Not a Slack-specific issue, but I assume that many folks here find the light/fast/features mix of XFCE4 a nice complement to the distro's similar attributes.
The latest XFCE4 allows the session manager to call a shutdown helper to provide shutdown or reboot options without bailing to GDM, KDM or XDM. Sudo must be installed and used as described in the docs: http://www.loculus.nl/xfce/documenta...#xfsm-shutdown
The problem I ran into is that it would not work on my system until I added nopassword to the sudoers file, even though I was not being prompted for one.
This line did it:
myuser hostname=NOPASSWD: /usr/libexec/xfsm-shutdown-helper
Hopefully, that saves someone else some hair-pulling.