Allow controlling whether systemd is used or not

Currently this will switch the build system between using a plain D-BUS
service file, or a user controllable systemd unit that can be actively
stopped/started.

In most cases it is more desirable to use the systemd unit approach,
as plain D-BUS services cannot be controlled and are more difficult
to introspect via the log.

For fallback cases we'll have the plain D-BUS unit, and in future we
can use this to allow untying from systemd specifics.

Signed-off-by: Ikey Doherty <ikey@solus-project.com>

data/gamemoded.service.in

@@ -0,0 +1,10 @@
+[Unit]
+Description=gamemoded
+
+[Service]
+Type=dbus
+BusName=com.feralinteractive.GameMode
+ExecStart=@BINDIR@/gamemoded -l
+
+[Install]
+WantedBy=default.target

data/meson.build

@@ -2,15 +2,25 @@ data_conf = configuration_data()
 data_conf.set('BINDIR', path_bindir)
 data_conf.set('LIBEXECDIR', path_libexecdir)
 
-# Install the D-BUS service file
-configure_file(
-    input: 'com.feralinteractive.GameMode.service.in',
-    output: 'com.feralinteractive.GameMode.service',
-    configuration: data_conf,
-    install_dir: path_dbus_service_dir,
-)
+if with_systemd == true
+    # Install systemd user unit
+    configure_file(
+        input: 'gamemoded.service.in',
+        output: 'gamemoded.service',
+        configuration: data_conf,
+        install_dir: path_systemd_unit_dir,
+    )
+else
+    # Install the D-BUS service file
+    configure_file(
+        input: 'com.feralinteractive.GameMode.service.in',
+        output: 'com.feralinteractive.GameMode.service',
+        configuration: data_conf,
+        install_dir: path_dbus_service_dir,
+    )
+endif
 
-# Install the Polkit action file
+# Install the Polkit action file in all cases
 configure_file(
     input: 'com.feralinteractive.GameMode.policy.in',
     output: 'com.feralinteractive.GameMode.policy',

meson.build

@@ -44,10 +44,21 @@ dep_threads = dependency('threads')
 # On non glibc systems this might be a stub, i.e. for musl
 libdl = cc.find_library('dl', required: false)
 
-# Set the dbus path as appropriate.
-path_dbus_service_dir = get_option('with-dbus-service-dir')
-if path_dbus_service_dir == ''
-    path_dbus_service_dir = join_paths(path_datadir, 'dbus-1', 'services')
+with_systemd = get_option('with-systemd')
+if with_systemd == true
+    # If the path isn't explicitly set, ask systemd for the systemd user unit directory
+    path_systemd_unit_dir = get_option('with-systemd-user-unit-dir')
+    if path_systemd_unit_dir == ''
+        message('Asking pkg-config for systemd\'s directories')
+        pkgconfig_systemd = dependency('systemd')
+        path_systemd_unit_dir = pkgconfig_systemd.get_pkgconfig_variable('systemduserunitdir')
+    endif
+else
+    # Set the dbus path as appropriate.
+    path_dbus_service_dir = get_option('with-dbus-service-dir')
+    if path_dbus_service_dir == ''
+        path_dbus_service_dir = join_paths(path_datadir, 'dbus-1', 'services')
+    endif
 endif
 
 path_polkit_action_dir = join_paths(path_datadir, 'polkit-1', 'actions')
@@ -92,7 +103,20 @@ report = [
     '    libdir:                                 @0@'.format(path_libdir),
     '    libexecdir:                             @0@'.format(path_libexecdir),
     '    includedir:                             @0@'.format(path_includedir),
+]
+
+if with_systemd == true
+report += [
+    '    systemd user unit directory:            @0@'.format(path_systemd_unit_dir),
+]
+else
+report += [
     '    D-BUS service directory:                @0@'.format(path_dbus_service_dir),
+]
+endif
+
+report += [
+
     '    PolKit Action Directory:                @0@'.format(path_polkit_action_dir),
     '',
     '    Options:',
@@ -100,6 +124,7 @@ report = [
     '',
     '    daemon:                                 @0@'.format(with_daemon),
     '    examples:                               @0@'.format(with_examples),
+    '    systemd:                                @0@'.format(with_systemd),
 ]
 
 # Output some stuff to validate the build config

meson_options.txt

@@ -1,3 +1,11 @@
+option('with-systemd', type: 'boolean', description: 'Use systemd support (unit, etc)', value: 'true')
+
+# systemd specific
+option('with-systemd-user-unit-dir', type: 'string', description: 'Explicitly set the systemd user unit directory')
+
+# Not using systemd
 option('with-dbus-service-dir', type: 'string', description: 'Explicitly set the D-BUS session directory')
+
+# General options
 option('with-examples', type: 'boolean', description: 'Build sample programs', value: 'true')
 option('with-daemon', type: 'boolean', description: 'Build the daemon', value: 'true')