Merge pull request #10923 from smoogipoo/followpoint-pooling

Implement follow point pooling

osu.Game.Rulesets.Osu.Tests/TestSceneFollowPoints.cs

@@ -7,6 +7,7 @@ using NUnit.Framework;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Testing;
+using osu.Framework.Timing;
 using osu.Framework.Utils;
 using osu.Game.Beatmaps;
 using osu.Game.Beatmaps.ControlPoints;
@@ -94,9 +95,19 @@ namespace osu.Game.Rulesets.Osu.Tests
         {
             addMultipleObjectsStep();
 
-            AddStep("move hitobject", () => getObject(2).HitObject.Position = new Vector2(300, 100));
+            AddStep("move hitobject", () =>
+            {
+                var manualClock = new ManualClock();
+                followPointRenderer.Clock = new FramedClock(manualClock);
+
+                manualClock.CurrentTime = getObject(1).HitObject.StartTime;
+                followPointRenderer.UpdateSubTree();
+
+                getObject(2).HitObject.Position = new Vector2(300, 100);
+            });
 
             assertGroups();
+            assertDirections();
         }
 
         [TestCase(0, 0)] // Start -> Start
@@ -207,7 +218,7 @@ namespace osu.Game.Rulesets.Osu.Tests
 
         private void assertGroups()
         {
-            AddAssert("has correct group count", () => followPointRenderer.Connections.Count == hitObjectContainer.Count);
+            AddAssert("has correct group count", () => followPointRenderer.Entries.Count == hitObjectContainer.Count);
             AddAssert("group endpoints are correct", () =>
             {
                 for (int i = 0; i < hitObjectContainer.Count; i++)
@@ -215,10 +226,10 @@ namespace osu.Game.Rulesets.Osu.Tests
                     DrawableOsuHitObject expectedStart = getObject(i);
                     DrawableOsuHitObject expectedEnd = i < hitObjectContainer.Count - 1 ? getObject(i + 1) : null;
 
-                    if (getGroup(i).Start != expectedStart.HitObject)
+                    if (getEntry(i).Start != expectedStart.HitObject)
                         throw new AssertionException($"Object {i} expected to be the start of group {i}.");
 
-                    if (getGroup(i).End != expectedEnd?.HitObject)
+                    if (getEntry(i).End != expectedEnd?.HitObject)
                         throw new AssertionException($"Object {(expectedEnd == null ? "null" : i.ToString())} expected to be the end of group {i}.");
                 }
 
@@ -238,6 +249,12 @@ namespace osu.Game.Rulesets.Osu.Tests
                     if (expectedEnd == null)
                         continue;
 
+                    var manualClock = new ManualClock();
+                    followPointRenderer.Clock = new FramedClock(manualClock);
+
+                    manualClock.CurrentTime = expectedStart.HitObject.StartTime;
+                    followPointRenderer.UpdateSubTree();
+
                     var points = getGroup(i).ChildrenOfType<FollowPoint>().ToArray();
                     if (points.Length == 0)
                         continue;
@@ -255,7 +272,9 @@ namespace osu.Game.Rulesets.Osu.Tests
 
         private DrawableOsuHitObject getObject(int index) => hitObjectContainer[index];
 
-        private FollowPointConnection getGroup(int index) => followPointRenderer.Connections[index];
+        private FollowPointLifetimeEntry getEntry(int index) => followPointRenderer.Entries[index];
+
+        private FollowPointConnection getGroup(int index) => followPointRenderer.ChildrenOfType<FollowPointConnection>().Single(c => c.Entry == getEntry(index));
 
         private class TestHitObjectContainer : Container<DrawableOsuHitObject>
         {

osu.Game.Rulesets.Osu/Objects/Drawables/Connections/FollowPoint.cs

@@ -7,6 +7,7 @@ using osu.Framework.Extensions.Color4Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
 using osu.Framework.Graphics.Effects;
+using osu.Framework.Graphics.Pooling;
 using osu.Framework.Graphics.Shapes;
 using osu.Game.Skinning;
 
@@ -15,7 +16,7 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables.Connections
     /// <summary>
     /// A single follow point positioned between two adjacent <see cref="DrawableOsuHitObject"/>s.
     /// </summary>
-    public class FollowPoint : Container, IAnimationTimeReference
+    public class FollowPoint : PoolableDrawable, IAnimationTimeReference
     {
         private const float width = 8;
 
@@ -25,7 +26,7 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables.Connections
         {
             Origin = Anchor.Centre;
 
-            Child = new SkinnableDrawable(new OsuSkinComponent(OsuSkinComponents.FollowPoint), _ => new CircularContainer
+            InternalChild = new SkinnableDrawable(new OsuSkinComponent(OsuSkinComponents.FollowPoint), _ => new CircularContainer
             {
                 Masking = true,
                 AutoSizeAxes = Axes.Both,

osu.Game.Rulesets.Osu/Objects/Drawables/Connections/FollowPointConnection.cs

@@ -2,11 +2,8 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
-using System.Diagnostics;
-using JetBrains.Annotations;
-using osu.Framework.Bindables;
 using osu.Framework.Graphics;
-using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Pooling;
 using osu.Game.Rulesets.Objects;
 using osuTK;
 
@@ -15,150 +12,106 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables.Connections
     /// <summary>
     /// Visualises the <see cref="FollowPoint"/>s between two <see cref="DrawableOsuHitObject"/>s.
     /// </summary>
-    public class FollowPointConnection : CompositeDrawable
+    public class FollowPointConnection : PoolableDrawable
     {
         // Todo: These shouldn't be constants
-        private const int spacing = 32;
+        public const int SPACING = 32;
-        private const double preempt = 800;
+        public const double PREEMPT = 800;
 
-        public override bool RemoveWhenNotAlive => false;
+        public FollowPointLifetimeEntry Entry;
+        public DrawablePool<FollowPoint> Pool;
 
-        /// <summary>
+        protected override void PrepareForUse()
-        /// The start time of <see cref="Start"/>.
-        /// </summary>
-        public readonly Bindable<double> StartTime = new BindableDouble();
-
-        /// <summary>
-        /// The <see cref="DrawableOsuHitObject"/> which <see cref="FollowPoint"/>s will exit from.
-        /// </summary>
-        [NotNull]
-        public readonly OsuHitObject Start;
-
-        /// <summary>
-        /// Creates a new <see cref="FollowPointConnection"/>.
-        /// </summary>
-        /// <param name="start">The <see cref="DrawableOsuHitObject"/> which <see cref="FollowPoint"/>s will exit from.</param>
-        public FollowPointConnection([NotNull] OsuHitObject start)
         {
-            Start = start;
+            base.PrepareForUse();
 
-            RelativeSizeAxes = Axes.Both;
+            Entry.Invalidated += onEntryInvalidated;
 
-            StartTime.BindTo(start.StartTimeBindable);
+            refreshPoints();
         }
 
-        protected override void LoadComplete()
+        protected override void FreeAfterUse()
         {
-            base.LoadComplete();
+            base.FreeAfterUse();
-            bindEvents(Start);
+
+            Entry.Invalidated -= onEntryInvalidated;
+
+            // Return points to the pool.
+            ClearInternal(false);
+
+            Entry = null;
         }
 
-        private OsuHitObject end;
+        private void onEntryInvalidated() => refreshPoints();
 
-        /// <summary>
+        private void refreshPoints()
-        /// The <see cref="DrawableOsuHitObject"/> which <see cref="FollowPoint"/>s will enter.
-        /// </summary>
-        [CanBeNull]
-        public OsuHitObject End
         {
-            get => end;
+            ClearInternal(false);
-            set
-            {
-                end = value;
 
-                if (end != null)
+            OsuHitObject start = Entry.Start;
-                    bindEvents(end);
+            OsuHitObject end = Entry.End;
 
-                if (IsLoaded)
+            double startTime = start.GetEndTime();
-                    scheduleRefresh();
-                else
-                    refresh();
-            }
-        }
 
-        private void bindEvents(OsuHitObject obj)
+            Vector2 startPosition = start.StackedEndPosition;
-        {
+            Vector2 endPosition = end.StackedPosition;
-            obj.PositionBindable.BindValueChanged(_ => scheduleRefresh());
-            obj.DefaultsApplied += _ => scheduleRefresh();
-        }
-
-        private void scheduleRefresh()
-        {
-            Scheduler.AddOnce(refresh);
-        }
-
-        private void refresh()
-        {
-            double startTime = Start.GetEndTime();
-
-            LifetimeStart = startTime;
-
-            if (End == null || End.NewCombo || Start is Spinner || End is Spinner)
-            {
-                // ensure we always set a lifetime for full LifetimeManagementContainer benefits
-                LifetimeEnd = LifetimeStart;
-                return;
-            }
-
-            Vector2 startPosition = Start.StackedEndPosition;
-            Vector2 endPosition = End.StackedPosition;
-            double endTime = End.StartTime;
 
             Vector2 distanceVector = endPosition - startPosition;
             int distance = (int)distanceVector.Length;
             float rotation = (float)(Math.Atan2(distanceVector.Y, distanceVector.X) * (180 / Math.PI));
-            double duration = endTime - startTime;
 
-            double? firstTransformStartTime = null;
             double finalTransformEndTime = startTime;
 
-            int point = 0;
+            for (int d = (int)(SPACING * 1.5); d < distance - SPACING; d += SPACING)
-
-            ClearInternal();
-
-            for (int d = (int)(spacing * 1.5); d < distance - spacing; d += spacing)
             {
                 float fraction = (float)d / distance;
                 Vector2 pointStartPosition = startPosition + (fraction - 0.1f) * distanceVector;
                 Vector2 pointEndPosition = startPosition + fraction * distanceVector;
-                double fadeOutTime = startTime + fraction * duration;
+
-                double fadeInTime = fadeOutTime - preempt;
+                GetFadeTimes(start, end, (float)d / distance, out var fadeInTime, out var fadeOutTime);
 
                 FollowPoint fp;
 
-                AddInternal(fp = new FollowPoint());
+                AddInternal(fp = Pool.Get());
-
-                Debug.Assert(End != null);
 
+                fp.ClearTransforms();
                 fp.Position = pointStartPosition;
                 fp.Rotation = rotation;
                 fp.Alpha = 0;
-                fp.Scale = new Vector2(1.5f * End.Scale);
+                fp.Scale = new Vector2(1.5f * end.Scale);
-
-                firstTransformStartTime ??= fadeInTime;
 
                 fp.AnimationStartTime = fadeInTime;
 
                 using (fp.BeginAbsoluteSequence(fadeInTime))
                 {
-                    fp.FadeIn(End.TimeFadeIn);
+                    fp.FadeIn(end.TimeFadeIn);
-                    fp.ScaleTo(End.Scale, End.TimeFadeIn, Easing.Out);
+                    fp.ScaleTo(end.Scale, end.TimeFadeIn, Easing.Out);
-                    fp.MoveTo(pointEndPosition, End.TimeFadeIn, Easing.Out);
+                    fp.MoveTo(pointEndPosition, end.TimeFadeIn, Easing.Out);
-                    fp.Delay(fadeOutTime - fadeInTime).FadeOut(End.TimeFadeIn);
+                    fp.Delay(fadeOutTime - fadeInTime).FadeOut(end.TimeFadeIn);
 
-                    finalTransformEndTime = fadeOutTime + End.TimeFadeIn;
+                    finalTransformEndTime = fadeOutTime + end.TimeFadeIn;
                 }
-
-                point++;
             }
 
-            int excessPoints = InternalChildren.Count - point;
-            for (int i = 0; i < excessPoints; i++)
-                RemoveInternal(InternalChildren[^1]);
-
             // todo: use Expire() on FollowPoints and take lifetime from them when https://github.com/ppy/osu-framework/issues/3300 is fixed.
-            LifetimeStart = firstTransformStartTime ?? startTime;
+            Entry.LifetimeEnd = finalTransformEndTime;
-            LifetimeEnd = finalTransformEndTime;
+        }
+
+        /// <summary>
+        /// Computes the fade time of follow point positioned between two hitobjects.
+        /// </summary>
+        /// <param name="start">The first <see cref="OsuHitObject"/>, where follow points should originate from.</param>
+        /// <param name="end">The second <see cref="OsuHitObject"/>, which follow points should target.</param>
+        /// <param name="fraction">The fractional distance along <paramref name="start"/> and <paramref name="end"/> at which the follow point is to be located.</param>
+        /// <param name="fadeInTime">The fade-in time of the follow point/</param>
+        /// <param name="fadeOutTime">The fade-out time of the follow point.</param>
+        public static void GetFadeTimes(OsuHitObject start, OsuHitObject end, float fraction, out double fadeInTime, out double fadeOutTime)
+        {
+            double startTime = start.GetEndTime();
+            double duration = end.StartTime - startTime;
+
+            fadeOutTime = startTime + fraction * duration;
+            fadeInTime = fadeOutTime - PREEMPT;
         }
     }
 }

osu.Game.Rulesets.Osu/Objects/Drawables/Connections/FollowPointLifetimeEntry.cs

@@ -0,0 +1,98 @@
+// 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 osu.Framework.Bindables;
+using osu.Framework.Graphics.Performance;
+using osu.Game.Rulesets.Objects;
+using osuTK;
+
+namespace osu.Game.Rulesets.Osu.Objects.Drawables.Connections
+{
+    public class FollowPointLifetimeEntry : LifetimeEntry
+    {
+        public event Action Invalidated;
+        public readonly OsuHitObject Start;
+
+        public FollowPointLifetimeEntry(OsuHitObject start)
+        {
+            Start = start;
+            LifetimeStart = Start.StartTime;
+
+            bindEvents();
+        }
+
+        private OsuHitObject end;
+
+        public OsuHitObject End
+        {
+            get => end;
+            set
+            {
+                UnbindEvents();
+
+                end = value;
+
+                bindEvents();
+
+                refreshLifetimes();
+            }
+        }
+
+        private void bindEvents()
+        {
+            UnbindEvents();
+
+            // Note: Positions are bound for instantaneous feedback from positional changes from the editor, before ApplyDefaults() is called on hitobjects.
+            Start.DefaultsApplied += onDefaultsApplied;
+            Start.PositionBindable.ValueChanged += onPositionChanged;
+
+            if (End != null)
+            {
+                End.DefaultsApplied += onDefaultsApplied;
+                End.PositionBindable.ValueChanged += onPositionChanged;
+            }
+        }
+
+        public void UnbindEvents()
+        {
+            if (Start != null)
+            {
+                Start.DefaultsApplied -= onDefaultsApplied;
+                Start.PositionBindable.ValueChanged -= onPositionChanged;
+            }
+
+            if (End != null)
+            {
+                End.DefaultsApplied -= onDefaultsApplied;
+                End.PositionBindable.ValueChanged -= onPositionChanged;
+            }
+        }
+
+        private void onDefaultsApplied(HitObject obj) => refreshLifetimes();
+
+        private void onPositionChanged(ValueChangedEvent<Vector2> obj) => refreshLifetimes();
+
+        private void refreshLifetimes()
+        {
+            if (End == null || End.NewCombo || Start is Spinner || End is Spinner)
+            {
+                LifetimeEnd = LifetimeStart;
+                return;
+            }
+
+            Vector2 startPosition = Start.StackedEndPosition;
+            Vector2 endPosition = End.StackedPosition;
+            Vector2 distanceVector = endPosition - startPosition;
+
+            // The lifetime start will match the fade-in time of the first follow point.
+            float fraction = (int)(FollowPointConnection.SPACING * 1.5) / distanceVector.Length;
+            FollowPointConnection.GetFadeTimes(Start, End, fraction, out var fadeInTime, out _);
+
+            LifetimeStart = fadeInTime;
+            LifetimeEnd = double.MaxValue; // This will be set by the connection.
+
+            Invalidated?.Invoke();
+        }
+    }
+}

osu.Game.Rulesets.Osu/Objects/Drawables/Connections/FollowPointRenderer.cs

@@ -2,53 +2,74 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System.Collections.Generic;
-using System.Linq;
+using osu.Framework.Allocation;
+using osu.Framework.Bindables;
 using osu.Framework.Extensions;
 using osu.Framework.Graphics;
 using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Performance;
+using osu.Framework.Graphics.Pooling;
+using osu.Game.Rulesets.Objects;
 
 namespace osu.Game.Rulesets.Osu.Objects.Drawables.Connections
 {
     /// <summary>
     /// Visualises connections between <see cref="DrawableOsuHitObject"/>s.
     /// </summary>
-    public class FollowPointRenderer : LifetimeManagementContainer
+    public class FollowPointRenderer : CompositeDrawable
     {
-        /// <summary>
-        /// All the <see cref="FollowPointConnection"/>s contained by this <see cref="FollowPointRenderer"/>.
-        /// </summary>
-        internal IReadOnlyList<FollowPointConnection> Connections => connections;
-
-        private readonly List<FollowPointConnection> connections = new List<FollowPointConnection>();
-
         public override bool RemoveCompletedTransforms => false;
 
-        /// <summary>
+        public IReadOnlyList<FollowPointLifetimeEntry> Entries => lifetimeEntries;
-        /// Adds the <see cref="FollowPoint"/>s around an <see cref="OsuHitObject"/>.
-        /// This includes <see cref="FollowPoint"/>s leading into <paramref name="hitObject"/>, and <see cref="FollowPoint"/>s exiting <paramref name="hitObject"/>.
-        /// </summary>
-        /// <param name="hitObject">The <see cref="OsuHitObject"/> to add <see cref="FollowPoint"/>s for.</param>
-        public void AddFollowPoints(OsuHitObject hitObject)
-            => addConnection(new FollowPointConnection(hitObject).With(g => g.StartTime.BindValueChanged(_ => onStartTimeChanged(g))));
 
-        /// <summary>
+        private DrawablePool<FollowPointConnection> connectionPool;
-        /// Removes the <see cref="FollowPoint"/>s around an <see cref="OsuHitObject"/>.
+        private DrawablePool<FollowPoint> pointPool;
-        /// This includes <see cref="FollowPoint"/>s leading into <paramref name="hitObject"/>, and <see cref="FollowPoint"/>s exiting <paramref name="hitObject"/>.
-        /// </summary>
-        /// <param name="hitObject">The <see cref="OsuHitObject"/> to remove <see cref="FollowPoint"/>s for.</param>
-        public void RemoveFollowPoints(OsuHitObject hitObject) => removeGroup(connections.Single(g => g.Start == hitObject));
 
-        /// <summary>
+        private readonly List<FollowPointLifetimeEntry> lifetimeEntries = new List<FollowPointLifetimeEntry>();
-        /// Adds a <see cref="FollowPointConnection"/> to this <see cref="FollowPointRenderer"/>.
+        private readonly Dictionary<LifetimeEntry, FollowPointConnection> connectionsInUse = new Dictionary<LifetimeEntry, FollowPointConnection>();
-        /// </summary>
+        private readonly Dictionary<HitObject, IBindable> startTimeMap = new Dictionary<HitObject, IBindable>();
-        /// <param name="connection">The <see cref="FollowPointConnection"/> to add.</param>
+        private readonly LifetimeEntryManager lifetimeManager = new LifetimeEntryManager();
-        /// <returns>The index of <paramref name="connection"/> in <see cref="connections"/>.</returns>
+
-        private void addConnection(FollowPointConnection connection)
+        public FollowPointRenderer()
         {
-            // Groups are sorted by their start time when added such that the index can be used to post-process other surrounding connections
+            lifetimeManager.EntryBecameAlive += onEntryBecameAlive;
-            int index = connections.AddInPlace(connection, Comparer<FollowPointConnection>.Create((g1, g2) =>
+            lifetimeManager.EntryBecameDead += onEntryBecameDead;
+        }
+
+        [BackgroundDependencyLoader]
+        private void load()
+        {
+            InternalChildren = new Drawable[]
             {
-                int comp = g1.StartTime.Value.CompareTo(g2.StartTime.Value);
+                connectionPool = new DrawablePoolNoLifetime<FollowPointConnection>(1, 200),
+                pointPool = new DrawablePoolNoLifetime<FollowPoint>(50, 1000)
+            };
+        }
+
+        public void AddFollowPoints(OsuHitObject hitObject)
+        {
+            addEntry(hitObject);
+
+            var startTimeBindable = hitObject.StartTimeBindable.GetBoundCopy();
+            startTimeBindable.ValueChanged += _ => onStartTimeChanged(hitObject);
+            startTimeMap[hitObject] = startTimeBindable;
+        }
+
+        public void RemoveFollowPoints(OsuHitObject hitObject)
+        {
+            removeEntry(hitObject);
+
+            startTimeMap[hitObject].UnbindAll();
+            startTimeMap.Remove(hitObject);
+        }
+
+        private void addEntry(OsuHitObject hitObject)
+        {
+            var newEntry = new FollowPointLifetimeEntry(hitObject);
+
+            var index = lifetimeEntries.AddInPlace(newEntry, Comparer<FollowPointLifetimeEntry>.Create((e1, e2) =>
+            {
+                int comp = e1.Start.StartTime.CompareTo(e2.Start.StartTime);
 
                 if (comp != 0)
                     return comp;
@@ -61,19 +82,19 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables.Connections
                 return -1;
             }));
 
-            if (index < connections.Count - 1)
+            if (index < lifetimeEntries.Count - 1)
             {
                 // Update the connection's end point to the next connection's start point
                 //     h1 -> -> -> h2
                 //    connection    nextGroup
 
-                FollowPointConnection nextConnection = connections[index + 1];
+                FollowPointLifetimeEntry nextEntry = lifetimeEntries[index + 1];
-                connection.End = nextConnection.Start;
+                newEntry.End = nextEntry.Start;
             }
             else
             {
                 // The end point may be non-null during re-ordering
-                connection.End = null;
+                newEntry.End = null;
             }
 
             if (index > 0)
@@ -82,23 +103,22 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables.Connections
                 //     h1 -> -> -> h2
                 //  prevGroup    connection
 
-                FollowPointConnection previousConnection = connections[index - 1];
+                FollowPointLifetimeEntry previousEntry = lifetimeEntries[index - 1];
-                previousConnection.End = connection.Start;
+                previousEntry.End = newEntry.Start;
             }
 
-            AddInternal(connection);
+            lifetimeManager.AddEntry(newEntry);
         }
 
-        /// <summary>
+        private void removeEntry(OsuHitObject hitObject)
-        /// Removes a <see cref="FollowPointConnection"/> from this <see cref="FollowPointRenderer"/>.
-        /// </summary>
-        /// <param name="connection">The <see cref="FollowPointConnection"/> to remove.</param>
-        /// <returns>Whether <paramref name="connection"/> was removed.</returns>
-        private void removeGroup(FollowPointConnection connection)
         {
-            RemoveInternal(connection);
+            int index = lifetimeEntries.FindIndex(e => e.Start == hitObject);
 
-            int index = connections.IndexOf(connection);
+            var entry = lifetimeEntries[index];
+            entry.UnbindEvents();
+
+            lifetimeEntries.RemoveAt(index);
+            lifetimeManager.RemoveEntry(entry);
 
             if (index > 0)
             {
@@ -106,18 +126,61 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables.Connections
                 //     h1 -> -> -> h2 -> -> -> h3
                 //  prevGroup    connection       nextGroup
                 // The current connection's end point is used since there may not be a next connection
-                FollowPointConnection previousConnection = connections[index - 1];
+                FollowPointLifetimeEntry previousEntry = lifetimeEntries[index - 1];
-                previousConnection.End = connection.End;
+                previousEntry.End = entry.End;
             }
-
-            connections.Remove(connection);
         }
 
-        private void onStartTimeChanged(FollowPointConnection connection)
+        protected override bool CheckChildrenLife()
         {
-            // Naive but can be improved if performance becomes an issue
+            bool anyAliveChanged = base.CheckChildrenLife();
-            removeGroup(connection);
+            anyAliveChanged |= lifetimeManager.Update(Time.Current);
-            addConnection(connection);
+            return anyAliveChanged;
+        }
+
+        private void onEntryBecameAlive(LifetimeEntry entry)
+        {
+            var connection = connectionPool.Get(c =>
+            {
+                c.Entry = (FollowPointLifetimeEntry)entry;
+                c.Pool = pointPool;
+            });
+
+            connectionsInUse[entry] = connection;
+
+            AddInternal(connection);
+        }
+
+        private void onEntryBecameDead(LifetimeEntry entry)
+        {
+            RemoveInternal(connectionsInUse[entry]);
+            connectionsInUse.Remove(entry);
+        }
+
+        private void onStartTimeChanged(OsuHitObject hitObject)
+        {
+            removeEntry(hitObject);
+            addEntry(hitObject);
+        }
+
+        protected override void Dispose(bool isDisposing)
+        {
+            base.Dispose(isDisposing);
+
+            foreach (var entry in lifetimeEntries)
+                entry.UnbindEvents();
+            lifetimeEntries.Clear();
+        }
+
+        private class DrawablePoolNoLifetime<T> : DrawablePool<T>
+            where T : PoolableDrawable, new()
+        {
+            public override bool RemoveWhenNotAlive => false;
+
+            public DrawablePoolNoLifetime(int initialSize, int? maximumSize = null)
+                : base(initialSize, maximumSize)
+            {
+            }
         }
     }
 }