Make colorbars constructible with dataless ScalarMappables.

anntzer · anntzer · commit 961742ce5f13 · 2018-11-07T21:58:18.000+01:00
This allows creating "bare" colorbars with the one-liner

    fig.colorbar(cm.ScalarMappable(norm=norm, cmap=cmap))
diff --git a/lib/matplotlib/colorbar.py b/lib/matplotlib/colorbar.py
@@ -1069,7 +1069,8 @@ class Colorbar(ColorbarBase):
     def __init__(self, ax, mappable, **kw):
         # Ensure the given mappable's norm has appropriate vmin and vmax set
         # even if mappable.draw has not yet been called.
-        mappable.autoscale_None()
+        if mappable.get_array() is not None:
+            mappable.autoscale_None()
 
         self.mappable = mappable
         kw['cmap'] = cmap = mappable.cmap
