Fix draggable annotations on subfigures.

- Picking on subfigures was broken because `ax = getattr(a, 'axes', None)`
  would return the SubFigure.axes *list* when `a` is a subfigure, so the
  axes identity test would just be completely wrong.  Fix that by
  special-casing subfigures.  (Ideally I would entirely remove the axes
  equality test because that also breaks in the case of overlapping axes,
  but that's a much bigger change.)
- `ref_artist.figure._canvas_callbacks` would fail when the ref_artist
  is on a subfigure because subfigures don't have a _canvas_callbacks
  attribute; instead use `ref_artist.figure.canvas.callbacks` where
  accessing the canvas attribute correctly goes back to the toplevel
  figure first.

See test for an example (which would previously fail with an
AttributeError).

Author: anntzer

lib/matplotlib/artist.py

@@ -537,7 +537,8 @@ def pick(self, mouseevent):
         for a in self.get_children():
             # make sure the event happened in the same Axes
             ax = getattr(a, 'axes', None)
-            if (mouseevent.inaxes is None or ax is None
+            if (isinstance(a, mpl.figure.SubFigure)
+                    or mouseevent.inaxes is None or ax is None
                     or mouseevent.inaxes == ax):
                 # we need to check if mouseevent.inaxes is None
                 # because some objects associated with an Axes (e.g., a

lib/matplotlib/offsetbox.py

@@ -1458,7 +1458,7 @@ def __init__(self, ref_artist, use_blit=False):
             ref_artist.set_picker(True)
         self.got_artist = False
         self._use_blit = use_blit and self.canvas.supports_blit
-        callbacks = ref_artist.figure._canvas_callbacks
+        callbacks = self.canvas.callbacks
         self._disconnectors = [
             functools.partial(
                 callbacks.disconnect, callbacks._connect_picklable(name, func))
@@ -1471,7 +1471,6 @@ def __init__(self, ref_artist, use_blit=False):
 
     # A property, not an attribute, to maintain picklability.
     canvas = property(lambda self: self.ref_artist.figure.canvas)
-
     cids = property(lambda self: [
         disconnect.args[0] for disconnect in self._disconnectors[:2]])
 

lib/matplotlib/tests/test_offsetbox.py

@@ -450,3 +450,13 @@ def test_remove_draggable():
     an.draggable(True)
     an.remove()
     MouseEvent("button_release_event", fig.canvas, 1, 1)._process()
+
+
+def test_draggable_in_subfigure():
+    fig = plt.figure()
+    # Put annotation at lower left corner to make it easily pickable below.
+    ann = fig.subfigures().add_axes([0, 0, 1, 1]).annotate("foo", (0, 0))
+    ann.draggable(True)
+    fig.canvas.draw()  # Texts are non-pickable until the first draw.
+    MouseEvent("button_press_event", fig.canvas, 1, 1)._process()
+    assert ann._draggable.got_artist