How to have an /etc/xdg/autostart/app.desktop service wait for a (systemd) service?

[Patrick Schleizer]

Hi!

TLDR:

How to have an `/etc/xdg/autostart/app.desktop` service wait for a
systemd service?

Long:

I have an app started by `/etc/xdg/autostart/app.desktop` that requires
a systemd service to be started first.

I would like to avoid some sleep/wait/custom code if there is an
existing tool for such purposes.

Is there some kind of `wait_for_service_to_be_running <service-name>`
(systemd) command line tool?

Cheers,
Patrick