gammastep: add module

Fixes #1396

.github/CODEOWNERS

@@ -148,6 +148,8 @@
 
 /modules/services/fluidsynth.nix                      @Valodim
 
+/modules/services/gammastep.nix                       @petabyteboy
+
 /modules/services/gnome-keyring.nix                   @rycee
 
 /modules/services/gpg-agent.nix                       @rycee

modules/misc/news.nix

@@ -1705,6 +1705,14 @@ in
           A new zsh submodule is available: 'programs.zsh.prezto'.
         '';
       }
+
+      {
+        time = "2020-10-22T21:10:38+00:00";
+        condition = hostPlatform.isLinux;
+        message = ''
+          A new module is available: 'services.gammastep'.
+        '';
+      }
     ];
   };
 }

modules/modules.nix

@@ -140,6 +140,7 @@ let
     (loadModule ./services/emacs.nix { condition = hostPlatform.isLinux; })
     (loadModule ./services/flameshot.nix { })
     (loadModule ./services/fluidsynth.nix { condition = hostPlatform.isLinux; })
+    (loadModule ./services/gammastep.nix { condition = hostPlatform.isLinux; })
     (loadModule ./services/getmail.nix { condition = hostPlatform.isLinux; })
     (loadModule ./services/gnome-keyring.nix { })
     (loadModule ./services/gpg-agent.nix { })

modules/services/gammastep.nix

@@ -0,0 +1,166 @@
+# Adapted from Nixpkgs.
+
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.services.gammastep;
+
+in {
+  meta.maintainers = [ maintainers.petabyteboy ];
+
+  options.services.gammastep = {
+    enable = mkOption {
+      type = types.bool;
+      default = false;
+      example = true;
+      description = ''
+        Enable Gammastep to change your screen's colour temperature depending on
+        the time of day.
+      '';
+    };
+
+    latitude = mkOption {
+      type = types.nullOr types.str;
+      default = null;
+      description = ''
+        Your current latitude, between <literal>-90.0</literal> and
+        <literal>90.0</literal>. Must be provided along with
+        longitude.
+      '';
+    };
+
+    longitude = mkOption {
+      type = types.nullOr types.str;
+      default = null;
+      description = ''
+        Your current longitude, between <literal>-180.0</literal> and
+        <literal>180.0</literal>. Must be provided along with
+        latitude.
+      '';
+    };
+
+    provider = mkOption {
+      type = types.enum [ "manual" "geoclue2" ];
+      default = "manual";
+      description = ''
+        The location provider to use for determining your location. If set to
+        <literal>manual</literal> you must also provide latitude/longitude.
+        If set to <literal>geoclue2</literal>, you must also enable the global
+        geoclue2 service.
+      '';
+    };
+
+    temperature = {
+      day = mkOption {
+        type = types.int;
+        default = 5500;
+        description = ''
+          Colour temperature to use during the day, between
+          <literal>1000</literal> and <literal>25000</literal> K.
+        '';
+      };
+
+      night = mkOption {
+        type = types.int;
+        default = 3700;
+        description = ''
+          Colour temperature to use at night, between
+          <literal>1000</literal> and <literal>25000</literal> K.
+        '';
+      };
+    };
+
+    brightness = {
+      day = mkOption {
+        type = types.str;
+        default = "1";
+        description = ''
+          Screen brightness to apply during the day,
+          between <literal>0.1</literal> and <literal>1.0</literal>.
+        '';
+      };
+
+      night = mkOption {
+        type = types.str;
+        default = "1";
+        description = ''
+          Screen brightness to apply during the night,
+          between <literal>0.1</literal> and <literal>1.0</literal>.
+        '';
+      };
+    };
+
+    package = mkOption {
+      type = types.package;
+      default = pkgs.gammastep;
+      defaultText = literalExample "pkgs.gammastep";
+      description = ''
+        gammastep derivation to use.
+      '';
+    };
+
+    tray = mkOption {
+      type = types.bool;
+      default = false;
+      example = true;
+      description = ''
+        Start the gammastep-indicator tray applet.
+      '';
+    };
+
+    extraOptions = mkOption {
+      type = types.listOf types.str;
+      default = [ ];
+      example = [ "-v" "-m randr" ];
+      description = ''
+        Additional command-line arguments to pass to
+        <command>gammastep</command>.
+      '';
+    };
+  };
+
+  config = mkIf cfg.enable {
+    assertions = [{
+      assertion = cfg.provider == "manual" -> cfg.latitude != null
+        && cfg.longitude != null;
+      message = "Must provide services.gammastep.latitude and"
+        + " services.gammastep.latitude when"
+        + " services.gammastep.provider is set to \"manual\".";
+    }];
+
+    systemd.user.services.gammastep = {
+      Unit = {
+        Description = "Gammastep colour temperature adjuster";
+        After = [ "graphical-session-pre.target" ];
+        PartOf = [ "graphical-session.target" ];
+      };
+
+      Install = { WantedBy = [ "graphical-session.target" ]; };
+
+      Service = {
+        ExecStart = let
+          providerString = if cfg.provider == "manual" then
+            "${cfg.latitude}:${cfg.longitude}"
+          else
+            cfg.provider;
+
+          args = [
+            "-l ${providerString}"
+            "-t ${toString cfg.temperature.day}:${
+              toString cfg.temperature.night
+            }"
+            "-b ${toString cfg.brightness.day}:${toString cfg.brightness.night}"
+          ] ++ cfg.extraOptions;
+
+          command = if cfg.tray then "gammastep-indicator" else "gammastep";
+        in "${cfg.package}/bin/${command} ${concatStringsSep " " args}";
+        RestartSec = 3;
+        Restart = "always";
+      };
+    };
+  };
+
+}