig_handle, '_original_facecolor',
                            orig_handle.get_facecolor())
        legend_handle.set_facecolor(first_color(facecolor))
        legend_handle.set_fill(orig_handle.get_fill())
        legend_handle.set_hatch(orig_handle.get_hatch())
        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())
        legend_handle.set_alpha(orig_handle.get_alpha())

    def create_artists(self, legend, orig_handle,
                       xdescent, ydescent, width, height, fontsize, trans):
        p = Rectangle(xy=(-xdescent, -ydescent),
                      width=width, height=height)
        self.update_prop(p, orig_handle, legend)
        p.set_transform(trans)
        return [p]