Handle CLOSEPOLY's in Path.interpolated

rcomer · rcomer · commit 9e1888c5a415 · 2025-04-16T09:52:45.000+01:00
diff --git a/doc/users/next_whats_new/path_interpolated.rst b/doc/users/next_whats_new/path_interpolated.rst
@@ -1,5 +1,6 @@
-``Path.interpolated`` now handles internal ``MOVETO``'s
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+``Path.interpolated`` now handles ``CLOSEPOLY``'s and internal ``MOVETO``'s
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 If `.Path` contains internal `~.Path.MOVETO` codes, the `~.Path.interpolated` method
-is now applied to each sub-path delineated by those codes.
+is now applied to each sub-path delineated by those codes.  `~.Path.CLOSEPOLY` is
+also now correctly handled.
diff --git a/lib/matplotlib/path.py b/lib/matplotlib/path.py
@@ -669,7 +669,7 @@ def interpolated(self, steps):
         """
         Return a new path with each segment divided into *steps* parts.
 
-        Codes other than `LINETO` and `MOVETO` are not handled correctly.
+        Codes other than `LINETO` `MOVETO` and `CLOSEPOLY` are not handled correctly.
 
         Parameters
         ----------
@@ -688,7 +688,13 @@ def interpolated(self, steps):
             return self.make_compound_path(
                 *(p.interpolated(steps) for p in self._iter_connected_components()))
 
-        vertices = simple_linear_interpolation(self.vertices, steps)
+        if self.codes[-1] == self.CLOSEPOLY and not np.all(self.vertices[-1] ==
+                                                           self.vertices[0]):
+            vertices = np.concatenate([self.vertices[:-1], self.vertices[:1]], axis=0)
+        else:
+            vertices = self.vertices
+
+        vertices = simple_linear_interpolation(vertices, steps)
         codes = self.codes
         if codes is not None:
             new_codes = np.full((len(codes) - 1) * steps + 1, Path.LINETO,
diff --git a/lib/matplotlib/tests/test_path.py b/lib/matplotlib/tests/test_path.py
@@ -559,3 +559,23 @@ def test_interpolated_moveto():
     # Result should have two subpaths with six LINETOs each
     expected_subpath_codes = [Path.MOVETO] + [Path.LINETO] * 6
     np.testing.assert_array_equal(result.codes, expected_subpath_codes * 2)
+
+
+def test_interpolated_closepoly():
+    codes = [Path.MOVETO] + [Path.LINETO]*2 + [Path.CLOSEPOLY]
+    vertices = [(4, 4), (5, 5), (5, 4), (0, 0)]
+
+    path = Path(vertices, codes)
+    result = path.interpolated(2)
+
+    expected_vertices = np.array([[4, 4],
+                                  [4.5, 4.5],
+                                  [5, 5],
+                                  [5, 4.5],
+                                  [5, 4],
+                                  [4.5, 4],
+                                  [4, 4]])
+    expected_codes = [Path.MOVETO] + [Path.LINETO]*5 + [Path.CLOSEPOLY]
+
+    np.testing.assert_allclose(result.vertices, expected_vertices)
+    np.testing.assert_array_equal(result.codes, expected_codes)
