osu-lazer/osu.Game.Rulesets.Osu/Edit/DrawableOsuEditPool.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;
using System.Linq;
using osu.Framework.Graphics;
using osu.Game.Rulesets.Objects.Drawables;
using osu.Game.Rulesets.Osu.Objects.Drawables;

namespace osu.Game.Rulesets.Osu.Edit
{
    public class DrawableOsuEditPool<T> : DrawableOsuPool<T>
        where T : DrawableHitObject, new()
    {
        /// <summary>
        /// Hit objects are intentionally made to fade out at a constant slower rate than in gameplay.
        /// This allows a mapper to gain better historical context and use recent hitobjects as reference / snap points.
        /// </summary>
        private const double editor_hit_object_fade_out_extension = 700;

        public DrawableOsuEditPool(Func<DrawableHitObject, double, bool> checkHittable, Action<Drawable> onLoaded, int initialSize, int? maximumSize = null)
            : base(checkHittable, onLoaded, initialSize, maximumSize)
        {
        }

        protected override T CreateNewDrawable() => base.CreateNewDrawable().With(d => d.ApplyCustomUpdateState += updateState);

        private void updateState(DrawableHitObject hitObject, ArmedState state)
        {
            if (state == ArmedState.Idle)
                return;

            // adjust the visuals of certain object types to make them stay on screen for longer than usual.
            switch (hitObject)
            {
                default:
                    // there are quite a few drawable hit types we don't want to extend (spinners, ticks etc.)
                    return;

                case DrawableSlider _:
                    // no specifics to sliders but let them fade slower below.
                    break;

                case DrawableHitCircle circle: // also handles slider heads
                    circle.ApproachCircle
                          .FadeOutFromOne(editor_hit_object_fade_out_extension)
                          .Expire();
                    break;
            }

            // Get the existing fade out transform
            var existing = hitObject.Transforms.LastOrDefault(t => t.TargetMember == nameof(Alpha));

            if (existing == null)
                return;

            hitObject.RemoveTransform(existing);

            using (hitObject.BeginAbsoluteSequence(existing.StartTime))
                hitObject.FadeOut(editor_hit_object_fade_out_extension).Expire();
        }
    }
}