Warn in colorbar() when mappable.axes != figure.gca().

anntzer · tacaswell · commit 96cae15e0b72 · 2020-06-25T21:33:20.000-04:00
diff --git a/doc/api/api_changes_3.4/deprecations.rst b/doc/api/api_changes_3.4/deprecations.rst
@@ -1,6 +1,20 @@
 Deprecations
 ------------
 
+Figure.colorbar now warns when the mappable's axes is different from the current axes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Currently, `.Figure.colorbar` steals space by default from the current axes
+to place the colorbar.  In a future version, it will steal space from the
+mappable's axes instead.  In preparation for this change, `.Figure.colorbar`
+now emits a warning when the current axes is not the same as the mappable's
+axes.
+
+The ``.ax`` attribute to `.ContourSet` is deprecated in favor of
+``.axes`` for consistency with artists (even though `.ContourSet` is not an
+`.Artist` subclass).
+
+
 ``dpi_cor`` property of `.FancyArrowPatch`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 This parameter is considered internal and deprecated.
diff --git a/lib/matplotlib/blocking_input.py b/lib/matplotlib/blocking_input.py
@@ -277,7 +277,7 @@ class BlockingContourLabeler(BlockingMouseInput):
 
     def __init__(self, cs):
         self.cs = cs
-        BlockingMouseInput.__init__(self, fig=cs.ax.figure)
+        BlockingMouseInput.__init__(self, fig=cs.axes.figure)
 
     def add_click(self, event):
         self.button1(event)
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -2323,13 +2323,20 @@ def colorbar(self, mappable, cax=None, ax=None, use_gridspec=True, **kw):
         """
         if ax is None:
             ax = self.gca()
+            if hasattr(mappable, "axes") and ax is not mappable.axes:
+                cbook.warn_deprecated(
+                    "3.4", message="Starting from Matplotlib 3.6, colorbar() "
+                    "will steal space from the mappable's axes, rather than "
+                    "from the current axes, to place the colorbar.  To "
+                    "silence this warning, explicitly pass the 'ax' argument "
+                    "to colorbar().")
 
         # Store the value of gca so that we can set it back later on.
         current_ax = self.gca()
 
         if cax is None:
-            if use_gridspec and isinstance(ax, SubplotBase)  \
-                     and (not self.get_constrained_layout()):
+            if (use_gridspec and isinstance(ax, SubplotBase)
+                    and not self.get_constrained_layout()):
                 cax, kw = cbar.make_axes_gridspec(ax, **kw)
             else:
                 cax, kw = cbar.make_axes(ax, **kw)
