Further sync axes_grid colorbars with standard colorbars.

Remap the cbid and locator attributes to the ones of standard colorbars.
Move most functionality of CbarAxes to CbarAxesBase, leaving only the
multiple-inheritance part, so that axisartist.axes_grid.CbarAxes can
likewise just limit itself to multiple-inheritance.

doc/api/api_changes_3.3/deprecations.rst

@@ -515,3 +515,8 @@ experimental and may change in the future.
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 These are unused and can be easily reproduced by other date tools.
 `.get_epoch` will return Matplotlib's epoch.
+
+``axes_grid1.CbarAxes`` attributes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The ``cbid`` and ``locator`` attribute are deprecated.  Use
+``mappable.colorbar_cid`` and ``colorbar.locator``, as for standard colorbars.

lib/mpl_toolkits/axes_grid1/axes_grid.py

@@ -19,6 +19,11 @@ def _tick_only(ax, bottom_on, left_on):
 
 
 class CbarAxesBase:
+    def __init__(self, *args, orientation, **kwargs):
+        self.orientation = orientation
+        self._default_label_on = True
+        self._locator = None  # deprecated.
+        super().__init__(*args, **kwargs)
 
     @cbook._rename_parameter("3.2", "locator", "ticks")
     def colorbar(self, mappable, *, ticks=None, **kwargs):
@@ -38,21 +43,30 @@ def colorbar(self, mappable, *, ticks=None, **kwargs):
             if ticks is None:
                 ticks = ticker.MaxNLocator(5)  # For backcompat.
             from .colorbar import Colorbar
+            cb = Colorbar(
+                self, mappable, orientation=orientation, ticks=ticks, **kwargs)
+            self._cbid = mappable.callbacksSM.connect(
+                'changed', cb.update_normal)
+            mappable.colorbar = cb
+            self._locator = cb.cbar_axis.get_major_locator()
         else:
-            from matplotlib.colorbar import Colorbar
-        cb = Colorbar(
-            self, mappable, orientation=orientation, ticks=ticks, **kwargs)
-        self._config_axes()
+            cb = mpl.colorbar.colorbar_factory(
+                self, mappable, orientation=orientation, ticks=ticks, **kwargs)
+            self._cbid = mappable.colorbar_cid  # deprecated.
+            self._locator = cb.locator  # deprecated.
 
-        self.cbid = mappable.callbacksSM.connect('changed', cb.update_normal)
-        mappable.colorbar = cb
+        self._config_axes()
+        return cb
 
-        if mpl.rcParams["mpl_toolkits.legacy_colorbar"]:
-            self.locator = cb.cbar_axis.get_major_locator()
-        else:
-            self.locator = cb.locator
+    @cbook.deprecated("3.3", alternative="mappable.colorbar_cid")
+    @property
+    def cbid(self):
+        return self._cbid
 
-        return cb
+    @cbook.deprecated("3.3", alternative=".colorbar().locator")
+    @property
+    def locator(self):
+        return self._locator
 
     def _config_axes(self):
         """Make an axes patch and outline."""
@@ -67,19 +81,15 @@ def toggle_label(self, b):
         axis = self.axis[self.orientation]
         axis.toggle(ticklabels=b, label=b)
 
-
-class CbarAxes(CbarAxesBase, Axes):
-    def __init__(self, *args, orientation, **kwargs):
-        self.orientation = orientation
-        self._default_label_on = True
-        self.locator = None
-        super().__init__(*args, **kwargs)
-
     def cla(self):
         super().cla()
         self._config_axes()
 
 
+class CbarAxes(CbarAxesBase, Axes):
+    pass
+
+
 class Grid:
     """
     A grid of Axes.

lib/mpl_toolkits/axisartist/axes_grid.py

@@ -3,15 +3,7 @@
 
 
 class CbarAxes(axes_grid_orig.CbarAxesBase, Axes):
-    def __init__(self, *args, orientation, **kwargs):
-        self.orientation = orientation
-        self._default_label_on = False
-        self.locator = None
-        super().__init__(*args, **kwargs)
-
-    def cla(self):
-        super().cla()
-        self._config_axes()
+    pass
 
 
 class Grid(axes_grid_orig.Grid):