A color background which interpolates the background color between a top and a bottom colors.
$Date: 2005/10/23 11:10:45 $
$Revision: 1.5 $
-- Initialise background with a_top_color and a_bottom_color.
-- Bottom color
-- Top color
-- Set bottom_color to a_color.
-- Set top_color to a_color.
-- Draw background on widget.
-- (From EM_BACKGROUND)
A color background which interpolates the background color
between a top and a bottom colors.