Implement storyboard samples

osu.Game/Storyboards/Drawables/DrawableStoryboardSample.cs

@@ -0,0 +1,68 @@
+// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System.IO;
+using osu.Framework.Allocation;
+using osu.Framework.Audio.Sample;
+using osu.Framework.Graphics;
+using osu.Game.Beatmaps;
+
+namespace osu.Game.Storyboards.Drawables
+{
+    public class DrawableStoryboardSample : Component
+    {
+        /// <summary>
+        /// The amount of time allowable beyond the start time of the sample, for the sample to start.
+        /// </summary>
+        private const double allowable_late_start = 100;
+
+        private readonly StoryboardSample sample;
+        private SampleChannel channel;
+
+        public override bool RemoveWhenNotAlive => false;
+
+        public DrawableStoryboardSample(StoryboardSample sample)
+        {
+            this.sample = sample;
+            LifetimeStart = sample.Time;
+        }
+
+        [BackgroundDependencyLoader]
+        private void load(IBindableBeatmap beatmap)
+        {
+            // Try first with the full name, then attempt with no path
+            channel = beatmap.Value.Skin.GetSample(sample.Path) ?? beatmap.Value.Skin.GetSample(Path.ChangeExtension(sample.Path, null));
+
+            if (channel != null)
+                channel.Volume.Value = sample.Volume / 100;
+        }
+
+        protected override void Update()
+        {
+            base.Update();
+
+            if (Time.Current < sample.Time)
+            {
+                // We've rewound before the start time of the sample
+                channel?.Stop();
+
+                // In the case that the user fast-forwards to a point far beyond the start time of the sample,
+                // we want to be able to fall into the if-conditional below (therefore we must not have a life time end)
+                LifetimeStart = sample.Time;
+                LifetimeEnd = double.MaxValue;
+            }
+            else if (Time.Current - Time.Elapsed < sample.Time)
+            {
+                // We've passed the start time of the sample. We only play the sample if we're within an allowable range
+                // from the sample's start, to reduce layering if we've been fast-forwarded far into the future
+                if (Time.Current - sample.Time < allowable_late_start)
+                    channel?.Play();
+
+                // In the case that the user rewinds to a point far behind the start time of the sample,
+                // we want to be able to fall into the if-conditional above (therefore we must not have a life time start)
+                LifetimeStart = double.MinValue;
+                LifetimeEnd = sample.Time;
+            }
+        }
+    }
+}

osu.Game/Storyboards/StoryboardSample.cs

@@ -2,14 +2,14 @@
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
 using osu.Framework.Graphics;
-using System;
+using osu.Game.Storyboards.Drawables;
 
 namespace osu.Game.Storyboards
 {
     public class StoryboardSample : IStoryboardElement
     {
         public string Path { get; set; }
-        public bool IsDrawable => false;
+        public bool IsDrawable => true;
 
         public double Time;
         public float Volume;
@@ -21,9 +21,6 @@ namespace osu.Game.Storyboards
             Volume = volume;
         }
 
-        public Drawable CreateDrawable()
-        {
-            throw new InvalidOperationException();
-        }
+        public Drawable CreateDrawable() => new DrawableStoryboardSample(this);
     }
 }