The "problem" is that by default (on most distros, anyway), X11
restricts who (which user from which machine) is allowed to display
stuff on your desktop. Since the event-handler is a system process
rather than an application you're running as yourself it isn't
permitted to display anything on screen.
With those few lines you tell it to a) run as yourself, b) which file
to use to make sure there's permission to write, and c) to which display
to actually display xosd to.
This is a bit over-simplified, but you hopefully get enough info
to understand what's going on?
Last edited by Tinkster; 08-17-2008 at 12:35 AM.