Refactor InputCountController to not require being added to foreign body via Attach

I've made the flow match `ClicksPerSecondCalculator` as close as
possible. Hopefully this reads better.

osu.Game.Tests/Visual/Gameplay/TestSceneKeyCounter.cs

@@ -48,13 +48,16 @@ namespace osu.Game.Tests.Visual.Gameplay
                 }
             };
 
-            controller.AddRange(new InputTrigger[]
+            var inputTriggers = new InputTrigger[]
             {
                 new KeyCounterKeyboardTrigger(Key.X),
                 new KeyCounterKeyboardTrigger(Key.X),
                 new KeyCounterMouseTrigger(MouseButton.Left),
                 new KeyCounterMouseTrigger(MouseButton.Right),
-            });
+            };
+
+            AddRange(inputTriggers);
+            controller.AddRange(inputTriggers);
 
             AddStep("Add random", () =>
             {

osu.Game/Rulesets/UI/RulesetInputManager.cs

@@ -162,25 +162,22 @@ namespace osu.Game.Rulesets.UI
 
         public void Attach(InputCountController inputCountController)
         {
-            KeyBindingContainer.Add(inputCountController);
+            var triggers = KeyBindingContainer.DefaultKeyBindings
-
-            inputCountController.AddRange(KeyBindingContainer.DefaultKeyBindings
                                               .Select(b => b.GetAction<T>())
                                               .Distinct()
                                               .OrderBy(action => action)
-                                                             .Select(action => new KeyCounterActionTrigger<T>(action)));
+                                              .Select(action => new KeyCounterActionTrigger<T>(action))
+                                              .ToArray();
+
+            KeyBindingContainer.AddRange(triggers);
+            inputCountController.AddRange(triggers);
         }
 
         #endregion
 
         #region Keys per second Counter Attachment
 
-        public void Attach(ClicksPerSecondCalculator calculator)
+        public void Attach(ClicksPerSecondCalculator calculator) => KeyBindingContainer.Add(new ActionListener(calculator));
-        {
-            var listener = new ActionListener(calculator);
-
-            KeyBindingContainer.Add(listener);
-        }
 
         private partial class ActionListener : Component, IKeyBindingHandler<T>
         {

osu.Game/Screens/Play/HUD/InputCountController.cs

@@ -1,7 +1,6 @@
 // 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.Bindables;
 using osu.Framework.Extensions.IEnumerableExtensions;
@@ -17,26 +16,20 @@ namespace osu.Game.Screens.Play.HUD
     {
         public readonly Bindable<bool> IsCounting = new BindableBool(true);
 
-        public event Action<InputTrigger>? OnNewTrigger;
+        private readonly BindableList<InputTrigger> triggers = new BindableList<InputTrigger>();
 
-        private readonly Container<InputTrigger> triggers;
+        public IBindableList<InputTrigger> Triggers => triggers;
 
-        public IReadOnlyList<InputTrigger> Triggers => triggers;
+        public void AddRange(IEnumerable<InputTrigger> triggers) => triggers.ForEach(Add);
-
-        public InputCountController()
-        {
-            InternalChild = triggers = new Container<InputTrigger>();
-        }
 
         public void Add(InputTrigger trigger)
         {
+            // Note that these triggers are not added to the hierarchy here. It is presumed they are added externally at a
+            // more correct location (ie. inside a RulesetInputManager).
             triggers.Add(trigger);
             trigger.IsCounting.BindTo(IsCounting);
-            OnNewTrigger?.Invoke(trigger);
         }
 
-        public void AddRange(IEnumerable<InputTrigger> inputTriggers) => inputTriggers.ForEach(Add);
-
         public override bool HandleNonPositionalInput => true;
         public override bool HandlePositionalInput => true;
     }

osu.Game/Screens/Play/HUD/KeyCounterDisplay.cs

@@ -1,11 +1,9 @@
 // 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 System.Collections.Specialized;
 using osu.Framework.Allocation;
 using osu.Framework.Bindables;
-using osu.Framework.Extensions.IEnumerableExtensions;
-using osu.Framework.Extensions.ObjectExtensions;
 using osu.Framework.Graphics.Containers;
 using osu.Game.Configuration;
 using osu.Game.Rulesets.UI;
@@ -24,35 +22,17 @@ namespace osu.Game.Screens.Play.HUD
         /// </summary>
         public Bindable<bool> AlwaysVisible { get; } = new Bindable<bool>(true);
 
-        /// <summary>
-        /// The <see cref="KeyCounter"/>s contained in this <see cref="KeyCounterDisplay"/>.
-        /// </summary>
-        public IEnumerable<KeyCounter> Counters => KeyFlow;
-
         protected abstract FillFlowContainer<KeyCounter> KeyFlow { get; }
 
         protected readonly Bindable<bool> ConfigVisibility = new Bindable<bool>();
 
+        private readonly IBindableList<InputTrigger> triggers = new BindableList<InputTrigger>();
+
         [Resolved]
         private InputCountController controller { get; set; } = null!;
 
         protected abstract void UpdateVisibility();
 
-        /// <summary>
-        /// Add a <see cref="InputTrigger"/> to this display.
-        /// </summary>
-        public void Add(InputTrigger trigger)
-        {
-            var keyCounter = CreateCounter(trigger);
-
-            KeyFlow.Add(keyCounter);
-        }
-
-        /// <summary>
-        /// Add a range of <see cref="InputTrigger"/> to this display.
-        /// </summary>
-        public void AddRange(IEnumerable<InputTrigger> triggers) => triggers.ForEach(Add);
-
         protected abstract KeyCounter CreateCounter(InputTrigger trigger);
 
         [BackgroundDependencyLoader]
@@ -68,19 +48,18 @@ namespace osu.Game.Screens.Play.HUD
         {
             base.LoadComplete();
 
-            controller.OnNewTrigger += Add;
+            triggers.BindTo(controller.Triggers);
-            AddRange(controller.Triggers);
+            triggers.BindCollectionChanged(triggersChanged, true);
 
             AlwaysVisible.BindValueChanged(_ => UpdateVisibility());
             ConfigVisibility.BindValueChanged(_ => UpdateVisibility(), true);
         }
 
-        protected override void Dispose(bool isDisposing)
+        private void triggersChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
-            base.Dispose(isDisposing);
+            KeyFlow.Clear();
-
+            foreach (var trigger in controller.Triggers)
-            if (controller.IsNotNull())
+                KeyFlow.Add(CreateCounter(trigger));
-                controller.OnNewTrigger -= Add;
         }
 
         public bool UsesFixedAnchor { get; set; }

osu.Game/Screens/Play/HUDOverlay.cs

@@ -111,9 +111,6 @@ namespace osu.Game.Screens.Play
 
             RelativeSizeAxes = Axes.Both;
 
-            // intentionally not added to hierarchy here as it will be attached via `BindDrawableRuleset()`.
-            InputCountController = new InputCountController();
-
             Children = new[]
             {
                 CreateFailingLayer(),
@@ -161,6 +158,7 @@ namespace osu.Game.Screens.Play
                     Spacing = new Vector2(5)
                 },
                 clicksPerSecondCalculator = new ClicksPerSecondCalculator(),
+                InputCountController = new InputCountController(),
             };
 
             hideTargets = new List<Drawable> { mainComponents, rulesetComponents, topRightElements };