From d16d899a67415dff193f5eb11a272cd99265916a Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Thu, 11 Jan 2024 15:46:59 +0900
Subject: [PATCH] Remove allocation overhead from `KeyBindingContainer` key
 handling

---
 .../Input/Bindings/KeyBindingContainer.cs     | 37 +++++++++++++------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/osu.Framework/Input/Bindings/KeyBindingContainer.cs b/osu.Framework/Input/Bindings/KeyBindingContainer.cs
index da69d71c05..6fcb2ba06b 100644
--- a/osu.Framework/Input/Bindings/KeyBindingContainer.cs
+++ b/osu.Framework/Input/Bindings/KeyBindingContainer.cs
@@ -202,6 +202,8 @@ private bool handleRepeat(InputState state)
             return drawables.FirstOrDefault(d => triggerKeyBindingEvent(d, pressEvent)) != null;
         }
 
+        private readonly List<IKeyBinding> newlyPressed = new List<IKeyBinding>();
+
         private bool handleNewPressed(InputState state, InputKey newKey, Vector2? scrollDelta = null, bool isPrecise = false)
         {
             pressedInputKeys.Add(newKey);
@@ -210,10 +212,20 @@ private bool handleNewPressed(InputState state, InputKey newKey, Vector2? scroll
             var pressedCombination = new KeyCombination(pressedInputKeys);
 
             bool handled = false;
-            var bindings = KeyBindings?.Except(pressedBindings) ?? Enumerable.Empty<IKeyBinding>();
 
-            var newlyPressed = bindings.Where(m =>
-                m.KeyCombination.IsPressed(pressedCombination, matchingMode));
+            newlyPressed.Clear();
+
+            if (KeyBindings != null)
+            {
+                foreach (IKeyBinding binding in KeyBindings)
+                {
+                    if (pressedBindings.Contains(binding))
+                        continue;
+
+                    if (binding.KeyCombination.IsPressed(pressedCombination, matchingMode))
+                        newlyPressed.Add(binding);
+                }
+            }
 
             if (KeyCombination.IsModifierKey(newKey))
             {
@@ -221,11 +233,15 @@ private bool handleNewPressed(InputState state, InputKey newKey, Vector2? scroll
                 // lambda expression is used so that the delegate is cached (see: https://github.com/dotnet/roslyn/issues/5835)
                 // TODO: remove when we switch to .NET 7.
                 // ReSharper disable once ConvertClosureToMethodGroup
-                newlyPressed = newlyPressed.Where(b => b.KeyCombination.Keys.All(key => KeyCombination.IsModifierKey(key)));
+                for (int i = 0; i < newlyPressed.Count; i++)
+                {
+                    if (!newlyPressed[i].KeyCombination.Keys.All(key => KeyCombination.IsModifierKey(key)))
+                        newlyPressed.RemoveAt(i--);
+                }
             }
 
             // we want to always handle bindings with more keys before bindings with less.
-            newlyPressed = newlyPressed.OrderByDescending(b => b.KeyCombination.Keys.Length).ToList();
+            newlyPressed.Sort(static (a, b) => b.KeyCombination.Keys.Length.CompareTo(a.KeyCombination.Keys.Length));
 
             pressedBindings.AddRange(newlyPressed);
 
@@ -343,14 +359,13 @@ private void handleNewReleased(InputState state, InputKey releasedKey)
             // we don't want to consider exact matching here as we are dealing with bindings, not actions.
             var pressedCombination = new KeyCombination(pressedInputKeys);
 
-            var newlyReleased = pressedInputKeys.Count == 0
-                ? pressedBindings.ToList()
-                : pressedBindings.Where(b => !b.KeyCombination.IsPressed(pressedCombination, KeyCombinationMatchingMode.Any)).ToList();
-
-            foreach (var binding in newlyReleased)
+            for (int i = 0; i < pressedBindings.Count; i++)
             {
-                pressedBindings.Remove(binding);
+                var binding = pressedBindings[i];
+
+                if (binding.KeyCombination.IsPressed(pressedCombination, KeyCombinationMatchingMode.Any)) continue;
 
+                pressedBindings.RemoveAt(i--);
                 PropagateReleased(getInputQueue(binding).Where(d => d.IsRootedAt(this)), state, binding.GetAction<T>());
                 keyBindingQueues[binding].Clear();
             }