improved the .service file

service/data/ximper-unified-theme-switcher.service

 [Unit]
-After=graphical-session.target
 Description=Ximper unified theme switcher
+After=graphical-session.target
 
 [Service]
 ExecStart=/usr/bin/ximper-unified-theme-switcher-service
-Restart=on-failure
+Type=simple
+Restart=always
 RestartSec=1
 
 [Install]

service/data/ximper-unified-theme-switcher.timer

+[Unit]
+Description=Ximper unified theme switcher timer
+
+[Timer]
+OnStartupSec=3
+Unit=ximper-unified-theme-switcher.service
+
+[Install]
+WantedBy=default.target

service/meson.build

@@ -11,6 +11,10 @@ install_data(
     './data/ximper-unified-theme-switcher.service',
     install_dir: join_paths(prefix, 'lib', 'systemd', 'user')
 )
+install_data(
+    './data/ximper-unified-theme-switcher.timer',
+    install_dir: join_paths(prefix, 'lib', 'systemd', 'user')
+)
 
 cfg_dir = join_paths(sysconfdir, 'ximper-unified-theme-switcher')