data: Create generic org.gnome.Shell.target

Move the GNOME shell service file adapation for x11/wayland into the
target/service files. This means that the session definition can simply
pull in org.gnome.Shell.target, without having to care about whether it
is starting an X11 or wayland session.

Note that this currently requires fork'ing to do the test. This will
however not be needed in the long term when ConditionEnvironment becomes
available (see https://github.com/systemd/systemd/pull/15817).

We technically do not need to use template units. But doing so means
that the unit can be translated to the app id more easily (though it is
not yet completely clear how this should look like in the long term).

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/895

data/meson.build

@@ -101,21 +101,20 @@ if have_systemd
   unitconf.set('bindir', bindir)
 
   configure_file(
-    input: 'org.gnome.Shell-x11.service.in',
+    input: 'org.gnome.Shell@x11.service.in',
-    output: 'org.gnome.Shell-x11.service',
+    output: 'org.gnome.Shell@x11.service',
     configuration: unitconf,
     install_dir: systemduserunitdir
   )
 
   configure_file(
-    input: 'org.gnome.Shell-wayland.service.in',
+    input: 'org.gnome.Shell@wayland.service.in',
-    output: 'org.gnome.Shell-wayland.service',
+    output: 'org.gnome.Shell@wayland.service',
     configuration: unitconf,
     install_dir: systemduserunitdir
   )
 
-  units = files('org.gnome.Shell-x11.target',
+  units = files('org.gnome.Shell.target',
-                'org.gnome.Shell-wayland.target',
                 'org.gnome.Shell-disable-extensions.service')
 
   install_data(units, install_dir: systemduserunitdir)

data/org.gnome.Shell-x11.target

@@ -1,10 +0,0 @@
-[Unit]
-Description=GNOME Shell on X11
-DefaultDependencies=no
-
-Requisite=gnome-session-initialized.target
-PartOf=gnome-session-initialized.target
-Before=gnome-session-initialized.target
-
-Requires=org.gnome.Shell-x11.service
-After=org.gnome.Shell-x11.service

data/org.gnome.Shell.target

@@ -6,5 +6,5 @@ Requisite=gnome-session-initialized.target
 PartOf=gnome-session-initialized.target
 Before=gnome-session-initialized.target
 
-Requires=org.gnome.Shell-wayland.service
+Wants=org.gnome.Shell@wayland.service
-After=org.gnome.Shell-wayland.service
+Wants=org.gnome.Shell@x11.service

data/org.gnome.Shell@wayland.service.in

@@ -15,13 +15,18 @@ Before=gnome-session-initialized.target
 
 [Service]
 Type=notify
+# NOTE: This can be replaced with ConditionEnvironment=XDG_SESSION_TYPE=%I
+#       with systemd >= 245. Also, the current solution is kind of painful
+#       as systemd had a bug where it retries the condition.
+# Only start if the template instance matches the session type.
+ExecCondition=/bin/sh -c 'test "$XDG_SESSION_TYPE" = "%I" || exit 2'
 ExecStart=@bindir@/gnome-shell
+# Exit code 1 means we are probably *not* dealing with an extension failure
+SuccessExitStatus=1
 
 # unset some environment variables that were set by the shell and won't work now that the shell is gone
 ExecStopPost=-systemctl --user unset-environment GNOME_SETUP_DISPLAY WAYLAND_DISPLAY DISPLAY XAUTHORITY
 
-# Exit code 1 means we are probably *not* dealing with an extension failure
-SuccessExitStatus=1
 # On wayland we cannot restart
 Restart=no
 # Kill any stubborn child processes after this long

data/org.gnome.Shell@x11.service.in

@@ -19,9 +19,17 @@ StartLimitBurst=3
 
 [Service]
 Type=notify
+# NOTE: This can be replaced with ConditionEnvironment=XDG_SESSION_TYPE=%I
+#       with systemd >= 245. Also, the current solution is kind of painful
+#       as systemd had a bug where it retries the condition.
+# Only start if the template instance matches the session type.
+ExecCondition=/bin/sh -c 'test "$XDG_SESSION_TYPE" = "%I" || exit 2'
 ExecStart=@bindir@/gnome-shell
 # Exit code 1 means we are probably *not* dealing with an extension failure
 SuccessExitStatus=1
+
+# On X11 we do not need to unset any variables
+
 # On X11 we want to restart on-success (Alt+F2 + r) and on-failure.
 Restart=always
 # Do not wait before restarting the shell