FIX: macosx, clear pending timers when the figure is destroyed

greglucas · greglucas · commit 364194e1d982 · 2023-03-19T09:08:05.000-06:00
Running the macosx backend without calling show() would cause
Timers to pile up and not fire because the event loop was not running.
This leaked objects when closing/opening multiple figures. To fix this,
we keep track of the timers on the canvas and remove all of the pending
timers when destroying the figure to clear all back-references.
diff --git a/lib/matplotlib/backends/backend_macosx.py b/lib/matplotlib/backends/backend_macosx.py
@@ -39,6 +39,8 @@ def __init__(self, figure):
         super().__init__(figure=figure)
         self._draw_pending = False
         self._is_drawing = False
+        # Keep track of the timers that are alive
+        self._timers = set()
 
     def draw(self):
         """Render the figure and update the macosx canvas."""
@@ -61,14 +63,16 @@ def draw_idle(self):
 
     def _single_shot_timer(self, callback):
         """Add a single shot timer with the given callback"""
-        # We need to explicitly stop (called from delete) the timer after
+        # We need to explicitly stop and remove the timer after
         # firing, otherwise segfaults will occur when trying to deallocate
         # the singleshot timers.
         def callback_func(callback, timer):
             callback()
-            del timer
+            self._timers.remove(timer)
+            timer.stop()
         timer = self.new_timer(interval=0)
         timer.add_callback(callback_func, callback, timer)
+        self._timers.add(timer)
         timer.start()
 
     def _draw_idle(self):
@@ -161,6 +165,14 @@ def _close_button_pressed(self):
         Gcf.destroy(self)
         self.canvas.flush_events()
 
+    def destroy(self):
+        # We need to clear any pending timers that never fired, otherwise
+        # we get a memory leak from the timer callbacks holding a reference
+        while self.canvas._timers:
+            timer = self.canvas._timers.pop()
+            timer.stop()
+        super().destroy()
+
     @_api.deprecated("3.6")
     def close(self):
         return self._close_button_pressed()
