{
  hardware.nvidia.prime.intelBusId = "PCI:0:2:0";
  hardware.nvidia.prime.nvidiaBusId = "PCI:1:0:0";

  ### NVIDIA-only using MUX switch in BIOS.
  #
  # good:
  #   simple, always works.
  #   max performance everywhere.
  #
  # bad:
  #   requires BIOS setting changes, which is annoying.
  #
  boot.kernelParams = [ "module_blacklist=i915" ];
  services.xserver.displayManager.gdm.wayland = false;
  services.xserver.videoDrivers = [ "nvidia" ];
  services.xserver.screenSection = ''
    Option "metamodes" "DP-2: 2560x1440_165 +0+0 {AllowGSYNCCompatible=On}"
  '';
}

################################################################################

### "sync mode"
#
# good:
#   max performance on external displays
#   no BIOS settings change needed
#
# bad:
#   graphics performance overhead on internal display
#   internal display capped at 60hz
#
# hardware.nvidia.prime.sync.enable = true;
# hardware.nvidia.modesetting.enable = true;
# services.xserver.displayManager.gdm.wayland = false;
# services.xserver.videoDrivers = [ "nvidia" ];
# # xrandr workaround for laptop panel not showing up with GDM. Reference:
# # https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/hardware/video/nvidia.nix
# services.xserver.displayManager.sessionCommands = ''
#   ${pkgs.xorg.xrandr}/bin/xrandr --setprovideroutputsource modesetting NVIDIA-0
# '';

################################################################################

### nvidia drivers disabled
#
# Not well tested. Possibly Incomplete.
# Won't allow external displays connected to nvidia GPU.
#
# Shutting off Nvidia GPU would theoretically save power.
# I do not think this actually powers down the Nvidia GPU, just stops using it.
#
# boot.kernelParams = [ "module_blacklist=nouveau" ];

################################################################################

### hybrid graphics
#
# Not well tested. Possibly Incomplete.
# Won't allow external displays connected to nvidia GPU.
#
# Everything would use intel by default,
# but specific apps would run on the nvidia GPU under the script.
#
# hardware.nvidia.prime.offload.enable = true;
# services.xserver.videoDrivers = [ "nvidia" ];
# environment.systemPackages = [
#   (pkgs.writeShellScriptBin "nv" ''
#     export __NV_PRIME_RENDER_OFFLOAD=1
#     export __NV_PRIME_RENDER_OFFLOAD_PROVIDER=NVIDIA-G0
#     export __GLX_VENDOR_LIBRARY_NAME=nvidia
#     export __VK_LAYER_NV_optimus=NVIDIA_only
#     exec "$@"
#   '')
# ];