When a widget that has a native window handle is inside another widget then the mouse events are offset when started on a secondary display. This only happens if the widget has a parent when its window handle is created and only happens with widgets with the WA_NativeWindow attribute.

To reproduce, start the example and then click at the top corner of the red area. The otuput should be very close to 0x0, but it never gets past 21 in the y direction.