GNOME 3 external dependency proposal (accounts service)

[Ray Strode <halfline gmail com>]

Hi guys,

Right now gnome-shell uses a cut-and-paste version of some code from
GDM for showing its user switch applet (and also its login dialog).
That code isn't very GDM specific, and really belongs in a library. At
this point, it's basically a thin caching layer around the accounts
service and consolekit dbus apis on freedesktop.org with some fallback
code for when the accounts service isn't available.  So I think it
probably makes sense to have that code in the accounts service module.

I've done that today here:
http://cgit.freedesktop.org/accountsservice/commit/?id=8c031bce3f6fe67bd5f0f782a457aebd6af0ceba

Vincent and Jon McCann talked recently about moving the user switch
applet to the gnome-panel.  This is in the vein of matching the gnome
2 fallback experience with the default gnome 3 experience for 3.0.
That means the panel will too need to depend on this same bit of code,
in the near future.

Also, there's been some discussion on IRC and elsewhere about putting
the accounts dialog in control-center.

These three things together mean we really need an external dependency
on accounts service, I think.  The accounts service is a small module
Matthias wrote for enumerating the users on a system and storing some
metadata (well mainly just the face icon right now) outside of the
users home directory, so it's available by other users and before the
user is logged in.  I agreed to help him comaintain it a few days ago.

Sound good?
--Ray