Check to see that the mouse is within the boundries of the bar.
Check the current mouse position to see if it is within the bounds of the adjustment bar. It is only necessary to check if the mouse is with in one direction of the bar's alloted space. For example, we only care if the mouse is within the y-range of a vertical adjustment.
This method makes it possible to put a label, pixmap, or any other widget into the bar in order to alter the bar's appearance. When combined with setBarMask(), this method makes the style an shape of the adjustment bar completely controllable by the programmer.
The previous contents of the bar are returned after the new contents have been added.