Hi Guix,

in the XFCE panel there is an item called “Action Buttons” offering
screen locking, log out, switch user, shutdown and reboot.  Shutdown and
reboot do not work at the moment.

I investigated a little and came up with a configuration in which these
two features do work.

First I had to patch our xfce-session package.  Upower is checked for at
configure time and needed for shutdown and reboot.  Polkit’s “pkexec” is
required to run the shutdown helper.

The helper contains a bunch of hardcoded paths to /sbin/shutdown, which
are replaced in a build phase — not in a snippet because eventually we
should also fix the paths to pm-{suspend,hibernate}, which would be
provided by an input that is currently not present(?).

I also needed to change my system configuration to add “pkexec” to the
list of setuid programs:

  (setuid-programs (cons #~(string-append #$polkit "/bin/pkexec")
                           %setuid-programs))

Maybe this should just be added to %setuid-programs?

Is it okay to use /run/setuid-programs/pkexec in the shutdown helper or
should this rather be a reference to the polkit input?

Here’s the patch: