Add background image service (based on feh calls)

users/ellmau/autorandr.nix

@@ -126,6 +126,7 @@ with lib; {
         };
         hooks.postswitch = {
           "polybar" = "systemctl --user restart polybar.service";
+          change-bg = "/home/ellmau/.fehbg";
         };
       };
     };

users/ellmau/background-x.nix

@@ -0,0 +1,34 @@
+{
+  config,
+  pkgs,
+  lib,
+  nixosConfig,
+  ...
+}:
+with lib; {
+  config = let
+    cfg = nixosConfig.elss.graphical.xserver;
+    fehArgs = "--bg-fill --no-fehbg";
+  in
+    mkIf cfg.enable {
+      systemd.user = {
+        services = {
+          desktop-background = {
+            Unit = {
+              Description = "Set desktop background";
+              Documentation = ["man:feh(1)"];
+              After = ["graphical-session-pre.target"];
+              ParOf = ["graphical-session.target"];
+            };
+
+            Service = {
+              type = "oneshot";
+              ExecStart = "${pkgs.feh}/bin/feh ${fehArgs} ${config.xdg.configHome}/background.png";
+            };
+
+            Install = {WantedBy = ["graphical-session.target"];};
+          };
+        };
+      };
+    };
+}

users/ellmau/default.nix

@@ -24,6 +24,7 @@
     ./waybar.nix
 
     ./graphical.nix
+    ./background-x.nix
   ];
   services = {
     gnome-keyring = {