This requires, certainly, consolekit
to be installed and. xinitrc with
"startxfce4 --with-ck-launch"
I don't have an opportunity to
try myself, as I dumped Xfce
a quarter ago in favour of Openbox
and then dwm, but the shenanigans
I'm sending were sent by me
earlier in the list and thus were tested.
I didn't incorporate the use of any kind
of display manager though, neither
then, nor do now.