Backport PR #15206: FIX: be more forgiving about expecting internal state in draw_idle

dstansby · tacaswell · commit 04a2d1149063 · 2019-09-06T19:50:47.000-04:00
Merge pull request #15206 from tacaswell/fix_python_ion_second_qtcanvas_init FIX: be more forgiving about expecting internal state in draw_idle Conflicts: lib/matplotlib/tests/test_backend_qt.py - no tests on this branch, did not backport test
diff --git a/lib/matplotlib/backends/backend_qt5.py b/lib/matplotlib/backends/backend_qt5.py
@@ -506,7 +506,8 @@ def draw_idle(self):
         # current event loop in order to ensure thread affinity and to
         # accumulate multiple draw requests from event handling.
         # TODO: queued signal connection might be safer than singleShot
-        if not (self._draw_pending or self._is_drawing):
+        if not (getattr(self, '_draw_pending', False) or
+                getattr(self, '._is_drawing', False)):
             self._draw_pending = True
             QtCore.QTimer.singleShot(0, self._draw_idle)
 
