compton: add module

modules/default.nix

@@ -35,6 +35,7 @@ let
     ./programs/vim.nix
     ./programs/zsh.nix
     ./services/blueman-applet.nix
+    ./services/compton.nix
     ./services/dunst.nix
     ./services/gnome-keyring.nix
     ./services/gpg-agent.nix

modules/misc/news.nix

@@ -178,6 +178,13 @@ in
           A new service is available: 'services.blueman-applet'.
         '';
       }
+
+      {
+        time = "2017-09-13T11:30:22+00:00";
+        message = ''
+          A new service is available: 'services.compton'.
+        '';
+      }
     ];
   };
 }

modules/services/compton.nix

@@ -0,0 +1,29 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+{
+  options = {
+    services.compton = {
+      enable = mkEnableOption "Compton X11 compositor";
+    };
+  };
+
+  config = mkIf config.services.compton.enable {
+    systemd.user.services.compton = {
+        Unit = {
+          Description = "Compton X11 compositor";
+          After = [ "graphical-session-pre.target" ];
+          PartOf = [ "graphical-session.target" ];
+        };
+
+        Install = {
+          WantedBy = [ "graphical-session.target" ];
+        };
+
+        Service = {
+          ExecStart = "${pkgs.compton}/bin/compton";
+        };
+    };
+  };
+}