swayosd: add systemdTarget option

modules/services/swayosd.nix

@@ -43,6 +43,15 @@ in {
         X display to use.
       '';
     };
+
+    systemdTarget = mkOption {
+      type = types.str;
+      default = "graphical-session.target";
+      example = "sway-session.target";
+      description = ''
+        Systemd target to bind to.
+      '';
+    };
   };
 
   config = mkIf cfg.enable {
@@ -56,8 +65,8 @@ in {
       services.swayosd = {
         Unit = {
           Description = "Volume/backlight OSD indicator";
-          PartOf = [ "graphical-session.target" ];
-          After = [ "graphical-session.target" ];
+          PartOf = [ cfg.systemdTarget ];
+          After = [ cfg.systemdTarget ];
           ConditionEnvironment = "WAYLAND_DISPLAY";
           Documentation = "man:swayosd(1)";
         };

tests/modules/services/swayosd/swayosd.nix

@@ -10,6 +10,7 @@
     display = "DISPLAY";
     stylePath = "/etc/xdg/swayosd/style.css";
     topMargin = 0.1;
+    systemdTarget = "test.target";
   };
 
   nmt.script = ''
@@ -26,11 +27,11 @@
           Type=simple
 
           [Unit]
-          After=graphical-session.target
+          After=test.target
           ConditionEnvironment=WAYLAND_DISPLAY
           Description=Volume/backlight OSD indicator
           Documentation=man:swayosd(1)
-          PartOf=graphical-session.target
+          PartOf=test.target
         ''
       }
   '';