naively pasted code from our forum discussion

dell/xps/15-9560/default.nix

@@ -4,36 +4,30 @@
     ../../../common/gpu/intel/kaby-lake
     ../../../common/pc/laptop
     ./xps-common.nix
-
-    # FIXME: remove this when bumblebee works again
-    ../../../common/gpu/nvidia/disable.nix
   ];
 
+# enable opengpl and gpu drivers
+  hardware.opengl = {
+    enable = true;
+    driSupport = true;
+    driSupport32Bit = true;
+  };
 
-  /* Bumblebee seems to fail to evaluate:
+  services.xserver.videoDrivers = ["nvidia"];
-    (stack trace truncated; use '--show-trace' to show the full trace)
 
-  error: assertion '(useSettings -> (! libsOnly))' failed
+  hardware.nvidia.modesetting.enable = true;
 
-  at /home/joerg/git/nixpkgs/pkgs/os-specific/linux/nvidia-x11/generic.nix:61:1:
+  hardware.nvidia.prime = {
+    offload = {
+      enable = true;
+      enableOffloadCmd = true;  # provides the nvidia-offload command
+    };
 
-      60|
+# integrated
-      61| assert useSettings -> !libsOnly;
+    intelBusId = "PCI:0:2:0";
-        | ^
-      62| assert !libsOnly -> kernel != null;
 
-  # This configuration makes intel default and optionaly applications could run nvidia with optirun.
+# dedicated
-  # To Optimize for your use case import intel or nvidia only configuration instead
+    nvidiaBusId = "PCI:1:0:0";
-  # xps-9560/intel
+  };
-  # or
-  # xps-9560/nvidia
 
-
-  ##### bumblebee working, needs reboot to take affect and to use it run: optirun "<application>"
-  services.xserver.videoDrivers = [ "intel" "nvidia" ];
-  boot.blacklistedKernelModules = [ "nouveau" "bbswitch" ];
-  boot.extraModulePackages = [ config.boot.kernelPackages.nvidia_x11 ];
-  hardware.bumblebee.enable = lib.mkDefault true;
-  hardware.bumblebee.pmMethod = lib.mkDefault "none";
-  */
 }