use dbus to get notifications of screensaver state changes

[Antoine Martin]

On linux we use xlib to know the "idle time" of the X session and compare that against the timeout value.

We could just do something more similar to what we do on win32 and get notifications when the screensaver is (de)activated:

dbus-monitor --session "type='signal',interface='org.gnome.ScreenSaver',member='SessionIdleChanged'"

More information about the dbus interface, and in particular the ActiveChanged signal in the ​gnome-screensaver doc

The FAQ contains an example of actions using dbus-monitor: ​perform_actions_when_the_screensaver...

For reference, the win32 code is ​track-session-events (from the great win32_how_do_i)

Synergy+ has a bug entry with useful links in it: ​Support for gnome-screensaver as well as xscreensaver

Some other useful pointers:

• ​gnome screensaver discussion on mailing list, dated 2006. Refers to org.gnome.ScreenSaver
• ​idle.c module for X11 used by gajim, which calls XScreenSaverQueryInfo.
• ​idle.c module for OSX (uses IOKIT via C)

[Antoine Martin]

Seeing the painful bugs we had with avahi/dbus python integrating with twisted (removed them in r1626), it might be difficult to integrate this asynchronous dbus stuff with twisted... not sure. If it is, maybe we could just launch a separate process to shield us from this (and monitor/parse its output): very ugly solution but also much safer!

[Antoine Martin]

Found code that does exactly that (both as a process and with direct dbus calls): ​http://nxsy.org/getting-amarok-to-pause-when-the-screen-locks-using-python-of-course

[Antoine Martin]

The dbus-monitor approach should work now that we have a convenience wrapper for line processes via twisted.