base: move common Xorg options under gui option

base/gui-programs.nix

@@ -1,8 +1,26 @@
-{ pkgs, lib, config, ... }:
+{ pkgs, lib, config, options, ... }:
 {
-  options.my.gui.enable = lib.mkEnableOption "System has some kind of screen attached";
+  options.my.gui = {
+    enable = lib.mkEnableOption "System has some kind of screen attached";
+    isNvidia = lib.mkEnableOption "System a NVIDIA GPU";
+  };
 
   config = lib.mkIf config.my.gui.enable {
+    my.displayManager.sddm.enable = true;
+
+    services = {
+      xserver = {
+        enable = true;
+        # NOTE: could use `mkOptionDefault` but this feels more explicit
+        videoDrivers = options.services.xserver.videoDrivers.default
+                       ++ lib.optional config.my.gui.isNvidia "nvidia";
+        windowManager.i3.enable = true;
+        layout = "fr";
+        xkbVariant = "us";
+        libinput.enable = true;
+      };
+    };
+
     environment.systemPackages = with pkgs; [
       element-desktop
       feh

hosts/boreal/default.nix

@@ -91,18 +91,11 @@ in
       permitRootLogin = "no";
       passwordAuthentication = false;
     };
-
+  };
-    xserver = {
+  my.gui = {
     enable = true;
-      videoDrivers = [ "nvidia" ];
+    isNvidia = true;
-      windowManager.i3.enable = true;
-      layout = "fr";
-      xkbVariant = "us";
-      libinput.enable = true;
   };
-  };
-  my.displayManager.sddm.enable = true;
-  my.gui.enable = true;
 
   my.wakeonwlan.interfaces.phy0.methods = [
     "magic-packet"

hosts/zephyrus/default.nix

@@ -46,13 +46,6 @@ in
   };
 
   services = {
-    xserver = {
-      enable = true;
-      windowManager.i3.enable = true;
-      layout = "fr";
-      xkbVariant = "us";
-      libinput.enable = true;
-    };
     tlp = {
       settings = {
         START_CHARGE_THRESH_BAT0 = 70;
@@ -61,7 +54,6 @@ in
     };
     fwupd.enable = true;
   };
-  my.displayManager.sddm.enable = true;
   my.gui.enable = true;
 
   environment.systemPackages = with pkgs; [