QGraphicsView rendering issue

[guilugi]

Hi !

I'm working on a QGraphicsView widget, meant to display interactive graphical items, that I can move / reshape / delete as I want.

It works perfectly fine, the QGraphicsView framework is really good

In order to filter this view with a color or a texture, I wanted to set a custom foreground brush to the scene, with this line :
my_view->setForegroundBrush(QColor(255, 255, 255, 127));

It applies well to the whole view, but when I move any item, I have some painting problems, described by the snapshot in attachment.

I checked all the render hints, the painting methods for items, but I can't point the mistake.

Any idea ?

Thanks,
Guilugi.