Make a MusicPlayer singleton to manage music and add music fade out

dialogues/intro_1.json

@@ -36,7 +36,7 @@
     {"name": "Ely", "text": "Also, what made you the first crab to talk to me [i]ever[/i]?"},
     {"name": "Herbert", "text": "I'll tell you my tale, but then please tell me yours."},
     {"name": "Ely", "text": "Sure!"},
-    {"name": "Crab", "text": "Everything was fine."},
+    {"name": "Crab", "text": "Everything was fine.", "audio": ""},
     {"name": "Crab", "text": "I was fine, my friends were fine..."},
     {"name": "Crab", "text": "Even my brother Gary was starting to overcome his depression."},
     {"name": "Crab", "text": "And then..."}

project.godot

@@ -38,6 +38,10 @@ boot_splash/image="res://images/titleCrab.png"
 boot_splash/use_filter=false
 config/icon="res://images/icon.png"
 
+[autoload]
+
+MusicPlayer="*res://scripts/MusicPlayer.gd"
+
 [display]
 
 window/size/width=192

scenes/campfire.tscn

@@ -39,7 +39,6 @@ __meta__ = {
 
 [node name="Dialog" parent="UI" instance=ExtResource( 3 )]
 visible = false
-audio_player_node_path = NodePath("../../AudioStreamPlayer")
 
 [node name="IntroScript" type="Node" parent="."]
 script = ExtResource( 4 )
@@ -47,5 +46,3 @@ dialogue_box_path = NodePath("../UI/Dialog")
 ely_sprite_path = NodePath("../Ely")
 herbert_sprite_path = NodePath("../Herbert")
 intro_dialogue = "res://dialogues/intro_1.json"
-
-[node name="AudioStreamPlayer" type="AudioStreamPlayer" parent="."]

scripts/DialogueBox.gd

@@ -13,8 +13,7 @@ onready var text_label = get_node(text_label_path) as RichTextLabel
 export (NodePath) var expression_node_path
 onready var expression_node = get_node(expression_node_path) as RichTextLabel
 
-export (NodePath) var audio_player_node_path
-onready var audio_player_node = get_node(audio_player_node_path) as AudioStreamPlayer
+onready var music_player = get_node('/root/MusicPlayer') as MusicPlayer
 
 var dialogue : Array
 var index : int
@@ -28,7 +27,7 @@ var auto_advance = false
 func _ready():
 	assert(name_label != null)
 	assert(text_label != null)
-	assert(audio_player_node != null)
+	assert(music_player != null)
 
 func start(_dialogue : Array):
 	dialogue = _dialogue
@@ -68,12 +67,12 @@ func update() -> void:
 		waiting = true
 	
 	# Audio
-	var audio = line.get('audio', '')
-	if audio != '':
-		var path = "res://sounds/" + audio + ".ogg"
-		assert(File.new().file_exists(path))
-		audio_player_node.stream = load(path)
-		audio_player_node.play()
+	var audio = line.get('audio', null)
+	if audio != null:
+		if audio == '':
+			music_player.fade_out()
+		else:
+			music_player.play(audio)
 	
 	# UI
 	name_label.bbcode_text = character_name

scripts/MusicPlayer.gd

@@ -0,0 +1,68 @@
+extends Node
+
+var fading = false
+var animation_time : float
+var animation_duration : float
+var target_track : AudioStreamPlayer
+var previous_tracks : Array
+
+func play(music, offset=0, duration=2):
+	print('Play music: ' + music)
+	var path = "res://sounds/" + music + ".ogg"
+	if !File.new().file_exists(path):
+		path = "res://sounds/" + music
+		assert(File.new().file_exists(path))
+	var stream = load(path)
+	
+	target_track = get_free_track()
+	previous_tracks = get_playing_tracks()
+	
+	if previous_tracks.size() > 0:
+		fading = true
+		animation_time = 0
+		animation_duration = duration
+	
+	target_track.stream = stream
+	target_track.play(offset)
+
+func fade_out(duration=2):
+	target_track = null
+	previous_tracks = get_playing_tracks()
+	fading = true
+	animation_time = 0
+	animation_duration = duration
+
+func get_playing_tracks() -> Array:
+	var tracks = []
+	for track in get_children():
+		if track.playing:
+			tracks.append(track)
+	return tracks
+
+func get_free_track() -> AudioStreamPlayer:
+	var free_track = null
+	for track in get_children():
+		if !track.playing:
+			free_track = track
+	if free_track == null:
+		free_track = AudioStreamPlayer.new()
+		print('yo')
+		add_child(free_track)
+	print(free_track)
+	return free_track
+
+func _process(delta):
+	if fading:
+		animation_time += delta
+		var p = clamp(animation_time / animation_duration, 0, 1)
+		
+		if target_track != null:
+			target_track.volume_db = lerp(-90, 0, clamp(p * 2, 0, 1))
+		for previous_track in previous_tracks:
+			previous_track.volume_db = lerp(0, -90, clamp((p * 2) - 1, 0, 1))
+		
+		if p == 1:
+			fading = false
+			for previous_track in previous_tracks:
+				previous_track.stop()
+				previous_track.queue_free()