Add programs.ibus config option to enable ibus and plugins.

nixos/modules/module-list.nix

@@ -60,6 +60,7 @@
   ./programs/dconf.nix
   ./programs/environment.nix
   ./programs/info.nix
+  ./programs/ibus.nix
   ./programs/light.nix
   ./programs/nano.nix
   ./programs/screen.nix

nixos/modules/programs/ibus.nix

@@ -0,0 +1,51 @@
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+let
+  cfg = config.programs.ibus;
+in
+{
+  options = {
+
+    programs.ibus = {
+      enable = mkOption {
+        type = types.bool;
+        default = false;
+        example = true;
+        description = "Enable IBus input method";
+      };
+      plugins = mkOption {
+        type = lib.types.listOf lib.types.path;
+        default = [];
+        description = ''
+          IBus plugin packages
+        '';
+      };
+    };
+
+  };
+
+  config = mkIf cfg.enable {
+    environment.systemPackages = [ pkgs.ibus ];
+
+    gtkPlugins = [ pkgs.ibus ];
+    qtPlugins = [ pkgs.ibus ];
+
+    environment.variables =
+      let
+        env = pkgs.buildEnv {
+          name = "ibus-env";
+          paths = [ pkgs.ibus ] ++ cfg.plugins;
+        };
+      in {
+        GTK_IM_MODULE = "ibus";
+        QT_IM_MODULE = "ibus";
+        XMODIFIERS = "@im=ibus";
+
+        IBUS_COMPONENT_PATH = "${env}/share/ibus/component";
+      };
+
+    services.xserver.displayManager.sessionCommands = "${pkgs.ibus}/bin/ibus-daemon -d -t none";
+  };
+}