add bgm playback, scrolling based on bgm time

Scripts/Scenes/DebugChartLoader.cs

@@ -91,7 +91,6 @@ namespace WacK.Scenes
 			var songPath = $"user://songs/{songsButton.Text}";
 			var chartPath = $"{songPath}/{difficultyButton.Selected}.mer";
 			var soundPath = $"{songPath}/{soundButton.Text}";
-			GD.Print($"Song: {songPath}\nChart: {chartPath}\nSound: {soundPath}");
 
 			// folder check
 			using var dir = DirAccess.Open(songPath);

Scripts/Scenes/Play/Audio/BGM.cs

@@ -0,0 +1,46 @@
+using Godot;
+using Godot.Collections;
+using System;
+
+public partial class BGM : AudioStreamPlayer
+{
+	public void LoadFromUser(string path)
+	{
+		if (!path.StartsWith("user://"))
+		{
+			GD.Print("Tried to load audio that isn't in user directory.");
+			return;
+		}
+
+		var f = FileAccess.Open(path, FileAccess.ModeFlags.Read);
+		if (f == null)
+		{
+			GD.PrintErr($"Unable to open {path} for loading audio! {FileAccess.GetOpenError()}");
+			return;
+		}
+		GD.Print("hi");
+		var ext = path.Split('.')[^1].ToLower();
+		switch (ext)
+		{
+			case "mp3":
+				var mp3 = new AudioStreamMP3()
+				{
+					Data = f.GetBuffer((long)f.GetLength())
+				};
+				Stream = mp3;
+				break;
+			case "wav":
+			case "wave":
+				var wav = new AudioStreamWav()
+				{
+					Data = f.GetBuffer((long)f.GetLength())
+				};
+				Stream = wav;
+				break;
+			case "ogg":
+				// TODO: implement
+				GD.PrintErr("External OGGs not supported in Godot 4.1...");
+				break;
+		}
+	}
+}

Scripts/Scenes/Play/Audio/SFX.cs

@@ -0,0 +1,15 @@
+using Godot;
+using System;
+
+public partial class SFX : Node
+{
+	// Called when the node enters the scene tree for the first time.
+	public override void _Ready()
+	{
+	}
+
+	// Called every frame. 'delta' is the elapsed time since the previous frame.
+	public override void _Process(double delta)
+	{
+	}
+}

Scripts/Scenes/Play/Play.cs

@@ -22,6 +22,7 @@ namespace WacK.Scenes
 		{
 			chartPath = chPath;
 			soundPath = snPath;
+			GD.Print($"Chart: {chartPath}\nSound: {soundPath}");
 		}
 	}
 	public partial class Play : Node
@@ -34,6 +35,14 @@ namespace WacK.Scenes
 		public static PackedScene noteHold = GD.Load<PackedScene>("res://Things/TunnelObjects/Notes/NoteHold.tscn");
 		public static PackedScene noteChain = GD.Load<PackedScene>("res://Things/TunnelObjects/Notes/NoteChain.tscn");
 
+		[ExportCategory("Audio")]
+		[Export]
+		private BGM bgmController;
+		[Export]
+		private SFX sfxController;
+
+		[ExportCategory("2D")]
+		[ExportSubgroup("2D Things")]
 		[Export]
 		public Control noteDisplay;
 		[Export]
@@ -41,6 +50,7 @@ namespace WacK.Scenes
 		[Export]
 		public Background background;
 
+		[ExportSubgroup("Out-of-bounds Viewports")]
 		[Export]
 		public Viewport mainViewport;
 		[Export]
@@ -69,6 +79,10 @@ namespace WacK.Scenes
 			// parse mer and create chart for current play
 			chart = new(playParams.chartPath);
 			RealizeChart();
+
+			// audio setup
+			bgmController.LoadFromUser(playParams.soundPath);
+			bgmController.Play();
 		}
 
 		/// <summary>
@@ -107,8 +121,10 @@ namespace WacK.Scenes
 
         public override void _Process(double delta)
         {
+			double time = bgmController.GetPlaybackPosition() + AudioServer.GetTimeSinceLastMix() - AudioServer.GetOutputLatency();
+			
 			var nPos = noteDisplay.Position;
-			nPos.Y += (float)delta * scrollPxPerSec;
+			nPos.Y = ((float)time * scrollPxPerSec) + 1920;
 			noteDisplay.Position = nPos;
 			scrollDisplay.Position = nPos;
         }