Sylpheed/port/scripts/boot.gd

# Entry point.
#
# P1 shows one exported screen, statically, so that its pixels can be diffed
# against `sylpheed-cli screen render` of the same build. The boot sequence
# proper (splash -> intro -> title -> menu) is P3 and is not here.
#
#   godot --path port -- --screen=main_menu
#   godot --path port -- --screen=main_menu --capture=/tmp/godot.png
#   godot --path port -- --screen=main_menu --time=0.5 --capture=/tmp/at-half.png
#   godot --path port -- --screen=main_menu --pose=rest --capture=/tmp/rest.png
#   godot --path port -- --screen=title --overlay=press_start --time=4
#   godot --path port -- --boot                      # the whole boot sequence
#   godot --path port -- --boot --film=/tmp/boot     # ...and a frame every 0.25 s
#   godot --path port -- --menu                      # P5: navigate the menus
#   godot --path port -- --menu=extras               # ...starting somewhere else
#   godot --path port -- --boot --play               # boot, then hand over to P5
#   godot --path port -- --menu --script=down,down,accept,cancel --shots=/tmp/p5
#   godot --path port -- --menu --script=down,accept --audio=/tmp/p6.wav
#
# `--menu` is the P5 mode: the d-pad moves the cursor, (A) opens, (B) goes back.
# `--script` drives the SAME input path with synthetic events -- it does not call
# the navigation functions directly, because then the artifact would prove
# nothing about whether a human's press arrives. `--shots` writes one PNG per
# scripted step, after the screen it produced has settled.
#
# `--audio=` records the MASTER BUS to a WAV for the whole run. Neither container
# has a sound card, so "does it actually play?" cannot be answered by listening --
# but it can be answered by measurement, and an `AudioEffectRecord` on Master
# captures the mixed output from inside a headless run with no device at all.
# `docs/port/AUDIO-VERIFICATION.md` §2. The run PRINTS the audio driver it used,
# because "recorded under a dummy driver" is a weaker claim than "heard" and the
# write-up has to be able to say which one it is making.
#
# `--time` is in SECONDS and freezes the timeline there; without it the screen
# animates in real time from t=0. `--pose=rest` draws the export's declared
# resting pose instead of the timeline -- what the reference renderer draws, so
# that a renderer-vs-renderer diff compares like with like.
#
# The screen is drawn into a SubViewport sized to the export's own `design`
# rectangle and shown through a container that scales it to the window. That is
# the same separation the project settings already make -- design space is
# fixed, the window is not -- and it makes `--capture` exact: the PNG is the
# design rectangle itself, never the window, so it is directly comparable with
# `screen render`'s composite with no cropping or rescaling.
extends Node

const DEFAULT_SCREEN := "main_menu"

var view: ScreenView = null
var viewport: SubViewport = null
var audio: MenuAudio = null

## The second build, drawn OVER `view`. The boot title is the only place in this
## port where two builds are on screen at once (`authored/flow.json`, the boot's
## `title` step): build 4 presents alone, and the `PRESS Ⓐ BUTTON` plate --
## build 2 -- is composited over it 2.13 s after build 4 settles. MEASURED, two
## boots agreeing to 6 ms; see the step's `why`.
##
## A second ScreenView rather than a second screen inside one, because that is
## what "two builds at once" actually is: each has its own timeline, its own
## textures and its own hold, and Node2D siblings already draw in tree order.
## Teaching ScreenView about a subordinate screen would have been the same
## information expressed less directly, and would have put an `if overlay` in
## every method that walks elements.
var overlay: ScreenView = null


func _ready() -> void:
	var args := _args()
	for flag: String in ["capture", "film", "shots"]:
		if args.has(flag) and not _has_display(flag):
			get_tree().quit(4)
			return
	var export_tree := ExportTree.locate()
	if export_tree.root == "":
		push_error(export_tree.error)
		get_tree().quit(2)
		return

	_flow = export_tree.authored("flow.json")
	if _flow == null and (args.has("boot") or args.has("menu")):
		push_error(export_tree.error)
		get_tree().quit(2)
		return
	if args.has("boot"):
		for step: Dictionary in _flow["boot"]:
			_sequence.append(step)
	# P6. Audio is loaded even for a static `--screen` run: it costs nothing when
	# the export has none, and a mode that silently cannot play sound is a mode
	# that hides the failure this milestone is about.
	audio = MenuAudio.new()
	add_child(audio)
	if not audio.configure(export_tree):
		push_error(audio.error)
		get_tree().quit(2)
		return
	if audio.silent():
		print("this export carries no audio -- run the exporter against a disc for P6")
	_record_to = args.get("audio", "")
	if _record_to != "":
		_start_recording()

	# In `--boot` the capture is taken at the END, not in `_ready`: the frame
	# worth having is the composited title, and `_ready` runs 150 s before it.
	if args.has("boot"):
		_capture_to = args.get("capture", "")
	_film = args.get("film", "")
	_shots = args.get("shots", "")
	if args.has("script"):
		_script = args["script"].split(",", false)
	# P5. `--play` boots first and hands over on the title; `--menu` starts on a
	# screen directly, which is what makes an unattended run cheap -- it does not
	# sit through 137 s of intro to press a d-pad.
	_play = args.has("play") or args.has("menu")
	if _play:
		_menu = MenuFlow.new()
		if not _menu.configure(_flow):
			push_error(_menu.error)
			get_tree().quit(2)
			return

	var name: String = String(_sequence[0].get("screen", "")) if not _sequence.is_empty() \
		else args.get("menu", args.get("screen", DEFAULT_SCREEN))
	if name == "1":
		name = DEFAULT_SCREEN  # bare `--menu`
	if name == "":
		name = DEFAULT_SCREEN  # the sequence opens on a video; load something to size the viewport
	var screen: Dictionary = export_tree.screen(name)
	if screen.is_empty():
		push_error(export_tree.error)
		print("screens in this export: ", ", ".join(export_tree.screen_names()))
		get_tree().quit(2)
		return
	var design: Array = screen.get("design", [1280, 720])

	var container := SubViewportContainer.new()
	container.stretch = true
	container.set_anchors_preset(Control.PRESET_FULL_RECT)
	add_child(container)

	viewport = SubViewport.new()
	viewport.size = Vector2i(int(design[0]), int(design[1]))
	viewport.transparent_bg = false
	viewport.render_target_update_mode = SubViewport.UPDATE_ALWAYS
	container.add_child(viewport)

	view = ScreenView.new()
	# The export is a 1:1 copy of the disc's texels and elements are drawn at up
	# to 500 %. Nearest is also what the reference renderer does
	# (`ui_layout::blit` maps destination to source by integer division), so a
	# filter difference cannot masquerade as a placement difference in the diff.
	view.texture_filter = CanvasItem.TEXTURE_FILTER_NEAREST
	view.focused_id = args.get("focus", "")
	if args.get("pose", "") == "rest":
		view.pose_mode = ScreenView.Pose.REST

	# The keyframe unit is MEASURED, not on the disc, so it is authored and read
	# in exactly one place -- here.
	var timing: Variant = export_tree.authored("timing.json")
	if timing == null:
		push_error(export_tree.error)
		get_tree().quit(2)
		return
	view.units_per_second = float(timing["keyframe_units_per_second"])
	# The one unknown duration per screen: the ramp into the final untimed
	# keyframe. Authored, because the disc has no time slot there.
	view.exit_ramp_units = float(timing["exit_ramp_units"])
	viewport.add_child(view)

	if not view.load_screen(export_tree, name):
		push_error(export_tree.error)
		get_tree().quit(2)
		return

	# Not booting: `--menu` opens straight onto a screen, so the stack starts here.
	if _menu != null and _sequence.is_empty():
		_menu_enter(name, true)

	var settle := view.settle_time()
	print("screen %s: %d elements, %d in paint order, design %dx%d, settles at t=%d (%.3f s)" % [
		name, view.screen["elements"].size(), view.screen["paint_order"].size(),
		design[0], design[1], settle, settle / view.units_per_second])

	if args.has("time"):
		_frozen = true
		view.time_units = float(args["time"]) * view.units_per_second
		view.queue_redraw()

	if _film != "":
		set_process(true)
		_film_capture()

	# `--overlay=<screen>` composites a second build immediately, without waiting
	# for a boot. It exists because the only other way to see two builds at once
	# is a 156 s `--boot`, of which 137 s is the intro movie -- which under Xvfb's
	# software Theora decode is several minutes to answer "is the plate on top of
	# the title". This raises the same second `ScreenView` by the same code path,
	# so what it photographs is the real composite and not a mock-up. It applies
	# NO delay: the delay is a measurement and lives in `authored/flow.json`,
	# where the boot reads it.
	if args.has("overlay") and not args.has("boot"):
		_overlay_spec = {"screen": args["overlay"]}
		_overlay_due = 0.0
		_overlay_process(0.0)
		if overlay != null and args.has("time"):
			overlay.time_units = float(args["time"]) * overlay.units_per_second
			overlay.queue_redraw()

	# `--boot --capture=` is deferred to the end of the sequence (`_finish_boot`);
	# in every other mode the frame worth having is this one.
	if args.has("capture") and _capture_to == "":
		await _capture(args["capture"])
		get_tree().quit(0)


var _frozen := false
var _flow: Variant = null
var _menu: MenuFlow = null
var _play := false
var _pending: Variant = null
var _script: PackedStringArray = PackedStringArray()
var _shots := ""
var _script_started := false
var _sequence: Array[Dictionary] = []
var _player: VideoStreamPlayer = null
var _step := 0
var _film := ""
var _film_frame := 0
var _film_next := 0.0
var _elapsed := 0.0
var _boot_done := false


func _process(delta: float) -> void:
	if _frozen or view == null:
		return
	view.time_units += delta * view.units_per_second
	_elapsed += delta
	view.queue_redraw()
	_overlay_process(delta)

	if _player != null:
		return

	# A menu transition. This is checked BEFORE the boot sequence and outside
	# its emptiness guard: `--menu` has no sequence at all, and an earlier
	# version returned here, so the screen faded out and nothing ever arrived.
	if _pending != null:
		if view.time_units >= view.exit_time():
			_menu_arrive()
		return

	if _sequence.is_empty():
		return

	# A screen holds at `rest` until it has arrived, then plays itself out and
	# the next one begins. Nothing waits on a timer the disc does not carry: the
	# pacing is each group's own timeline (authored/flow.json, `dwell`).
	if view.holding and view.time_units >= view.settle_time():
		# The LAST screen in the sequence keeps holding. A screen plays itself
		# out because something is taking its place; nothing is taking the
		# title's place here, and a boot that ends by fading to black is a boot
		# that looks like it crashed. P4 puts the intro video in front of the
		# title, and P5 gives the title somewhere to go.
		if _step + 1 < _sequence.size():
			view.holding = false
		elif not _boot_done:
			_boot_done = true
			print("boot sequence complete after %.2f s, holding on %s" % [_elapsed, _sequence[_step].get("screen", _sequence[_step])])
			# The plate is timed from HERE -- the moment the screen reaches its
			# own hold -- and not from the frame it first appeared. That is the
			# finding, not a detail: measured from first-draw the two oracle
			# runs disagree by 0.48 s, because the build-in's own duration is
			# the emulator's frame pacing rather than the game's clock.
			var spec: Variant = _sequence[_step].get("overlay", null)
			if typeof(spec) == TYPE_DICTIONARY:
				_overlay_spec = spec
				_overlay_due = _elapsed + float(spec.get("after_settle_seconds", 0.0))
				print("  overlay %s due at %.2f s (+%.2f s after settle)"
					% [spec.get("screen", "?"), _overlay_due, _overlay_due - _elapsed])
			# P5 takes over here: the boot ends on the title and the title has
			# somewhere to go. Without `--play` the run still stops, because a
			# boot that ends by waiting for a key it will never get is worse
			# than one that exits.
			if _play:
				_menu_enter(String(_sequence[_step].get("screen", "")), true)
			elif _film == "" and _overlay_spec.is_empty():
				get_tree().quit(0)
	elif not view.holding and view.time_units >= view.exit_time():
		_advance()


func _advance() -> void:
	_drop_overlay()
	_step += 1
	var next: Dictionary = _sequence[_step]
	if next.has("video"):
		_play_video(String(next["video"]), bool(next.get("skippable", false)))
		return
	var name := String(next["screen"])
	print("  -> %s at %.2f s" % [name, _elapsed])
	view.holding = true
	view.time_units = 0.0
	if not view.load_screen(view.tree, name):
		push_error(view.tree.error)
		get_tree().quit(2)


## Play one transcoded movie, full-bleed over the screen.
##
## The port never reads WMV: the exporter transcoded this to Ogg Theora and
## recorded the exact ffmpeg command in the manifest (MISSION §6), so a modder
## who dislikes the quality re-runs one line.
func _play_video(name: String, skippable: bool) -> void:
	var v := view.tree.video(name)
	if v.is_empty():
		push_error(view.tree.error)
		get_tree().quit(2)
		return
	print("  -> video %s at %.2f s (%s)" % [name, _elapsed, v["path"]])

	var stream := VideoStreamTheora.new()
	stream.file = v["path"]
	_player = VideoStreamPlayer.new()
	_player.stream = stream
	_player.expand = true
	_player.set_anchors_preset(Control.PRESET_FULL_RECT)
	# Into the SubViewport, not beside it. Everything this port draws composes in
	# the export's own 1280x720 design space; a player parented to the Boot node
	# renders to the window instead and is invisible to `--capture`, which reads
	# the SubViewport. That is not only a capture artefact -- it would also put
	# the movie outside the space every screen coordinate is expressed in.
	viewport.add_child(_player)
	_skippable = skippable
	# `play()` needs the node in the tree; calling it before that is an error
	# the engine reports and then ignores, which looks like a video that simply
	# never starts.
	await get_tree().process_frame
	_player.finished.connect(_video_finished)
	_player.play()


var _skippable := false


func _video_finished() -> void:
	print("     video ended at %.2f s" % _elapsed)
	_player.queue_free()
	_player = null
	_advance()


func _unhandled_input(event: InputEvent) -> void:
	# HANDOFF Q9, measured: one (A) press skips a movie -- the title was reached
	# at 57 s against a 193 s baseline.
	if _player != null:
		if _skippable and (event.is_action_pressed("ui_accept") or event.is_action_pressed("ui_cancel")):
			print("     video skipped at %.2f s" % _elapsed)
			_player.stop()
			_video_finished()
		return
	if _menu == null or _menu.stack.is_empty():
		return
	# AUTHORED, not measured: a press during a screen's fade-out is dropped.
	# `authored/flow.json` says why -- nobody has watched what the game does
	# here, and dropping invents less than queueing.
	if _pending != null:
		return
	var buttons: Array = view.screen.get("buttons", [])
	if event.is_action_pressed("ui_up"):
		_menu_move(-1, buttons)
	elif event.is_action_pressed("ui_down"):
		_menu_move(1, buttons)
	elif event.is_action_pressed("ui_left") or event.is_action_pressed("ui_right"):
		# MEASURED, HANDOFF Q5: left/right do nothing. Written out rather than
		# left unhandled so that "the game ignores it" and "we never wired it"
		# are different lines of code.
		pass
	elif event.is_action_pressed("ui_accept"):
		_menu_activate(_menu.accept(buttons), "confirm")
	elif event.is_action_pressed("ui_cancel"):
		_menu_activate(_menu.cancel(), "back")


func _menu_move(step: int, buttons: Array) -> void:
	# MEASURED, HANDOFF Q8 + Q5: the cue fires on a press that MOVES the cursor.
	# `move()` returns whether it did, so a press that changes nothing cannot
	# click -- which also means left/right stay silent by construction rather
	# than by a rule written twice.
	if _menu.move(step, buttons):
		view.focused_id = _menu.focus()
		view.queue_redraw()
		audio.play("move")
		print("  focus -> %s" % view.focused_id)


## Act on what the flow returned. A destination starts the screen playing itself
## out; the arrival happens in `_process` when the exit ramp is done, so the
## fade is the transition HANDOFF Q7 measured and not a cut.
func _menu_activate(action: Dictionary, cue: String = "") -> void:
	# AUTHORED, NOT MEASURED: the cue fires when the press does something, and
	# not when nothing is bound to it. Nobody has watched the game take a dead
	# press. Silence invents the less of the two -- a sound the game does not
	# make is a wrong fact you can hear. `blocked` counts as doing something:
	# that destination WAS measured off the running game and is missing from
	# this export, not from the game. See port/scripts/menu_audio.gd.
	if cue != "" and String(action.get("kind", "none")) != "none":
		audio.play(cue)
	match String(action.get("kind", "none")):
		"enter":
			print("  (%s) -> %s" % [action.get("label", ""), action["goto"]])
			_pending = action
			view.holding = false
		"blocked":
			# A real, measured destination that is not in this export. Say which
			# -- silence here would read as a dead button.
			print("  (%s) opens a screen this export does not carry: %s"
				% [action.get("label", ""), action.get("why", "")])
		_:
			pass


## Enter a screen with the menu live. `fresh` seeds the stack rather than
## replacing the top, which is what a boot handover and `--menu` both want.
func _menu_enter(name: String, fresh: bool) -> void:
	if name == "" or not _menu.known(name):
		push_warning("flow.json describes no screen named %s -- navigation stops here" % name)
		return
	if fresh:
		_menu.enter(name, view.screen.get("buttons", []))
	view.focused_id = _menu.focus()
	view.queue_redraw()
	# AUTHORED, and the weakest thing in P6: HANDOFF Q10 says nothing on the disc
	# names which track a menu plays, so `authored/audio.json` picks one. It
	# starts when the menu becomes live and CARRIES ACROSS submenus -- `play_bed`
	# is idempotent, because music that restarts every time you press (B) is the
	# kind of wrong that reads as "the audio works".
	audio.play_bed("main_menu")
	print("  menu on %s, focus %s" % [name, _focus_label(view.focused_id)])
	if not _script.is_empty() and not _script_started:
		_script_started = true
		_run_script()


## The moment a screen has finished fading out and the next one takes over.
func _menu_arrive() -> void:
	# The plate goes with the screen it was measured on. See `_drop_overlay`.
	_drop_overlay()
	var action: Dictionary = _pending
	_pending = null
	var name := String(action["goto"])
	view.holding = true
	view.time_units = 0.0
	if not view.load_screen(view.tree, name):
		push_error(view.tree.error)
		get_tree().quit(2)
		return
	var buttons: Array = view.screen.get("buttons", [])
	if action.get("pop", false):
		# MEASURED, HANDOFF Q5: (B) restores the focus you came from.
		_menu.pop()
		_menu.stack[_menu.stack.size() - 1]["focus"] = String(action["restore_focus"])
		view.focused_id = _menu.focus()
		view.queue_redraw()
		print("  menu on %s, focus restored to %s" % [name, _focus_label(view.focused_id)])
	else:
		_menu_enter(name, true)


## Whether this process can produce a picture at all.
##
## MEASURED here, not assumed: under `--headless` Godot's dummy renderer never
## emits `RenderingServer.frame_post_draw`, so every `await` on it blocks
## forever. `godot-headless --path port -- --screen=main_menu --capture=…`
## therefore hung with NO OUTPUT until it was killed -- the same run with
## `--quit` prints and exits, which is how the difference was isolated.
##
## That is the worst shape a failure can take in an unattended loop: it does not
## fail, it waits, and a job that waits forever reads as a job still working.
## So the flags that need a frame refuse at STARTUP and say what to run instead,
## rather than dying somewhere in the middle of a filmstrip.
func _has_display(flag: String) -> bool:
	if DisplayServer.get_name() != "headless":
		return true
	push_error(("--%s needs a drawn frame, and --headless never draws one: " +
		"Godot's dummy renderer does not emit frame_post_draw, so this would " +
		"hang rather than fail. Run it under Xvfb instead:\n" +
		"    xvfb-run -a godot --path port -- …--%s=…") % [flag, flag])
	return false


## How a focus reads in the log. The title has no focusable item at all -- it is
## a screen with no `buttons` that still takes (A) -- and an empty string there
## printed as a line that trailed off, which reads like the value went missing
## rather than like there is none.
static func _focus_label(id: String) -> String:
	return id if id != "" else "(none -- this screen has no focusable item)"


func _capture(path: String) -> void:
	# Two frames: the first is the one this callback is still inside of.
	await RenderingServer.frame_post_draw
	await RenderingServer.frame_post_draw
	var img := viewport.get_texture().get_image()
	print("t = %.2f units (%.3f s), pose = %s" % [
		view.time_units, view.time_units / view.units_per_second,
		"rest" if view.pose_mode == ScreenView.Pose.REST else "timeline"])
	print("drew %d: %s" % [view.drawn.size(), ", ".join(view.drawn)])
	if not view.skipped.is_empty():
		print("not drawn %d: %s" % [view.skipped.size(), ", ".join(view.skipped)])
	# The overlay is a second build in the same frame, so it needs its own line.
	# Folding its elements into the list above would make the capture report a
	# screen that does not exist; leaving it out entirely made the first
	# composited capture read as though the plate had not been drawn at all.
	if overlay != null:
		print("overlay %s at t = %.2f units (%.3f s), drew %d: %s" % [
			overlay.screen.get("name", "?"), overlay.time_units,
			overlay.time_units / overlay.units_per_second,
			overlay.drawn.size(), ", ".join(overlay.drawn)])
	var err := img.save_png(path)
	if err != OK:
		push_error("cannot write %s (%d)" % [path, err])
		return
	print("captured %dx%d -> %s" % [img.get_width(), img.get_height(), path])


## A frame every 0.25 s for the whole run, so an unattended boot leaves a
## filmstrip behind rather than requiring someone to be watching it.
func _film_capture() -> void:
	while true:
		await RenderingServer.frame_post_draw
		if _elapsed >= _film_next:
			var img := viewport.get_texture().get_image()
			img.save_png("%s_%03d.png" % [_film, _film_frame])
			_film_frame += 1
			_film_next += 0.25


# Godot passes everything after `--` through untouched; take `--key=value`.
static func _args() -> Dictionary:
	var out := {}
	for arg in OS.get_cmdline_user_args():
		if arg.begins_with("--") and arg.contains("="):
			var pair := arg.substr(2).split("=", true, 1)
			out[pair[0]] = pair[1]
		elif arg.begins_with("--"):
			out[arg.substr(2)] = "1"
	return out


# ── The scripted walk ───────────────────────────────────────────────────────
#
# `--script=down,down,accept,cancel` presses those buttons in order and, with
# `--shots=`, leaves one PNG per step behind. This is the P5 artifact for an
# unattended run.
#
# It sends synthetic events through `Input.parse_input_event`, so they arrive at
# `_unhandled_input` exactly as a d-pad's would. Calling the navigation
# functions directly would have been three lines shorter and would have proved
# nothing: the thing most likely to be broken is the wiring between a press and
# the cursor, and that is the part a direct call skips.

const SCRIPT_ACTIONS := {
	"up": "ui_up", "down": "ui_down", "left": "ui_left", "right": "ui_right",
	"accept": "ui_accept", "a": "ui_accept", "cancel": "ui_cancel", "b": "ui_cancel",
}

## How long a single step may take before the run is called stuck, in seconds.
## A screen that never settles would otherwise hang an unattended job forever;
## the title's own timeline is 4.5 s, so this is generous rather than tuned.
const SCRIPT_STEP_TIMEOUT := 20.0


func _run_script() -> void:
	if not await _script_settled("start"):
		return
	await _shoot("00_start")
	for i in range(_script.size()):
		var token := _script[i].strip_edges().to_lower()
		if token == "wait":
			pass
		elif SCRIPT_ACTIONS.has(token):
			print("script[%d] %s" % [i + 1, token])
			_press(String(SCRIPT_ACTIONS[token]))
		else:
			push_error("--script: no such step %s (have %s, wait)" % [token, ", ".join(SCRIPT_ACTIONS.keys())])
			get_tree().quit(2)
			return
		# `Input.parse_input_event` is flushed with the frame, not on the call.
		# Without these two frames the settle check runs while the press has not
		# been delivered yet, decides nothing is moving, and photographs the
		# screen the press was about to leave.
		await get_tree().process_frame
		await get_tree().process_frame
		if not await _script_settled(token):
			return
		await _shoot("%02d_%s" % [i + 1, token])
	print("script complete after %.2f s on %s, focus %s"
		% [_elapsed, _menu.current(), _focus_label(view.focused_id)])
	get_tree().quit(0)


func _press(action: String) -> void:
	for down in [true, false]:
		var e := InputEventAction.new()
		e.action = action
		e.pressed = down
		Input.parse_input_event(e)


## Wait until nothing is moving: no transition pending, and the screen has
## reached its own hold. Shooting before that would photograph a fade.
func _script_settled(what: String) -> bool:
	var deadline := _elapsed + SCRIPT_STEP_TIMEOUT
	while _pending != null or _player != null or not view.holding \
			or view.time_units < view.settle_time():
		if _elapsed > deadline:
			# Stop the run. Carrying on would write a whole filmstrip of the
			# screen that got stuck and call it a walk through the menus.
			push_error("--script: %s never settled within %.0f s -- stopping"
				% [what, SCRIPT_STEP_TIMEOUT])
			get_tree().quit(3)
			return false
		await get_tree().process_frame
	# Only a run that is about to photograph the frame needs to wait for one to
	# be drawn. `--script` on its own is a navigation check and must still work
	# where nothing draws -- see `_has_display`.
	if _shots != "":
		await RenderingServer.frame_post_draw
		await RenderingServer.frame_post_draw
	return true


func _shoot(label: String) -> void:
	if _shots == "":
		return
	var path := "%s_%s.png" % [_shots, label]
	var img := viewport.get_texture().get_image()
	# Write to a temp name and rename on completion: another agent probing a
	# file this is still writing gets a confident wrong number.
	var tmp := path + ".part"
	if img.save_png(tmp) != OK:
		push_error("cannot write %s" % tmp)
		return
	DirAccess.rename_absolute(tmp, path)
	print("     shot %s (%s, focus %s)" % [path, _menu.current(), _focus_label(view.focused_id)])


# ── Recording the master bus ──────────────────────────────────────────────────
#
# `docs/port/AUDIO-VERIFICATION.md` §2. This is what closes the loop that file
# opens: comparing an exported Ogg against the disc proves the ASSET is right and
# says nothing about whether the engine ever reached it. A WAV captured off the
# Master bus proves both, and needs no sound card to do it.
#
# It is saved in `_exit_tree` rather than beside each `quit()` because there are
# eight of those and the one that would get missed is an error path -- exactly
# the run whose audio somebody wants to look at.

var _record_to := ""
var _record: AudioEffectRecord = null


func _start_recording() -> void:
	var bus := AudioServer.get_bus_index("Master")
	_record = AudioEffectRecord.new()
	AudioServer.add_bus_effect(bus, _record)
	_record.set_recording_active(true)
	print("recording the Master bus to %s (audio driver: %s)" % [_record_to, MenuAudio.driver()])


func _exit_tree() -> void:
	if _record == null:
		return
	_record.set_recording_active(false)
	var wav := _record.get_recording()
	_record = null
	if wav == null:
		push_error("--audio: the Master bus recorded nothing at all")
		return
	# Write to a temp name and rename on completion, as everything else in this
	# project does: another agent probing a file still being written gets a
	# confident wrong duration rather than an error.
	#
	# ⚠️ The temp name ends in `.wav`, and that is not cosmetic. `save_to_wav`
	# APPENDS `.wav` when the path does not already end in it, so `p6.wav.part`
	# silently became `p6.wav.part.wav` -- and the rename below then failed to
	# find its source and returned an error nobody read, leaving a run that
	# printed success beside a file that was not there. This is the same bug the
	# exporter's `run_ffmpeg` had in a different dialect: a temp-name convention
	# must preserve the extension, because tools dispatch on it.
	var tmp := _record_to + ".part.wav"
	if wav.save_to_wav(tmp) != OK:
		push_error("--audio: cannot write %s" % tmp)
		return
	var moved := DirAccess.rename_absolute(tmp, _record_to)
	if moved != OK:
		# Say so rather than print the success line below. A rename that fails
		# quietly is worse than one that fails loudly: the caller measures a
		# path that does not exist and reads "no such file" as "no audio".
		push_error("--audio: wrote %s but could not rename it to %s (%d)"
			% [tmp, _record_to, moved])
		return
	print("recorded %.3f s of Master bus -> %s (driver %s)"
		% [float(wav.data.size()) / float(wav.mix_rate * 2 * (2 if wav.stereo else 1)),
		   _record_to, MenuAudio.driver()])


# ── The second build ─────────────────────────────────────────────────────────

## The overlay the current boot step owes, if it has not been raised yet.
var _overlay_spec: Dictionary = {}
## Wall-clock second at which it is raised, measured from the screen's settle.
var _overlay_due: float = 0.0


func _overlay_process(delta: float) -> void:
	if overlay != null:
		overlay.time_units += delta * overlay.units_per_second
		overlay.queue_redraw()
		if _overlay_quit_at >= 0.0 and _elapsed >= _overlay_quit_at:
			print("boot ends on %s + %s at %.2f s"
				% [view.screen.get("name", "?"), overlay.screen.get("name", "?"), _elapsed])
			_overlay_quit_at = -1.0
			_finish_boot()
		return
	if _overlay_spec.is_empty() or _elapsed < _overlay_due:
		return
	_raise_overlay(String(_overlay_spec.get("screen", "")))


## Composite a second build over the first.
##
## It starts at `time_units = 0` and plays its OWN group, so the plate rises and
## fades in exactly as the disc declares -- alpha 0x00 at t=214, 0xff by t=238 --
## rather than appearing as a cut. `holding` then parks it at its settle, which
## for this build is the visible pose.
##
## ⚠️ It does NOT pulse, and that is a decision with arithmetic behind it rather
## than an omission. See `authored/flow.json`, `no_pulse_why`.
func _raise_overlay(name: String) -> void:
	var spec := _overlay_spec
	_overlay_spec = {}
	if name == "":
		return
	overlay = ScreenView.new()
	overlay.texture_filter = CanvasItem.TEXTURE_FILTER_NEAREST
	overlay.units_per_second = view.units_per_second
	overlay.exit_ramp_units = view.exit_ramp_units
	overlay.holding = true
	overlay.time_units = 0.0
	if not overlay.load_screen(view.tree, name):
		push_error(view.tree.error)
		overlay.queue_free()
		overlay = null
		return
	# After `view`, so it draws over it: Node2D siblings paint in tree order and
	# the export's own `paint_order` only orders WITHIN a build.
	viewport.add_child(overlay)
	print("  overlay %s raised at %.2f s, %d element(s), settles at t=%d"
		% [name, _elapsed, overlay.screen.get("elements", []).size(), int(overlay.settle_time())])
	# A boot with no menu to hand over to has now finished: it was held open for
	# this. Give the plate its own group time to play before leaving, so the
	# artifact shows the composited state rather than the frame it began on.
	var visible_at := overlay.settle_time() / overlay.units_per_second
	# The two lines below describe a BOOT. `--screen --overlay=` raises the same
	# composite with no delay, as a fast check, and must not narrate a sequence
	# it is not running -- a log line that lies is worse than no log line.
	if _sequence.is_empty():
		return
	# 🔴 SAY THE NUMBER OUT LOUD. `authored/flow.json` implements the RE agent's
	# instruction literally -- "when build 4 has settled, wait 2.13 s, composite
	# build 2" -- and build 2 then takes its OWN declared 238 units to fade in.
	# So the plate is first VISIBLE at settle + 2.13 + 3.97 s, while the thing
	# that was measured is the plate becoming visible at settle + 2.13 s. The two
	# cannot both be right and the port is not the one to choose. Printed on
	# every boot so the disagreement cannot go quiet.
	print("  ⚠ plate raised at settle+%.2f s but its own group reaches full alpha %.2f s later, \
so it is first VISIBLE at settle+%.2f s -- the measurement is settle+%.2f s. See docs/port/BLOCKED.md."
		% [float(spec.get("after_settle_seconds", 0.0)), visible_at,
		   float(spec.get("after_settle_seconds", 0.0)) + visible_at,
		   float(spec.get("after_settle_seconds", 0.0))])
	if not _play and _film == "":
		_overlay_quit_at = _elapsed + visible_at
		print("  boot ends at %.2f s, once the plate has settled" % _overlay_quit_at)
	# `spec` is read only for the log; the reasoning lives in flow.json where a
	# reader looking for a decision will find it.
	if spec.has("why"):
		print("     why: %s" % String(spec["why"]).substr(0, 96))


var _overlay_quit_at: float = -1.0


## Take the overlay away with the screen it belongs to.
##
## The plate was measured on the BOOT title only. Whether it is there when the
## title is reached again -- (B) from the main menu, or after the attract movie
## -- is not measured, so leaving it up would be claiming something nobody has
## watched. `authored/flow.json` says the same thing in the step's `scope_why`.
func _drop_overlay() -> void:
	_overlay_spec = {}
	_overlay_quit_at = -1.0
	if overlay != null:
		overlay.queue_free()
		overlay = null


## End a `--boot` run, photographing the composited end state first if asked.
##
## `--capture` used to be a `--screen`-only flag, taken in `_ready`. The boot had
## no artifact of its own except a whole `--film` filmstrip, which is 600+ PNGs
## to answer one question: is the plate on top of the title at the end. This
## takes that one frame.
func _finish_boot() -> void:
	if _capture_to != "":
		await _capture(_capture_to)
	get_tree().quit(0)


var _capture_to := ""