[systemd-devel] Using systemd --user to manage graphical sessions?

[Luke Shumaker]

On Wed, 11 May 2016 12:13:45 -0400,
Martin Pitt wrote:
> Or is someone actually using systemd --user for graphical sessions
> already and found a trick that I missed?

I am!  For several months now (and before that, I was still using
systemd --user for graphical stuff, but not consistently/coherently).

My configuration: https://lukeshu.com/git/dotfiles/tree/.config
Crappy write-up: https://lukeshu.com/blog/x11-systemd.html

One thing to note is that I don't use a DE, and have minimal
bus-activated services.

The big difference between what I do and what you wrote is that I
don't tie the DISPLAY name to the XDG_SESSION_ID (actually, the
session ID isn't even set in the graphical session).

The short version of how I have it work:

My ~/.xinitrc (AKA: script that starts the initial X11 clients)
contains:

    _DISPLAY="$(systemd-escape -- "$DISPLAY")"
    mkfifo "${XDG_RUNTIME_DIR}/x11-wm@${_DISPLAY}"
    cat < "${XDG_RUNTIME_DIR}/x11-wm@${_DISPLAY}" &
    systemctl --user start "X11@${_DISPLAY}.target" &
    wait
    systemctl --user stop "X11@${_DISPLAY}.target"

Which basically says: start X11@:0.target, wait for something to open
"${XDG_RUNTIME_DIR}/x11-wm@${_DISPLAY}" for writing and then close it,
then stop X11@:0.target.  Then I have my window manager configured to
open/close the file when I want to quit X11/log out (really, I have it
open at start, then just exit on quit; implicitly closing it).

Then, each of the whatever@${DISPLAY}.service files contains:

    [Unit]
    After=X11@%i.target
    Requisite=X11@%i.target
    [Service]
    Environment=DISPLAY=%I

Now, when I launch a program from the window manager, I have it launch
with `systemd-run --user --scope -- sh -c "COMMAND HERE"`, so that
systemd can tell the difference between it and the window manager.  I
imagine that this would be problematic with less configurable window
managers.

As I type this, I have two graphical logins to the same user.  One on
a real screen, and the other with a fake screen via `vncserver` (of
course, managed as a systemd user unit :-) ).

The only problem I have with this setup is that dunst (my desktop
notification daemon) isn't happy running multiple instances on
different displays.  I think it's because it isn't happy sharing the
dbus, but I haven't spent even 1 minute debugging it yet.

-- 
Happy hacking,
~ Luke Shumaker