Nomarchy/tools/monitor-fallback.nix

# Undock blackout-rescue harness — boots the full desktop headlessly
# (softGL Hyprland, same recipe as theme-shot.nix) and replays the
# dangerous sequence: add a headless "external", soft-disable the
# internal panel (the Display menu's "Laptop screen off" command), then
# remove the external. Hyprland does NOT re-enable a disabled monitor on
# its own (verified 2026-07-12 — the session ends with zero active
# outputs), so the display-profile watcher's rescue_blackout
# (modules/home/hyprland.nix) must bring the panel back; this asserts it
# does. KNOWN FLAKE (2026-07-12, Hyprland 0.55.4): the zero-active-output
# state itself crashes Hyprland in this VM ~4/5 runs (ABRT in aquamarine
# CBackend::dispatchIdle, faster than any userland rescue) — a control
# run removing the external with the internal ACTIVE survives every
# time, so it's the zero-output state, not headless removal. A crashed
# run is that upstream bug, not a rescue regression; the assertion can
# only pass on a surviving run. Maintainer tool, NOT a checks.* gate
# (full-desktop VM — same weight call as theme-shot.nix). Run:
#   nix build --impure -f tools/monitor-fallback.nix --no-link -L
let
  flake = builtins.getFlake ("git+file://" + toString ../.);
  inherit (flake.inputs) nixpkgs home-manager;
  pkgs = import nixpkgs {
    system = "x86_64-linux";
    overlays = [ flake.overlays.default ];
    config.allowUnfree = true;
  };
in
pkgs.testers.runNixOSTest {
  name = "monitor-fallback";
  node.pkgsReadOnly = false;
  node.specialArgs = { username = "nomarchy"; };
  nodes.machine = { pkgs, lib, ... }: {
    imports = [ flake.nixosModules.nomarchy home-manager.nixosModules.home-manager ];
    virtualisation.memorySize = 4096;
    virtualisation.cores = 4;
    hardware.graphics.enable = true;
    environment.variables.LIBGL_ALWAYS_SOFTWARE = "1";
    boot.initrd.availableKernelModules = [ "virtio_gpu" ];
    virtualisation.qemu.options = [ "-vga none" "-device virtio-gpu-pci,xres=1920,yres=1080" ];
    users.users.nomarchy = {
      isNormalUser = true;
      password = "test";
      extraGroups = [ "wheel" "video" ];
    };
    nomarchy.system.stateFile = flake + "/themes/boreal.json";
    systemd.tmpfiles.rules = [
      "d /home/nomarchy/.nomarchy 0755 nomarchy users -"
      "C /home/nomarchy/.nomarchy/theme-state.json 0644 nomarchy users - ${flake + "/themes/boreal.json"}"
    ];
    services.greetd.settings.initial_session = {
      command = "start-hyprland";
      user = "nomarchy";
    };
    home-manager.useGlobalPkgs = true;
    home-manager.users.nomarchy = {
      imports = [ flake.homeModules.nomarchy ];
      nomarchy.stateFile = flake + "/themes/boreal.json";
      nomarchy.idle.enable = false;
    };
  };
  testScript = ''
    import json, time

    machine.wait_for_unit("multi-user.target")
    machine.wait_for_file("/run/user/1000/hypr", 180)
    machine.sleep(20)  # softGL first paint settle

    hy = ("su - nomarchy -c 'XDG_RUNTIME_DIR=/run/user/1000 "
          "HYPRLAND_INSTANCE_SIGNATURE=$(ls /run/user/1000/hypr | head -1) hyprctl ")

    def mons(all=False):
        out = machine.succeed(hy + ("-j monitors all'" if all else "-j monitors'"))
        return json.loads(out)

    initial = mons()
    assert len(initial) == 1, f"expected 1 initial monitor, got {initial}"
    internal = initial[0]["name"]
    print(f"internal panel: {internal}")

    # "Plug the dock": add a headless output as the external monitor.
    machine.succeed(hy + "output create headless'")
    for _ in range(20):
        if len(mons()) == 2: break
        time.sleep(1)
    names = [x["name"] for x in mons()]
    ext = [n for n in names if n != internal][0]
    print(f"external (headless): {ext}")

    # Menu action: "Laptop screen off" — the exact command the row runs.
    machine.succeed(hy + f"keyword monitor {internal},disable'")
    for _ in range(20):
        if [x["name"] for x in mons()] == [ext]: break
        time.sleep(1)
    assert [x["name"] for x in mons()] == [ext], f"disable failed: {mons()}"
    alln = {x["name"]: x.get("disabled", False) for x in mons(all=True)}
    assert alln.get(internal) is True, f"{internal} not marked disabled: {alln}"
    print("laptop panel disabled, only external active — now yank it")

    # Sudden undock: remove the external while the internal is disabled.
    machine.succeed(hy + f"output remove {ext}'")
    recovered = False
    for i in range(30):
        if [x["name"] for x in mons()] == [internal]:
            recovered = True
            print(f"recovered after {i+1}s: {internal} re-enabled")
            break
        time.sleep(1)
    print(f"monitors now: {mons(all=True)}")
    assert recovered, "internal panel did NOT come back after undock"
  '';
}