xfce4-notifyd-0.3.0 terminates automatically and can't be restarted by dbus
Some minutes after being started, xfce4-notifyd always terminates silently,
without any error message or core dump and without any external influence
(don't know why).
This happens both when started by the xfce session startup
and when started on the commandline of an xfce terminal.
Now, when a notification is to be displayed after xfce4-notifyd terminated,
dbus tries to restart xfce4-notifyd, but that fails.
From the systemd journal:
Aug 10 19:18:25 lap dbus-daemon: Activating via systemd: service name='org.freedesktop.Notifications' unit='xfce4-notifyd.service'
Aug 10 19:18:25 lap systemd: Starting XFCE notifications service...
Aug 10 19:18:25 lap xfce4-notifyd: (xfce4-notifyd:976): Gtk-WARNING **: cannot open display:
Aug 10 19:18:25 lap systemd: xfce4-notifyd.service: Main process exited, code=exited, status=1/FAILURE
Aug 10 19:18:25 lap systemd: Failed to start XFCE notifications service.
Aug 10 19:18:25 lap systemd: xfce4-notifyd.service: Unit entered failed state.
Aug 10 19:18:25 lap systemd: xfce4-notifyd.service: Failed with result 'exit-code'.
The result is quite fatal:
The applications which tried to send the notifications (in my case,
usually the mail program, same for the xfce4-notifyd-config test message)
hang infinitely until being killed.
I think the error message from xfce4-notifyd about "cannot open display"
is technically correct:
I start X the clean way, logging into a vt in text mode and then startig X
within the same systemd session from the text terminal session.
Hence, as far as I can tell, the user systemd process and the session dbus process seem to be started by login *before* I start X and consequently
do not have any X environment, i.e. no DISPLAY.