Optimize Theming hot paths: O(1) hash cache in Theme, delegate caching in BaseThemeBinder, Zero-GC dynamic listeners in ThemeDataSource, and add comprehensive test suite

Author: keveleigh

org.mixedrealitytoolkit.theming/AssemblyInfo.cs

@@ -8,6 +8,8 @@
 [assembly: AssemblyCopyright("Copyright (c) Mixed Reality Toolkit Contributors")]
 
 [assembly: InternalsVisibleTo("MixedReality.Toolkit.Theming.Editor")]
+[assembly: InternalsVisibleTo("MixedReality.Toolkit.Theming.Editor.Tests")]
+[assembly: InternalsVisibleTo("MixedReality.Toolkit.Theming.Runtime.Tests")]
 
 // The AssemblyVersion attribute is checked-in and is recommended not to be changed often.
 // https://docs.microsoft.com/troubleshoot/visualstudio/general/assembly-version-assembly-file-version

org.mixedrealitytoolkit.theming/Binders/BaseThemeBinder.cs

@@ -48,19 +48,22 @@ protected void OnThemeChanged(ChangeEvent<Theme> changeEvent)
             Apply(value);
         }
 
+        private UnityEngine.Events.UnityAction<ChangeEvent<Theme>> cachedOnThemeChanged;
+
         void IBinder.Subscribe(ThemeDataSource themeDataSource)
         {
             if (themeDataSource != null)
             {
-                themeDataSource.AddListener(OnThemeChanged);
+                cachedOnThemeChanged ??= OnThemeChanged;
+                themeDataSource.AddListener(cachedOnThemeChanged);
             }
         }
 
         void IBinder.Unsubscribe(ThemeDataSource themeDataSource)
         {
-            if (themeDataSource != null)
+            if (themeDataSource != null && cachedOnThemeChanged != null)
             {
-                themeDataSource.RemoveListener(OnThemeChanged);
+                themeDataSource.RemoveListener(cachedOnThemeChanged);
             }
         }
     }

org.mixedrealitytoolkit.theming/CHANGELOG.md

@@ -9,6 +9,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 * Added serializable theme item data types for booleans. [PR #1130](https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/pull/1130)
 * Added built-in binders for skybox materials and behaviour enabled states. [PR #1130](https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/pull/1130)
 * Added edit mode tests for validating custom theming types and their dependencies. [PR #1133](https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/pull/1133)
+* Added runtime performance benchmark and regression tests for theming hot paths. [PR #1133](https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/pull/1133)
+
+### Changed
+
+* Optimized `Theme.TryGetItemData<T>` from an $O(N)$ linear list scan to an $O(1)$ hash table lookup with automatic cache invalidation on deserialization, inspector modifications, and enable events. [PR #1133](https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/pull/1133)
+* Optimized `BaseThemeBinder` by caching `UnityAction<ChangeEvent<Theme>>` delegates, eliminating heap allocations during repeated subscribe/unsubscribe cycles. [PR #1133](https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/pull/1133)
+* Optimized `ThemeDataSource` to route programmatic subscribers through a Zero-GC dynamic listener list, avoiding delegate allocations while preserving inspector `UnityEvent` invocations. [PR #1133](https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/pull/1133)
 
 ## [1.0.0-pre.1] - 2026-05-20
 

org.mixedrealitytoolkit.theming/Tests/Runtime.meta

@@ -0,0 +1,27 @@
+{
+    "name": "MixedReality.Toolkit.Theming.Runtime.Tests",
+    "rootNamespace": "MixedReality.Toolkit.Theming.Tests.Runtime",
+    "references": [
+        "MixedReality.Toolkit.Core",
+        "MixedReality.Toolkit.Core.TestUtilities",
+        "MixedReality.Toolkit.Theming",
+        "MixedReality.Toolkit.UXCore",
+        "MixedReality.Toolkit.UXCore.Theming",
+        "UnityEngine.TestRunner",
+        "UnityEditor.TestRunner",
+        "Unity.TextMeshPro"
+    ],
+    "includePlatforms": [],
+    "excludePlatforms": [],
+    "allowUnsafeCode": false,
+    "overrideReferences": true,
+    "precompiledReferences": [
+        "nunit.framework.dll"
+    ],
+    "autoReferenced": false,
+    "defineConstraints": [
+        "UNITY_INCLUDE_TESTS"
+    ],
+    "versionDefines": [],
+    "noEngineReferences": false
+}