Backport PR #16298: Don't recursively call draw_idle when updating artists at draw time.

tacaswell · meeseeksmachine · commit e90e8ec6dcd3 · 2020-01-27T18:42:26.000Z
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -1652,8 +1652,10 @@ def _fix_ipython_backend2gui(cls):
     @contextmanager
     def _idle_draw_cntx(self):
         self._is_idle_drawing = True
-        yield
-        self._is_idle_drawing = False
+        try:
+            yield
+        finally:
+            self._is_idle_drawing = False
 
     def is_saving(self):
         """
diff --git a/lib/matplotlib/backends/backend_qt5.py b/lib/matplotlib/backends/backend_qt5.py
@@ -481,16 +481,17 @@ def draw_idle(self):
             QtCore.QTimer.singleShot(0, self._draw_idle)
 
     def _draw_idle(self):
-        if not self._draw_pending:
-            return
-        self._draw_pending = False
-        if self.height() < 0 or self.width() < 0:
-            return
-        try:
-            self.draw()
-        except Exception:
-            # Uncaught exceptions are fatal for PyQt5, so catch them instead.
-            traceback.print_exc()
+        with self._idle_draw_cntx():
+            if not self._draw_pending:
+                return
+            self._draw_pending = False
+            if self.height() < 0 or self.width() < 0:
+                return
+            try:
+                self.draw()
+            except Exception:
+                # Uncaught exceptions are fatal for PyQt5, so catch them.
+                traceback.print_exc()
 
     def drawRectangle(self, rect):
         # Draw the zoom rectangle to the QPainter.  _draw_rect_callback needs
diff --git a/lib/matplotlib/pyplot.py b/lib/matplotlib/pyplot.py
@@ -586,8 +586,15 @@ def _auto_draw_if_interactive(fig, val):
     fig : Figure
         A figure object which is assumed to be associated with a canvas
     """
-    if val and matplotlib.is_interactive() and not fig.canvas.is_saving():
-        fig.canvas.draw_idle()
+    if (val and matplotlib.is_interactive()
+            and not fig.canvas.is_saving()
+            and not fig.canvas._is_idle_drawing):
+        # Some artists can mark themselves as stale in the middle of drawing
+        # (e.g. axes position & tick labels being computed at draw time), but
+        # this shouldn't trigger a redraw because the current redraw will
+        # already take them into account.
+        with fig.canvas._idle_draw_cntx():
+            fig.canvas.draw_idle()
 
 
 def gcf():
