MNT: Use a context manager to change the norm in colorbar code

greglucas · greglucas · commit 7d35771eafca · 2022-02-21T15:11:50.000-07:00
This removes a deepcopy of the norm in Colorbar, instead updating
the vmin/vmax via the context manager and ignoring any
callback updates in the process.
diff --git a/lib/matplotlib/colorbar.py b/lib/matplotlib/colorbar.py
@@ -11,14 +11,13 @@
    End-users most likely won't need to directly use this module's API.
 """
 
-import copy
 import logging
 import textwrap
 
 import numpy as np
 
 import matplotlib as mpl
-from matplotlib import _api, collections, cm, colors, contour, ticker
+from matplotlib import _api, cbook, collections, cm, colors, contour, ticker
 import matplotlib.artist as martist
 import matplotlib.patches as mpatches
 import matplotlib.path as mpath
@@ -1158,22 +1157,22 @@ def _mesh(self):
         # vmax of the colorbar, not the norm.  This allows the situation
         # where the colormap has a narrower range than the colorbar, to
         # accommodate extra contours:
-        norm = copy.deepcopy(self.norm)
-        norm.vmin = self.vmin
-        norm.vmax = self.vmax
-        y, extendlen = self._proportional_y()
-        # invert:
-        if (isinstance(norm, (colors.BoundaryNorm, colors.NoNorm)) or
-                self.boundaries is not None):
-            y = y * (self.vmax - self.vmin) + self.vmin  # not using a norm.
-        else:
-            y = norm.inverse(y)
-        self._y = y
-        X, Y = np.meshgrid([0., 1.], y)
-        if self.orientation == 'vertical':
-            return (X, Y, extendlen)
-        else:
-            return (Y, X, extendlen)
+        with self.norm.callbacks.blocked(), \
+                cbook._setattr_cm(self.norm, vmin=self.vmin, vmax=self.vmax):
+            y, extendlen = self._proportional_y()
+            # invert:
+            if (isinstance(self.norm, (colors.BoundaryNorm, colors.NoNorm))
+                    or self.boundaries is not None):
+                # not using a norm.
+                y = y * (self.vmax - self.vmin) + self.vmin
+            else:
+                y = self.norm.inverse(y)
+            self._y = y
+            X, Y = np.meshgrid([0., 1.], y)
+            if self.orientation == 'vertical':
+                return (X, Y, extendlen)
+            else:
+                return (Y, X, extendlen)
 
     def _forward_boundaries(self, x):
         # map boundaries equally between 0 and 1...
