Merge pull request matplotlib#30696 from timhoffm/fix-tightbox

FIX: Account for horizontal/vertical lines in tightbox

Author: rcomer

lib/matplotlib/axes/_base.py

@@ -4632,9 +4632,7 @@ def get_tightbbox(self, renderer=None, *, call_axes_locator=True,
 
         for a in bbox_artists:
             bbox = a.get_tightbbox(renderer)
-            if (bbox is not None
-                    and 0 < bbox.width < np.inf
-                    and 0 < bbox.height < np.inf):
+            if bbox is not None and bbox._is_finite():
                 bb.append(bbox)
         return mtransforms.Bbox.union(
             [b for b in bb if b.width != 0 or b.height != 0])

lib/matplotlib/axis.py

@@ -1383,8 +1383,7 @@ def get_tightbbox(self, renderer=None, *, for_layout_only=False):
                     bb.y0 = (bb.y0 + bb.y1) / 2 - 0.5
                     bb.y1 = bb.y0 + 1.0
             bboxes.append(bb)
-        bboxes = [b for b in bboxes
-                  if 0 < b.width < np.inf and 0 < b.height < np.inf]
+        bboxes = [b for b in bboxes if b._is_finite()]
         if bboxes:
             return mtransforms.Bbox.union(bboxes)
         else:

lib/matplotlib/tests/test_transforms.py

@@ -835,6 +835,16 @@ def assert_bbox_eq(bbox1, bbox2):
     assert_array_equal(bbox1.bounds, bbox2.bounds)
 
 
+def test_bbox_is_finite():
+    assert not Bbox([(1, 1), (1, 1)])._is_finite()
+    assert not Bbox([(0, 0), (np.inf, 1)])._is_finite()
+    assert not Bbox([(-np.inf, 0), (2, 2)])._is_finite()
+    assert not Bbox([(np.nan, 0), (2, 2)])._is_finite()
+    assert Bbox([(0, 0), (0, 2)])._is_finite()
+    assert Bbox([(0, 0), (2, 0)])._is_finite()
+    assert Bbox([(0, 0), (1, 2)])._is_finite()
+
+
 def test_bbox_frozen_copies_minpos():
     bbox = mtransforms.Bbox.from_extents(0.0, 0.0, 1.0, 1.0, minpos=1.0)
     frozen = bbox.frozen()

lib/matplotlib/transforms.py

@@ -377,6 +377,29 @@ def extents(self):
     def get_points(self):
         raise NotImplementedError
 
+    def _is_finite(self):
+        """
+        Return whether the bounding box is finite and not degenerate to a
+        single point.
+
+        We count the box as finite if neither width nor height are infinite
+        and at least one direction is non-zero; i.e. a point is not finite,
+        but a horizontal or vertical line is.
+
+        .. versionadded:: 3.11
+
+        Notes
+        -----
+        We keep this private for now because concise naming is hard and
+        because we are not sure how universal the concept is. It is
+        currently used only for filtering bboxes to be included in
+        tightbbox calculation, but I'm unsure whether single points
+        should be included there as well.
+        """
+        width = self.width
+        height = self.height
+        return (width > 0 or height > 0) and width < np.inf and height < np.inf
+
     def containsx(self, x):
         """
         Return whether *x* is in the closed (:attr:`x0`, :attr:`x1`) interval.

lib/matplotlib/transforms.pyi

@@ -65,6 +65,7 @@ class BboxBase(TransformNode):
     @property
     def extents(self) -> tuple[float, float, float, float]: ...
     def get_points(self) -> np.ndarray: ...
+    def _is_finite(self) -> bool: ...
     def containsx(self, x: float) -> bool: ...
     def containsy(self, y: float) -> bool: ...
     def contains(self, x: float, y: float) -> bool: ...