Sylpheed/port/scripts/menu_audio.gd

# The menu's sound: three cues and one music bed.
#
# EVERYTHING THIS CLASS PLAYS IS AUTHORED OR MEASURED, and the two are not the
# same. `authored/audio.json` carries the distinction and the exporter copies it
# into `manifest.json` alongside each file, so a reader of the export tree sees
# it without having to find this project:
#
#   * WHICH WAVE a menu event plays was MEASURED off the running game (HANDOFF
#     Q8) -- it is on the disc in no findable form. `Static.slb` has no RIFF, no
#     seek chunk and no container.
#   * WHICH TRACK the menu plays is CHOSEN. HANDOFF Q10 is a negative: all 32
#     banks are named BGM_001..BGM_109 and nothing on the disc says which one a
#     menu uses.
#   * WHEN a cue fires is authored here, and §"When a cue fires" below says
#     exactly which parts of that nobody has watched the game do.
#
# The wall (MISSION §2): this class reads **Ogg Vorbis**. It has never heard of
# XMA, of `sound.pak` or of `Static.slb`, and it must not learn. The exporter
# converts; the runtime plays.
class_name MenuAudio
extends Node

## Cue name -> stream, from `manifest.json`'s `audio` entries of kind `se`.
var cues: Dictionary = {}
## Role -> {stream, loop}, from the entries of kind `bgm`.
var beds: Dictionary = {}
var error: String = ""

## One player per cue name, so a move and a confirm can overlap rather than
## cutting each other off. Three cues is not worth a pool.
var _players: Dictionary = {}
var _bed: AudioStreamPlayer = null
var _bed_role := ""


## Load every audio entry the manifest declares.
##
## Missing audio is NOT an error and does not stop a run: every milestone before
## P6 exported none, and `--menu` must stay usable against one of those trees.
## A cue that is listed but unreadable IS an error, because that is a broken
## export rather than an old one.
func configure(tree: ExportTree) -> bool:
	var manifest := tree.manifest()
	if manifest.is_empty():
		error = tree.error
		return false
	for entry: Dictionary in manifest.get("audio", []):
		# Through the resolver, so a mod can replace a cue or the music bed by
		# dropping a file at the same relative path (MODDING rule 4). Reading
		# `tree.root` directly here would have made audio the one asset kind a
		# mod could not touch, for no reason a modder could have guessed.
		var path := tree.resolve(String(entry.get("file", "")))
		var stream := AudioStreamOggVorbis.load_from_file(path)
		if stream == null:
			error = "manifest lists audio %s but %s is not a readable Ogg Vorbis file" \
				% [entry.get("name", "?"), path]
			return false
		match String(entry.get("kind", "")):
			"se":
				# A cue ends. Nothing measured says otherwise, and a looping
				# cue would be a bug you hear rather than one you read.
				stream.loop = false
				cues[String(entry["name"])] = stream
			"bgm":
				# AUTHORED, and audibly imperfect on purpose. HANDOFF Q10: no
				# loop-point field has been identified, so `restart` replays
				# from sample 0 -- the listener hears the track's own fade-out
				# and its trailing silence before the music returns. Trimming to
				# the fade would sound better and would INVENT a loop point,
				# which is worse: an invented one is indistinguishable from a
				# decoded one a month later. See authored/audio.json loop_why.
				stream.loop = String(entry.get("loop_mode", "")) == "restart"
				beds[String(entry["name"])] = stream
			_:
				push_warning("manifest audio entry %s has kind %s, which this build does not play"
					% [entry.get("name", "?"), entry.get("kind", "?")])
	return true


## True when this export carries no audio at all -- an export taken before P6.
func silent() -> bool:
	return cues.is_empty() and beds.is_empty()


# --- When a cue fires ---------------------------------------------------------
#
# MEASURED (HANDOFF Q5 + Q8): a d-pad press that MOVES the cursor plays the move
# cue, and left/right play nothing at all. `MenuFlow.move()` returns whether the
# cursor actually moved for exactly this reason, so a press at the end of a
# non-wrapping list cannot click.
#
# NOT MEASURED, and authored here: whether Ⓐ or Ⓑ click when nothing is bound to
# them. Nobody has watched the game take a dead press. This class stays silent in
# that case, which is the choice that invents the least -- a sound the game does
# not make is a wrong fact you can hear, whereas a missing one is a gap. Ask the
# RE agent before relying on it either way.


func play(cue: String) -> void:
	if not cues.has(cue):
		return
	if not _players.has(cue):
		var p := AudioStreamPlayer.new()
		p.stream = cues[cue]
		add_child(p)
		_players[cue] = p
	(_players[cue] as AudioStreamPlayer).play()


## Start the music bed for a role, or do nothing if it is already playing.
##
## Idempotent because the menu re-enters screens constantly -- Ⓑ back to the main
## menu must not restart the music, and a bed that restarts on every navigation
## is the kind of wrong that reads as "the audio works".
func play_bed(role: String) -> void:
	if not beds.has(role) or _bed_role == role:
		return
	if _bed == null:
		_bed = AudioStreamPlayer.new()
		add_child(_bed)
	_bed.stream = beds[role]
	_bed_role = role
	_bed.play()


func stop_bed() -> void:
	if _bed != null:
		_bed.stop()
	_bed_role = ""


## What the audio server is actually doing, for a run's write-up.
##
## `docs/port/AUDIO-VERIFICATION.md`: "recorded under a dummy driver" is a
## weaker claim than "heard", and the difference matters -- so the claim is
## printed by the run that makes it rather than assumed by the person reading it.
static func driver() -> String:
	return AudioServer.get_driver_name()