[systemd-devel] Xorg or Wayland Environment

[Mantas Mikulėnas]

On Sun, Sep 19, 2021 at 4:05 AM Ed Greshko <ed.greshko at greshko.com> wrote:

> Not a everyday systemd service writer....
>
> I've written a user service file to start an app on login.  It works well
> for Xorg with Environment=DISPLAY=:0.
>
> But I've found that under Wayland the DISPLAY=:1 after a logout of Xorg
> and login to a
> Wayland session.
>
> What would be the proper way to get the DISPLAY environment varible use it
> as opposed
> to "hard" coding it?
>

The proper way is to have *the desktop environment* upload DISPLAY (and
whatever else is relevant, such as XAUTHORITY or WAYLAND_DISPLAY or
XDG_SESSION_TYPE) into systemd --user, so that it would be automatically
available to your service *without *doing anything special.

For example, gnome-session does this for GNOME (it calls systemd's
UnsetAndSetEnvironment in gsm-util.c), and
/etc/X11/xinit/xinitrc.d/50-systemd-user.sh handles the bare minimum for
other Xorg-based desktops (when startx is used).

If KDE integrates with systemd --user in any way (i.e. if it actually has a
"plasma-core.target" that you mention), I'd really expect it to do the same
before it tries to start its own targets, otherwise they would be kind of
useless.

-- 
Mantas Mikulėnas
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