QWidget::frameGeometry() and QWidget::frameSize() need more info about frame

The descriptions of the functions QWidget::frameGeometry() and QWidget::frameSize() don't mention that the size of the frame is unknown until the window is shown for the first time. This causes confusion, because it seems that the functions are returning erroneous values if the window is not shown yet.

Therefore I suggest an additional sentence to the function descriptions about the invalidity of the frame size and geometry values before the window is actually shown.