Move x11 config into separate file

modules/nixos/x11/default.nix

@@ -0,0 +1,56 @@
+{
+  # Snowfall Lib provides a customized `lib` instance with access to your flake's library
+  # as well as the libraries available from your flake's inputs.
+  lib,
+  # An instance of `pkgs` with your overlays and packages applied is also available.
+  pkgs,
+  # You also have access to your flake's inputs.
+  inputs,
+
+  # Additional metadata is provided by Snowfall Lib.
+  namespace, # The namespace used for your flake, defaulting to "internal" if not set.
+  system, # The system architecture for this host (eg. `x86_64-linux`).
+  target, # The Snowfall Lib target for this system (eg. `x86_64-iso`).
+  format, # A normalized name for the system target (eg. `iso`).
+  virtual, # A boolean to determine whether this system is a virtual target using nixos-generators.
+  systems, # An attribute map of your defined hosts.
+
+  # All other arguments come from the module system.
+  config,
+  ...
+}:
+
+let
+  cfg = config.modules.x11;
+in
+{
+  options.modules.x11 = {
+    enable = lib.mkOption { default = false; };
+  };
+
+  config = lib.mkIf cfg.enable {
+    services.xserver.windowManager.i3.enable = true;
+    services.xserver.windowManager.i3.package = pkgs.i3-gaps;
+
+    services.xserver.wacom.enable = true;
+
+    # TODO: move into i3 module
+    programs.xss-lock = {
+      # responds to "loginctl lock-session" via dbus
+      enable = true;
+      lockerCommand = "${pkgs.i3lock}/bin/i3lock --ignore-empty-password --color=000000";
+    };
+    # services.xserver.xautolock = { # TODO: does not work
+    #   enable = true;
+    #   time = 1;
+    # };
+
+    # Configure keymap in X11
+    services.xserver = {
+      enable = true;
+      displayManager.gdm.enable = true;
+      xkb.layout = "de";
+      xkb.variant = "";
+    };
+  };
+}