from collections import namedtuple
import contextlib
from functools import wraps
import inspect
from inspect import Signature, Parameter
import logging
from numbers import Number
import re
import warnings

import numpy as np

import matplotlib as mpl
from . import _api, cbook
from .cm import ScalarMappable
from .path import Path
from .transforms import (Bbox, IdentityTransform, Transform, TransformedBbox,
                         TransformedPatchPath, TransformedPath)

_log = logging.getLogger(__name__)


def allow_rasterization(draw):
    """
    Decorator for Artist.draw method. Provides routines
    that run before and after the draw call. The before and after functions
    are useful for changing artist-dependent renderer attributes or making
    other setup function calls, such as starting and flushing a mixed-mode
    renderer.
    """

    @wraps(draw)
    def draw_wrapper(artist, renderer):
        try:
            if artist.get_rasterized():
                if renderer._raster_depth == 0 and not renderer._rasterizing:
                    renderer.start_rasterizing()
                    renderer._rasterizing = True
                renderer._raster_depth += 1
            else:
                if renderer._raster_depth == 0 and renderer._rasterizing:
                    # Only stop when we are not in a rasterized parent
                    # and something has be rasterized since last stop
                    renderer.stop_rasterizing()
                    renderer._rasterizing = False

            if artist.get_agg_filter() is not None:
                renderer.start_filter()

            return draw(artist, renderer)
        finally:
            if artist.get_agg_filter() is not None:
                renderer.stop_filter(artist.get_agg_filter())
            if artist.get_rasterized():
                renderer._raster_depth -= 1
            if (renderer._rasterizing and artist.figure and
                    artist.figure.suppressComposite):
                # restart rasterizing to prevent merging
                renderer.stop_rasterizing()
                renderer.start_rasterizing()

    draw_wrapper._supports_rasterization = True
    return draw_wrapper


def _finalize_rasterization(draw):
    """
    Decorator for Artist.draw method. Needed on the outermost artist, i.e.
    Figure, to finish up if the render is still in rasterized mode.
    """
    @wraps(draw)
    def draw_wrapper(artist, renderer, *args, **kwargs):
        result = draw(artist, renderer, *args, **kwargs)
        if renderer._rasterizing:
            renderer.stop_rasterizing()
            renderer._rasterizing = False
        return result
    return draw_wrapper


def _stale_axes_callback(self, val):
    if self.axes:
        self.axes.stale = val


_XYPair = namedtuple("_XYPair", "x y")


class _Unset:
    def __repr__(self):
        return "<UNSET>"
_UNSET = _Unset()


class Artist:
    """
    Abstract base class for objects that render into a FigureCanvas.

    Typically, all visible elements in a figure are subclasses of Artist.
    """

    zorder = 0

    def __init_subclass__(cls):
        # Inject custom set() methods into the subclass with signature and
        # docstring based on the subclasses' properties.

        if not hasattr(cls.set, '_autogenerated_signature'):
            # Don't overwrite cls.set if the subclass or one of its parents
            # has defined a set method set itself.
            # If there was no explicit definition, cls.set is inherited from
            # the hierarchy of auto-generated set methods, which hold the
            # flag _autogenerated_signature.
            return

        cls.set = lambda self, **kwargs: Artist.set(self, **kwargs)
        cls.set.__name__ = "set"
        cls.set.__qualname__ = f"{cls.__qualname__}.set"
        cls._update_set_signature_and_docstring()

    _PROPERTIES_EXCLUDED_FROM_SET = [
        'navigate_mode',  # not a user-facing function
        'figure',         # changing the figure is such a profound operation
                          # that we don't want this in set()
        '3d_properties',  # cannot be used as a keyword due to leading digit
    ]

    @classmethod
    def _update_set_signature_and_docstring(cls):
        """
        Update the signature of the set function to list all properties
        as keyword arguments.

        Property aliases are not listed in the signature for brevity, but
        are still accepted as keyword arguments.
        """
        cls.set.__signature__ = Signature(
            [Parameter("self", Parameter.POSITIONAL_OR_KEYWORD),
             *[Parameter(prop, Parameter.KEYWORD_ONLY, default=_UNSET)
               for prop in ArtistInspector(cls).get_setters()
               if prop not in Artist._PROPERTIES_EXCLUDED_FROM_SET]])
        cls.set._autogenerated_signature = True

        cls.set.__doc__ = (
            "Set multiple properties at once.\n\n"
            "Supported properties are\n\n"
            + kwdoc(cls))

    def __init__(self):
        self._stale = True
        self.stale_callback = None
        self._axes = None
        self.figure = None

        self._transform = None
        self._transformSet = False
        self._visible = True
        self._animated = False
        self._alpha = None
        self.clipbox = None
        self._clippath = None
        self._clipon = True
        self._label = ''
        self._picker = None
        self._rasterized = False
        self._agg_filter = None
        # Normally, artist classes need to be queried for mouseover info if and
        # only if they override get_cursor_data.
        self._mouseover = type(self).get_cursor_data != Artist.get_cursor_data
        self._callbacks = cbook.CallbackRegistry()
        try:
            self.axes = None
        except AttributeError:
            # Handle self.axes as a read-only property, as in Figure.
            pass
        self._remove_method = None
        self._url = None
        self._gid = None
        self._snap = None
        self._sketch = mpl.rcParams['path.sketch']
        self._path_effects = mpl.rcParams['path.effects']
        self._sticky_edges = _XYPair([], [])
        self._in_layout = True

    def __getstate__(self):
        d = self.__dict__.copy()
        # remove the unpicklable remove method, this will get re-added on load
        # (by the axes) if the artist lives on an axes.
        d['stale_callback'] = None
        return d

    def remove(self):
        """
        Remove the artist from the figure if possible.

        The effect will not be visible until the figure is redrawn, e.g.,
        with `.FigureCanvasBase.draw_idle`.  Call `~.axes.Axes.relim` to
        update the axes limits if desired.

        Note: `~.axes.Axes.relim` will not see collections even if the
        collection was added to the axes with *autolim* = True.

        Note: there is no support for removing the artist's legend entry.
        """

        # There is no method to set the callback.  Instead the parent should
        # set the _remove_method attribute directly.  This would be a
        # protected attribute if Python supported that sort of thing.  The
        # callback has one parameter, which is the child to be removed.
        if self._remove_method is not None:
            self._remove_method(self)
            # clear stale callback
            self.stale_callback = None
            _ax_flag = False
            if hasattr(self, 'axes') and self.axes:
                # remove from the mouse hit list
                self.axes._mouseover_set.discard(self)
                # mark the axes as stale
                self.axes.stale = True
                # decouple the artist from the axes
                self.axes = None
                _ax_flag = True

            if self.figure:
                self.figure = None
                if not _ax_flag:
                    self.figure = True

        else:
            raise NotImplementedError('cannot remove artist')
        # TODO: the fix for the collections relim problem is to move the
        # limits calculation into the artist itself, including the property of
        # whether or not the artist should affect the limits.  Then there will
        # be no distinction between axes.add_line, axes.add_patch, etc.
        # TODO: add legend support

    def have_units(self):
        """Return whether units are set on any axis."""
        ax = self.axes
        return ax and any(axis.have_units() for axis in ax._get_axis_list())

    def convert_xunits(self, x):
        """
        Convert *x* using the unit type of the xaxis.

        If the artist is not in contained in an Axes or if the xaxis does not
        have units, *x* itself is returned.
        """
        ax = getattr(self, 'axes', None)
        if ax is None or ax.xaxis is None:
            return x
        return ax.xaxis.convert_units(x)

    def convert_yunits(self, y):
        """
        Convert *y* using the unit type of the yaxis.

        If the artist is not in contained in an Axes or if the yaxis does not
        have units, *y* itself is returned.
        """
        ax = getattr(self, 'axes', None)
        if ax is None or ax.yaxis is None:
            return y
        return ax.yaxis.convert_units(y)

    @property
    def axes(self):
        """The `~.axes.Axes` instance the artist resides in, or *None*."""
        return self._axes

    @axes.setter
    def axes(self, new_axes):
        if (new_axes is not None and self._axes is not None
                and new_axes != self._axes):
            raise ValueError("Can not reset the axes.  You are probably "
                             "trying to re-use an artist in more than one "
                             "Axes which is not supported")
        self._axes = new_axes
        if new_axes is not None and new_axes is not self:
            self.stale_callback = _stale_axes_callback

    @property
    def stale(self):
        """
        Whether the artist is 'stale' and needs to be re-drawn for the output
        to match the internal state of the artist.
        """
        return self._stale

    @stale.setter
    def stale(self, val):
        self._stale = val

        # if the artist is animated it does not take normal part in the
        # draw stack and is not expected to be drawn as part of the normal
        # draw loop (when not saving) so do not propagate this change
        if self.get_animated():
            return

        if val and self.stale_callback is not None:
            self.stale_callback(self, val)

    def get_window_extent(self, renderer):
        """
        Get the artist's bounding box in display space.

        The bounding box' width and height are nonnegative.

        Subclasses should override for inclusion in the bounding box
        "tight" calculation. Default is to return an empty bounding
        box at 0, 0.

        Be careful when using this function, the results will not update
        if the artist window extent of the artist changes.  The extent
        can change due to any changes in the transform stack, such as
        changing the axes limits, the figure size, or the canvas used
        (as is done when saving a figure).  This can lead to unexpected
        behavior where interactive figures will look fine on the screen,
        but will save incorrectly.
        """
        return Bbox([[0, 0], [0, 0]])

    def _get_clipping_extent_bbox(self):
        """
        Return a bbox with the extents of the intersection of the clip_path
        and clip_box for this artist, or None if both of these are
        None, or ``get_clip_on`` is False.
        """
        bbox = None
        if self.get_clip_on():
            clip_box = self.get_clip_box()
            if clip_box is not None:
                bbox = clip_box
            clip_path = self.get_clip_path()
            if clip_path is not None and bbox is not None:
                clip_path = clip_path.get_fully_transformed_path()
                bbox = Bbox.intersection(bbox, clip_path.get_extents())
        return bbox

    def get_tightbbox(self, renderer):
        """
        Like `.Artist.get_window_extent`, but includes any clipping.

        Parameters
        ----------
        renderer : `.RendererBase` subclass
            renderer that will be used to draw the figures (i.e.
            ``fig.canvas.get_renderer()``)

        Returns
        -------
        `.Bbox`
            The enclosing bounding box (in figure pixel coordinates).
        """
        bbox = self.get_window_extent(renderer)
        if self.get_clip_on():
            clip_box = self.get_clip_box()
            if clip_box is not None:
                bbox = Bbox.intersection(bbox, clip_box)
            clip_path = self.get_clip_path()
            if clip_path is not None and bbox is not None:
                clip_path = clip_path.get_fully_transformed_path()
                bbox = Bbox.intersection(bbox, clip_path.get_extents())
        return bbox

    def add_callback(self, func):
        """
        Add a callback function that will be called whenever one of the
        `.Artist`'s properties changes.

        Parameters
        ----------
        func : callable
            The callback function. It must have the signature::

                def func(artist: Artist) -> Any

            where *artist* is the calling `.Artist`. Return values may exist
            but are ignored.

        Returns
        -------
        int
            The observer id associated with the callback. This id can be
            used for removing the callback with `.remove_callback` later.

        See Also
        --------
        remove_callback
        """
        # Wrapping func in a lambda ensures it can be connected multiple times
        # and never gets weakref-gc'ed.
        return self._callbacks.connect("pchanged", lambda: func(self))

    def remove_callback(self, oid):
        """
        Remove a callback based on its observer id.

        See Also
        --------
        add_callback
        """
        self._callbacks.disconnect(oid)

    def pchanged(self):
        """
        Call all of the registered callbacks.

        This function is triggered internally when a property is changed.

        See Also
        --------
        add_callback
        remove_callback
        """
        self._callbacks.process("pchanged")

    def is_transform_set(self):
        """
        Return whether the Artist has an explicitly set transform.

        This is *True* after `.set_transform` has been called.
        """
        return self._transformSet

    def set_transform(self, t):
        """
        Set the artist transform.

        Parameters
        ----------
        t : `.Transform`
        """
        self._transform = t
        self._transformSet = True
        self.pchanged()
        self.stale = True

    def get_transform(self):
        """Return the `.Transform` instance used by this artist."""
        if self._transform is None:
            self._transform = IdentityTransform()
        elif (not isinstance(self._transform, Transform)
              and hasattr(self._transform, '_as_mpl_transform')):
            self._transform = self._transform._as_mpl_transform(self.axes)
        return self._transform

    def get_children(self):
        r"""Return a list of the child `.Artist`\s of this `.Artist`."""
        return []

    def _default_contains(self, mouseevent, figure=None):
        """
        Base impl. for checking whether a mouseevent happened in an artist.

        1. If the artist figure is known and the event did not occur in that
           figure (by checking its ``canvas`` attribute), reject it.
        2. Otherwise, return `None, {}`, indicating that the subclass'
           implementation should be used.

        Subclasses should start their definition of `contains` as follows:

            inside, info = self._default_contains(mouseevent)
            if inside is not None:
                return inside, info
            # subclass-specific implementation follows

        The *figure* kwarg is provided for the implementation of
        `.Figure.contains`.
        """
        if figure is not None and mouseevent.canvas is not figure.canvas:
            return False, {}
        return None, {}

    def contains(self, mouseevent):
        """
        Test whether the artist contains the mouse event.

        Parameters
        ----------
        mouseevent : `matplotlib.backend_bases.MouseEvent`

        Returns
        -------
        contains : bool
            Whether any values are within the radius.
        details : dict
            An artist-specific dictionary of details of the event context,
            such as which points are contained in the pick radius. See the
            individual Artist subclasses for details.
        """
        inside, info = self._default_contains(mouseevent)
        if inside is not None:
            return inside, info
        _log.warning("%r needs 'contains' method", self.__class__.__name__)
        return False, {}

    def pickable(self):
        """
        Return whether the artist is pickable.

        See Also
        --------
        set_picker, get_picker, pick
        """
        return self.figure is not None and self._picker is not None

    def pick(self, mouseevent):
        """
        Process a pick event.

        Each child artist will fire a pick event if *mouseevent* is over
        the artist and the artist has picker set.

        See Also
        --------
        set_picker, get_picker, pickable
        """
        # Pick self
        if self.pickable():
            picker = self.get_picker()
            if callable(picker):
                inside, prop = picker(self, mouseevent)
            else:
                inside, prop = self.contains(mouseevent)
            if inside:
                self.figure.canvas.pick_event(mouseevent, self, **prop)

        # Pick children
        for a in self.get_children():
            # make sure the event happened in the same axes
            ax = getattr(a, 'axes', None)
            if (mouseevent.inaxes is None or ax is None
                    or mouseevent.inaxes == ax):
                # we need to check if mouseevent.inaxes is None
                # because some objects associated with an axes (e.g., a
                # tick label) can be outside the bounding box of the
                # axes and inaxes will be None
                # also check that ax is None so that it traverse objects
                # which do no have an axes property but children might
                a.pick(mouseevent)

    def set_picker(self, picker):
        """
        Define the picking behavior of the artist.

        Parameters
        ----------
        picker : None or bool or float or callable
            This can be one of the following:

            - *None*: Picking is disabled for this artist (default).

            - A boolean: If *True* then picking will be enabled and the
              artist will fire a pick event if the mouse event is over
              the artist.

            - A float: If picker is a number it is interpreted as an
              epsilon tolerance in points and the artist will fire
              off an event if its data is within epsilon of the mouse
              event.  For some artists like lines and patch collections,
              the artist may provide additional data to the pick event
              that is generated, e.g., the indices of the data within
              epsilon of the pick event

            - A function: If picker is callable, it is a user supplied
              function which determines whether the artist is hit by the
              mouse event::

                hit, props = picker(artist, mouseevent)

              to determine the hit test.  if the mouse event is over the
              artist, return *hit=True* and props is a dictionary of
              properties you want added to the PickEvent attributes.
        """
        self._picker = picker

    def get_picker(self):
        """
        Return the picking behavior of the artist.

        The possible values are described in `.set_picker`.

        See Also
        --------
        set_picker, pickable, pick
        """
        return self._picker

    def get_url(self):
        """Return the url."""
        return self._url

    def set_url(self, url):
        """
        Set the url for the artist.

        Parameters
        ----------
        url : str
        """
        self._url = url

    def get_gid(self):
        """Return the group id."""
        return self._gid

    def set_gid(self, gid):
        """
        Set the (group) id for the artist.

        Parameters
        ----------
        gid : str
        """
        self._gid = gid

    def get_snap(self):
        """
        Return the snap setting.

        See `.set_snap` for details.
        """
        if mpl.rcParams['path.snap']:
            return self._snap
        else:
            return False

    def set_snap(self, snap):
        """
        Set the snapping behavior.

        Snapping aligns positions with the pixel grid, which results in
        clearer images. For example, if a black line of 1px width was
        defined at a position in between two pixels, the resulting image
        would contain the interpolated value of that line in the pixel grid,
        which would be a grey value on both adjacent pixel positions. In
        contrast, snapping will move the line to the nearest integer pixel
        value, so that the resulting image will really contain a 1px wide
        black line.

        Snapping is currently only supported by the Agg and MacOSX backends.

        Parameters
        ----------
        snap : bool or None
            Possible values:

            - *True*: Snap vertices to the nearest pixel center.
            - *False*: Do not modify vertex positions.
            - *None*: (auto) If the path contains only rectilinear line
              segments, round to the nearest pixel center.
        """
        self._snap = snap
        self.stale = True

    def get_sketch_params(self):
        """
        Return the sketch parameters for the artist.

        Returns
        -------
        tuple or None

            A 3-tuple with the following elements:

            - *scale*: The amplitude of the wiggle perpendicular to the
              source line.
            - *length*: The length of the wiggle along the line.
            - *randomness*: The scale factor by which the length is
              shrunken or expanded.

            Returns *None* if no sketch parameters were set.
        """
        return self._sketch

    def set_sketch_params(self, scale=None, length=None, randomness=None):
        """
        Set the sketch parameters.

        Parameters
        ----------
        scale : float, optional
            The amplitude of the wiggle perpendicular to the source
            line, in pixels.  If scale is `None`, or not provided, no
            sketch filter will be provided.
        length : float, optional
             The length of the wiggle along the line, in pixels
             (default 128.0)
        randomness : float, optional
            The scale factor by which the length is shrunken or
            expanded (default 16.0)

            The PGF backend uses this argument as an RNG seed and not as
            described above. Using the same seed yields the same random shape.

            .. ACCEPTS: (scale: float, length: float, randomness: float)
        """
        if scale is None:
            self._sketch = None
        else:
            self._sketch = (scale, length or 128.0, randomness or 16.0)
        self.stale = True

    def set_path_effects(self, path_effects):
        """
        Set the path effects.

        Parameters
        ----------
        path_effects : `.AbstractPathEffect`
        """
        self._path_effects = path_effects
        self.stale = True

    def get_path_effects(self):
        return self._path_effects

    def get_figure(self):
        """Return the `.Figure` instance the artist belongs to."""
        return self.figure

    def set_figure(self, fig):
        """
        Set the `.Figure` instance the artist belongs to.

        Parameters
        ----------
        fig : `.Figure`
        """
        # if this is a no-op just return
        if self.figure is fig:
            return
        # if we currently have a figure (the case of both `self.figure`
        # and *fig* being none is taken care of above) we then user is
        # trying to change the figure an artist is associated with which
        # is not allowed for the same reason as adding the same instance
        # to more than one Axes
        if self.figure is not None:
            raise RuntimeError("Can not put single artist in "
                               "more than one figure")
        self.figure = fig
        if self.figure and self.figure is not self:
            self.pchanged()
        self.stale = True

    def set_clip_box(self, clipbox):
        """
        Set the artist's clip `.Bbox`.

        Parameters
        ----------
        clipbox : `.Bbox`
        """
        self.clipbox = clipbox
        self.pchanged()
        self.stale = True

    def set_clip_path(self, path, transform=None):
        """
        Set the artist's clip path.

        Parameters
        ----------
        path : `.Patch` or `.Path` or `.TransformedPath` or None
            The clip path. If given a `.Path`, *transform* must be provided as
            well. If *None*, a previously set clip path is removed.
        transform : `~matplotlib.transforms.Transform`, optional
            Only used if *path* is a `.Path`, in which case the given `.Path`
            is converted to a `.TransformedPath` using *transform*.

        Notes
        -----
        For efficiency, if *path* is a `.Rectangle` this method will set the
        clipping box to the corresponding rectangle and set the clipping path
        to ``None``.

        For technical reasons (support of `~.Artist.set`), a tuple
        (*path*, *transform*) is also accepted as a single positional
        parameter.

        .. ACCEPTS: Patch or (Path, Transform) or None
        """
        from matplotlib.patches import Patch, Rectangle

        success = False
        if transform is None:
            if isinstance(path, Rectangle):
                self.clipbox = TransformedBbox(Bbox.unit(),
                                               path.get_transform())
                self._clippath = None
                success = True
            elif isinstance(path, Patch):
                self._clippath = TransformedPatchPath(path)
                success = True
            elif isinstance(path, tuple):
                path, transform = path

        if path is None:
            self._clippath = None
            success = True
        elif isinstance(path, Path):
            self._clippath = TransformedPath(path, transform)
            success = True
        elif isinstance(path, TransformedPatchPath):
            self._clippath = path
            success = True
        elif isinstance(path, TransformedPath):
            self._clippath = path
            success = True

        if not success:
            raise TypeError(
                "Invalid arguments to set_clip_path, of type {} and {}"
                .format(type(path).__name__, type(transform).__name__))
        # This may result in the callbacks being hit twice, but guarantees they
        # will be hit at least once.
        self.pchanged()
        self.stale = True

    def get_alpha(self):
        """
        Return the alpha value used for blending - not supported on all
        backends.
        """
        return self._alpha

    def get_visible(self):
        """Return the visibility."""
        return self._visible

    def get_animated(self):
        """Return whether the artist is animated."""
        return self._animated

    def get_in_layout(self):
        """
        Return boolean flag, ``True`` if artist is included in layout
        calculations.

        E.g. :doc:`/tutorials/intermediate/constrainedlayout_guide`,
        `.Figure.tight_layout()`, and
        ``fig.savefig(fname, bbox_inches='tight')``.
        """
        return self._in_layout

    def get_clip_on(self):
        """Return whether the artist uses clipping."""
        return self._clipon

    def get_clip_box(self):
        """Return the clipbox."""
        return self.clipbox

    def get_clip_path(self):
        """Return the clip path."""
        return self._clippath

    def get_transformed_clip_path_and_affine(self):
        """
        Return the clip path with the non-affine part of its
        transformation applied, and the remaining affine part of its
        transformation.
        """
        if self._clippath is not None:
            return self._clippath.get_transformed_path_and_affine()
        return None, None

    def set_clip_on(self, b):
        """
        Set whether the artist uses clipping.

        When False artists will be visible outside of the axes which
        can lead to unexpected results.

        Parameters
        ----------
        b : bool
        """
        self._clipon = b
        # This may result in the callbacks being hit twice, but ensures they
        # are hit at least once
        self.pchanged()
        self.stale = True

    def _set_gc_clip(self, gc):
        """Set the clip properly for the gc."""
        if self._clipon:
            if self.clipbox is not None:
                gc.set_clip_rectangle(self.clipbox)
            gc.set_clip_path(self._clippath)
        else:
            gc.set_clip_rectangle(None)
            gc.set_clip_path(None)

    def get_rasterized(self):
        """Return whether the artist is to be rasterized."""
        return self._rasterized

    def set_rasterized(self, rasterized):
        """
        Force rasterized (bitmap) drawing for vector graphics output.

        Rasterized drawing is not supported by all artists. If you try to
        enable this on an artist that does not support it, the command has no
        effect and a warning will be issued.

        This setting is ignored for pixel-based output.

        See also :doc:`/gallery/misc/rasterization_demo`.

        Parameters
        ----------
        rasterized : bool
        """
        if rasterized and not hasattr(self.draw, "_supports_rasterization"):
            _api.warn_external(f"Rasterization of '{self}' will be ignored")

        self._rasterized = rasterized

    def get_agg_filter(self):
        """Return filter function to be used for agg filter."""
        return self._agg_filter

    def set_agg_filter(self, filter_func):
        """
        Set the agg filter.

        Parameters
        ----------
        filter_func : callable
            A filter function, which takes a (m, n, 3) float array and a dpi
            value, and returns a (m, n, 3) array.

            .. ACCEPTS: a filter function, which takes a (m, n, 3) float array
                and a dpi value, and returns a (m, n, 3) array
        """
        self._agg_filter = filter_func
        self.stale = True

    def draw(self, renderer):
        """
        Draw the Artist (and its children) using the given renderer.

        This has no effect if the artist is not visible (`.Artist.get_visible`
        returns False).

        Parameters
        ----------
        renderer : `.RendererBase` subclass.

        Notes
        -----
        This method is overridden in the Artist subclasses.
        """
        if not self.get_visible():
            return
        self.stale = False

    def set_alpha(self, alpha):
        """
        Set the alpha value used for blending - not supported on all backends.

        Parameters
        ----------
        alpha : scalar or None
            *alpha* must be within the 0-1 range, inclusive.
        """
        if alpha is not None and not isinstance(alpha, Number):
            raise TypeError(
                f'alpha must be numeric or None, not {type(alpha)}')
        if alpha is not None and not (0 <= alpha <= 1):
            raise ValueError(f'alpha ({alpha}) is outside 0-1 range')
        self._alpha = alpha
        self.pchanged()
        self.stale = True

    def _set_alpha_for_array(self, alpha):
        """
        Set the alpha value used for blending - not supported on all backends.

        Parameters
        ----------
        alpha : array-like or scalar or None
            All values must be within the 0-1 range, inclusive.
            Masked values and nans are not supported.
        """
        if isinstance(alpha, str):
            raise TypeError("alpha must be numeric or None, not a string")
        if not np.iterable(alpha):
            Artist.set_alpha(self, alpha)
            return
        alpha = np.asarray(alpha)
        if not (0 <= alpha.min() and alpha.max() <= 1):
            raise ValueError('alpha must be between 0 and 1, inclusive, '
                             f'but min is {alpha.min()}, max is {alpha.max()}')
        self._alpha = alpha
        self.pchanged()
        self.stale = True

    def set_visible(self, b):
        """
        Set the artist's visibility.

        Parameters
        ----------
        b : bool
        """
        self._visible = b
        self.pchanged()
        self.stale = True

    def set_animated(self, b):
        """
        Set whether the artist is intended to be used in an animation.

        If True, the artist is excluded from regular drawing of the figure.
        You have to call `.Figure.draw_artist` / `.Axes.draw_artist`
        explicitly on the artist. This appoach is used to speed up animations
        using blitting.

        See also `matplotlib.animation` and
        :doc:`/tutorials/advanced/blitting`.

        Parameters
        ----------
        b : bool
        """
        if self._animated != b:
            self._animated = b
            self.pchanged()

    def set_in_layout(self, in_layout):
        """
        Set if artist is to be included in layout calculations,
        E.g. :doc:`/tutorials/intermediate/constrainedlayout_guide`,
        `.Figure.tight_layout()`, and
        ``fig.savefig(fname, bbox_inches='tight')``.

        Parameters
        ----------
        in_layout : bool
        """
        self._in_layout = in_layout

    def update(self, props):
        """
        Update this artist's properties from the dict *props*.

        Parameters
        ----------
        props : dict
        """
        ret = []
        with cbook._setattr_cm(self, eventson=False):
            for k, v in props.items():
                # Allow attributes we want to be able to update through
                # art.update, art.set, setp.
                if k == "axes":
                    ret.append(setattr(self, k, v))
                else:
                    func = getattr(self, f"set_{k}", None)
                    if not callable(func):
                        raise AttributeError(f"{type(self).__name__!r} object "
                                             f"has no property {k!r}")
                    ret.append(func(v))
        if ret:
            self.pchanged()
            self.stale = True
        return ret

    def get_label(self):
        """Return the label used for this artist in the legend."""
        return self._label

    def set_label(self, s):
        """
        Set a label that will be displayed in the legend.

        Parameters
        ----------
        s : object
            *s* will be converted to a string by calling `str`.
        """
        if s is not None:
            self._label = str(s)
        else:
            self._label = None
        self.pchanged()
        self.stale = True

    def get_zorder(self):
        """Return the artist's zorder."""
        return self.zorder

    def set_zorder(self, level):
        """
        Set the zorder for the artist.  Artists with lower zorder
        values are drawn first.

        Parameters
        ----------
        level : float
        """
        if level is None:
            level = self.__class__.zorder
        self.zorder = level
        self.pchanged()
        self.stale = True

    @property
    def sticky_edges(self):
        """
        ``x`` and ``y`` sticky edge lists for autoscaling.

        When performing autoscaling, if a data limit coincides with a value in
        the corresponding sticky_edges list, then no margin will be added--the
        view limit "sticks" to the edge. A typical use case is histograms,
        where one usually expects no margin on the bottom edge (0) of the
        histogram.

        Moreover, margin expansion "bumps" against sticky edges and cannot
        cross them.  For example, if the upper data limit is 1.0, the upper
        view limit computed by simple margin application is 1.2, but there is a
        sticky edge at 1.1, then the actual upper view limit will be 1.1.

        This attribute cannot be assigned to; however, the ``x`` and ``y``
        lists can be modified in place as needed.

        Examples
        --------
        >>> artist.sticky_edges.x[:] = (xmin, xmax)
        >>> artist.sticky_edges.y[:] = (ymin, ymax)

        """
        return self._sticky_edges

    def update_from(self, other):
        """Copy properties from *other* to *self*."""
        self._transform = other._transform
        self._transformSet = other._transformSet
        self._visible = other._visible
        self._alpha = other._alpha
        self.clipbox = other.clipbox
        self._clipon = other._clipon
        self._clippath = other._clippath
        self._label = other._label
        self._sketch = other._sketch
        self._path_effects = other._path_effects
        self.sticky_edges.x[:] = other.sticky_edges.x.copy()
        self.sticky_edges.y[:] = other.sticky_edges.y.copy()
        self.pchanged()
        self.stale = True

    def properties(self):
        """Return a dictionary of all the properties of the artist."""
        return ArtistInspector(self).properties()

    def set(self, **kwargs):
        # docstring and signature are auto-generated via
        # Artist._update_set_signature_and_docstring() at the end of the
        # module.
        kwargs = cbook.normalize_kwargs(kwargs, self)
        return self.update(kwargs)

    @contextlib.contextmanager
    def _cm_set(self, **kwargs):
        """
        `.Artist.set` context-manager that restores original values at exit.
        """
        orig_vals = {k: getattr(self, f"get_{k}")() for k in kwargs}
        try:
            self.set(**kwargs)
            yield
        finally:
            self.set(**orig_vals)

    def findobj(self, match=None, include_self=True):
        """
        Find artist objects.

        Recursively find all `.Artist` instances contained in the artist.

        Parameters
        ----------
        match
            A filter criterion for the matches. This can be

            - *None*: Return all objects contained in artist.
            - A function with signature ``def match(artist: Artist) -> bool``.
              The result will only contain artists for which the function
              returns *True*.
            - A class instance: e.g., `.Line2D`. The result will only contain
              artists of this class or its subclasses (``isinstance`` check).

        include_self : bool
            Include *self* in the list to be checked for a match.

        Returns
        -------
        list of `.Artist`

        """
        if match is None:  # always return True
            def matchfunc(x):
                return True
        elif isinstance(match, type) and issubclass(match, Artist):
            def matchfunc(x):
                return isinstance(x, match)
        elif callable(match):
            matchfunc = match
        else:
            raise ValueError('match must be None, a matplotlib.artist.Artist '
                             'subclass, or a callable')

        artists = sum([c.findobj(matchfunc) for c in self.get_children()], [])
        if include_self and matchfunc(self):
            artists.append(self)
        return artists

    def get_cursor_data(self, event):
        """
        Return the cursor data for a given event.

        .. note::
            This method is intended to be overridden by artist subclasses.
            As an end-user of Matplotlib you will most likely not call this
            method yourself.

        Cursor data can be used by Artists to provide additional context
        information for a given event. The default implementation just returns
        *None*.

        Subclasses can override the method and return arbitrary data. However,
        when doing so, they must ensure that `.format_cursor_data` can convert
        the data to a string representation.

        The only current use case is displaying the z-value of an `.AxesImage`
        in the status bar of a plot window, while moving the mouse.

        Parameters
        ----------
        event : `matplotlib.backend_bases.MouseEvent`

        See Also
        --------
        format_cursor_data

        """
        return None

    def format_cursor_data(self, data):
        """
        Return a string representation of *data*.

        .. note::
            This method is intended to be overridden by artist subclasses.
            As an end-user of Matplotlib you will most likely not call this
            method yourself.

        The default implementation converts ints and floats and arrays of ints
        and floats into a comma-separated string enclosed in square brackets,
        unless the artist has an associated colorbar, in which case scalar
        values are formatted using the colorbar's formatter.

        See Also
        --------
        get_cursor_data
        """
        if np.ndim(data) == 0 and isinstance(self, ScalarMappable):
            # This block logically belongs to ScalarMappable, but can't be
            # implemented in it because most ScalarMappable subclasses inherit
            # from Artist first and from ScalarMappable second, so
            # Artist.format_cursor_data would always have precedence over
            # ScalarMappable.format_cursor_data.
            n = self.cmap.N
            if np.ma.getmask(data):
                return "[]"
            normed = self.norm(data)
            if np.isfinite(normed):
                # Midpoints of neighboring color intervals.
                neighbors = self.norm.inverse(
                    (int(self.norm(data) * n) + np.array([0, 1])) / n)
                delta = abs(neighbors - data).max()
                g_sig_digits = cbook._g_sig_digits(data, delta)
            else:
                g_sig_digits = 3  # Consistent with default below.
            return "[{:-#.{}g}]".format(data, g_sig_digits)
        else:
            try:
                data[0]
            except (TypeError, IndexError):
                data = [data]
            data_str = ', '.join('{:0.3g}'.format(item) for item in data
                                 if isinstance(item, Number))
            return "[" + data_str + "]"

    @property
    def mouseover(self):
        """
        If this property is set to *True*, the artist will be queried for
        custom context information when the mouse cursor moves over it.

        See also :meth:`get_cursor_data`, :class:`.ToolCursorPosition` and
        :class:`.NavigationToolbar2`.
        """
        return self._mouseover

    @mouseover.setter
    def mouseover(self, val):
        val = bool(val)
        self._mouseover = val
        ax = self.axes
        if ax:
            if val:
                ax._mouseover_set.add(self)
            else:
                ax._mouseover_set.discard(self)


class ArtistInspector:
    """
    A helper class to inspect an `~matplotlib.artist.Artist` and return
    information about its settable properties and their current values.
    """

    def __init__(self, o):
        r"""
        Initialize the artist inspector with an `Artist` or an iterable of
        `Artist`\s.  If an iterable is used, we assume it is a homogeneous
        sequence (all `Artist`\s are of the same type) and it is your
        responsibility to make sure this is so.
        """
        if not isinstance(o, Artist):
            if np.iterable(o):
                o = list(o)
                if len(o):
                    o = o[0]

        self.oorig = o
        if not isinstance(o, type):
            o = type(o)
        self.o = o

        self.aliasd = self.get_aliases()

    def get_aliases(self):
        """
        Get a dict mapping property fullnames to sets of aliases for each alias
        in the :class:`~matplotlib.artist.ArtistInspector`.

        e.g., for lines::

          {'markerfacecolor': {'mfc'},
           'linewidth'      : {'lw'},
          }
        """
        names = [name for name in dir(self.o)
                 if name.startswith(('set_', 'get_'))
                    and callable(getattr(self.o, name))]
        aliases = {}
        for name in names:
            func = getattr(self.o, name)
            if not self.is_alias(func):
                continue
            propname = re.search("`({}.*)`".format(name[:4]),  # get_.*/set_.*
                                 inspect.getdoc(func)).group(1)
            aliases.setdefault(propname[4:], set()).add(name[4:])
        return aliases

    _get_valid_values_regex = re.compile(
        r"\n\s*(?:\.\.\s+)?ACCEPTS:\s*((?:.|\n)*?)(?:$|(?:\n\n))"
    )

    def get_valid_values(self, attr):
        """
        Get the legal arguments for the setter associated with *attr*.

        This is done by querying the docstring of the setter for a line that
        begins with "ACCEPTS:" or ".. ACCEPTS:", and then by looking for a
        numpydoc-style documentation for the setter's first argument.
        """

        name = 'set_%s' % attr
        if not hasattr(self.o, name):
            raise AttributeError('%s has no function %s' % (self.o, name))
        func = getattr(self.o, name)

        docstring = inspect.getdoc(func)
        if docstring is None:
            return 'unknown'

        if docstring.startswith('Alias for '):
            return None

        match = self._get_valid_values_regex.search(docstring)
        if match is not None:
            return re.sub("\n *", " ", match.group(1))

        # Much faster than list(inspect.signature(func).parameters)[1],
        # although barely relevant wrt. matplotlib's total import time.
        param_name = func.__code__.co_varnames[1]
        # We could set the presence * based on whether the parameter is a
        # varargs (it can't be a varkwargs) but it's not really worth the it.
        match = re.search(r"(?m)^ *\*?{} : (.+)".format(param_name), docstring)
        if match:
            return match.group(1)

        return 'unknown'

    def _replace_path(self, source_class):
        """
        Changes the full path to the public API path that is used
        in sphinx. This is needed for links to work.
        """
        replace_dict = {'_base._AxesBase': 'Axes',
                        '_axes.Axes': 'Axes'}
        for key, value in replace_dict.items():
            source_class = source_class.replace(key, value)
        return source_class

    def get_setters(self):
        """
        Get the attribute strings with setters for object.

        For example, for a line, return ``['markerfacecolor', 'linewidth',
        ....]``.
        """
        setters = []
        for name in dir(self.o):
            if not name.startswith('set_'):
                continue
            func = getattr(self.o, name)
            if (not callable(func)
                    or len(inspect.signature(func).parameters) < 2
                    or self.is_alias(func)):
                continue
            setters.append(name[4:])
        return setters

    def is_alias(self, o):
        """Return whether method object *o* is an alias for another method."""
        ds = inspect.getdoc(o)
        if ds is None:
            return False
        return ds.startswith('Alias for ')

    def aliased_name(self, s):
        """
        Return 'PROPNAME or alias' if *s* has an alias, else return 'PROPNAME'.

        e.g., for the line markerfacecolor property, which has an
        alias, return 'markerfacecolor or mfc' and for the transform
        property, which does not, return 'transform'.
        """
        aliases = ''.join(' or %s' % x for x in sorted(self.aliasd.get(s, [])))
        return s + aliases

    _NOT_LINKABLE = {
        # A set of property setter methods that are not available in our
        # current docs. This is a workaround used to prevent trying to link
        # these setters which would lead to "target reference not found"
        # warnings during doc build.
        'matplotlib.image._ImageBase.set_alpha',
        'matplotlib.image._ImageBase.set_array',
        'matplotlib.image._ImageBase.set_data',
        'matplotlib.image._ImageBase.set_filternorm',
        'matplotlib.image._ImageBase.set_filterrad',
        'matplotlib.image._ImageBase.set_interpolation',
        'matplotlib.image._ImageBase.set_interpolation_stage',
        'matplotlib.image._ImageBase.set_resample',
        'matplotlib.text._AnnotationBase.set_annotation_clip',
    }

    def aliased_name_rest(self, s, target):
        """
        Return 'PROPNAME or alias' if *s* has an alias, else return 'PROPNAME',
        formatted for reST.

        e.g., for the line markerfacecolor property, which has an
        alias, return 'markerfacecolor or mfc' and for the transform
        property, which does not, return 'transform'.
        """
        # workaround to prevent "reference target not found"
        if target in self._NOT_LINKABLE:
            return f'``{s}``'

        aliases = ''.join(' or %s' % x for x in sorted(self.aliasd.get(s, [])))
        return ':meth:`%s <%s>`%s' % (s, target, aliases)

    def pprint_setters(self, prop=None, leadingspace=2):
        """
        If *prop* is *None*, return a list of strings of all settable
        properties and their valid values.

        If *prop* is not *None*, it is a valid property name and that
        property will be returned as a string of property : valid
        values.
        """
        if leadingspace:
            pad = ' ' * leadingspace
        else:
            pad = ''
        if prop is not None:
            accepts = self.get_valid_values(prop)
            return '%s%s: %s' % (pad, prop, accepts)

        lines = []
        for prop in sorted(self.get_setters()):
            accepts = self.get_valid_values(prop)
            name = self.aliased_name(prop)
            lines.append('%s%s: %s' % (pad, name, accepts))
        return lines

    def pprint_setters_rest(self, prop=None, leadingspace=4):
        """
        If *prop* is *None*, return a list of reST-formatted strings of all
        settable properties and their valid values.

        If *prop* is not *None*, it is a valid property name and that
        property will be returned as a string of "property : valid"
        values.
        """
        if leadingspace:
            pad = ' ' * leadingspace
        else:
            pad = ''
        if prop is not None:
            accepts = self.get_valid_values(prop)
            return '%s%s: %s' % (pad, prop, accepts)

        prop_and_qualnames = []
        for prop in sorted(self.get_setters()):
            # Find the parent method which actually provides the docstring.
            for cls in self.o.__mro__:
                method = getattr(cls, f"set_{prop}", None)
                if method and method.__doc__ is not None:
                    break
            else:  # No docstring available.
                method = getattr(self.o, f"set_{prop}")
            prop_and_qualnames.append(
                (prop, f"{method.__module__}.{method.__qualname__}"))

        names = [self.aliased_name_rest(prop, target)
                 .replace('_base._AxesBase', 'Axes')
                 .replace('_axes.Axes', 'Axes')
                 for prop, target in prop_and_qualnames]
        accepts = [self.get_valid_values(prop)
                   for prop, _ in prop_and_qualnames]

        col0_len = max(len(n) for n in names)
        col1_len = max(len(a) for a in accepts)
        table_formatstr = pad + '   ' + '=' * col0_len + '   ' + '=' * col1_len

        return [
            '',
            pad + '.. table::',
            pad + '   :class: property-table',
            '',
            table_formatstr,
            pad + '   ' + 'Property'.ljust(col0_len)
            + '   ' + 'Description'.ljust(col1_len),
            table_formatstr,
            *[pad + '   ' + n.ljust(col0_len) + '   ' + a.ljust(col1_len)
              for n, a in zip(names, accepts)],
            table_formatstr,
            '',
        ]

    def properties(self):
        """Return a dictionary mapping property name -> value."""
        o = self.oorig
        getters = [name for name in dir(o)
                   if name.startswith('get_') and callable(getattr(o, name))]
        getters.sort()
        d = {}
        for name in getters:
            func = getattr(o, name)
            if self.is_alias(func):
                continue
            try:
                with warnings.catch_warnings():
                    warnings.simplefilter('ignore')
                    val = func()
            except Exception:
                continue
            else:
                d[name[4:]] = val
        return d

    def pprint_getters(self):
        """Return the getters and actual values as list of strings."""
        lines = []
        for name, val in sorted(self.properties().items()):
            if getattr(val, 'shape', ()) != () and len(val) > 6:
                s = str(val[:6]) + '...'
            else:
                s = str(val)
            s = s.replace('\n', ' ')
            if len(s) > 50:
                s = s[:50] + '...'
            name = self.aliased_name(name)
            lines.append('    %s = %s' % (name, s))
        return lines


def getp(obj, property=None):
    """
    Return the value of an `.Artist`'s *property*, or print all of them.

    Parameters
    ----------
    obj : `.Artist`
        The queried artist; e.g., a `.Line2D`, a `.Text`, or an `~.axes.Axes`.

    property : str or None, default: None
        If *property* is 'somename', this function returns
        ``obj.get_somename()``.

        If it's None (or unset), it *prints* all gettable properties from
        *obj*.  Many properties have aliases for shorter typing, e.g. 'lw' is
        an alias for 'linewidth'.  In the output, aliases and full property
        names will be listed as:

          property or alias = value

        e.g.:

          linewidth or lw = 2

    See Also
    --------
    setp
    """
    if property is None:
        insp = ArtistInspector(obj)
        ret = insp.pprint_getters()
        print('\n'.join(ret))
        return
    return getattr(obj, 'get_' + property)()

# alias
get = getp


def setp(obj, *args, file=None, **kwargs):
    """
    Set one or more properties on an `.Artist`, or list allowed values.

    Parameters
    ----------
    obj : `.Artist` or list of `.Artist`
        The artist(s) whose properties are being set or queried.  When setting
        properties, all artists are affected; when querying the allowed values,
        only the first instance in the sequence is queried.

        For example, two lines can be made thicker and red with a single call:

        >>> x = arange(0, 1, 0.01)
        >>> lines = plot(x, sin(2*pi*x), x, sin(4*pi*x))
        >>> setp(lines, linewidth=2, color='r')

    file : file-like, default: `sys.stdout`
        Where `setp` writes its output when asked to list allowed values.

        >>> with open('output.log') as file:
        ...     setp(line, file=file)

        The default, ``None``, means `sys.stdout`.

    *args, **kwargs
        The properties to set.  The following combinations are supported:

        - Set the linestyle of a line to be dashed:

          >>> line, = plot([1, 2, 3])
          >>> setp(line, linestyle='--')

        - Set multiple properties at once:

          >>> setp(line, linewidth=2, color='r')

        - List allowed values for a line's linestyle:

          >>> setp(line, 'linestyle')
          linestyle: {'-', '--', '-.', ':', '', (offset, on-off-seq), ...}

        - List all properties that can be set, and their allowed values:

          >>> setp(line)
          agg_filter: a filter function, ...
          [long output listing omitted]

        `setp` also supports MATLAB style string/value pairs.  For example, the
        following are equivalent:

        >>> setp(lines, 'linewidth', 2, 'color', 'r')  # MATLAB style
        >>> setp(lines, linewidth=2, color='r')        # Python style

    See Also
    --------
    getp
    """

    if isinstance(obj, Artist):
        objs = [obj]
    else:
        objs = list(cbook.flatten(obj))

    if not objs:
        return

    insp = ArtistInspector(objs[0])

    if not kwargs and len(args) < 2:
        if args:
            print(insp.pprint_setters(prop=args[0]), file=file)
        else:
            print('\n'.join(insp.pprint_setters()), file=file)
        return

    if len(args) % 2:
        raise ValueError('The set args must be string, value pairs')

    funcvals = dict(zip(args[::2], args[1::2]))
    ret = [o.update(funcvals) for o in objs] + [o.set(**kwargs) for o in objs]
    return list(cbook.flatten(ret))


def kwdoc(artist):
    r"""
    Inspect an `~matplotlib.artist.Artist` class (using `.ArtistInspector`) and
    return information about its settable properties and their current values.

    Parameters
    ----------
    artist : `~matplotlib.artist.Artist` or an iterable of `Artist`\s

    Returns
    -------
    str
        The settable properties of *artist*, as plain text if
        :rc:`docstring.hardcopy` is False and as a rst table (intended for
        use in Sphinx) if it is True.
    """
    ai = ArtistInspector(artist)
    return ('\n'.join(ai.pprint_setters_rest(leadingspace=4))
            if mpl.rcParams['docstring.hardcopy'] else
            'Properties:\n' + '\n'.join(ai.pprint_setters(leadingspace=4)))

# We defer this to the end of them module, because it needs ArtistInspector
# to be defined.
Artist._update_set_signature_and_docstring()
