osu/osu.Game/Skinning/SkinnableDrawable.cs

// Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
// Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE

using System;
using osu.Framework.Allocation;
using osu.Framework.Configuration;
using osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;

namespace osu.Game.Skinning
{
    public class SkinnableDrawable : SkinnableDrawable<Drawable>
    {
        public SkinnableDrawable(string name, Func<string, Drawable> defaultImplementation, bool fallback = true)
            : base(name, defaultImplementation, fallback)
        {
            RelativeSizeAxes = Axes.Both;
        }
    }

    public class SkinnableDrawable<T> : CompositeDrawable
        where T : Drawable
    {
        private Bindable<Skin> skin;
        protected Func<string, T> CreateDefault;

        public readonly string ComponentName;

        public readonly bool DefaultFallback;

        public SkinnableDrawable(string name, Func<string, T> defaultImplementation, bool fallback = true)
        {
            DefaultFallback = fallback;
            ComponentName = name;
            CreateDefault = defaultImplementation;
        }

        [BackgroundDependencyLoader]
        private void load(SkinManager skinManager)
        {
            skin = skinManager.CurrentSkin.GetBoundCopy();
            skin.ValueChanged += updateComponent;
            skin.TriggerChange();
        }

        private void updateComponent(Skin skin)
        {
            var drawable = skin.GetDrawableComponent(ComponentName);
            if (drawable == null && (DefaultFallback || skin.SkinInfo == SkinInfo.Default))
                drawable = CreateDefault(ComponentName);

            if (drawable != null)
                InternalChild = drawable;
            else
                ClearInternal();
        }
    }
}