title: Qt QPoint global/local mapping
body: <p>I am trying to change the dimensions of a QPushButton subclass while anchoring a user-defined corner (not always the top left corner). The QPushButton defines a QFrame as its parent, and is free-floating in the window. When I try to change the size of the QPushButton subclass in the subclass code, I believe it is giving me trouble since the QPoints provided by mouseEvents are local. 
  I have tried to work with the myButton->mapToGlobal(QPoint) and myButton->mapFromGlobal but I don't think I quite understand how they work. A search for examples has left me empty handed. Can anyone provide a short example? </p>