Fix OffsetBox custom picker

As with the custom picker, `Artist.contains` returns a boolean and a
dictionary in a tuple. This non-empty tuple is always true, so the
custom picker would always return True for any non-scroll event. It
would also lose the related dictionary.

Author: QuLogic

lib/matplotlib/offsetbox.py

@@ -1504,7 +1504,9 @@ def __init__(self, ref_artist, use_blit=False):
     @staticmethod
     def _picker(artist, mouseevent):
         # A custom picker to prevent dragging on mouse scroll events
-        return (artist.contains(mouseevent) and mouseevent.name != "scroll_event"), {}
+        if mouseevent.name == "scroll_event":
+            return False, {}
+        return artist.contains(mouseevent)
 
     # A property, not an attribute, to maintain picklability.
     canvas = property(lambda self: self.ref_artist.get_figure(root=True).canvas)

lib/matplotlib/tests/test_offsetbox.py

@@ -460,3 +460,13 @@ def test_draggable_in_subfigure():
     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
+    # Stop dragging the annotation.
+    MouseEvent("button_release_event", fig.canvas, 1, 1)._process()
+    assert not ann._draggable.got_artist
+    # A scroll event should not initiate a drag.
+    MouseEvent("scroll_event", fig.canvas, 1, 1)._process()
+    assert not ann._draggable.got_artist
+    # An event outside the annotation should not initiate a drag.
+    bbox = ann.get_window_extent()
+    MouseEvent("button_press_event", fig.canvas, bbox.x1+2, bbox.y1+2)._process()
+    assert not ann._draggable.got_artist