Dynamically generate CbarAxes.

This is a followup to the introduction of _make_class_factory, and
avoids having to define a separate CbarAxes class in axisartist.

Author: anntzer

doc/api/next_api_changes/deprecations/20606-AL.rst

@@ -0,0 +1,4 @@
+``axes_grid1.axes_grid.CbarAxes`` and ``axes_grid1.axisartist.CbarAxes``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+These classes are deprecated (they are now dynamically generated based on the
+owning axes class).

lib/mpl_toolkits/axes_grid1/axes_grid.py

@@ -3,7 +3,7 @@
 
 import numpy as np
 
-from matplotlib import _api
+from matplotlib import _api, cbook
 from matplotlib.gridspec import SubplotSpec
 
 from .axes_divider import Size, SubplotDivider, Divider
@@ -43,10 +43,14 @@ def cla(self):
         self.orientation = orientation
 
 
+@_api.deprecated("3.5")
 class CbarAxes(CbarAxesBase, Axes):
     pass
 
 
+_cbaraxes_class_factory = cbook._make_class_factory(CbarAxesBase, "Cbar{}")
+
+
 class Grid:
     """
     A grid of Axes.
@@ -310,8 +314,6 @@ def get_vsize_hsize(self):
 class ImageGrid(Grid):
     # docstring inherited
 
-    _defaultCbarAxesClass = CbarAxes
-
     def __init__(self, fig,
                  rect,
                  nrows_ncols,
@@ -416,7 +418,7 @@ def _init_locators(self):
             else:
                 self._colorbar_pad = self._vert_pad_size.fixed_size
         self.cbar_axes = [
-            self._defaultCbarAxesClass(
+            _cbaraxes_class_factory(self._defaultAxesClass)(
                 self.axes_all[0].figure, self._divider.get_position(),
                 orientation=self._colorbar_location)
             for _ in range(self.ngrids)]

lib/mpl_toolkits/axisartist/axes_grid.py

@@ -1,7 +1,9 @@
+from matplotlib import _api
 import mpl_toolkits.axes_grid1.axes_grid as axes_grid_orig
 from .axislines import Axes
 
 
+@_api.deprecated("3.5")
 class CbarAxes(axes_grid_orig.CbarAxesBase, Axes):
     pass
 
@@ -12,7 +14,6 @@ class Grid(axes_grid_orig.Grid):
 
 class ImageGrid(axes_grid_orig.ImageGrid):
     _defaultAxesClass = Axes
-    _defaultCbarAxesClass = CbarAxes
 
 
 AxesGrid = ImageGrid