"Solution":

There was a problem in defining the rectangle returned from boundingRect().

I had defined it as a point to point rectangle but had not taken into account that upper left must indeed be upper left. And after some transformations of the graphics view, upper left was anything _but_ upper left from my point of view.

The system only recognized as within the bounding box where the two rectangles would overlap.

The biggest problem was that when I tried actually drawing the returned boundingRect(), it looked perfectly all right.

Time for a break!