Move lastevent handling to LocationEvent.process.

anntzer · anntzer · commit ee5710c6539d · 2020-10-25T20:34:59.000+01:00
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -1350,7 +1350,7 @@ class LocationEvent(Event):
         y data coordinate of the mouse.
     """
 
-    lastevent = None  # the last event that was triggered before this one
+    lastevent = None  # The last event processed so far.
 
     def __init__(self, name, canvas, x, y, guiEvent=None):
         """
@@ -1367,7 +1367,6 @@ def __init__(self, name, canvas, x, y, guiEvent=None):
 
         if x is None or y is None:
             # cannot check if event was in axes if no (x, y) info
-            self._update_enter_leave()
             return
 
         if self.canvas.mouse_grabber is None:
@@ -1385,33 +1384,21 @@ def __init__(self, name, canvas, x, y, guiEvent=None):
                 self.xdata = xdata
                 self.ydata = ydata
 
-        self._update_enter_leave()
-
-    def _update_enter_leave(self):
-        """Process the figure/axes enter leave events."""
-        if LocationEvent.lastevent is not None:
-            last = LocationEvent.lastevent
-            if last.inaxes != self.inaxes:
-                # process axes enter/leave events
+    def process(self):
+        last = LocationEvent.lastevent
+        last_axes = last.inaxes if last is not None else None
+        if last_axes != self.inaxes:
+            if last_axes is not None:
                 try:
-                    if last.inaxes is not None:
-                        last.canvas.callbacks.process('axes_leave_event', last)
+                    last.canvas.callbacks.process("axes_leave_event", last)
                 except Exception:
+                    # The last canvas may already have been torn down.
                     pass
-                    # See ticket 2901582.
-                    # I think this is a valid exception to the rule
-                    # against catching all exceptions; if anything goes
-                    # wrong, we simply want to move on and process the
-                    # current event.
-                if self.inaxes is not None:
-                    self.canvas.callbacks.process('axes_enter_event', self)
-
-        else:
-            # process a figure enter event
             if self.inaxes is not None:
-                self.canvas.callbacks.process('axes_enter_event', self)
-
-        LocationEvent.lastevent = self
+                self.canvas.callbacks.process("axes_enter_event", self)
+        LocationEvent.lastevent = (
+            None if self.name == "figure_leave_event" else self)
+        super().process()
 
 
 class MouseButton(IntEnum):
