nixos/compton: add user service (#16652)

nixos/modules/module-list.nix

@@ -477,6 +477,7 @@
   ./services/web-servers/winstone.nix
   ./services/web-servers/zope2.nix
   ./services/x11/colord.nix
+  ./services/x11/compton.nix
   ./services/x11/unclutter.nix
   ./services/x11/desktop-managers/default.nix
   ./services/x11/display-managers/auto.nix

nixos/modules/services/x11/compton.nix

@@ -0,0 +1,225 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+with builtins;
+
+let
+
+  cfg = config.services.compton;
+
+  configFile = pkgs.writeText "compton.conf"
+    (optionalString cfg.fade ''
+      # fading
+      fading = true;
+      fade-delta    = ${toString cfg.fadeDelta};
+      fade-in-step  = ${elemAt cfg.fadeSteps 0};
+      fade-out-step = ${elemAt cfg.fadeSteps 1};
+      fade-exclude  = ${toJSON cfg.fadeExclude};
+    '' + 
+    optionalString cfg.shadow ''
+
+      # shadows
+      shadow = true;
+      shadow-offset-x = ${toString (elemAt cfg.shadowOffsets 0)};
+      shadow-offset-y = ${toString (elemAt cfg.shadowOffsets 1)};
+      shadow-opacity  = ${cfg.shadowOpacity};
+      shadow-exclude  = ${toJSON cfg.shadowExclude};
+    '' + ''
+
+      # opacity
+      active-opacity   = ${cfg.activeOpacity};
+      inactive-opacity = ${cfg.inactiveOpacity};
+      menu-opacity     = ${cfg.menuOpacity};
+      
+      # other options
+      backend = ${toJSON cfg.backend};
+      vsync = ${toJSON cfg.vSync};
+      refresh-rate = ${toString cfg.refreshRate};
+    '' + cfg.extraOptions);
+
+in {
+
+  options.services.compton = {
+    enable = mkOption {
+      type = types.bool;
+      default = false;
+      example = true;
+      description = ''
+        Whether of not to enable Compton as the X.org composite manager.
+      '';
+    };
+
+    fade = mkOption {
+      type = types.bool;
+      default = false;
+      example = true;
+      description = ''
+        Fade windows in and out.
+      '';
+    };
+
+    fadeDelta = mkOption {
+      type = types.int;
+      default = 10;
+      example = 5;
+      description = ''
+        Time between fade animation step (in ms).
+      '';
+    };
+
+    fadeSteps = mkOption {
+      type = types.listOf types.str;
+      default = [ "0.028" "0.03" ];
+      example = [ "0.04" "0.04" ];
+      description = ''
+        Opacity change between fade steps (in and out).
+      '';
+    };
+
+    fadeExclude = mkOption {
+      type = types.listOf types.str;
+      default = [];
+      example = [
+        "window_type *= 'menu'"
+        "name ~= 'Firefox$'"
+        "focused = 1" 
+      ];
+      description = ''
+        List of condition of windows that should have no shadow.
+        See <literal>compton(1)</literal> man page for more examples.
+      '';
+    };
+
+    shadow = mkOption {
+      type = types.bool;
+      default = false;
+      example = true;
+      description = ''
+        Draw window shadows.
+      '';
+    };
+
+    shadowOffsets = mkOption {
+      type = types.listOf types.int;
+      default = [ (-15) (-15) ];
+      example = [ (-10) (-15) ];
+      description = ''
+        Left and right offset for shadows (in pixels).
+      '';
+    };
+
+    shadowOpacity = mkOption {
+      type = types.str;
+      default = "0.75";
+      example = "0.8";
+      description = ''
+        Window shadows opacity (number in range 0 - 1).
+      '';
+    };
+
+    shadowExclude = mkOption {
+      type = types.listOf types.str;
+      default = [];
+      example = [
+        "window_type *= 'menu'"
+        "name ~= 'Firefox$'"
+        "focused = 1" 
+      ];
+      description = ''
+        List of condition of windows that should have no shadow.
+        See <literal>compton(1)</literal> man page for more examples.
+      '';
+    };
+
+    activeOpacity = mkOption {
+      type = types.str;
+      default = "1.0";
+      example = "0.8";
+      description = ''
+        Opacity of active windows.
+      '';
+    };
+
+    inactiveOpacity = mkOption {
+      type = types.str;
+      default = "1.0";
+      example = "0.8";
+      description = ''
+        Opacity of inactive windows.
+      '';
+    };
+
+    menuOpacity = mkOption {
+      type = types.str;
+      default = "1.0";
+      example = "0.8";
+      description = ''
+        Opacity of dropdown and popup menu.
+      '';
+    };
+
+    backend = mkOption {
+      type = types.str;
+      default = "glx";
+      description = ''
+        Backend to use: <literal>glx</literal> or <literal>xrender</literal>.
+      '';
+    };
+
+    vSync = mkOption {
+     type = types.str;
+     default = "none";
+     example = "opengl-swc";
+     description = ''
+       Enable vertical synchronization using the specified method.
+       See <literal>compton(1)</literal> man page available methods.
+     '';
+    };
+
+    refreshRate = mkOption {
+      type = types.int;
+      default = 0;
+      example = 60;
+      description = ''
+       Screen refresh rate (0 = automatically detect).
+      '';
+    };
+
+    package = mkOption {
+      type = types.package;
+      default = pkgs.compton;
+      example = literalExample "pkgs.compton";
+      description = ''
+        Compton derivation to use.
+      '';
+    };
+
+    extraOptions = mkOption {
+      type = types.str;
+      default = "";
+      example = ''
+        unredir-if-possible = true;
+        dbe = true;
+      '';
+      description = ''
+        Additional Compton configuration.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    systemd.user.services.compton = {
+      description = "Compton composite manager";
+      wantedBy = [ "default.target" ];
+      serviceConfig = {
+        ExecStart = "${cfg.package}/bin/compton --config ${configFile}";
+        RestartSec = 3;
+        Restart = "always";
+      };
+      environment.DISPLAY = ":0";
+    };
+
+    environment.systemPackages = [ cfg.package ];
+  };
+
+}