Page "Stacking window manager" Paragraph 10

Another method of lessening the limitations of stacking is through the use of a hardware overlay and chroma keying.

Since the video hardware can draw on the outgoing screen, a window is drawn containing a known colour, which allows the video hardware to detect which parts of the window are showing and should be drawn on.

3D and 2D accelerated video and animation may be added to windows using this method.