Disable touchscreen when screen is off
This was originally filed as an RFE for GTK+, so the functionality could be implemented in a non-X11 specific way in gnome-settings-daemon, but it's a better idea for gnome-settings-daemon not to handle this at all.
mutter has enough information to be able to disable touchscreens when the screen is actually setup, but not other touch devices such as graphics tablets.
See https://bugzilla.gnome.org/show_bug.cgi?id=658274 for the GTK+ bug See gnome-settings-daemon#5 (closed) for the gnome-settings-daemon changes