TST: add extra processEvents call in test

tacaswell · tacaswell · commit 884334de7c90 · 2017-09-21T21:40:18.000-04:00
The resizeEvent call does put another paint onto the event queue,
however it seems that processEvents only processes events on the queue
when it is called (not events added while it is processing).  This is
not clearly documented, but makes sense as this method is for keeping
GUIs responsive during otherwise long-running tasks so it should not
be able to extend it's run indefinitely by populating the queue.

This is required because a previous commit removed the explicit
processEvents call in paintEvent as it would occasionally cause
recursive painting which may kill Qt.
diff --git a/lib/matplotlib/tests/test_backend_qt5.py b/lib/matplotlib/tests/test_backend_qt5.py
@@ -145,6 +145,7 @@ def test_dpi_ratio_change():
 
         qt_canvas.draw()
         qApp.processEvents()
+        qApp.processEvents()
 
         # The DPI and the renderer width/height change
         assert fig.dpi == 240
