Extract playfield scaling into a separate class

And make it more general.

osu.Game/Rulesets/UI/Playfield.cs

@@ -3,52 +3,37 @@
 
 using System.Collections.Generic;
 using osu.Framework.Graphics;
-using osu.Framework.Graphics.Containers;
 using osu.Game.Rulesets.Objects.Drawables;
-using OpenTK;
 using osu.Framework.Allocation;
 
 namespace osu.Game.Rulesets.UI
 {
-    public abstract class Playfield : Container
+    public abstract class Playfield : ScalableContainer
     {
         /// <summary>
         /// The HitObjects contained in this Playfield.
         /// </summary>
         public HitObjectContainer HitObjects { get; private set; }
 
-        public Container<Drawable> ScaledContent;
-
-        protected override Container<Drawable> Content => content;
-        private readonly Container<Drawable> content;
-
-        private List<Playfield> nestedPlayfields;
-
         /// <summary>
         /// All the <see cref="Playfield"/>s nested inside this playfield.
         /// </summary>
         public IReadOnlyList<Playfield> NestedPlayfields => nestedPlayfields;
+        private List<Playfield> nestedPlayfields;
 
         /// <summary>
         /// A container for keeping track of DrawableHitObjects.
         /// </summary>
-        /// <param name="customWidth">Whether we want our internal coordinate system to be scaled to a specified width.</param>
-        protected Playfield(float? customWidth = null)
+        /// <param name="customWidth">The width to scale the internal coordinate space to.
+        /// May be null if scaling based on <paramref name="customHeight"/> is desired. If <paramref name="customHeight"/> is also null, no scaling will occur.
+        /// </param>
+        /// <param name="customHeight">The height to scale the internal coordinate space to.
+        /// May be null if scaling based on <paramref name="customWidth"/> is desired. If <paramref name="customWidth"/> is also null, no scaling will occur.
+        /// </param>
+        protected Playfield(float? customWidth = null, float? customHeight = null)
+            : base(customWidth, customHeight)
         {
             RelativeSizeAxes = Axes.Both;
-
-            AddInternal(ScaledContent = new ScaledContainer
-            {
-                CustomWidth = customWidth,
-                RelativeSizeAxes = Axes.Both,
-                Children = new[]
-                {
-                    content = new Container
-                    {
-                        RelativeSizeAxes = Axes.Both,
-                    }
-                }
-            });
         }
 
         [BackgroundDependencyLoader]
@@ -94,22 +79,5 @@ namespace osu.Game.Rulesets.UI
         /// Creates the container that will be used to contain the <see cref="DrawableHitObject"/>s.
         /// </summary>
         protected virtual HitObjectContainer CreateHitObjectContainer() => new HitObjectContainer();
-
-        private class ScaledContainer : Container
-        {
-            /// <summary>
-            /// A value (in game pixels that we should scale our content to match).
-            /// </summary>
-            public float? CustomWidth;
-
-            //dividing by the customwidth will effectively scale our content to the required container size.
-            protected override Vector2 DrawScale => CustomWidth.HasValue ? new Vector2(DrawSize.X / CustomWidth.Value) : base.DrawScale;
-
-            protected override void Update()
-            {
-                base.Update();
-                RelativeChildSize = new Vector2(DrawScale.X, RelativeChildSize.Y);
-            }
-        }
     }
 }

osu.Game/Rulesets/UI/ScalableContainer.cs

@@ -0,0 +1,86 @@
+// 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.UI
+{
+    /// <summary>
+    /// A <see cref="Container"/> which can have its internal coordinate system scaled to a specific size.
+    /// </summary>
+    public class ScalableContainer : Container
+    {
+        /// <summary>
+        /// The scaled content.
+        /// </summary>
+        public readonly Container ScaledContent;
+
+        protected override Container<Drawable> Content => content;
+        private readonly Container content;
+
+        /// <summary>
+        /// A <see cref="Container"/> which can have its internal coordinate system scaled to a specific size.
+        /// </summary>
+        /// <param name="customWidth">The width to scale the internal coordinate space to.
+        /// May be null if scaling based on <paramref name="customHeight"/> is desired. If <paramref name="customHeight"/> is also null, no scaling will occur.
+        /// </param>
+        /// <param name="customHeight">The height to scale the internal coordinate space to.
+        /// May be null if scaling based on <paramref name="customWidth"/> is desired. If <paramref name="customWidth"/> is also null, no scaling will occur.
+        /// </param>
+        public ScalableContainer(float? customWidth = null, float? customHeight = null)
+        {
+            AddInternal(ScaledContent = new ScaledContainer
+            {
+                CustomWidth = customWidth,
+                CustomHeight = customHeight,
+                RelativeSizeAxes = Axes.Both,
+                Child = content = new Container { RelativeSizeAxes = Axes.Both }
+            });
+        }
+
+        public class ScaledContainer : Container
+        {
+            /// <summary>
+            /// The value to scale the width of the content to match.
+            /// If null, <see cref="CustomHeight"/> is used.
+            /// </summary>
+            public float? CustomWidth;
+
+            /// <summary>
+            /// The value to scale the height of the content to match.
+            /// if null, <see cref="CustomWidth"/> is used.
+            /// </summary>
+            public float? CustomHeight;
+
+            /// <summary>
+            /// The scale that is required for the size of the content to match <see cref="CustomWidth"/> and <see cref="CustomHeight"/>.
+            /// </summary>
+            private Vector2 sizeScale
+            {
+                get
+                {
+                    if (CustomWidth.HasValue && CustomHeight.HasValue)
+                        return Vector2.Divide(DrawSize, new Vector2(CustomWidth.Value, CustomHeight.Value));
+                    if (CustomWidth.HasValue)
+                        return new Vector2(DrawSize.X / CustomWidth.Value);
+                    if (CustomHeight.HasValue)
+                        return new Vector2(DrawSize.Y / CustomHeight.Value);
+                    return Vector2.One;
+                }
+            }
+
+            /// <summary>
+            /// Scale the content to the required container size by multiplying by <see cref="sizeScale"/>.
+            /// </summary>
+            protected override Vector2 DrawScale => sizeScale * base.DrawScale;
+
+            protected override void Update()
+            {
+                base.Update();
+                RelativeChildSize = sizeScale;
+            }
+        }
+    }
+}

osu.Game/Rulesets/UI/Scrolling/ScrollingPlayfield.cs

@@ -62,9 +62,14 @@ namespace osu.Game.Rulesets.UI.Scrolling
         /// Creates a new <see cref="ScrollingPlayfield"/>.
         /// </summary>
         /// <param name="direction">The direction in which <see cref="DrawableHitObject"/>s in this container should scroll.</param>
-        /// <param name="customWidth">Whether we want our internal coordinate system to be scaled to a specified width</param>
-        protected ScrollingPlayfield(ScrollingDirection direction, float? customWidth = null)
-            : base(customWidth)
+        /// <param name="customWidth">The width to scale the internal coordinate space to.
+        /// May be null if scaling based on <paramref name="customHeight"/> is desired. If <paramref name="customHeight"/> is also null, no scaling will occur.
+        /// </param>
+        /// <param name="customHeight">The height to scale the internal coordinate space to.
+        /// May be null if scaling based on <paramref name="customWidth"/> is desired. If <paramref name="customWidth"/> is also null, no scaling will occur.
+        /// </param>
+        protected ScrollingPlayfield(ScrollingDirection direction, float? customWidth = null, float? customHeight = null)
+            : base(customWidth, customHeight)
         {
             this.direction = direction;
         }

osu.Game/osu.Game.csproj

@@ -357,6 +357,7 @@
     <Compile Include="Overlays\Social\SocialPanel.cs" />
     <Compile Include="Rulesets\Mods\IApplicableToDrawableHitObject.cs" />
     <Compile Include="Rulesets\Objects\HitWindows.cs" />
+    <Compile Include="Rulesets\UI\ScalableContainer.cs" />
     <Compile Include="Screens\Play\PlayerSettings\VisualSettings.cs" />
     <Compile Include="Rulesets\Objects\CatmullApproximator.cs" />
     <Compile Include="Rulesets\UI\HitObjectContainer.cs" />