Comment 3 for bug 886192

I think the primary cause of this bug is that the move plugin uses relative movement;
   window->move(dx, dy)
whereas it should be absolute; something like:
   window->moveTo(x, y)

You can always know the coordinate of the title bar (or the window) that the user grabbed, and ensure you are always moving the window to a location that keeps the location of the pointer relative to the window constant.