There are three distinct functions that rely on different underlying OS services, and their effects may be combined:

1) setWindowMask(): shape mask: sets the window area, which affects both received events and displayed pixels. This is a bitmap mask; any pixels with non-zero alpha are included in the mask. 2) setWindowAlpha(): constant alpha: applies a constant alpha level to all pixels 3) setWindowTransparent(): by default, none of the window is painted; pixels painted by your application are composited with whatever is under the window. Whether transparent pixels respond to user events is platform-dependent.