Introduce PreviewTrackManager

osu.Game/Audio/PreviewTrackManager.cs

@@ -0,0 +1,60 @@
+// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using osu.Framework.Allocation;
+using osu.Framework.Audio;
+using osu.Framework.Audio.Track;
+using osu.Framework.Configuration;
+using osu.Framework.IO.Stores;
+
+namespace osu.Game.Audio
+{
+    public class PreviewTrackManager : TrackManager
+    {
+        private AudioManager audio;
+        private Track currentTrack;
+        private readonly BindableDouble muteBindable;
+
+        public PreviewTrackManager()
+            : base(new OnlineStore())
+        {
+            muteBindable = new BindableDouble();
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(AudioManager audio, FrameworkConfigManager config)
+        {
+            this.audio = audio;
+
+            audio.AddItem(this);
+
+            config.BindWith(FrameworkSetting.VolumeMusic, Volume);
+        }
+
+        protected override void UpdateState()
+        {
+            if (currentTrack?.HasCompleted ?? false)
+                onStop();
+
+            base.UpdateState();
+        }
+
+        public void Play(Track track)
+        {
+            currentTrack?.Stop();
+            currentTrack = track;
+            currentTrack.Restart();
+            onPlay();
+        }
+
+        private void onPlay() => audio.Track.AddAdjustment(AdjustableProperty.Volume, muteBindable);
+
+        public void Stop()
+        {
+            currentTrack?.Stop();
+            onStop();
+        }
+
+        private void onStop() => audio.Track.RemoveAdjustment(AdjustableProperty.Volume, muteBindable);
+    }
+}