Merge pull request #11370 from jdollichon/issue-#11369

jklymak · web-flow · commit 300e4c9afbc9 · 2018-07-05T08:15:25.000-07:00
Sorting drawn artists by their zorder when blitting using FuncAnimation
diff --git a/doc/api/next_api_changes/2018-06-03-JD-funcani-zorder.rst b/doc/api/next_api_changes/2018-06-03-JD-funcani-zorder.rst
@@ -0,0 +1,9 @@
+`.FuncAnimation` now draws artists according to their zorder when blitting
+--------------------------------------------------------------------------
+
+`.FuncAnimation` now draws artists returned by the user-
+function according to their zorder when using blitting,
+instead of using the order in which they are being passed.
+However, note that only zorder of passed artists will be
+respected, as they are drawn on top of any existing artists
+(see `#11369 <https://github.com/matplotlib/matplotlib/issues/11369>`_).
diff --git a/lib/matplotlib/animation.py b/lib/matplotlib/animation.py
@@ -1607,8 +1607,10 @@ def init_func() -> iterable_of_artists:
        of frames is completed.  Defaults to ``True``.
 
     blit : bool, optional
-       Controls whether blitting is used to optimize drawing.  Defaults
-       to ``False``.
+       Controls whether blitting is used to optimize drawing. Note: when using
+       blitting any animated artists will be drawn according to their zorder.
+       However, they will be drawn on top of any previous artists, regardless
+       of their zorder.  Defaults to ``False``.
 
     '''
     def __init__(self, fig, func, frames=None, init_func=None, fargs=None,
@@ -1723,7 +1725,8 @@ def _draw_frame(self, framedata):
 
         # Call the func with framedata and args. If blitting is desired,
         # func needs to return a sequence of any artists that were modified.
-        self._drawn_artists = self._func(framedata, *self._args)
+        self._drawn_artists = sorted(self._func(framedata, *self._args),
+                                     key=lambda x: x.get_zorder())
         if self._blit:
             if self._drawn_artists is None:
                 raise RuntimeError('The animation function must return a '
