Thank you very much alex. I just tried what you suggested and it works perfectly.
I thought about slots and timer too, as suggested in the examples on qt's site, but it requires subclassing a QGraphicsItem for each item in the QGraphicsView. The problem is, I don't know the number of items that will be generated until runtime, and apart from this, creating 10.000 classes (one for each item) would be very resource intensive, I think.
Anyway, the method above, the one with
QCoreApplication::processEvents () ;
works perfectly for my purpose.
So thanks both for your politeness: it is very nice to see such a great community :)