osu-lazer/osu.Game/Storyboards/Drawables/DrawableStoryboardSample.cs

// 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();

            // TODO: this logic will need to be consolidated with other game samples like hit sounds.
            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;
            }
        }
    }
}