DOC: add comment to tests on why double processEvent

tacaswell · tacaswell · commit 04ee64d9d162 · 2017-09-25T15:11:10.000-04:00
diff --git a/lib/matplotlib/tests/test_backend_qt5.py b/lib/matplotlib/tests/test_backend_qt5.py
@@ -145,6 +145,10 @@ def test_dpi_ratio_change():
 
         qt_canvas.draw()
         qApp.processEvents()
+        # this second processEvents is required to fully run the draw.
+        # On `update` we notice the DPI has changed and trigger a
+        # resize event to refresh, the second processEvents is
+        # required to process that and fully update the window sizes.
         qApp.processEvents()
 
         # The DPI and the renderer width/height change
