modify gui config, add sddm for launching niri

nixos/modules/default.nix

@@ -20,6 +20,9 @@
       ./dae
       ./openssh.nix
       ./nh.nix
+      ./i18n.nix
+      ./gui.nix
+      ./steam.nix
     ];
 
   config = {

nixos/modules/gui.nix

@@ -0,0 +1,103 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  cfg = config.youthlic.gui;
+in
+{
+  options = {
+    youthlic.gui = {
+      enabled = lib.mkOption {
+        type = lib.types.nullOr (
+          lib.types.enum [
+            "cosmic"
+            "niri"
+          ]
+        );
+        default = null;
+        example = "cosmic";
+      };
+    };
+  };
+  config = lib.mkMerge [
+    (lib.mkIf (cfg.enabled == "cosmic") {
+      # Enable the X11 windowing system.
+      # You can disable this if you're only using the Wayland session.
+      services.xserver = {
+        display = 0;
+        enable = true;
+        xkb = {
+          layout = "cn";
+          variant = "";
+        };
+      };
+
+      services.desktopManager.cosmic.enable = true;
+      services.displayManager.cosmic-greeter.enable = true;
+    })
+    (lib.mkIf (cfg.enabled == "niri") {
+      services.displayManager.sddm = {
+        enable = true;
+        wayland = {
+          enable = true;
+          compositorCommand = "niri";
+        };
+      };
+      programs.niri = {
+        enable = true;
+        package = pkgs.niri-unstable;
+      };
+    })
+    (lib.mkIf (cfg.enabled != null) {
+      environment.systemPackages = with pkgs; [
+        fontconfig
+      ];
+      programs.firefox.enable = true;
+
+      fonts = {
+        enableDefaultPackages = false;
+        packages = with pkgs; [
+          nerd-fonts.fira-code
+          noto-fonts
+          noto-fonts-cjk-sans
+          noto-fonts-cjk-serif
+          noto-fonts-emoji
+          lxgw-wenkai
+        ];
+        fontconfig.defaultFonts = pkgs.lib.mkForce {
+          serif = [
+            "LXGW WenKai"
+            "Noto Serif CJK SC"
+            "Noto Serif"
+          ];
+          sansSerif = [
+            "Noto Serif CJK SC"
+            "Noto Serif"
+          ];
+          monospace = [
+            "FiraCode Nerd Font"
+          ];
+          emoji = [ "Noto Color Emoji" ];
+        };
+      };
+
+      services.pulseaudio.enable = false;
+      security.rtkit.enable = true;
+      services.pipewire = {
+        enable = true;
+        alsa.enable = true;
+        alsa.support32Bit = true;
+        pulse.enable = true;
+        # If you want to use JACK applications, uncomment this
+        #jack.enable = true;
+
+        # use the example session manager (no others are packaged yet so this is enabled by default,
+        # no need to redefine it in your config for now)
+        #media-session.enable = true;
+      };
+    })
+  ];
+}