Add the concept of nested DrawableHitObjects.

- Applies to Slider Ticks and start circle. repeat/endpoints still need addressing.
- Removed SliderTicksLayer abstraction for now.

osu.Game.Modes.Osu/Objects/Drawables/DrawableOsuHitObject.cs

@@ -73,5 +73,7 @@ namespace osu.Game.Modes.Osu.Objects.Drawables
         Hit100,
         [Description(@"300")]
         Hit300,
+        [Description(@"10")]
+        SliderTick
     }
 }

osu.Game.Modes.Osu/Objects/Drawables/DrawableSlider.cs

@@ -7,6 +7,7 @@ using osu.Game.Modes.Objects.Drawables;
 using osu.Game.Modes.Osu.Objects.Drawables.Pieces;
 using System.Collections.Generic;
 using System.Linq;
+using osu.Framework.Graphics.Containers;
 
 namespace osu.Game.Modes.Osu.Objects.Drawables
 {
@@ -18,11 +19,12 @@ namespace osu.Game.Modes.Osu.Objects.Drawables
 
         private List<ISliderProgress> components = new List<ISliderProgress>();
 
+        private Container<DrawableSliderTick> ticks;
+
         SliderBody body;
         SliderBall ball;
 
         SliderBouncer bouncer1, bouncer2;
-        SliderTicksRenderer ticks;
 
         public DrawableSlider(Slider s) : base(s)
         {
@@ -35,13 +37,7 @@ namespace osu.Game.Modes.Osu.Objects.Drawables
                     Position = s.StackedPosition,
                     PathWidth = s.Scale * 64,
                 },
-                ticks = new SliderTicksRenderer
-                {
-                    Position = s.StackedPosition,
-                    StartTime = s.StartTime,
-                    RepeatDuration = s.Curve.Length / s.Velocity,
-                    Ticks = s.Ticks,
-                },
+                ticks = new Container<DrawableSliderTick>(),
                 bouncer1 = new SliderBouncer(s, false)
                 {
                     Position = s.Curve.PositionAt(1),
@@ -72,6 +68,26 @@ namespace osu.Game.Modes.Osu.Objects.Drawables
             components.Add(ball);
             components.Add(bouncer1);
             components.Add(bouncer2);
+
+            AddNested(initialCircle);
+
+            var repeatDuration = s.Curve.Length / s.Velocity;
+            foreach (var tick in s.Ticks)
+            {
+                var repeatStartTime = s.StartTime + tick.RepeatIndex * repeatDuration;
+                var fadeInTime = repeatStartTime + (tick.StartTime - repeatStartTime) / 2 - (tick.RepeatIndex == 0 ? TIME_FADEIN : TIME_FADEIN / 2);
+                var fadeOutTime = repeatStartTime + repeatDuration;
+
+                var drawableTick = new DrawableSliderTick(tick)
+                {
+                    FadeInTime = fadeInTime,
+                    FadeOutTime = fadeOutTime,
+                    Position = tick.Position,
+                };
+
+                ticks.Add(drawableTick);
+                AddNested(drawableTick);
+            }
         }
 
         // Since the DrawableSlider itself is just a container without a size we need to
@@ -105,8 +121,8 @@ namespace osu.Game.Modes.Osu.Objects.Drawables
             if (initialCircle.Judgement?.Result != HitResult.Hit)
                 initialCircle.Position = slider.Curve.PositionAt(progress);
 
-            components.ForEach(c => c.UpdateProgress(progress, repeat));
-            ticks.ShouldHit = ball.Tracking;
+            foreach (var c in components) c.UpdateProgress(progress, repeat);
+            foreach (var t in ticks.Children) t.Tracking = ball.Tracking;
         }
 
         protected override void CheckJudgement(bool userTriggered)

osu.Game.Modes.Osu/Objects/Drawables/DrawableSliderTick.cs

@@ -22,7 +22,7 @@ namespace osu.Game.Modes.Osu.Objects.Drawables
         public double FadeInTime;
         public double FadeOutTime;
 
-        public bool ShouldHit;
+        public bool Tracking;
 
         public override bool RemoveWhenNotAlive => false;
 
@@ -35,7 +35,6 @@ namespace osu.Game.Modes.Osu.Objects.Drawables
             Masking = true;
             CornerRadius = Size.X / 2;
 
-            Anchor = Anchor.Centre;
             Origin = Anchor.Centre;
 
             BorderThickness = 2;
@@ -70,8 +69,13 @@ namespace osu.Game.Modes.Osu.Objects.Drawables
 
         protected override void CheckJudgement(bool userTriggered)
         {
+            var j = Judgement as OsuJudgementInfo;
+
             if (Judgement.TimeOffset >= 0)
-                Judgement.Result = ShouldHit ? HitResult.Hit : HitResult.Miss;
+            {
+                j.Result = Tracking ? HitResult.Hit : HitResult.Miss;
+                j.Score = Tracking ? OsuScoreResult.SliderTick : OsuScoreResult.Miss;
+            }
         }
         
         protected override void UpdatePreemptState()

osu.Game.Modes.Osu/Objects/Drawables/SliderTicksLayer.cs

@@ -1,96 +0,0 @@
-// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
-// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
-
-using osu.Framework.Allocation;
-using osu.Framework.Caching;
-using osu.Framework.Graphics.Containers;
-using System.Collections.Generic;
-
-namespace osu.Game.Modes.Osu.Objects.Drawables.Pieces
-{
-    public class SliderTicksRenderer : Container<DrawableSliderTick>
-    {
-        private Cached drawableTicks = new Cached();
-
-        private double startTime;
-        public double StartTime
-        {
-            get { return startTime; }
-            set
-            {
-                startTime = value;
-                drawableTicks.Invalidate();
-            }
-        }
-
-        private double repeatDuration;
-        public double RepeatDuration
-        {
-            get { return repeatDuration; }
-            set
-            {
-                repeatDuration = value;
-                drawableTicks.Invalidate();
-            }
-        }
-
-        private IEnumerable<SliderTick> ticks;
-        public IEnumerable<SliderTick> Ticks
-        {
-            get { return ticks; }
-            set
-            {
-                ticks = value;
-                drawableTicks.Invalidate();
-            }
-        }
-
-        public bool ShouldHit
-        {
-            set
-            {
-                foreach (var tick in Children)
-                    tick.ShouldHit = value;
-            }
-        }
-
-        protected override void Update()
-        {
-            base.Update();
-            updateDrawableTicks();
-        }
-
-        [BackgroundDependencyLoader]
-        private void load()
-        {
-            updateDrawableTicks();
-        }
-
-        private void updateDrawableTicks()
-        {
-            if (drawableTicks.EnsureValid())
-                return;
-
-            drawableTicks.Refresh(delegate
-            {
-                Clear();
-                if (ticks == null || repeatDuration == 0)
-                    return;
-
-                foreach (var tick in ticks)
-                {
-                    var repeatStartTime = startTime + tick.RepeatIndex * repeatDuration;
-                    var fadeInTime = repeatStartTime + (tick.StartTime - repeatStartTime) / 2 - (tick.RepeatIndex == 0 ? DrawableOsuHitObject.TIME_FADEIN : DrawableOsuHitObject.TIME_FADEIN / 2);
-                    var fadeOutTime = repeatStartTime + repeatDuration;
-
-                    Add(new DrawableSliderTick(tick)
-                    {
-                        FadeInTime = fadeInTime,
-                        FadeOutTime = fadeOutTime,
-                        Position = tick.Position,
-                    });
-                }
-            });
-        }
-    }
-}

osu.Game.Modes.Osu/Objects/Slider.cs

@@ -96,7 +96,7 @@ namespace osu.Game.Modes.Osu.Objects
                         {
                             RepeatIndex = repeat,
                             StartTime = repeatStartTime + timeProgress * repeatDuration,
-                            Position = Curve.PositionAt(distanceProgress) - StackedPosition,
+                            Position = Curve.PositionAt(distanceProgress),
                             StackHeight = StackHeight,
                             Scale = Scale,
                             Colour = Colour,