Handle proxied approach layer better and add slider's approach circle (previously missing).

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

@@ -11,7 +11,7 @@ using OpenTK;
 
 namespace osu.Game.Modes.Osu.Objects.Drawables
 {
-    public class DrawableHitCircle : DrawableOsuHitObject
+    public class DrawableHitCircle : DrawableOsuHitObject, IDrawableHitObjectWithProxiedApproach
     {
         private HitCircle osuObject;
 
@@ -156,5 +156,7 @@ namespace osu.Game.Modes.Osu.Objects.Drawables
                     break;
             }
         }
+
+        public Drawable ProxiedLayer => ApproachCircle;
     }
 }

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

@@ -6,11 +6,10 @@ using osu.Framework.Graphics;
 using osu.Game.Modes.Objects.Drawables;
 using osu.Game.Modes.Osu.Objects.Drawables.Pieces;
 using OpenTK;
-using osu.Framework.Input;
 
 namespace osu.Game.Modes.Osu.Objects.Drawables
 {
-    class DrawableSlider : DrawableOsuHitObject
+    public class DrawableSlider : DrawableOsuHitObject, IDrawableHitObjectWithProxiedApproach
     {
         private Slider slider;
 
@@ -133,6 +132,8 @@ namespace osu.Game.Modes.Osu.Objects.Drawables
 
             FadeOut(800);
         }
+
+        public Drawable ProxiedLayer => initialCircle.ApproachCircle;
     }
 
     internal interface ISliderProgress

osu.Game.Modes.Osu/UI/OsuPlayfield.cs

@@ -60,10 +60,10 @@ namespace osu.Game.Modes.Osu.UI
         public override void Add(DrawableHitObject h)
         {
             h.Depth = (float)h.HitObject.StartTime;
-            DrawableHitCircle c = h as DrawableHitCircle;
+            IDrawableHitObjectWithProxiedApproach c = h as IDrawableHitObjectWithProxiedApproach;
             if (c != null)
             {
-                approachCircles.Add(c.ApproachCircle.CreateProxy());
+                approachCircles.Add(c.ProxiedLayer.CreateProxy());
             }
 
             h.OnJudgement += judgement;

osu.Game/Modes/Objects/Drawables/IDrawableHitObjectWithProxiedApproach.cs

@@ -0,0 +1,17 @@
+// Copyright (c) 2007-2017 ppy Pty Ltd <contact@ppy.sh>.
+// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using osu.Framework.Graphics;
+
+namespace osu.Game.Modes.Objects.Drawables
+{
+    public interface IDrawableHitObjectWithProxiedApproach
+    {
+        Drawable ProxiedLayer { get; }
+    }
+}

osu.Game/osu.Game.csproj

@@ -75,6 +75,7 @@
     <Compile Include="Graphics\UserInterface\OsuSliderBar.cs" />
     <Compile Include="Graphics\UserInterface\OsuTextBox.cs" />
     <Compile Include="Graphics\UserInterface\TwoLayerButton.cs" />
+    <Compile Include="Modes\Objects\Drawables\IDrawableHitObjectWithProxiedApproach.cs" />
     <Compile Include="Modes\Objects\HitObjectParser.cs" />
     <Compile Include="Modes\Score.cs" />
     <Compile Include="Modes\ScoreProcesssor.cs" />