nix vm: add documentation, add Gnome/X11 VM

CONTRIBUTING.md

@@ -77,3 +77,58 @@ pull request will be accepted with a high degree of certainty.
 > **Pull requests are NOT a place to discuss feature design.** Please do
 > not open a WIP pull request to discuss a feature. Instead, use a discussion
 > and link to your branch.
+
+## Nix Virtual Machines
+
+Several Nix virtual machine definitions are provided by the project for testing
+and developing Ghostty against multiple different Linux desktop environments.
+
+Running these requires a working Nix installation, either Nix on your
+favorite Linux distribution, NixOS, or macOS with nix-darwin installed. Futher
+requirements for macOS are detailed below.
+
+VMs should only be run on your local desktop and then powered off when not in
+use, which will discard any changes to the VM.
+
+The VM definitions provide minimal software "out of the box" but additional
+software can be installed by using standard Nix mechanisms like `nix run nixpkgs#<package>`.
+
+### Linux
+
+1. Check out the Ghostty source and change to the directory.
+2. Run `nix run .#<vmtype>`. `<vmtype>` can be any of the VMs defined in the
+   `nix/vm` directory (without the `.nix` suffix) excluding any file prefixed
+   with `common`.
+3. The VM will build and then launch. Depending on the speed of your system, this
+   can take a while, but eventually you should get a new VM window.
+4. The Ghostty source directory should be mounted to `/tmp/shared` in the VM. Depending
+   on what UID and GID of the user that you launched the VM as, `/tmp/shared` _may_ be
+   writable by the VM user, so be careful!
+
+### macOS
+
+1. To run the VMs on macOS you will need to enable the Linux builder in your `nix-darwin`
+   config. This _should_ be as simple as adding `nix.linux-builder.enable=true` to your
+   configuration and then rebuilding. See [this](https://nixcademy.com/posts/macos-linux-builder/)
+   blog post for more information about the Linux builder and how to tune the performance.
+2. Once the Linux builder has been enabled, you should be able to follow the Linux instructions
+   above to launch a VM.
+
+### Contributing new VM definitions
+
+#### Acceptance Criteria
+
+We welcome the contribution of new VM definitions, as long as they meet the following criteria:
+
+1. The should be different enough from existing VM definitions that they represent a distinct
+   user (and developer) experience.
+2. There's a significant Ghostty user population that uses a similar environment.
+3. The VMs can be built using only packages from the current stable NixOS release.
+
+#### VM Definition Criteria
+
+1. VMs should be as minimal as possible so that they build and launch quickly.
+   Additonal software can be added at runtime with a command like `nix run nixpkgs#<package name>`.
+2. VMs should not expose any services to the network, or run any remote access
+   software like SSH, VNC or RDP.
+3. VMs should auto-login using the "ghostty" user.

flake.nix

@@ -80,6 +80,7 @@
             );
           in {
             "wayland-gnome-${system}" = makeVM ./nix/vm/wayland-gnome.nix;
+            "x11-gnome-${system}" = makeVM ./nix/vm/x11-gnome.nix;
           };
 
           apps.${system} = let
@@ -98,6 +99,7 @@
             );
           in {
             wayland-gnome = wrapVM "wayland-gnome";
+            x11-gnome = wrapVM "x11-gnome";
           };
         }
         # Our supported systems are the same supported systems as the Zig binaries.

nix/vm/common-gnome.nix

@@ -0,0 +1,133 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}: {
+  services.xserver = {
+    enable = true;
+    displayManager = {
+      gdm = {
+        enable = true;
+        autoSuspend = false;
+      };
+    };
+    desktopManager = {
+      gnome = {
+        enable = true;
+      };
+    };
+  };
+
+  environment.systemPackages = [
+    pkgs.gnomeExtensions.no-overview
+  ];
+
+  environment.gnome.excludePackages = with pkgs; [
+    atomix
+    baobab
+    cheese
+    epiphany
+    evince
+    file-roller
+    geary
+    gnome-backgrounds
+    gnome-calculator
+    gnome-calendar
+    gnome-clocks
+    gnome-connections
+    gnome-contacts
+    gnome-disk-utility
+    gnome-extension-manager
+    gnome-logs
+    gnome-maps
+    gnome-music
+    gnome-photos
+    gnome-software
+    gnome-system-monitor
+    gnome-text-editor
+    gnome-themes-extra
+    gnome-tour
+    gnome-user-docs
+    gnome-weather
+    hitori
+    iagno
+    loupe
+    nautilus
+    orca
+    seahorse
+    simple-scan
+    snapshot
+    sushi
+    tali
+    totem
+    yelp
+  ];
+
+  services.gnome = {
+    gnome-browser-connector.enable = false;
+    gnome-initial-setup.enable = false;
+    gnome-online-accounts.enable = false;
+    gnome-remote-desktop.enable = false;
+    rygel.enable = false;
+  };
+
+  system.activationScripts = {
+    face = {
+      text = ''
+        mkdir -p /var/lib/AccountsService/{icons,users}
+
+        cp ${pkgs.ghostty}/share/icons/hicolor/1024x1024/apps/com.mitchellh.ghostty.png /var/lib/AccountsService/icons/ghostty
+
+        echo -e "[User]\nIcon=/var/lib/AccountsService/icons/ghostty\n" > /var/lib/AccountsService/users/ghostty
+
+        chown root:root /var/lib/AccountsService/users/ghostty
+        chmod 0600 /var/lib/AccountsService/users/ghostty
+
+        chown root:root /var/lib/AccountsService/icons/ghostty
+        chmod 0444 /var/lib/AccountsService/icons/ghostty
+      '';
+    };
+  };
+
+  programs.dconf = {
+    enable = true;
+    profiles.user.databases = [
+      {
+        settings = with lib.gvariant; {
+          "org/gnome/desktop/background" = {
+            picture-uri = "file://${pkgs.ghostty}/share/icons/hicolor/512x512/apps/com.mitchellh.ghostty.png";
+            picture-uri-dark = "file://${pkgs.ghostty}/share/icons/hicolor/512x512/apps/com.mitchellh.ghostty.png";
+            picture-options = "centered";
+            primary-color = "#000000000000";
+            secondary-color = "#000000000000";
+          };
+          "org/gnome/desktop/interface" = {
+            color-scheme = "prefer-dark";
+          };
+          "org/gnome/desktop/notifications" = {
+            show-in-lock-screen = false;
+          };
+          "org/gnome/desktop/screensaver" = {
+            lock-enabled = false;
+            picture-uri = "file://${pkgs.ghostty}/share/icons/hicolor/512x512/apps/com.mitchellh.ghostty.png";
+            picture-options = "centered";
+            primary-color = "#000000000000";
+            secondary-color = "#000000000000";
+          };
+          "org/gnome/desktop/session" = {
+            idle-delay = mkUint32 0;
+          };
+          "org/gnome/shell" = {
+            disable-user-extensions = false;
+            enabled-extensions = builtins.map (x: x.extensionUuid) (
+              lib.filter (p: p ? extensionUuid) config.environment.systemPackages
+            );
+          };
+        };
+      }
+    ];
+  };
+
+  programs.geary.enable = false;
+}

nix/vm/common.nix

@@ -11,6 +11,18 @@
     virtualisation.memorySize = 2048;
   };
 
+  nix = {
+    settings = {
+      trusted-users = [
+        "root"
+        "ghostty"
+      ];
+    };
+    extraOptions = ''
+      experimental-features = nix-command flakes
+    '';
+  };
+
   users.mutableUsers = true;
 
   users.groups.ghostty = {
@@ -26,10 +38,27 @@
     initialPassword = "ghostty";
   };
 
+  environment.etc = {
+    "xdg/autostart/com.mitchellh.ghostty.desktop" = {
+      source = "${pkgs.ghostty}/share/applications/com.mitchellh.ghostty.desktop";
+    };
+  };
+
   environment.systemPackages = [
     pkgs.kitty
     pkgs.ghostty
+    pkgs.zig_0_13
   ];
 
+  services.displayManager = {
+    autoLogin = {
+      user = "ghostty";
+    };
+  };
+
+  services.xserver = {
+    enable = true;
+  };
+
   system.stateVersion = "24.11";
 }