Flicker Prevention 2
lInstead of painting the background, then drawing on it, it is better to
ÒpaintÓ a complete image covering the visible area
of the Frame.
lThis image is known as an
off-screen buffer
because the buffer is not part of the Frame.
off-screen bufferbecause the buffer is not part of the Frame.
lThe buffer is drawn on prior to update().
lThe buffer contents is then painted in update().