FIX: allow norm limit to change and not change user-set ticks and format

jklymak · jklymak · commit 8759fe634155 · 2019-01-23T15:00:13.000-08:00
diff --git a/lib/matplotlib/colorbar.py b/lib/matplotlib/colorbar.py
@@ -1212,16 +1212,20 @@ def update_normal(self, mappable):
         meant to be called when the norm of the image or contour plot to which
         this colorbar belongs changes.
 
-        This resets the locator and formatter for the axis, so if these
-        have been customized, they will need to be customized again.
+        If the norm on the mappable is different than before, this resets the
+        locator and formatter for the axis, so if these have been customized,
+        they will need to be customized again.  However, if the norm only
+        changes values of *vmin*, *vmax* or *cmap* then the old formatter
+        and locator will be preserved.
         """
 
-        _log.debug('colorbar update normal')
+        _log.debug('colorbar update normal %r %r', mappable.norm, self.norm)
         self.mappable = mappable
         self.set_alpha(mappable.get_alpha())
         self.cmap = mappable.cmap
-        self.norm = mappable.norm
-        self._reset_locator_formatter_scale()
+        if mappable.norm != self.norm:
+            self.norm = mappable.norm
+            self._reset_locator_formatter_scale()
 
         self.draw_all()
         if isinstance(self.mappable, contour.ContourSet):
diff --git a/lib/matplotlib/tests/test_colorbar.py b/lib/matplotlib/tests/test_colorbar.py
@@ -477,6 +477,18 @@ def test_colorbar_format():
     fig.canvas.draw()
     assert cbar.ax.yaxis.get_ticklabels()[4].get_text() == '6.00e+04'
 
+    # make sure that if we change the clim of the mappable that the
+    # formatting is *not* lost:
+    im.set_clim([4, 200])
+    fig.canvas.draw()
+    assert cbar.ax.yaxis.get_ticklabels()[4].get_text() == '8.00e+01'
+
+    # but if we change the norm:
+    im.set_norm(LogNorm(vmin=0.1, vmax=10))
+    fig.canvas.draw()
+    assert (cbar.ax.yaxis.get_ticklabels()[0].get_text() ==
+            r'$\mathdefault{10^{-1}}$')
+
 
 def test_colorbar_scale_reset():
     x, y = np.ogrid[-4:4:31j, -4:4:31j]
