osu/osu.Game/Rulesets/UI/GameplaySampleTriggerSource.cs

// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.

using System.Linq;
using osu.Framework.Allocation;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;
using osu.Game.Audio;
using osu.Game.Rulesets.Objects;
using osu.Game.Skinning;

namespace osu.Game.Rulesets.UI
{
    /// <summary>
    /// A component which can trigger the most appropriate hit sound for a given point in time, based on the state of a <see cref="HitObjectContainer"/>
    /// </summary>
    public class GameplaySampleTriggerSource : CompositeDrawable
    {
        private readonly HitObjectContainer hitObjectContainer;

        private int nextHitSoundIndex;

        /// <summary>
        /// The number of concurrent samples allowed to be played concurrently so that it feels better when spam-pressing a key.
        /// </summary>
        private const int max_concurrent_hitsounds = OsuGameBase.SAMPLE_CONCURRENCY;

        private readonly Container<SkinnableSound> hitSounds;

        [Resolved]
        private DrawableRuleset drawableRuleset { get; set; }

        public GameplaySampleTriggerSource(HitObjectContainer hitObjectContainer)
        {
            this.hitObjectContainer = hitObjectContainer;
            InternalChildren = new Drawable[]
            {
                hitSounds = new Container<SkinnableSound>
                {
                    Name = "concurrent sample pool",
                    RelativeSizeAxes = Axes.Both,
                    Children = Enumerable.Range(0, max_concurrent_hitsounds).Select(_ => new SkinnableSound()).ToArray()
                },
            };
        }

        private ISampleInfo[] playableSampleInfo;

        /// <summary>
        /// Play the most appropriate hit sound for the current point in time.
        /// </summary>
        public void Play()
        {
            var nextObject =
                hitObjectContainer.AliveObjects.FirstOrDefault(h => h.HitObject.StartTime > Time.Current)?.HitObject ??
                // fallback to non-alive objects to find next off-screen object
                // TODO: make lookup more efficient?
                drawableRuleset.Objects.FirstOrDefault(h => h.StartTime > Time.Current) ??
                drawableRuleset.Objects.LastOrDefault();

            if (nextObject != null)
            {
                var hitSound = getNextSample();
                playableSampleInfo = GetPlayableSampleInfo(nextObject);
                hitSound.Samples = playableSampleInfo;
                hitSound.Play();
            }
        }

        protected virtual ISampleInfo[] GetPlayableSampleInfo(HitObject nextObject) =>
            // TODO: avoid cast somehow?
            nextObject.Samples.Cast<ISampleInfo>().ToArray();

        private SkinnableSound getNextSample()
        {
            var hitSound = hitSounds[nextHitSoundIndex];

            // round robin over available samples to allow for concurrent playback.
            nextHitSoundIndex = (nextHitSoundIndex + 1) % max_concurrent_hitsounds;

            return hitSound;
        }
    }
}