I have a new laptop with hybrid graphics where external monitors are
connected via a thunderbolt 3 dock. I haven't managed to get the
external monitors working yet, a Nvidia driver problem I believe.

However somehow the system does detect that there are monitors
connected, and at regular intervals xfce4-display-settings pops up
(uselessly, as only the laptop internal screen can be selected, but
that's not xfce4-display-settings' fault).

At one time I saw there were 30 xfce4-display-settings processes
running! I used killall to get rid of them, but IMHO it's pointless to
start a new process if there's another still running. So some sort of
lock file would be very useful.


Thanks,
Paul