Encapsulate mod hotkey selection logic in strategy pattern

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

@@ -139,7 +139,7 @@ namespace osu.Game.Tests.Visual.UserInterface
             {
                 RelativeSizeAxes = Axes.Both,
                 Padding = new MarginPadding(30),
-                Child = column = new ModColumn(ModType.DifficultyReduction, true, new[] { Key.Q, Key.W, Key.E, Key.R, Key.T, Key.Y, Key.U, Key.I, Key.O, Key.P })
+                Child = column = new ModColumn(ModType.DifficultyReduction, true)
                 {
                     Anchor = Anchor.Centre,
                     Origin = Anchor.Centre,

osu.Game/Overlays/Mods/Input/IModHotkeyHandler.cs

@@ -0,0 +1,22 @@
+// 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.Collections.Generic;
+using osuTK.Input;
+
+namespace osu.Game.Overlays.Mods.Input
+{
+    /// <summary>
+    /// Encapsulates strategies of handling mod hotkeys on the <see cref="ModSelectOverlay"/>.
+    /// </summary>
+    public interface IModHotkeyHandler
+    {
+        /// <summary>
+        /// Attempt to handle a press of the supplied <paramref name="hotkey"/> as a selection of one of the mods in <paramref name="availableMods"/>.
+        /// </summary>
+        /// <param name="hotkey">The key that was pressed by the user.</param>
+        /// <param name="availableMods">The list of currently available mods.</param>
+        /// <returns>Whether the <paramref name="hotkey"/> was handled as a mod selection/deselection.</returns>
+        bool HandleHotkeyPressed(Key hotkey, IEnumerable<ModState> availableMods);
+    }
+}

osu.Game/Overlays/Mods/Input/ModHotkeyHandler.cs

@@ -0,0 +1,30 @@
+// 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.Game.Rulesets.Mods;
+
+namespace osu.Game.Overlays.Mods.Input
+{
+    /// <summary>
+    /// Static factory class for <see cref="IModHotkeyHandler"/>s.
+    /// </summary>
+    public static class ModHotkeyHandler
+    {
+        /// <summary>
+        /// Creates an appropriate <see cref="IModHotkeyHandler"/> for the given <paramref name="modType"/>.
+        /// </summary>
+        public static IModHotkeyHandler Create(ModType modType)
+        {
+            switch (modType)
+            {
+                case ModType.DifficultyReduction:
+                case ModType.DifficultyIncrease:
+                case ModType.Automation:
+                    return SequentialModHotkeyHandler.Create(modType);
+
+                default:
+                    return new NoopModHotkeyHandler();
+            }
+        }
+    }
+}

osu.Game/Overlays/Mods/Input/NoopModHotkeyHandler.cs

@@ -0,0 +1,17 @@
+// 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.Collections.Generic;
+using osuTK.Input;
+
+namespace osu.Game.Overlays.Mods.Input
+{
+    /// <summary>
+    /// A no-op implementation of <see cref="IModHotkeyHandler"/>.
+    /// Used when a column is not handling any hotkeys at all.
+    /// </summary>
+    public class NoopModHotkeyHandler : IModHotkeyHandler
+    {
+        public bool HandleHotkeyPressed(Key hotkey, IEnumerable<ModState> availableMods) => false;
+    }
+}

osu.Game/Overlays/Mods/Input/SequentialModHotkeyHandler.cs

@@ -0,0 +1,58 @@
+// 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 System.Linq;
+using osu.Game.Rulesets.Mods;
+using osuTK.Input;
+
+namespace osu.Game.Overlays.Mods.Input
+{
+    /// <summary>
+    /// This implementation of <see cref="IModHotkeyHandler"/> receives a sequence of <see cref="Key"/>s,
+    /// and maps the sequence of keys onto the items it is provided in <see cref="HandleHotkeyPressed"/>.
+    /// In this case, particular mods are not bound to particular keys, the hotkeys are a byproduct of mod ordering.
+    /// </summary>
+    public class SequentialModHotkeyHandler : IModHotkeyHandler
+    {
+        public static SequentialModHotkeyHandler Create(ModType modType)
+        {
+            switch (modType)
+            {
+                case ModType.DifficultyReduction:
+                    return new SequentialModHotkeyHandler(new[] { Key.Q, Key.W, Key.E, Key.R, Key.T, Key.Y, Key.U, Key.I, Key.O, Key.P });
+
+                case ModType.DifficultyIncrease:
+                    return new SequentialModHotkeyHandler(new[] { Key.A, Key.S, Key.D, Key.F, Key.G, Key.H, Key.J, Key.K, Key.L });
+
+                case ModType.Automation:
+                    return new SequentialModHotkeyHandler(new[] { Key.Z, Key.X, Key.C, Key.V, Key.B, Key.N, Key.M });
+
+                default:
+                    throw new ArgumentOutOfRangeException(nameof(modType), modType, $"Cannot create {nameof(SequentialModHotkeyHandler)} for provided mod type");
+            }
+        }
+
+        private readonly Key[] toggleKeys;
+
+        private SequentialModHotkeyHandler(Key[] keys)
+        {
+            toggleKeys = keys;
+        }
+
+        public bool HandleHotkeyPressed(Key hotkey, IEnumerable<ModState> availableMods)
+        {
+            int index = Array.IndexOf(toggleKeys, hotkey);
+            if (index < 0)
+                return false;
+
+            var modState = availableMods.ElementAtOrDefault(index);
+            if (modState == null || modState.Filtered.Value)
+                return false;
+
+            modState.Active.Toggle();
+            return true;
+        }
+    }
+}

osu.Game/Overlays/Mods/ModColumn.cs

@@ -21,10 +21,10 @@ using osu.Game.Graphics;
 using osu.Game.Graphics.Containers;
 using osu.Game.Graphics.UserInterface;
 using osu.Game.Localisation;
+using osu.Game.Overlays.Mods.Input;
 using osu.Game.Rulesets.Mods;
 using osuTK;
 using osuTK.Graphics;
-using osuTK.Input;
 
 namespace osu.Game.Overlays.Mods
 {
@@ -70,7 +70,7 @@ namespace osu.Game.Overlays.Mods
 
         protected virtual ModPanel CreateModPanel(ModState mod) => new ModPanel(mod);
 
-        private readonly Key[]? toggleKeys;
+        private readonly IModHotkeyHandler hotkeyHandler;
 
         private readonly TextFlowContainer headerText;
         private readonly Box headerBackground;
@@ -86,10 +86,10 @@ namespace osu.Game.Overlays.Mods
 
         private const float header_height = 42;
 
-        public ModColumn(ModType modType, bool allowBulkSelection, Key[]? toggleKeys = null)
+        public ModColumn(ModType modType, bool allowBulkSelection)
         {
             ModType = modType;
-            this.toggleKeys = toggleKeys;
+            hotkeyHandler = ModHotkeyHandler.Create(modType);
 
             Width = 320;
             RelativeSizeAxes = Axes.Y;
@@ -425,17 +425,10 @@ namespace osu.Game.Overlays.Mods
 
         protected override bool OnKeyDown(KeyDownEvent e)
         {
-            if (e.ControlPressed || e.AltPressed || e.SuperPressed) return false;
+            if (e.ControlPressed || e.AltPressed || e.SuperPressed || e.Repeat)
-            if (toggleKeys == null) return false;
+                return false;
 
-            int index = Array.IndexOf(toggleKeys, e.Key);
+            return hotkeyHandler.HandleHotkeyPressed(e.Key, availableMods);
-            if (index < 0) return false;
-
-            var modState = availableMods.ElementAtOrDefault(index);
-            if (modState == null || modState.Filtered.Value) return false;
-
-            modState.Active.Toggle();
-            return true;
         }
 
         #endregion

osu.Game/Overlays/Mods/ModSelectOverlay.cs

@@ -21,7 +21,6 @@ using osu.Game.Localisation;
 using osu.Game.Rulesets.Mods;
 using osu.Game.Utils;
 using osuTK;
-using osuTK.Input;
 
 namespace osu.Game.Overlays.Mods
 {
@@ -68,7 +67,7 @@ namespace osu.Game.Overlays.Mods
         /// </summary>
         protected virtual bool AllowCustomisation => true;
 
-        protected virtual ModColumn CreateModColumn(ModType modType, Key[]? toggleKeys = null) => new ModColumn(modType, false, toggleKeys);
+        protected virtual ModColumn CreateModColumn(ModType modType) => new ModColumn(modType, false);
 
         protected virtual IReadOnlyList<Mod> ComputeNewModsFromSelection(IReadOnlyList<Mod> oldSelection, IReadOnlyList<Mod> newSelection) => newSelection;
 
@@ -160,9 +159,9 @@ namespace osu.Game.Overlays.Mods
                                 Padding = new MarginPadding { Bottom = 10 },
                                 Children = new[]
                                 {
-                                    createModColumnContent(ModType.DifficultyReduction, new[] { Key.Q, Key.W, Key.E, Key.R, Key.T, Key.Y, Key.U, Key.I, Key.O, Key.P }),
+                                    createModColumnContent(ModType.DifficultyReduction),
-                                    createModColumnContent(ModType.DifficultyIncrease, new[] { Key.A, Key.S, Key.D, Key.F, Key.G, Key.H, Key.J, Key.K, Key.L }),
+                                    createModColumnContent(ModType.DifficultyIncrease),
-                                    createModColumnContent(ModType.Automation, new[] { Key.Z, Key.X, Key.C, Key.V, Key.B, Key.N, Key.M }),
+                                    createModColumnContent(ModType.Automation),
                                     createModColumnContent(ModType.Conversion),
                                     createModColumnContent(ModType.Fun)
                                 }
@@ -264,9 +263,9 @@ namespace osu.Game.Overlays.Mods
                 column.DeselectAll();
         }
 
-        private ColumnDimContainer createModColumnContent(ModType modType, Key[]? toggleKeys = null)
+        private ColumnDimContainer createModColumnContent(ModType modType)
         {
-            var column = CreateModColumn(modType, toggleKeys).With(column =>
+            var column = CreateModColumn(modType).With(column =>
             {
                 // spacing applied here rather than via `columnFlow.Spacing` to avoid uneven gaps when some of the columns are hidden.
                 column.Margin = new MarginPadding { Right = 10 };

osu.Game/Overlays/Mods/UserModSelectOverlay.cs

@@ -1,14 +1,10 @@
 // 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.
 
-#nullable disable
-
 using System.Collections.Generic;
 using System.Linq;
-using JetBrains.Annotations;
 using osu.Game.Rulesets.Mods;
 using osu.Game.Utils;
-using osuTK.Input;
 
 namespace osu.Game.Overlays.Mods
 {
@@ -19,7 +15,7 @@ namespace osu.Game.Overlays.Mods
         {
         }
 
-        protected override ModColumn CreateModColumn(ModType modType, Key[] toggleKeys = null) => new UserModColumn(modType, false, toggleKeys);
+        protected override ModColumn CreateModColumn(ModType modType) => new UserModColumn(modType, false);
 
         protected override IReadOnlyList<Mod> ComputeNewModsFromSelection(IReadOnlyList<Mod> oldSelection, IReadOnlyList<Mod> newSelection)
         {
@@ -44,8 +40,8 @@ namespace osu.Game.Overlays.Mods
 
         private class UserModColumn : ModColumn
         {
-            public UserModColumn(ModType modType, bool allowBulkSelection, [CanBeNull] Key[] toggleKeys = null)
+            public UserModColumn(ModType modType, bool allowBulkSelection)
-                : base(modType, allowBulkSelection, toggleKeys)
+                : base(modType, allowBulkSelection)
             {
             }
 

osu.Game/Screens/OnlinePlay/FreeModSelectOverlay.cs

@@ -11,7 +11,6 @@ using osu.Framework.Graphics;
 using osu.Game.Graphics.UserInterface;
 using osu.Game.Overlays.Mods;
 using osu.Game.Rulesets.Mods;
-using osuTK.Input;
 
 namespace osu.Game.Screens.OnlinePlay
 {
@@ -33,7 +32,7 @@ namespace osu.Game.Screens.OnlinePlay
             IsValidMod = _ => true;
         }
 
-        protected override ModColumn CreateModColumn(ModType modType, Key[] toggleKeys = null) => new ModColumn(modType, true, toggleKeys);
+        protected override ModColumn CreateModColumn(ModType modType) => new ModColumn(modType, true);
 
         protected override IEnumerable<ShearedButton> CreateFooterButtons() => base.CreateFooterButtons().Prepend(
             new SelectAllModsButton(this)