Rewrite the way that cursor overrides are done game-wide

osu.Game/Graphics/Cursor/IProvideLocalCursor.cs

@@ -0,0 +1,22 @@
+// 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.Cursor;
+
+namespace osu.Game.Graphics.Cursor
+{
+    public interface IProvideLocalCursor : IDrawable
+    {
+        /// <summary>
+        /// The cursor provided by this <see cref="Drawable"/>.
+        /// </summary>
+        CursorContainer LocalCursor { get; }
+
+        /// <summary>
+        /// Whether the cursor provided by this <see cref="Drawable"/> should be displayed.
+        /// If this is false, a cursor occurring earlier in the draw hierarchy will be displayed instead.
+        /// </summary>
+        bool ProvidesUserCursor { get; }
+    }
+}

osu.Game/Graphics/Cursor/OsuCursorContainer.cs

@@ -0,0 +1,53 @@
+// 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.Linq;
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Framework.Graphics.Cursor;
+using osu.Framework.Input;
+
+namespace osu.Game.Graphics.Cursor
+{
+    public class OsuCursorContainer : Container, IProvideLocalCursor
+    {
+        protected override Container<Drawable> Content => content;
+        private readonly Container content;
+
+        public CursorContainer LocalCursor { get; }
+        public bool ProvidesUserCursor => true;
+
+        public OsuCursorContainer()
+        {
+            AddRangeInternal(new Drawable[]
+            {
+                LocalCursor = new MenuCursor { State = Visibility.Hidden },
+                content = new Container { RelativeSizeAxes = Axes.Both }
+            });
+        }
+
+        private InputManager inputManager;
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+            inputManager = GetContainingInputManager();
+        }
+
+        private IProvideLocalCursor currentTarget;
+        protected override void Update()
+        {
+            base.Update();
+
+            var newTarget = inputManager.HoveredDrawables.OfType<IProvideLocalCursor>().FirstOrDefault(t => t.ProvidesUserCursor) ?? this;
+
+            if (currentTarget == newTarget)
+                return;
+
+            currentTarget?.LocalCursor?.Hide();
+            newTarget.LocalCursor?.Show();
+
+            currentTarget = newTarget;
+        }
+    }
+}