Session DBus protocol

[Ryan Lortie <desrt desrt ca>]

hi,

Vincent and I are sitting on a couch here at UDS reviewing the DBus
protocol used by gnome-session.

I am interested in adding support to GtkApplication.

My biggest concern is that the "emit signal and wait 1 second" approach
for checking which clients want to stop the logout from happening is
really bad.

 1) Some clients might miss the deadline (if they are swapped, or the
    system is really bogged down).  Data loss here.

 2) We may end up waiting for 1 second completely unnecessarily.


I was wondering if maybe we could improve this interface to work more
like the following:

 1) Clients that may want to block the logout register themselves with
    gnome-session.

 2) gnome-session does a AddMatch on their NameOwnerChanged so it can
    tell if they exited (and unregister them).

 3) At logout time, gnome-session makes a method call to each registered
    app and *waits for a reply*.  The length of time to wait should be
    much longer than 1 second.  Similar to the close button on
    unresponsive windows, we could pop up a "this application is stuck"
    dialog in that case allowing the user to kill it if they explicitly
    choose to (but never assuming that no reply equals "no data to
    save").


Cheers