Comment # 2 on bug 1210562 from Takashi Iwai

I checked the code of xfce4-screensaver and found that it's likely some hackish
check of the existence of the monitor.
src/gs-manager.c contains the function

static gboolean
 gs_manager_is_real_monitor (GdkMonitor *monitor) {
     // avoiding some weird gdk bug
     // federico> avb: or if you don't care about a little unexplained
messiness,
     //                just discard monitors where both fields are null? :)
     if (gdk_monitor_get_manufacturer(monitor) == NULL &&
gdk_monitor_get_model(monitor) == NULL)
         return FALSE;
     return TRUE;
 }

... and quite a few stuff are skipped if this function returns false.  It
includes the creation of the overlay window.

This explains why the things got broken with efifb; it doesn't have the monitor
information, so it looks as if no monitor is connected.

So obviously there is a bug in the fallback code in xfce4-screensaver.  Or, we
may simply drop this check at all.

I tested quickly by commenting out those check and returning always TRUE, and
xfce4-screensaver starts working fine with efifb, too.