Merge pull request matplotlib#28375 from joe-saronic/fix-affine-delta-transform

FIX: Made AffineDeltaTransform pass-through properly

Author: QuLogic

doc/api/next_api_changes/behavior/28375-MP.rst

@@ -0,0 +1,5 @@
+``transforms.AffineDeltaTransform`` updates correctly on axis limit changes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Before this change, transform sub-graphs with ``AffineDeltaTransform`` did not update correctly.
+This PR ensures that changes to the child transform are passed through correctly.

lib/matplotlib/tests/test_transforms.py

@@ -341,6 +341,31 @@ def test_deepcopy(self):
         assert_array_equal(s.get_matrix(), a.get_matrix())
 
 
+class TestAffineDeltaTransform:
+    def test_invalidate(self):
+        before = np.array([[1.0, 4.0, 0.0],
+                           [5.0, 1.0, 0.0],
+                           [0.0, 0.0, 1.0]])
+        after = np.array([[1.0, 3.0, 0.0],
+                          [5.0, 1.0, 0.0],
+                          [0.0, 0.0, 1.0]])
+
+        # Translation and skew present
+        base = mtransforms.Affine2D.from_values(1, 5, 4, 1, 2, 3)
+        t = mtransforms.AffineDeltaTransform(base)
+        assert_array_equal(t.get_matrix(), before)
+
+        # Mess with the internal structure of `base` without invalidating
+        # This should not affect this transform because it's a passthrough:
+        # it's always invalid
+        base.get_matrix()[0, 1:] = 3
+        assert_array_equal(t.get_matrix(), after)
+
+        # Invalidate the base
+        base.invalidate()
+        assert_array_equal(t.get_matrix(), after)
+
+
 def test_non_affine_caching():
     class AssertingNonAffineTransform(mtransforms.Transform):
         """

lib/matplotlib/transforms.py

@@ -2721,9 +2721,12 @@ class AffineDeltaTransform(Affine2DBase):
     This class is experimental as of 3.3, and the API may change.
     """
 
+    pass_through = True
+
     def __init__(self, transform, **kwargs):
         super().__init__(**kwargs)
         self._base_transform = transform
+        self.set_children(transform)
 
     __str__ = _make_str_method("_base_transform")