Polkit as an optional dependency of xfce4-session

[Ali Abdallah]

Hi all,

So as HAL is deprecated, in order to keep supporting high level 
"shutdown" services such as consolekit and upower, we are in need to 
polkit in order to check if the user is allowed actually to 
suspend/hibernate the machine.

The old method that consists of sending a message which should not exist 
to HAL and see if the raised error is "permission denied" or a "method 
doesn't exist" doesn't work here since the polkit checks are done after 
the message reaches upower.

So, or we use libpolkit as an optional dependency and we can any time 
ask to see if the user is allowed to do specific actions without having 
to care about its details and without having to maintain extra code, or 
we can use dbus-glib to ask the polkitd about information that we need.

For the second solution, there is no problem about it, i already wrote 
the necessary dbus-glib types and calls to do that, but i'm always 
afraid about the possible API break of averything has a name that ends 
with "kit".

But anyway, in the good part, i should be able to branch from master 
(thanks jeromeg) and push the code by tomorrow, i need to do more 
testing, also for people without upower, consolekit, HAL, they can just 
use the configure switches to switch them off, so the session will not 
even try to see if HAL, consolekit, upower are running and just be using 
sudo saving some milliseconds :)

Cheers,
Ali