Displays the phase of the moon on the root window
xphoon [-b] [-t interval [-i]] [-s] [-display name]
Xphoon sets the X root window to a picture of the moon in its current phase, including the partial lighting of the dark side by reflected earthlight.
Defeats the earthlight feature, forcing the dark side to be black.
Have xphoon keep running and update the picture every interval minutes. (Normally, xphoon just sets the root picture and exits.)
Forks a background process and prints the process-id to stdout. Useful if you want to make menu commands to refresh or kill xphoon.
Rotate the whole picture 180 degrees, resulting in a moon picture as viewed fom the Southern hemisphere.
Demonstrate xphoon by rapidly stepping through moon phases.
The original motivation for this program was that xsetroot was too slow. Loading a full-screen bitmap took about 15 seconds. We made a trivial program that had fullmoon.bitmap compiled in, and it ran in less than a second. (And incidentally, the executable was smaller than fullmoon.xbm.) Then later we came up with the phase hacking, the earthlight, and the auto-scaling.
Copyright (C) 1988, 1991 by Jef Poskanzer and Craig Leres.
The moon-phase computation is from "moontool.c" by John Walker.