Add MangoHud module and enable it on hosts

Introduce a new `mangohud.nix` module with sensible defaults, import it
in
`modules/home/default.nix`, and add a `mangohud.enable` flag to the host
configurations (enabled for desktop and laptop, disabled for the default
host).

Comment out the default Gamescope arguments in `modules/core/steam.nix`
and
add a reference command line that includes the MangoHud flag.

modules/core/steam.nix

@@ -18,10 +18,10 @@
       dedicatedServer.openFirewall = true;
       gamescopeSession = lib.mkIf config.gamescope.enable {
         enable = true;
-        args = [
-          "--rt"
-          "--expose-wayland"
-        ];
+        # args = [
+        #   "--rt"
+        #   "--expose-wayland"
+        # ];
       };
       extraCompatPackages = [pkgs.proton-ge-bin];
     };
@@ -29,10 +29,10 @@
     gamescope = lib.mkIf config.gamescope.enable {
       enable = true;
       capSysNice = true;
-      args = [
-        "--rt"
-        "--expose-wayland"
-      ];
+      # args = [
+      #   # "--rt"
+      #   # "--expose-wayland"
+      # ];
     };
 
     gamemode = lib.mkIf config.gamemode.enable {
@@ -41,3 +41,5 @@
     };
   };
 }
+# gamescope -W 1920 -H 1080 -r 144 --force-grab-cursor -f --mangoapp --rt --expose-wayland --
+

modules/home/default.nix

@@ -24,6 +24,7 @@ _: {
     ./gtk.nix
     ./kdeConnect.nix
     ./lutris.nix
+    ./mangohud.nix
     ./nextcloud.nix
     ./obs-studio.nix
     ./ollama.nix

modules/home/mangohud.nix

@@ -0,0 +1,72 @@
+{
+  pkgs,
+  lib,
+  config,
+  ...
+}: {
+  options.mangohud.enable = lib.mkEnableOption "MangoHud";
+
+  config = lib.mkIf config.mangohud.enable {
+    programs.mangohud = {
+      enable = true;
+      package = pkgs.mangohud;
+      settings = lib.mkForce {
+        position = "top-right";
+        background_alpha = 0.4;
+        font_size = 18;
+        round_corners = 8;
+        no_display = 0;
+
+        gpu_color = "2e9ef4";
+        cpu_color = "39d353";
+        vram_color = "ad3aff";
+        ram_color = "c0c0c0";
+        engine_color = "eb5454";
+        frametime_color = "e8c446";
+        text_color = "ffffff";
+        background_color = "020202";
+        media_player_color = "ffffff";
+
+        fps_color_change = 1;
+        fps_color = "39d353,e8c446,eb5454";
+        fps_value = "60,30";
+
+        fps = 1;
+        fps_only = 0;
+
+        gpu_stats = 1;
+        gpu_load_change = 1;
+        gpu_load_value = "60,90";
+        gpu_load_color = "39d353,e8c446,eb5454";
+        gpu_temp = 1;
+        gpu_core_clock = 1;
+        gpu_mem_clock = 0;
+        gpu_power = 1;
+        gpu_name = 1;
+        vram = 1;
+
+        cpu_stats = 1;
+        cpu_load_change = 1;
+        cpu_load_value = "60,90";
+        cpu_load_color = "39d353,e8c446,eb5454";
+        cpu_temp = 1;
+        cpu_mhz = 1;
+        core_load = 0;
+
+        ram = 1;
+
+        frametime = 1;
+        frame_timing = 1;
+        histogram = 0;
+
+        engine_version = 1;
+        vulkan_driver = 1;
+        arch = 0;
+
+        fps_limit = 0;
+        toggle_hud = "Shift_R+F12";
+        toggle_fps_limit = "Shift_L+F1";
+      };
+    };
+  };
+}