nix-configuration/modules/ui/gnome.nix

{
  pkgs,
  config,
  lib,
  ...
}:

# UI and desktop-related options
let
  cfg = config.host.ui.gnome;
in
with lib;
{

  options = {
    host.ui.gnome.enable = mkEnableOption (mdDoc "Enables Gnome");
  };

  config = mkIf cfg.enable {
    host.ui = {
      audio.enable = true;
      flatpak.enable = true;
    };

    services = {
      # Configure the xserver
      xserver = {
        # Enable the X11 windowing system.
        enable = true;

        # Configure keymap in X11
        xkb = {
          layout = "us";
          variant = "";
        };

        # Enable Gnome
        desktopManager.gnome.enable = true;
        displayManager.gdm.enable = true;

        # Remove default packages that came with the install
        excludePackages = [ pkgs.xterm ];
      };

      # Install Flatpaks
      flatpak.packages = [
        "com.mattjakeman.ExtensionManager"
        "org.bluesabre.MenuLibre"
        "org.gnome.baobab"
        "org.gnome.Calculator"
        "org.gnome.Characters"
        "org.gnome.Calendar"
        "org.gnome.Evince"
        "org.gnome.Evolution"
        "org.gnome.FileRoller"
        "org.gnome.Firmware"
        "org.gnome.gitg"
        "org.gnome.Loupe" # Gnome's fancy new image viewer
        "org.gnome.Music"
        "org.gnome.seahorse.Application"
        "org.gnome.Shotwell"
        "org.gnome.TextEditor"
        "org.gnome.World.Secrets"
        "org.gtk.Gtk3theme.Adwaita-dark"
      ];

      printing.enable = true;
    };

    environment = {
      # Remove default Gnome packages that came with the install, then install the ones I actually use
      gnome.excludePackages =
        (with pkgs; [
          gnome-photos
          gnome-tour
          gnomeExtensions.extension-list
          gedit # text editor
        ])
        ++ (with pkgs.gnome; [
          cheese # webcam tool
          gnome-music
          gnome-calendar
          epiphany # web browser
          geary # email reader
          evince # document viewer
          gnome-characters
          gnome-software
          totem # video player
          tali # poker game
          iagno # go game
          hitori # sudoku game
          atomix # puzzle game
        ]);

      # Install additional packages
      systemPackages = with pkgs; [
        # Gnome tweak tools
        gnome.gnome-tweaks
        # Gnome extensions
        gnomeExtensions.alphabetical-app-grid
        gnomeExtensions.another-window-session-manager
        gnomeExtensions.appindicator
        gnomeExtensions.dash-to-panel
        gnomeExtensions.forge
        # Themeing
        gnome.gnome-themes-extra
        papirus-icon-theme
        qogir-icon-theme
      ];

      # Install GStreamer plugins
      # References: 
      #   https://wiki.nixos.org/wiki/GStreamer
      #   https://github.com/NixOS/nixpkgs/issues/195936
      sessionVariables.GST_PLUGIN_SYSTEM_PATH_1_0 = lib.makeSearchPathOutput "lib" "lib/gstreamer-1.0" (
        with pkgs.gst_all_1;
        [
          gstreamer
          gst-plugins-base
          gst-plugins-good
          gst-plugins-bad
          gst-plugins-ugly
          gst-libav
          gst-vaapi
        ]
      );
    };

    # Manage fonts
    fonts = {
      # Install extra fonts
      packages = with pkgs; [
        noto-fonts
        noto-fonts-cjk
        noto-fonts-emoji
        liberation_ttf
        fira-code
        fira-code-symbols
        fira
        roboto-slab
      ];

      # Enable font dir for use with Flatpak. See https://nixos.wiki/wiki/Fonts#Flatpak_applications_can.27t_find_system_fonts
      fontDir.enable = true;
    };

    # Gnome UI integration for KDE apps
    qt = {
      enable = true;
      platformTheme = "gnome";
      style = "adwaita-dark";
    };

    # Support for AppImage files
    programs.appimage = {
      enable = true;
      binfmt = true;
    };
  };
}