Backport PR #15283: Don't default axes_grid colorbar locator to MaxNLocator.

ivanov · MeeseeksDev[bot] · commit 9a10d8c7f5d1 · 2019-09-21T06:42:23.000Z
diff --git a/doc/api/prev_api_changes/api_changes_3.2.0/deprecations.rst b/doc/api/prev_api_changes/api_changes_3.2.0/deprecations.rst
@@ -45,10 +45,14 @@ The main differences are:
 
 - Setting the ticks on the colorbar is done by calling ``colorbar.set_ticks``
   rather than ``colorbar.cbar_axis.set_xticks`` or
-  ``colorbar.cbar_axis.set_yticks``.
+  ``colorbar.cbar_axis.set_yticks``; the ``locator`` parameter to ``colorbar()``
+  is deprecated in favor of its synonym ``ticks`` (which already existed
+  previously, and is consistent with :mod:`matplotlib.colorbar`).
 - The colorbar's long axis is accessed with ``colorbar.xaxis`` or
   ``colorbar.yaxis`` depending on the orientation, rather than
   ``colorbar.cbar_axis``.
+- The default ticker is no longer ``MaxNLocator(5)``, but a
+  ``_ColorbarAutoLocator``.
 - Overdrawing multiple colorbars on top of one another in a single Axes (e.g.
   when using the ``cax`` attribute of `~.axes_grid1.axes_grid.ImageGrid`
   elements) is not supported; if you previously relied on the second colorbar
diff --git a/lib/mpl_toolkits/axes_grid1/axes_grid.py b/lib/mpl_toolkits/axes_grid1/axes_grid.py
@@ -31,17 +31,8 @@ def _tick_only(ax, bottom_on, left_on):
 
 class CbarAxesBase:
 
-    def colorbar(self, mappable, *, locator=None, **kwargs):
-
-        if locator is None:
-            if "ticks" not in kwargs:
-                kwargs["ticks"] = ticker.MaxNLocator(5)
-        if locator is not None:
-            if "ticks" in kwargs:
-                raise ValueError("Either *locator* or *ticks* need" +
-                                 " to be given, not both")
-            else:
-                kwargs["ticks"] = locator
+    @cbook._rename_parameter("3.2", "locator", "ticks")
+    def colorbar(self, mappable, *, ticks=None, **kwargs):
 
         if self.orientation in ["top", "bottom"]:
             orientation = "horizontal"
@@ -55,10 +46,13 @@ def colorbar(self, mappable, *, locator=None, **kwargs):
                 "%(removal)s.  Set the 'mpl_toolkits.legacy_colorbar' rcParam "
                 "to False to use Matplotlib's default colorbar implementation "
                 "and suppress this deprecation warning.")
+            if ticks is None:
+                ticks = ticker.MaxNLocator(5)  # For backcompat.
             from .colorbar import Colorbar
         else:
             from matplotlib.colorbar import Colorbar
-        cb = Colorbar(self, mappable, orientation=orientation, **kwargs)
+        cb = Colorbar(
+            self, mappable, orientation=orientation, ticks=ticks, **kwargs)
         self._config_axes()
 
         def on_changed(m):
diff --git a/lib/mpl_toolkits/tests/test_axes_grid.py b/lib/mpl_toolkits/tests/test_axes_grid.py
@@ -48,4 +48,16 @@ def test_imagegrid_cbar_mode_edge(legacy_colorbar):
             # the "second" ones.  To achieve this, clear out the axes first.
             for ax in grid:
                 ax.cax.cla()
-                ax.cax.colorbar(ax.images[0])
+                cb = ax.cax.colorbar(
+                    ax.images[0],
+                    ticks=mpl.ticker.MaxNLocator(5))  # old default locator.
+
+
+def test_imagegrid():
+    mpl.rcParams["mpl_toolkits.legacy_colorbar"] = False
+    fig = plt.figure()
+    grid = ImageGrid(fig, 111, nrows_ncols=(1, 1))
+    ax = grid[0]
+    im = ax.imshow([[1, 2]], norm=mpl.colors.LogNorm())
+    cb = ax.cax.colorbar(im)
+    assert isinstance(cb.locator, mpl.colorbar._ColorbarLogLocator)
