Large rectangular graphicsitem classes have eight small rectangular graphicsitem members, now want to eight members of the small respectively were placed in the four corners of the large rectangle and the halfway point of the four edges, like viso, my method is to obtain large rectangular boundingrect, call the small rectangular object with setpos large rectangular corresponding coordinate point set, the overall effect is a success, but each point set in the right position, such as my setpos topcenter, actual position is bottomcenter, why?