matplotlib · anntzer · Sep 7, 2018 · Sep 7, 2018
diff --git a/lib/matplotlib/legend.py b/lib/matplotlib/legend.py
@@ -977,9 +977,11 @@ def get_title(self):
         'Return the `.Text` instance for the legend title.'
         return self._legend_title_box._text
 
-    def get_window_extent(self, *args, **kwargs):
+    def get_window_extent(self, renderer=None):
         'Return extent of the legend.'
-        return self._legend_box.get_window_extent(*args, **kwargs)
+        if renderer is None:
+            renderer = self.figure._cachedRenderer
+        return self._legend_box.get_window_extent(renderer=renderer)
 
     def get_tightbbox(self, renderer):
         """

diff --git a/lib/matplotlib/tests/test_legend.py b/lib/matplotlib/tests/test_legend.py
@@ -510,6 +510,17 @@ def test_legend_proper_window_extent():
     assert pytest.approx(x01*2, 0.1) == x02
 
 
+def test_window_extent_cached_renderer():
+    fig, ax = plt.subplots(dpi=100)
+    ax.plot(range(10), label='Aardvark')
+    leg = ax.legend()
+    leg2 = fig.legend()
+    fig.canvas.draw()
+    # check that get_window_extent will use the cached renderer
+    leg.get_window_extent()
+    leg2.get_window_extent()
+
+
 def test_legend_title_fontsize():
     # test the title_fontsize kwarg
     fig, ax = plt.subplots()