Merge pull request matplotlib#14840 from djdt/remove_get_matrix_invalid

MNT: Don't assume transform is valid on access to matrix.

Author: tacaswell

lib/matplotlib/tests/test_transforms.py

@@ -176,6 +176,17 @@ def test_Affine2D_from_values():
     assert_almost_equal(actual, expected)
 
 
+def test_affine_inverted_invalidated():
+    # Ensure that the an affine transform is not declared valid on access
+    point = [1.0, 1.0]
+    t = mtransforms.Affine2D()
+
+    assert_almost_equal(point, t.transform(t.inverted().transform(point)))
+    # Change and access the transform
+    t.translate(1.0, 1.0).get_matrix()
+    assert_almost_equal(point, t.transform(t.inverted().transform(point)))
+
+
 def test_clipping_of_log():
     # issue 804
     M, L, C = Path.MOVETO, Path.LINETO, Path.CLOSEPOLY

lib/matplotlib/transforms.py

@@ -1875,7 +1875,9 @@ def get_matrix(self):
 
         .
         """
-        self._invalid = 0
+        if self._invalid:
+            self._inverted = None
+            self._invalid = 0
         return self._mtx
 
     def set_matrix(self, mtx):