To compile the program, you have to install the "fltk-devel" package (the name
is different in every Linux distribution). After that, run

 % fltk-config --use-images --compile

The resulting binary called 'netwm-iconset' can be copied somewhere in the
$PATH, for example in /usr/local/bin or $HOME/bin for a per-user installation.


Just run 'netwm-iconset <windowid> <icon.png>' to set the icon of the currently
running program. The program is mainly designed for Terminals like the
xfce4-terminal that don't have the capability to modify the icon as a command
line parameter. The set the $WINDOWID environment so that you can just run

 % netwm-iconset $WINDOWID /usr/share/icons/mutt.png

for example to set the Terminal icon for Mutt (a dog instead of a Terminal