[systemd-devel] How to have systemd --user instance share the same environment variables as the X server?

[Patrick Schleizer]

Being on Debian stretch (Qubes). The display manager there does not yet
get started by systemd --user.

I find it useful to convert /etc/xdg/autostart/app.desktop files to
systemd --user unit files.

Therefore the environment variables have to be sorted out. On any Linux
we would have to set at least DISPLAY as well as XAUTHORITY.

On Qubes however, we need a few more environment variables. We need also
QT_X11_NO_MITSHM=1 and may need a few others ones.

Now, before I go through them manually and then have this break in
future when more/different environment variables are needed...

Is there a way to have the systemd --user session share the same
variables as the X server? Writing a parser for /etc/X11/Xsession.d/
seems wrong. Am I missing some tool to do that?

Would I add something like this?

ExecStartPre=dbus-update-activation-environment --systemd --all

Best regards,
Patrick