Widgets in QGraphicsView via QGraphicsProxyWidget can't receive QTabletEvent

Any QWidget subclasses put into QGraphicsView via QGraphicsProxyWidget have no way to receive QTabletEvent correctly.

There's no such API like tabletEvent() in QGraphicsProxyWidget, and all tablet actions automatically become mouse events (no way to stop this behavior).

Sadly, no way to distinguish mouse events, which cast from tablet events, from native mouse events.