osu-lazer/osu.Game.Rulesets.Osu/UI/PlayfieldLayer.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 osu.Framework.Graphics;
using osu.Framework.Graphics.Containers;
using OpenTK;

namespace osu.Game.Rulesets.Osu.UI
{
    public class PlayfieldLayer : Container
    {
        protected override Container<Drawable> Content => content;
        private readonly Container content;

        public PlayfieldLayer()
        {
            InternalChild = new Container
            {
                Anchor = Anchor.Centre,
                Origin = Anchor.Centre,
                RelativeSizeAxes = Axes.Both,
                FillMode = FillMode.Fit,
                FillAspectRatio = 4f / 3,
                Child = content = new ScalingContainer(OsuPlayfield.BASE_SIZE.X) { RelativeSizeAxes = Axes.Both }
            };
        }

        /// <summary>
        /// A <see cref="Container"/> which scales its content relative to a target width.
        /// </summary>
        private class ScalingContainer : Container
        {
            private readonly float targetWidth;

            public ScalingContainer(float targetWidth)
            {
                this.targetWidth = targetWidth;
            }

            protected override void Update()
            {
                base.Update();

                Scale = new Vector2(Parent.ChildSize.X / targetWidth);
                Size = Vector2.Divide(Vector2.One, Scale);
            }
        }
    }
}