When having multiple widgets in a QGridLayout and hiding and showing some of these when the parent widget is in WindowFullScreen state, then the parent's state gets reset to WindowNoState - and no QWindowStateChangeEvent seems to be sent.

The example attached demonstrates this behaviour. Note that the widgets are so large so that when the reset to WindowNoState happens, the widget still looks like it is in FullScreen but with cut off widgets as the window frame is outside the screen.