Fix legacy approach circles accepting alpha

osu.Game.Rulesets.Osu/Skinning/Legacy/LegacyApproachCircle.cs

@@ -0,0 +1,49 @@
+// 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 osu.Framework.Allocation;
+using osu.Framework.Bindables;
+using osu.Framework.Graphics;
+using osu.Game.Rulesets.Objects.Drawables;
+using osu.Game.Skinning;
+using osuTK;
+using osuTK.Graphics;
+
+namespace osu.Game.Rulesets.Osu.Skinning.Legacy
+{
+    public class LegacyApproachCircle : SkinnableSprite
+    {
+        private readonly IBindable<Color4> accentColour = new Bindable<Color4>();
+
+        [Resolved]
+        private DrawableHitObject drawableObject { get; set; }
+
+        public LegacyApproachCircle()
+            : base("approachcircle")
+        {
+        }
+
+        [BackgroundDependencyLoader]
+        private void load()
+        {
+            accentColour.BindTo(drawableObject.AccentColour);
+        }
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+            accentColour.BindValueChanged(colour => Colour = LegacyColourCompatibility.DisallowZeroAlpha(colour.NewValue), true);
+        }
+
+        protected override Drawable CreateDefault(ISkinComponent component)
+        {
+            var drawable = base.CreateDefault(component);
+
+            // account for the sprite being used for the default approach circle being taken from stable,
+            // when hitcircles have 5px padding on each size. this should be removed if we update the sprite.
+            drawable.Scale = new Vector2(128 / 118f);
+
+            return drawable;
+        }
+    }
+}

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

@@ -108,6 +108,9 @@ namespace osu.Game.Rulesets.Osu.Skinning.Legacy
                             return new LegacyOldStyleSpinner();
 
                         return null;
+
+                    case OsuSkinComponents.ApproachCircle:
+                        return new LegacyApproachCircle();
                 }
             }