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GDScript

class_name MusicController
extends Node
## Controller for music playback across scenes.
##
## This node persistently checks for stream players added to the scene tree.
## It detects stream players that match the audio bus and have autoplay on.
## It then reparents the stream players to itself, and handles blending.
## The expected use-case is to attach this script to an autoloaded scene.
const BLEND_BUS_PREFIX : String = "Blend"
const MAX_DEPTH = 16
const MINIMUM_VOLUME_DB = -80
## Detect stream players with matching audio bus.
@export var audio_bus : StringName = &"Music"
@export_group("Blending")
@export var fade_out_duration : float = 0.0 :
set(value):
fade_out_duration = value
if fade_out_duration < 0:
fade_out_duration = 0
@export var fade_in_duration : float = 0.0 :
set(value):
fade_in_duration = value
if fade_in_duration < 0:
fade_in_duration = 0
## Matched stream players with no stream set will stop current playback.
@export var empty_streams_stop_player : bool = true
var music_stream_player : AudioStreamPlayer
var blend_audio_bus : StringName
var blend_audio_bus_idx : int
func fade_out( duration : float = 0.0 ):
if not is_zero_approx(duration):
music_stream_player.bus = audio_bus
var tween = create_tween()
tween.tween_property(music_stream_player, "volume_db", MINIMUM_VOLUME_DB, duration)
return tween
func _set_sub_audio_volume_db(sub_volume_db : float):
AudioServer.set_bus_volume_db(blend_audio_bus_idx, sub_volume_db)
func fade_in( duration : float = 0.0 ):
if not is_zero_approx(duration):
music_stream_player.bus = blend_audio_bus
AudioServer.set_bus_volume_db(blend_audio_bus_idx, MINIMUM_VOLUME_DB)
var tween = create_tween()
tween.tween_method(_set_sub_audio_volume_db, MINIMUM_VOLUME_DB, 0, duration)
return tween
func blend_to( target_volume_db : float, duration : float = 0.0 ):
if not is_zero_approx(duration):
var tween = create_tween()
tween.tween_property(music_stream_player, "volume_db", target_volume_db, duration)
return tween
music_stream_player.volume_db = target_volume_db
func stop():
if music_stream_player == null:
return
music_stream_player.stop()
func play( playback_position : float = 0.0 ):
if music_stream_player == null:
return
if is_zero_approx(playback_position) and not music_stream_player.playing:
music_stream_player.play()
else:
music_stream_player.play(playback_position)
func _fade_out_and_free():
if music_stream_player == null:
return
var stream_player = music_stream_player
var tween = fade_out( fade_out_duration )
if tween != null:
await( tween.finished )
stream_player.queue_free()
func _play_and_fade_in():
play()
fade_in( fade_in_duration )
func _is_matching_stream( stream_player : AudioStreamPlayer ) -> bool:
if stream_player.bus != audio_bus:
return false
if music_stream_player == null:
return false
return music_stream_player.stream == stream_player.stream
func _connect_stream_on_tree_exiting( stream_player : AudioStreamPlayer ):
if not stream_player.tree_exiting.is_connected(_on_removed_music_player.bind(stream_player)):
stream_player.tree_exiting.connect(_on_removed_music_player.bind(stream_player))
func _blend_and_remove_stream_player( stream_player : AudioStreamPlayer ):
var playback_position := music_stream_player.get_playback_position() + AudioServer.get_time_since_last_mix()
var old_stream_player = music_stream_player
music_stream_player = stream_player
music_stream_player.bus = blend_audio_bus
play(playback_position)
old_stream_player.stop()
old_stream_player.queue_free()
_connect_stream_on_tree_exiting(music_stream_player)
func _blend_and_connect_stream_player( stream_player : AudioStreamPlayer ):
stream_player.bus = blend_audio_bus
_fade_out_and_free()
music_stream_player = stream_player
_play_and_fade_in()
_connect_stream_on_tree_exiting(music_stream_player)
func play_stream_player( stream_player : AudioStreamPlayer ):
if stream_player == music_stream_player : return
if stream_player.stream == null and not empty_streams_stop_player:
return
if _is_matching_stream(stream_player) :
_blend_and_remove_stream_player(stream_player)
else:
_blend_and_connect_stream_player(stream_player)
func get_stream_player( audio_stream : AudioStream ) -> AudioStreamPlayer:
var stream_player := AudioStreamPlayer.new()
stream_player.stream = audio_stream
stream_player.bus = audio_bus
add_child(stream_player)
return stream_player
func play_stream( audio_stream : AudioStream ) -> AudioStreamPlayer:
var stream_player := get_stream_player(audio_stream)
stream_player.play.call_deferred()
play_stream_player( stream_player )
return stream_player
func _clone_music_player( stream_player : AudioStreamPlayer ):
var playback_position := stream_player.get_playback_position() + AudioServer.get_time_since_last_mix()
var audio_stream := stream_player.stream
music_stream_player = get_stream_player(audio_stream)
music_stream_player.volume_db = stream_player.volume_db
music_stream_player.max_polyphony = stream_player.max_polyphony
music_stream_player.pitch_scale = stream_player.pitch_scale
music_stream_player.play.call_deferred(playback_position)
func _reparent_music_player( stream_player : AudioStreamPlayer ):
var playback_position := stream_player.get_playback_position() + AudioServer.get_time_since_last_mix()
stream_player.owner = null
stream_player.reparent.call_deferred(self)
stream_player.play.call_deferred(playback_position)
func _node_matches_checks( node : Node ) -> bool:
return node is AudioStreamPlayer and node.autoplay and node.bus == audio_bus
func _on_removed_music_player( node: Node ) -> void:
if music_stream_player == node:
if node.owner == null:
_clone_music_player(node)
else:
_reparent_music_player(node)
if node.tree_exiting.is_connected(_on_removed_music_player.bind(node)):
node.tree_exiting.disconnect(_on_removed_music_player.bind(node))
func _on_added_music_player( node: Node ) -> void:
if node == music_stream_player : return
if not (_node_matches_checks(node)) : return
play_stream_player(node)
func _enter_tree() -> void:
AudioServer.add_bus()
blend_audio_bus_idx = AudioServer.bus_count - 1
blend_audio_bus = AppSettings.SYSTEM_BUS_NAME_PREFIX + BLEND_BUS_PREFIX + audio_bus
AudioServer.set_bus_send(blend_audio_bus_idx, audio_bus)
AudioServer.set_bus_name(blend_audio_bus_idx, blend_audio_bus)
var tree_node = get_tree()
if not tree_node.node_added.is_connected(_on_added_music_player):
tree_node.node_added.connect(_on_added_music_player)
func _exit_tree():
var tree_node = get_tree()
if tree_node.node_added.is_connected(_on_added_music_player):
tree_node.node_added.disconnect(_on_added_music_player)