Add legacy slider body support

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

@@ -24,9 +24,11 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables
         public DrawableSliderHead HeadCircle => headContainer.Child;
         public DrawableSliderTail TailCircle => tailContainer.Child;
 
-        public readonly SnakingSliderBody Body;
         public readonly SliderBall Ball;
 
+        public SnakingSliderBody Body => (SnakingSliderBody)skinnedBody.Drawable;
+
+        private readonly SkinnableDrawable skinnedBody;
         private readonly Container<DrawableSliderHead> headContainer;
         private readonly Container<DrawableSliderTail> tailContainer;
         private readonly Container<DrawableSliderTick> tickContainer;
@@ -51,7 +53,7 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables
 
             InternalChildren = new Drawable[]
             {
-                Body = new SnakingSliderBody(s),
+                skinnedBody = new SkinnableDrawable(new OsuSkinComponent(OsuSkinComponents.SliderBody), _ => new SnakingSliderBody(), confineMode: ConfineMode.NoScaling),
                 tickContainer = new Container<DrawableSliderTick> { RelativeSizeAxes = Axes.Both },
                 repeatContainer = new Container<DrawableRepeatPoint> { RelativeSizeAxes = Axes.Both },
                 Ball = new SliderBall(s, this)

osu.Game.Rulesets.Osu/Objects/Drawables/Pieces/SnakingSliderBody.cs

@@ -6,6 +6,7 @@ using System.Collections.Generic;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
 using osu.Framework.Graphics;
+using osu.Game.Rulesets.Objects.Drawables;
 using osu.Game.Rulesets.Objects.Types;
 using osuTK;
 
@@ -50,16 +51,13 @@ namespace osu.Game.Rulesets.Osu.Objects.Drawables.Pieces
         /// </summary>
         private Vector2 snakedPathOffset;
 
-        private readonly Slider slider;
-
-        public SnakingSliderBody(Slider slider)
-        {
-            this.slider = slider;
-        }
+        private Slider slider;
 
         [BackgroundDependencyLoader]
-        private void load()
+        private void load(DrawableHitObject drawableObject)
         {
+            slider = (Slider)drawableObject.HitObject;
+
             Refresh();
         }
 

osu.Game.Rulesets.Osu/OsuSkinComponents.cs

@@ -14,6 +14,7 @@ namespace osu.Game.Rulesets.Osu
         ReverseArrow,
         HitCircleText,
         SliderFollowCircle,
-        SliderBall
+        SliderBall,
+        SliderBody,
     }
 }

osu.Game.Rulesets.Osu/Skinning/LegacySliderBody.cs

@@ -0,0 +1,47 @@
+// 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.Extensions.Color4Extensions;
+using osu.Framework.MathUtils;
+using osu.Game.Rulesets.Osu.Objects.Drawables.Pieces;
+using osuTK.Graphics;
+
+namespace osu.Game.Rulesets.Osu.Skinning
+{
+    public class LegacySliderBody : SnakingSliderBody
+    {
+        protected override DrawableSliderPath CreateSliderPath() => new LegacyDrawableSliderPath();
+
+        private class LegacyDrawableSliderPath : DrawableSliderPath
+        {
+            public new Color4 AccentColour => new Color4(base.AccentColour.R, base.AccentColour.G, base.AccentColour.B, 0.70f);
+
+            protected override Color4 ColourAt(float position)
+            {
+                if (CalculatedBorderPortion != 0f && position <= CalculatedBorderPortion)
+                    return BorderColour;
+
+                position -= BORDER_PORTION;
+
+                Color4 outerColour = AccentColour.Darken(0.1f);
+                Color4 innerColour = lighten(AccentColour, 0.5f);
+
+                return Interpolation.ValueAt(position / GRADIENT_PORTION, outerColour, innerColour, 0, 1);
+            }
+
+            /// <summary>
+            /// Lightens a colour in a way more friendly to dark or strong colours.
+            /// </summary>
+            private static Color4 lighten(Color4 color, float amount)
+            {
+                amount *= 0.5f;
+                return new Color4(
+                    Math.Min(1, color.R * (1 + 0.5f * amount) + 1 * amount),
+                    Math.Min(1, color.G * (1 + 0.5f * amount) + 1 * amount),
+                    Math.Min(1, color.B * (1 + 0.5f * amount) + 1 * amount),
+                    color.A);
+            }
+        }
+    }
+}

osu.Game.Rulesets.Osu/Skinning/OsuLegacySkinTransformer.cs

@@ -73,6 +73,12 @@ namespace osu.Game.Rulesets.Osu.Skinning
 
                     return null;
 
+                case OsuSkinComponents.SliderBody:
+                    if (hasHitCircle.Value)
+                        return new LegacySliderBody();
+
+                    return null;
+
                 case OsuSkinComponents.HitCircle:
                     if (hasHitCircle.Value)
                         return new LegacyMainCirclePiece();