The attached minimal example and screenshots (taken on macOS) show painting/updating issues I get inside a customer application when using a QGraphicsEffect.

I'm painting the source pixmap, and then a semi-transparent overlay on top. While everything should be uniformly "tinted" this way, this doesn't work reliably for item views and other QScrollArea-based views, where their behavior differs between widgets and platforms:

Linux (Kubuntu 18.04)/Windows 10: the text browser is usually painted correctly initially, but the QListView is not (white without tint). the background of the main window is all black where it should be tinted. When I resize the window, the listview is sometimes painted tinted and sometimes white.

macOS: initially, everything is painted correctly (tinted). If I command+tab the window to the background and to the foreground again, the text browser is painted white. Also, on the window background around the widgets, random painting artifacts can be seen. (but they can be avoided by doing setAutoFillBackground(true) on the main window, and thus are probably to be expected when autoFillBackground is false)

I get the same behavior with Qt 5.6.3, Qt 5.9.6 and Qt 5.11.2. (I didn't test more versions)