Fix double picks.

anntzer · anntzer · commit 4c11aad1c904 · 2021-03-05T01:24:44.000+01:00
pick_events were previously incorrectly emitted twice due to the
combination of two recent(ish) chnages: Figures now always start with a
FigureCanvasBase attached -- eventually switching to a concrete subclass
of FigureCanvasBase for display or saving --, and callbacks are now
actually stored at the Figure level rather than the Canvas level.
Hence, the button_pick_id callback (in charge of emitting picks) would
previously be both registered both through the FigureCanvasBase and the
concrete subclass.  The fix is to also move that callback to the Figure
level, so that each Figure only has one such callback.
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -1726,15 +1726,13 @@ def __init__(self, figure=None):
         self._button = None  # the button pressed
         self._key = None  # the key pressed
         self._lastx, self._lasty = None, None
-        self.button_pick_id = self.mpl_connect('button_press_event', self.pick)
-        self.scroll_pick_id = self.mpl_connect('scroll_event', self.pick)
         self.mouse_grabber = None  # the axes currently grabbing mouse
         self.toolbar = None  # NavigationToolbar2 will set me
         self._is_idle_drawing = False
 
-    @property
-    def callbacks(self):
-        return self.figure._canvas_callbacks
+    callbacks = property(lambda self: self.figure._canvas_callbacks)
+    button_pick_id = property(lambda self: self.figure._button_pick_id)
+    scroll_pick_id = property(lambda self: self.figure._scroll_pick_id)
 
     @classmethod
     @functools.lru_cache()
diff --git a/lib/matplotlib/figure.py b/lib/matplotlib/figure.py
@@ -2106,6 +2106,10 @@ def __init__(self,
         # a proxy property), but that actually need to be on the figure for
         # pickling.
         self._canvas_callbacks = cbook.CallbackRegistry()
+        self._button_pick_id = self._canvas_callbacks.connect(
+            'button_press_event', lambda event: self.canvas.pick(event))
+        self._scroll_pick_id = self._canvas_callbacks.connect(
+            'scroll_event', lambda event: self.canvas.pick(event))
 
         if figsize is None:
             figsize = mpl.rcParams['figure.figsize']
diff --git a/lib/matplotlib/tests/test_backend_bases.py b/lib/matplotlib/tests/test_backend_bases.py
@@ -120,6 +120,19 @@ def test_location_event_position(x, y):
         assert re.match("x=foo +y=foo", ax.format_coord(x, y))
 
 
+def test_pick():
+    fig = plt.figure()
+    fig.text(.5, .5, "hello", ha="center", va="center", picker=True)
+    fig.canvas.draw()
+    picks = []
+    fig.canvas.mpl_connect("pick_event", lambda event: picks.append(event))
+    start_event = MouseEvent(
+        "button_press_event", fig.canvas, *fig.transFigure.transform((.5, .5)),
+        MouseButton.LEFT)
+    fig.canvas.callbacks.process(start_event.name, start_event)
+    assert len(picks) == 1
+
+
 def test_interactive_zoom():
     fig, ax = plt.subplots()
     ax.set(xscale="logit")
