How exactly are you adding that proxy to the scene? Is it in the exact same manner as those black boxes, or is something different going on? There's a lot of things that could cause that kind of problem, like if you're using a layout that uses it's own padding or if you are trying to move the widget around using the wrong coordinate system. In either case, if you could provide us with a little bit of code I think it would allow us to give you more help.