Fix Text('').get_window_extent(dpi=...).

This special case does not correctly reset the figure dpi, so the figure
randomly gets bigger when it's called. This does not affect Text with
actual content.

Author: QuLogic

lib/matplotlib/tests/test_text.py

@@ -321,6 +321,22 @@ def test_set_position():
         assert a + shift_val == b
 
 
+@pytest.mark.parametrize('text', ['', 'O'], ids=['empty', 'non-empty'])
+def test_non_default_dpi(text):
+    fig, ax = plt.subplots()
+
+    t1 = ax.text(0.5, 0.5, text, ha='left', va='bottom')
+    fig.canvas.draw()
+    dpi = fig.dpi
+
+    bbox1 = t1.get_window_extent()
+    bbox2 = t1.get_window_extent(dpi=dpi * 10)
+    np.testing.assert_allclose(bbox2.get_points(), bbox1.get_points() * 10,
+                               rtol=5e-2)
+    # Text.get_window_extent should not permanently change dpi.
+    assert fig.dpi == dpi
+
+
 def test_get_rotation_string():
     assert mpl.text.get_rotation('horizontal') == 0.
     assert mpl.text.get_rotation('vertical') == 90.

lib/matplotlib/text.py

@@ -891,12 +891,12 @@ def get_window_extent(self, renderer=None, dpi=None):
         #return _unit_box
         if not self.get_visible():
             return Bbox.unit()
-        if dpi is not None:
-            dpi_orig = self.figure.dpi
-            self.figure.dpi = dpi
+        if dpi is None:
+            dpi = self.figure.dpi
         if self.get_text() == '':
-            tx, ty = self._get_xy_display()
-            return Bbox.from_bounds(tx, ty, 0, 0)
+            with cbook._setattr_cm(self.figure, dpi=dpi):
+                tx, ty = self._get_xy_display()
+                return Bbox.from_bounds(tx, ty, 0, 0)
 
         if renderer is not None:
             self._renderer = renderer
@@ -905,13 +905,12 @@ def get_window_extent(self, renderer=None, dpi=None):
         if self._renderer is None:
             raise RuntimeError('Cannot get window extent w/o renderer')
 
-        bbox, info, descent = self._get_layout(self._renderer)
-        x, y = self.get_unitless_position()
-        x, y = self.get_transform().transform((x, y))
-        bbox = bbox.translated(x, y)
-        if dpi is not None:
-            self.figure.dpi = dpi_orig
-        return bbox
+        with cbook._setattr_cm(self.figure, dpi=dpi):
+            bbox, info, descent = self._get_layout(self._renderer)
+            x, y = self.get_unitless_position()
+            x, y = self.get_transform().transform((x, y))
+            bbox = bbox.translated(x, y)
+            return bbox
 
     def set_backgroundcolor(self, color):
         """