Add editable beatmap skin

osu.Game/Screens/Edit/EditorBeatmap.cs

@@ -54,7 +54,7 @@ namespace osu.Game.Screens.Edit
         private readonly Bindable<bool> hasTiming = new Bindable<bool>();
 
         [CanBeNull]
-        public readonly ISkin BeatmapSkin;
+        public readonly EditorBeatmapSkin BeatmapSkin;
 
         [Resolved]
         private BindableBeatDivisor beatDivisor { get; set; }
@@ -69,7 +69,8 @@ namespace osu.Game.Screens.Edit
         public EditorBeatmap(IBeatmap playableBeatmap, ISkin beatmapSkin = null)
         {
             PlayableBeatmap = playableBeatmap;
-            BeatmapSkin = beatmapSkin;
+            if (beatmapSkin is Skin skin)
+                BeatmapSkin = new EditorBeatmapSkin(skin);
 
             beatmapProcessor = playableBeatmap.BeatmapInfo.Ruleset?.CreateInstance().CreateBeatmapProcessor(PlayableBeatmap);
 

osu.Game/Screens/Edit/EditorBeatmapSkin.cs

@@ -0,0 +1,59 @@
+// 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 System.Linq;
+using osu.Framework.Audio.Sample;
+using osu.Framework.Bindables;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.OpenGL.Textures;
+using osu.Framework.Graphics.Textures;
+using osu.Game.Audio;
+using osu.Game.Skinning;
+using osuTK.Graphics;
+
+namespace osu.Game.Screens.Edit
+{
+    /// <summary>
+    /// A beatmap skin which is being edited.
+    /// </summary>
+    public class EditorBeatmapSkin : ISkin
+    {
+        public event Action BeatmapSkinChanged;
+
+        /// <summary>
+        /// The combo colours of this skin.
+        /// If empty, the default combo colours will be used.
+        /// </summary>
+        public BindableList<Colour4> ComboColours;
+
+        private readonly Skin skin;
+
+        public EditorBeatmapSkin(Skin skin)
+        {
+            this.skin = skin;
+
+            ComboColours = new BindableList<Colour4>();
+            if (skin.Configuration.ComboColours != null)
+                ComboColours.AddRange(skin.Configuration.ComboColours.Select(c => (Colour4)c));
+            ComboColours.BindCollectionChanged((_, __) => updateColours());
+        }
+
+        private void invokeSkinChanged() => BeatmapSkinChanged?.Invoke();
+
+        private void updateColours()
+        {
+            skin.Configuration.CustomComboColours = ComboColours.Select(c => (Color4)c).ToList();
+            invokeSkinChanged();
+        }
+
+        #region Delegated ISkin implementation
+
+        public Drawable GetDrawableComponent(ISkinComponent component) => skin.GetDrawableComponent(component);
+        public Texture GetTexture(string componentName, WrapMode wrapModeS, WrapMode wrapModeT) => skin.GetTexture(componentName, wrapModeS, wrapModeT);
+        public ISample GetSample(ISampleInfo sampleInfo) => skin.GetSample(sampleInfo);
+        public IBindable<TValue> GetConfig<TLookup, TValue>(TLookup lookup) => skin.GetConfig<TLookup, TValue>(lookup);
+
+        #endregion
+    }
+}