From d0766fa1cdaa15c1a35a096e1364de4455dcefb5 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Mon, 19 Aug 2019 19:52:53 +0900
Subject: [PATCH] Add slider ball animation support

---
 .../Objects/Drawables/Pieces/SliderBall.cs    | 12 +++++-
 osu.Game/Skinning/LegacySkin.cs               | 42 +++++++++++++------
 2 files changed, 39 insertions(+), 15 deletions(-)

diff --git a/osu.Game.Rulesets.Osu/Objects/Drawables/Pieces/SliderBall.cs b/osu.Game.Rulesets.Osu/Objects/Drawables/Pieces/SliderBall.cs
index 8b72b23ca3..332e25750f 100644
--- a/osu.Game.Rulesets.Osu/Objects/Drawables/Pieces/SliderBall.cs
+++ b/osu.Game.Rulesets.Osu/Objects/Drawables/Pieces/SliderBall.cs
@@ -55,7 +55,6 @@ public SliderBall(Slider slider, DrawableSlider drawableSlider = null)
                     Child = new Container
                     {
                         RelativeSizeAxes = Axes.Both,
-                        // TODO: support skin filename animation (sliderb0, sliderb1...)
                         Child = new SkinnableDrawable("Play/osu/sliderball", _ => new DefaultSliderBall()),
                     }
                 }
@@ -168,9 +167,18 @@ private bool isValidTrackingAction(OsuAction action)
             return action == OsuAction.LeftButton || action == OsuAction.RightButton;
         }
 
+        private Vector2? lastPosition;
+
         public void UpdateProgress(double completionProgress)
         {
-            Position = slider.CurvePositionAt(completionProgress);
+            var newPos = slider.CurvePositionAt(completionProgress);
+
+            var diff = lastPosition.HasValue ? lastPosition.Value - newPos : newPos - slider.CurvePositionAt(completionProgress + 0.01f);
+
+            Position = newPos;
+            Rotation = 90 + (float)(-Math.Atan2(diff.X, diff.Y) * 180 / Math.PI);
+
+            lastPosition = newPos;
         }
 
         private class FollowCircleContainer : Container
diff --git a/osu.Game/Skinning/LegacySkin.cs b/osu.Game/Skinning/LegacySkin.cs
index 94421b1251..883e0ce3fc 100644
--- a/osu.Game/Skinning/LegacySkin.cs
+++ b/osu.Game/Skinning/LegacySkin.cs
@@ -1,4 +1,4 @@
-// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// 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;
@@ -92,8 +92,20 @@ public override Drawable GetDrawableComponent(string componentName)
                     return null;
 
                 case "Play/osu/sliderball":
-                    if (GetTexture("sliderb") != null)
-                        return new LegacySliderBall();
+                    var sliderBallContent = getAnimation("sliderb", true, true, "");
+
+                    if (sliderBallContent != null)
+                    {
+                        var size = sliderBallContent.Size;
+
+                        sliderBallContent.RelativeSizeAxes = Axes.Both;
+                        sliderBallContent.Size = Vector2.One;
+
+                        return new LegacySliderBall(sliderBallContent)
+                        {
+                            Size = size
+                        };
+                    }
 
                     return null;
 
@@ -169,16 +181,6 @@ private Drawable getAnimation(string componentName, bool animatable, bool loopin
             return (texture = GetTexture(componentName)) == null ? null : new Sprite { Texture = texture };
         }
 
-        public class LegacySliderBall : Sprite
-        {
-            [BackgroundDependencyLoader]
-            private void load(ISkinSource skin)
-            {
-                Texture = skin.GetTexture("sliderb");
-                Colour = skin.GetValue<SkinConfiguration, Color4?>(s => s.CustomColours.ContainsKey("SliderBall") ? s.CustomColours["SliderBall"] : (Color4?)null) ?? Color4.White;
-            }
-        }
-
         public override Texture GetTexture(string componentName)
         {
             float ratio = 2;
@@ -333,6 +335,20 @@ private void load(ISkinSource skin)
             }
         }
 
+        public class LegacySliderBall : CompositeDrawable
+        {
+            public LegacySliderBall(Drawable content)
+            {
+                InternalChild = content;
+            }
+
+            [BackgroundDependencyLoader]
+            private void load(ISkinSource skin)
+            {
+                Colour = skin.GetValue<SkinConfiguration, Color4?>(s => s.CustomColours.ContainsKey("SliderBall") ? s.CustomColours["SliderBall"] : (Color4?)null) ?? Color4.White;
+            }
+        }
+
         public class LegacyMainCirclePiece : CompositeDrawable
         {
             public LegacyMainCirclePiece()