nixos/gdm,nvidia: new options to enable GDM on Wayland and disabling it for nvidia drivers.

nixos/modules/hardware/video/nvidia.nix

@@ -40,6 +40,12 @@ in
 {
 
   config = mkIf enabled {
+    assertions = [
+      {
+        assertion = services.xserver.displayManager.gdm.wayland;
+        message = "NVidia drivers don't support wayland";
+      }
+    ];
 
     services.xserver.drivers = singleton
       { name = "nvidia"; modules = [ nvidia_x11.bin ]; libPath = [ nvidia_x11 ]; };

nixos/modules/services/x11/display-managers/gdm.nix

@@ -64,6 +64,14 @@ in
         };
       };
 
+      wayland = mkOption {
+        default = true;
+        description = ''
+          Allow GDM run on Wayland instead of Xserver
+        '';
+        type = types.bool;
+      };
+
     };
 
   };
@@ -139,6 +147,7 @@ in
     # presented and there's a little delay.
     environment.etc."gdm/custom.conf".text = ''
       [daemon]
+      WaylandEnable=${if cfg.gdm.wayland then "true" else "false"}
       ${optionalString cfg.gdm.autoLogin.enable (
         if cfg.gdm.autoLogin.delay > 0 then ''
           TimedLoginEnable=true