idle detection

[Sean Egan]

On 7/26/07, Ethan Blanton <elb at pidgin.im> wrote:
> What are the screensavers doing
> these days?  Do they rely on display capture?

Comments in gtkidle.c led me to
http://bugs.donarmstrong.com/cgi-bin/bugreport.cgi?bug=271639 in which
Luke appears to foolishly argue with jwz about the best way to handle
this. jwz makes reference to
http://www.google.com/codesearch?hl=en&q=+xscreensaver-command+show:6YCRwMaw3Ss:RFRcZxe98D8:t-Na2BO0Uug&sa=N&cd=2&ct=rc&cs_p=http://familiar.handhelds.org/source/v0.8.0/package-sources/xscreensaver-4.16.tar.gz&cs_f=xscreensaver-4.16/driver/xscreensaver-command.c#a0

It looks like both of these techniques are dependent on xscreensaver
running; at least when I try xscreensaver-command -time I get
"xscreensaver-command: no screensaver is running on display :0.0"

In either case, it seems just like more polling;

http://live.gnome.org/GnomeScreensaver/FrequentlyAskedQuestions says:

Is there a way to perform actions when the screensaver activates or
deactivates? Or when the session becomes idle?

One way is to watch for the D-Bus signals from gnome-screensaver.
Here's an example of how to perform actions when the session becomes
idle or is no longer idle:

my $cmd = "dbus-monitor --session
\"type='signal',interface='org.gnome.ScreenSaver',member='SessionIdleChanged'\"";

open (IN, "$cmd |");

while (<IN>) {
    if (m/^\s+boolean true/) {
        print "*** Session is idle ***\n";
    } elsif (m/^\s+boolean false/) {
        print "*** Session is no longer idle ***\n";
    }
}

which looks like a promising route, albeit specific to
'gnome-screensaver', which I didn't even realize existed.

Is it possible to, say, listen to events on the root window or something?

I think I'll do the above described for 2.1.0---poll with the
frequency set in preferences when not idle, and once every second or
two when idle (if people got by with polling for 7 years, they can
handle 3 more weeks), and then we can take care of this issue for real
in a subsequant release.

I suspect there's no good way to do this other than the special-case
hack for gnome-screensaver, though.

-s.