FIX: Implement caching for InputControlPath display name (#2344)

Author: josepmariapujol-unity

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Fixed
 
 - Improved New Input System warning dialog, Native Device Inputs Not Enabled [UUM-132151].
+- Fixed caching for InputControlPath display name [ISX-2501](https://jira.unity3d.com/browse/ISX-2501)
 
 ### Changed
 

Packages/com.unity.inputsystem/InputSystem/Editor/ControlPicker/InputControlPathEditor.cs

@@ -123,8 +123,12 @@ public void OnGUI(Rect rect, GUIContent label = null, SerializedProperty propert
                 return;
             }
 
-            ////TODO: this should be cached; generates needless GC churn
-            var displayName = InputControlPath.ToHumanReadableString(path);
+            // Cache the display name per path value and only recompute when the string actually changes.
+            if (!string.Equals(path, m_CachedPath, StringComparison.InvariantCultureIgnoreCase))
+            {
+                m_CachedPath = path;
+                m_CachedDisplayName = InputControlPath.ToHumanReadableString(path);
+            }
 
             // Either show dropdown control that opens path picker or show path directly as
             // text, if manual path editing is toggled on.
@@ -146,7 +150,7 @@ public void OnGUI(Rect rect, GUIContent label = null, SerializedProperty propert
             else
             {
                 // Dropdown that shows binding text and allows opening control picker.
-                if (EditorGUI.DropdownButton(bindingTextRect, new GUIContent(displayName), FocusType.Keyboard))
+                if (EditorGUI.DropdownButton(bindingTextRect, new GUIContent(m_CachedDisplayName), FocusType.Keyboard))
                 {
                     SetExpectedControlLayoutFromAttribute(serializedProperty);
                     ////TODO: for bindings that are part of composites, use the layout information from the [InputControl] attribute on the field
@@ -209,6 +213,9 @@ private void SetExpectedControlLayoutFromAttribute(SerializedProperty property)
         private string m_ExpectedControlLayout;
         private string[] m_ControlPathsToMatch;
 
+        private string m_CachedPath;
+        private string m_CachedDisplayName;
+
         private InputControlPickerDropdown m_PickerDropdown;
         private readonly InputControlPickerState m_PickerState;