@JonB

You are absolutely right! I was confused between the QGraphicsView and the QGraphicsScene. I just realised that when I was playing with my POC.

Actually, what change the size of the QGraphicsScene is done in another part of my code and is called later. If I recalculate the sceneRect according to my needs and call setSceneRect(), when my window is resized, everything works as expected.

Sorry for the inconvenience.

(One?) Solution is to call QGraphicsView( QRectF ) with QRectF obtained from QGraphicsScene::sceneRect() immediately after assigning a new scene rectangle.