DOC: Adding a what's new entry for the norm callback

greglucas · greglucas · commit 740cd418d72c · 2021-03-19T20:51:59.000-06:00
diff --git a/doc/users/next_whats_new/19553-GL.rst b/doc/users/next_whats_new/19553-GL.rst
@@ -0,0 +1,7 @@
+A callback registry has been added to `.Normalize`
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The new `.Normalize.callbacksNorm` callback registry can be connected
+to by other objects to be notified when the norm is updated.
+`.ScalarMappable` is now a listener and will register a change when the
+norm's vmin, vmax or other attributes are changed.
