Implement a three-state menu item

osu.Game.Tests/Visual/UserInterface/TestSceneThreeStateMenuItem.cs

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+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using System;
+using System.Collections.Generic;
+using osu.Framework.Graphics;
+using osu.Game.Graphics.UserInterface;
+
+namespace osu.Game.Tests.Visual.UserInterface
+{
+    public class TestSceneThreeStateMenuItem : OsuTestScene
+    {
+        public override IReadOnlyList<Type> RequiredTypes => new[]
+        {
+            typeof(OsuMenu),
+            typeof(ThreeStateMenuItem),
+            typeof(DrawableStatefulMenuItem)
+        };
+
+        public TestSceneThreeStateMenuItem()
+        {
+            Add(new OsuMenu(Direction.Vertical, true)
+            {
+                Anchor = Anchor.Centre,
+                Origin = Anchor.Centre,
+                Items = new[]
+                {
+                    new ThreeStateMenuItem("First"),
+                    new ThreeStateMenuItem("Second") { State = { Value = ThreeStates.Indeterminate } },
+                    new ThreeStateMenuItem("Third") { State = { Value = ThreeStates.Enabled } },
+                }
+            });
+        }
+    }
+}

osu.Game/Graphics/UserInterface/ThreeStateMenuItem.cs

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+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Graphics.Sprites;
+
+namespace osu.Game.Graphics.UserInterface
+{
+    public class ThreeStateMenuItem : StatefulMenuItem<ThreeStates>
+    {
+        public ThreeStateMenuItem(string text, MenuItemType type = MenuItemType.Standard)
+            : base(text, type, getNextState)
+        {
+        }
+
+        public override IconUsage? GetIconForState(ThreeStates state)
+        {
+            switch (state)
+            {
+                case ThreeStates.Indeterminate:
+                    return FontAwesome.Regular.Circle;
+
+                case ThreeStates.Enabled:
+                    return FontAwesome.Solid.Check;
+            }
+
+            return null;
+        }
+
+        private static ThreeStates getNextState(ThreeStates state)
+        {
+            switch (state)
+            {
+                case ThreeStates.Disabled:
+                    return ThreeStates.Enabled;
+
+                case ThreeStates.Indeterminate:
+                    return ThreeStates.Enabled;
+
+                case ThreeStates.Enabled:
+                    return ThreeStates.Disabled;
+            }
+
+            return ThreeStates.Disabled;
+        }
+    }
+
+    public enum ThreeStates
+    {
+        Disabled,
+        Indeterminate,
+        Enabled
+    }
+}