Share item cycling logic with GameplayMenuOverlay

osu.Game/Graphics/Containers/SelectionCycleFillFlowContainer.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;
+using osu.Framework.Graphics.Containers;
+using osu.Game.Graphics.UserInterface;
+
+namespace osu.Game.Graphics.Containers
+{
+    /// <summary>
+    /// A FillFlowContainer that provides functionality to cycle selection between children
+    /// The selection wraps around when overflowing past the first or last child.
+    /// </summary>
+    public class SelectionCycleFillFlowContainer<T> : FillFlowContainer<T> where T : Drawable, ISelectable
+    {
+        private int selectedIndex = -1;
+
+        private void setSelected(int value)
+        {
+            if (selectedIndex == value)
+                return;
+
+            // Deselect the previously-selected button
+            if (selectedIndex != -1)
+                this[selectedIndex].Selected = false;
+
+            selectedIndex = value;
+
+            // Select the newly-selected button
+            if (selectedIndex != -1)
+                this[selectedIndex].Selected = true;
+        }
+
+        public void SelectNext()
+        {
+            if (selectedIndex == -1 || selectedIndex == Count - 1)
+                setSelected(0);
+            else
+                setSelected(selectedIndex + 1);
+        }
+
+        public void SelectPrevious()
+        {
+            if (selectedIndex == -1 || selectedIndex == 0)
+                setSelected(Count - 1);
+            else
+                setSelected(selectedIndex - 1);
+        }
+
+        public void Deselect() => setSelected(-1);
+        public void Select(T item) => setSelected(IndexOf(item));
+
+        public T Selected => (selectedIndex >= 0 && selectedIndex < Count) ? this[selectedIndex] : null;
+    }
+}