Add a Figure._get_cachedRenderer() method

dstansby · dstansby · commit 41ece96f2eed · 2021-10-08T18:18:21.000+01:00
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -2378,6 +2378,13 @@ def axes(self):
 
     get_axes = axes.fget
 
+    def _get_cachedRenderer(self, error_if_none=True):
+        # Get the cached renderer, raising an error if it doesn't exist yet
+        if error_if_none and self._cachedRenderer is None:
+            raise AttributeError("This code can only be used after an "
+                                 "initial draw which caches the renderer.")
+        return self._cachedRenderer
+
     def _get_dpi(self):
         return self._dpi
 
@@ -2832,10 +2839,7 @@ def draw_artist(self, a):
         This method can only be used after an initial draw of the figure,
         because that creates and caches the renderer needed here.
         """
-        if self._cachedRenderer is None:
-            raise AttributeError("draw_artist can only be used after an "
-                                 "initial draw which caches the renderer")
-        a.draw(self._cachedRenderer)
+        a.draw(self._get_cachedRenderer())
 
     def __getstate__(self):
         state = super().__getstate__()
diff --git a/lib/matplotlib/legend.py b/lib/matplotlib/legend.py
@@ -896,7 +896,7 @@ def get_title(self):
     def get_window_extent(self, renderer=None):
         # docstring inherited
         if renderer is None:
-            renderer = self.figure._cachedRenderer
+            renderer = self.figure._get_cachedRenderer()
         return self._legend_box.get_window_extent(renderer=renderer)
 
     def get_tightbbox(self, renderer):
