MNT: Remove scalarmappable private update attributes

The updates to scalar mappable would only take effect if the
array was updated. This meant that updating the vmin/vmax of
the sm's norm would not be propagated to the drawn artists. This
update removes the update checks from scalar mappable to calculate
the colors regardless of updates to the array.

doc/api/next_api_changes/removals/19552-GL.rst

@@ -0,0 +1,5 @@
+ScalarMappable update checkers
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+``ScalarMappable.update_dict``, ``ScalarMappable.add_checker()``, and
+``ScalarMappable.check_update()`` have been removed. A callback can
+be registered in ``ScalarMappable.callbacksSM`` to be notified of updates.

lib/matplotlib/cm.py

@@ -264,7 +264,6 @@ def __init__(self, norm=None, cmap=None):
         #: The last colorbar associated with this ScalarMappable. May be None.
         self.colorbar = None
         self.callbacksSM = cbook.CallbackRegistry()
-        self._update_dict = {'array': False}
 
     def _scale_norm(self, norm, vmin, vmax):
         """
@@ -369,7 +368,6 @@ def set_array(self, A):
         A : ndarray or None
         """
         self._A = A
-        self._update_dict['array'] = True
 
     def get_array(self):
         """Return the data array."""
@@ -476,30 +474,10 @@ def autoscale_None(self):
         self.norm.autoscale_None(self._A)
         self.changed()
 
-    def _add_checker(self, checker):
-        """
-        Add an entry to a dictionary of boolean flags
-        that are set to True when the mappable is changed.
-        """
-        self._update_dict[checker] = False
-
-    def _check_update(self, checker):
-        """Return whether mappable has changed since the last check."""
-        if self._update_dict[checker]:
-            self._update_dict[checker] = False
-            return True
-        return False
-
     def changed(self):
         """
         Call this whenever the mappable is changed to notify all the
         callbackSM listeners to the 'changed' signal.
         """
         self.callbacksSM.process('changed', self)
-        for key in self._update_dict:
-            self._update_dict[key] = True
         self.stale = True
-
-    update_dict = _api.deprecate_privatize_attribute("3.3")
-    add_checker = _api.deprecate_privatize_attribute("3.3")
-    check_update = _api.deprecate_privatize_attribute("3.3")

lib/matplotlib/collections.py

@@ -851,7 +851,6 @@ def set_alpha(self, alpha):
             supported.
         """
         artist.Artist._set_alpha_for_array(self, alpha)
-        self._update_dict['array'] = True
         self._set_facecolor(self._original_facecolor)
         self._set_edgecolor(self._original_edgecolor)
 
@@ -907,7 +906,7 @@ def update_scalarmappable(self):
         if not self._set_mappable_flags():
             return
         # Allow possibility to call 'self.set_array(None)'.
-        if self._check_update("array") and self._A is not None:
+        if self._A is not None:
             # QuadMesh can map 2d arrays (but pcolormesh supplies 1d array)
             if self._A.ndim > 1 and not isinstance(self, QuadMesh):
                 raise ValueError('Collections can only map rank 1 arrays')
@@ -958,7 +957,6 @@ def update_from(self, other):
         self._A = other._A
         self.norm = other.norm
         self.cmap = other.cmap
-        # do we need to copy self._update_dict? -JJL
         self.stale = True
 
 

lib/matplotlib/tests/test_collections.py

@@ -715,6 +715,22 @@ def test_quadmesh_set_array():
     assert np.array_equal(coll.get_array(), np.ones(9))
 
 
+def test_quadmesh_vmin_vmax():
+    # test when vmin/vmax on the norm changes, the quadmesh gets updated
+    fig, ax = plt.subplots()
+    cmap = mpl.cm.get_cmap('plasma')
+    norm = mpl.colors.Normalize(vmin=0, vmax=1)
+    coll = ax.pcolormesh([[1]], cmap=cmap, norm=norm)
+    fig.canvas.draw()
+    assert np.array_equal(coll.get_facecolors()[0, :], cmap(norm(1)))
+
+    # Change the vmin/vmax of the norm so that the color is from
+    # the bottom of the colormap now
+    norm.vmin, norm.vmax = 1, 2
+    fig.canvas.draw()
+    assert np.array_equal(coll.get_facecolors()[0, :], cmap(norm(1)))
+
+
 def test_quadmesh_alpha_array():
     x = np.arange(4)
     y = np.arange(4)

lib/mpl_toolkits/mplot3d/art3d.py

@@ -695,13 +695,11 @@ def _update_scalarmappable(sm):
     """
     if sm._A is None:
         return
-    copy_state = sm._update_dict['array']
-    ret = sm.update_scalarmappable()
-    if copy_state:
-        if sm._face_is_mapped:
-            sm._facecolor3d = sm._facecolors
-        elif sm._edge_is_mapped:  # Should this be plain "if"?
-            sm._edgecolor3d = sm._edgecolors
+    sm.update_scalarmappable()
+    if sm._face_is_mapped:
+        sm._facecolor3d = sm._facecolors
+    elif sm._edge_is_mapped:  # Should this be plain "if"?
+        sm._edgecolor3d = sm._edgecolors
 
 
 def patch_collection_2d_to_3d(col, zs=0, zdir='z', depthshade=True):