thanks!
You are correct!

But then I don't understand the docs.
In the docs it says:
To write your own graphics item, you first create a subclass of QGraphicsItem, and then start by implementing its two pure virtual public functions: boundingRect(), which returns an estimate of the area painted by the item, and paint(), which implements the actual painting.
why is boundingRect() pure virtual if setRect() must be called as well?

Hmm. oh well, no time for that now, I need to work - big thanks!