QDialog: it keeps its size between hide and show only when move() or setGeometry() is called

refer to:
http://bugreports.qt.nokia.com/browse/QTBUG-9943

Currently the behavior of dialog is very strange.

• it comes back to its original position( centered) by default
• it keeps its geometry before hide() if the user specifies it original position by calling move() or setGeometry()
• it doesn't keep its geometry between hide() and show() without calling move() or setGeoemtry(), it goes back to be centered.

This behavior doesn't comply with the document:
http://qt.nokia.com/doc/4.6/qwidget.html#hide

In the document, it says dialog will be displayed in its original position when it is re-shown.