xcape: add service

modules/misc/news.nix

@@ -1012,6 +1012,13 @@ in
           A new module is available: 'programs.lsd'.
         '';
       }
+
+      {
+        time = "2019-04-09T20:10:22+00:00";
+        message = ''
+          A new module is available: 'services.xcape'.
+        '';
+      }
     ];
   };
 }

modules/modules.nix

@@ -118,6 +118,7 @@ let
     (loadModule ./services/window-managers/awesome.nix { })
     (loadModule ./services/window-managers/i3.nix { })
     (loadModule ./services/window-managers/xmonad.nix { })
+    (loadModule ./services/xcape.nix { condition = hostPlatform.isLinux; })
     (loadModule ./services/xembed-sni-proxy.nix { condition = hostPlatform.isLinux; })
     (loadModule ./services/xscreensaver.nix { })
     (loadModule ./systemd.nix { })

modules/services/xcape.nix

@@ -0,0 +1,76 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.services.xcape;
+
+in
+
+{
+  meta.maintainers = [ maintainers.nickhu ];
+
+  options = {
+    services.xcape = {
+      enable = mkEnableOption "xcape";
+
+      timeout = mkOption {
+        type = types.nullOr types.int;
+        default = null;
+        example = 500;
+        description = ''
+          If you hold a key longer than this timeout, xcape will not
+          generate a key event. Default is 500 ms.
+        '';
+      };
+
+      mapExpression = mkOption {
+        type = types.attrsOf types.str;
+        default = {};
+        example = { Shift_L = "Escape"; Control_L = "Control_L|O"; };
+        description = ''
+          The value has the grammar <literal>Key[|OtherKey]</literal>.
+          </para>
+          <para>
+          The list of key names is found in the header file
+          <filename>X11/keysymdef.h</filename> (remove the
+          <literal>XK_</literal> prefix). Note that due to limitations
+          of X11 shifted keys must be specified as a shift key
+          followed by the key to be pressed rather than the actual
+          name of the character. For example to generate "{" the
+          expression <literal>Shift_L|bracketleft</literal> could be
+          used (assuming that you have a key with "{" above "[").
+          </para>
+          <para>
+          You can also specify keys in decimal (prefix #), octal (#0),
+          or hexadecimal (#0x). They will be interpreted as keycodes
+          unless no corresponding key name is found.
+        '';
+      };
+    };
+  };
+
+  config = mkIf cfg.enable {
+    systemd.user.services.xcape = {
+      Unit = {
+        Description = "xcape";
+        After = [ "graphical-session-pre.target" ];
+        PartOf = [ "graphical-session.target" ];
+      };
+
+      Service = {
+        Type = "forking";
+        ExecStart = "${pkgs.xcape}/bin/xcape"
+          + optionalString (cfg.timeout != null) " -t ${toString cfg.timeout}"
+          + optionalString (cfg.mapExpression != {})
+            " -e '${builtins.concatStringsSep ";"
+              (attrsets.mapAttrsToList (n: v: "${n}=${v}") cfg.mapExpression)}'";
+      };
+
+      Install = {
+        WantedBy = [ "graphical-session.target" ];
+      };
+    };
+  };
+}