https://bugs.freedesktop.org/show_bug.cgi?id=34206
--- Comment #7 from Marek Olšák maraeo@gmail.com 2011-03-29 16:59:52 PDT --- I think the glow is broken because the WPOS input is unassigned. Glow is a screen-space effect and as such must either use (or emulate) gl_FragCoord.