The desktop demo contains three routines, each of which draws simple
shapes on the desktop.

"desktop -rotate" rotates a shaded square.  Some nice color work.

"desktop -poly" draws qix-like moving shapes.

"desktop -shadetext" and "-troll" draw pretty shaded text on the
desktop; "-shadewidget" and "-trollwidget" use the background as a
widget.  The latter can be used to make animated background widgets
that work efficiently, which is very cool but possibly not very
useful.
