[emacs] Modularize more and better pkg

Attempts to select the right emacs package based on whether the machine
is x11 only or not.

roles/desktop/default.nix

@@ -4,6 +4,29 @@ with lib;
 
 let
   cfg = config.roles.desktop;
+
+  basePackages = with pkgs; [
+
+  ];
+
+  x11BasePackages = with pkgs; [
+
+  ];
+
+  x11OnlyPackages = with pkgs; [
+    emacs
+  ];
+
+  waylandBasePackages = with pkgs; [
+    grim
+    slurp
+    wl-clipboard
+    mako
+  ];
+
+  waylandOnlyPackages = with pkgs; [
+    emacs-gtk
+  ];
 in
 {
   options.roles.desktop = {
@@ -40,12 +63,6 @@ in
       programs.dconf.enable = true;
       services.gnome.gnome-keyring.enable = true;
 
-      environment.systemPackages = with pkgs; mkIf (!cfg.x11Only) [
-        grim
-        slurp
-        wl-clipboard
-        mako
-      ];
       programs.sway = mkIf (!cfg.x11Only) {
         enable = true;
         wrapperFeatures.gtk = true;
@@ -73,6 +90,15 @@ in
 
       virtualisation.docker.enable = true;
       users.extraGroups.docker.members = [ "johno" ];
+
+      environment.systemPackages = with pkgs; mkMerge [
+        basePackages
+        x11BasePackages
+        (mkIf cfg.x11Only x11OnlyPackages)
+        # TODO: Do we need a "wayland only" mode?
+        (mkIf (!cfg.x11Only) waylandBasePackages)
+        (mkIf (!cfg.x11Only) waylandOnlyPackages)
+      ];
     };
 
 }