Allow AsyncLoadContainer's content to be a Drawable.

osu.Framework.VisualTests/Tests/TestCaseOnlineTextures.cs

@@ -46,7 +46,7 @@ public override void Reset()
                     Size = new Vector2(128),
                     Children = new Drawable[]
                     {
-                        new DelayedLoadContainer(new Container
+                        new DelayedLoadWrapper(new Container
                         {
                             RelativeSizeAxes = Axes.Both,
                             OnLoadComplete = d =>
@@ -73,7 +73,7 @@ public override void Reset()
                     }
                 });
 
-            var childrenWithAvatarsLoaded = flow.Children.Where(c => c.Children.OfType<DelayedLoadContainer>().First().Children.FirstOrDefault()?.IsLoaded ?? false);
+            var childrenWithAvatarsLoaded = flow.Children.Where(c => c.Children.OfType<DelayedLoadWrapper>().First().Children.FirstOrDefault()?.IsLoaded ?? false);
 
             AddWaitStep(10);
             AddStep("scroll down", () => scroll.ScrollToEnd());

osu.Framework/Graphics/Containers/AsyncLoadContainer.cs → osu.Framework/Graphics/Containers/AsyncLoadWrapper.cs

@@ -8,24 +8,31 @@
 namespace osu.Framework.Graphics.Containers
 {
     /// <summary>
-    /// A container which asynchronously loads its children.
+    /// A container which asynchronously loads specified content.
     /// </summary>
-    public class AsyncLoadContainer : Container
+    public class AsyncLoadWrapper : Container
     {
         /// <param name="content">The content which should be asynchronously loaded. Note that the <see cref="Drawable.RelativeSizeAxes"/> and <see cref="Container{T}.AutoSizeAxes"/> of this container
-        /// will be transferred as the default for this <see cref="AsyncLoadContainer"/>.</param>
-        public AsyncLoadContainer(Container content)
+        /// will be transferred as the default for this <see cref="AsyncLoadWrapper"/>.</param>
+        public AsyncLoadWrapper(Drawable content)
         {
             if (content == null)
-                throw new ArgumentNullException(nameof(content), $@"{nameof(AsyncLoadContainer)} required non-null {nameof(content)}.");
+                throw new ArgumentNullException(nameof(content), $@"{nameof(AsyncLoadWrapper)} required non-null {nameof(content)}.");
 
             this.content = content;
 
             RelativeSizeAxes = content.RelativeSizeAxes;
-            AutoSizeAxes = content.AutoSizeAxes;
+            AutoSizeAxes = (content as IContainer)?.AutoSizeAxes ?? AutoSizeAxes;
         }
 
-        private readonly Container content;
+        protected sealed override Container<Drawable> Content => base.Content;
+
+        public override void Add(Drawable drawable)
+        {
+            throw new InvalidOperationException($@"{nameof(AsyncLoadWrapper)} doesn't support manually adding children. Please specify loadable conetnt in the constructor.");
+        }
+
+        private readonly Drawable content;
 
         protected virtual bool ShouldLoadContent => true;
 

osu.Framework/Graphics/Containers/DelayedLoadContainer.cs → osu.Framework/Graphics/Containers/DelayedLoadWrapper.cs

@@ -7,12 +7,12 @@
 namespace osu.Framework.Graphics.Containers
 {
     /// <summary>
-    /// A container which delays the loading of children until we have been on-screen for a specified duration.
+    /// A wrapper which delays the loading of children until we have been on-screen for a specified duration.
     /// In order to benefit from delayed load, we must be inside a <see cref="ScrollContainer"/>.
     /// </summary>
-    public class DelayedLoadContainer : AsyncLoadContainer
+    public class DelayedLoadWrapper : AsyncLoadWrapper
     {
-        public DelayedLoadContainer(Container content)
+        public DelayedLoadWrapper(Drawable content)
             : base(content)
         {
         }

osu.Framework/Graphics/Containers/IContainer.cs

@@ -15,6 +15,8 @@ public interface IContainer : IDrawable
         void InvalidateFromChild(Invalidation invalidation);
 
         void Clear(bool dispose = true);
+
+        Axes AutoSizeAxes { get; set; }
     }
 
     public interface IContainerEnumerable<out T> : IContainer

osu.Framework/Graphics/Containers/ScrollContainer.cs

@@ -12,7 +12,7 @@
 
 namespace osu.Framework.Graphics.Containers
 {
-    public class ScrollContainer : Container, DelayedLoadContainer.IOnScreenOptimisingContainer
+    public class ScrollContainer : Container, DelayedLoadWrapper.IOnScreenOptimisingContainer
     {
         /// <summary>
         /// Determines whether the scroll dragger appears on the left side. If not, then it always appears on the right side.

osu.Framework/osu.Framework.csproj

@@ -110,8 +110,8 @@
     <Compile Include="Extensions\ExtensionMethods.cs" />
     <Compile Include="Extensions\IEnumerableExtensions\EnumerableExtensions.cs" />
     <Compile Include="Extensions\TypeExtensions\TypeExtensions.cs" />
-    <Compile Include="Graphics\Containers\AsyncLoadContainer.cs" />
-    <Compile Include="Graphics\Containers\DelayedLoadContainer.cs" />
+    <Compile Include="Graphics\Containers\AsyncLoadWrapper.cs" />
+    <Compile Include="Graphics\Containers\DelayedLoadWrapper.cs" />
     <Compile Include="Graphics\Containers\FillFlowContainer.cs" />
     <Compile Include="Graphics\Containers\TabbableContainer.cs" />
     <Compile Include="Graphics\UserInterface\BasicCheckbox.cs" />