code refine

README-ZH.md

 #### 七、图片导入设置
 请将图片放入StreamingAssets下，而后用```Image.file```读取
 
-#### 八、自动降低帧率
-目前在默认情况下，为了保证流畅度，项目在各个平台上均会以最高的刷新频率运行。不过您可以通过在代码中设置```SchedulerBinding.MEnableAutoAdjustFramerate = true```的方式来开启自动降帧的功能：该功能开启后，在UI内容不变的情况下我们将降低项目的刷新率来降低耗电。
+#### 八、移动设备优化
+目前在默认情况下，为了保证流畅度，项目在各个平台上均会以最高的刷新频率运行。不过您可以通过在代码中设置```UIWidgetsGlobalConfiguration.EnableAutoAdjustFramerate = true```的方式来开启自动降帧的功能：该功能开启后，在UI内容不变的情况下我们将降低项目的刷新率来降低耗电。
+
+在移动设备上UI绘制的流畅度受到GC影响较大。项目默认会开启OnDemandGC来接管并优化整体GC效果。如果您不需要GC被UIWidgets控制，请在代码中设置```UIWidgetsGlobalConfiguration.EnableIncrementalGC = false```。
 
 
 ## 调试UIWidgets应用程序
-如果想在runtime选择是否debug，请修改文件```com.unity.uiwidgets/com.unity.uiwidgets/Runtime/foundation/debug.cs```中的```static bool debugEnableAtRuntimeInternal```
+如果想在runtime开启debug模式，请在项目代码中设置```UIWidgetsGlobalConfiguration.EnableDebugAtRuntime = true```。在默认情况下debug模式为关闭状态。
 
 ## 使用Window Scope保护外部调用
 如果您在调试时遇到 `AssertionError: Window.instance is null` 或者在调用 `Window.instance` 时得到空指针, 那么您需要

README.md

 #### Image Import Setting
 Please put images under StreamingAssets folder, a and loading it using ```Image.file```.
 
-#### Automatic Framerate Adjustment
-You can enable this feature by setting ```SchedulerBinding.MEnableAutoAdjustFramerate = true``` in your project, which will automatically drop the frame rate of your App to 0 if the UI contents of UIWidgetsPanel is not changed for some time. This will help to prevent battery drain on mobile devices significantly. 
+#### Performance Optimization on Mobile devices
+By setting ```UIWidgetsGlobalConfiguration.EnableAutoAdjustFramerate = true``` in your project, UIWidgets will drop the frame rate of your App to 0 if the UI contents of UIWidgetsPanel is not changed for some time. This will help to prevent battery drain on mobile devices significantly. Note that this feature is disabled by default.
-Note that this feature is disabled by default though.
+Long time garbage collection may cause App to stuck frequently. In UIWidgets we enable incremental garbage collection to avoid it. However, you can disable this feature by setting ```UIWidgetsGlobalConfiguration.EnableIncrementalGC = false```.
-If you want to change different mode in runtime, please modify the file “com.unity.uiwidgets/com.unity.uiwidgets/Runtime/foundation/debug.cs” by making “static bool debugEnableAtRuntimeInternal” to true or false. Note that the value is set to false by default.
+You can also enable debug mode in runtime by setting ```UIWidgetsGlobalConfiguration.EnableDebugAtRuntime = true``` in your project. Note that this value is set to false by default.
 
 ## Using Window Scope
 If you see the error `AssertionError: Window.instance is null` or null pointer error of `Window.instance`,

com.unity.uiwidgets/Runtime/engine/UIWidgetsPanel.cs

                 Window.instance.onMetricsChanged?.Invoke();
             }
         }
-        
-        // 8 MB
-        const long kCollectAfterAllocating = 8 * 1024 * 1024;
-        
-        long lastFrameMemory = 0;
-        long nextCollectAt = 0;
-        
+
         protected virtual void Update() {
             if (!_viewMetricsCallbackRegistered) {
                 _viewMetricsCallbackRegistered = true;
             
-            CollectGarbegeOndemend();
+#if !UNITY_EDITOR
+            CollectGarbageOnDemand();
+#endif
-        void CollectGarbegeOndemend() {
-            long mem = Profiler.GetMonoUsedSizeLong();
+        #region OnDemandGC
+#if !UNITY_EDITOR
+        // 8 MB
+        const long kCollectAfterAllocating = 8 * 1024 * 1024;
+        
+        long lastFrameMemory = 0;
+        long nextCollectAt = 0;
+
+        void TryEnableOnDemandGC() 
+        {
+            if (UIWidgetsGlobalConfiguration.EnableIncrementalGC)
+            {
+                GarbageCollector.GCMode = GarbageCollector.Mode.Disabled;
+                Application.lowMemory += GC.Collect;
+            }
+        }
+
+        void CollectGarbageOnDemand() 
+        {
+            if (!UIWidgetsGlobalConfiguration.EnableIncrementalGC)
+            {
+                return;
+            }
+            
+            var mem = Profiler.GetMonoUsedSizeLong();
             if (mem < lastFrameMemory)
             {
                 // GC happened.
 
             lastFrameMemory = mem;
         }
+#endif
+        #endregion
 
 #if !UNITY_EDITOR && UNITY_ANDROID
         bool AndroidInitialized = true;
             //the hook API cannot be automatically called on IOS, so we need try hook it here
             Hooks.tryHook();
 #endif
+            
-            GarbageCollector.GCMode = GarbageCollector.Mode.Disabled;
+            TryEnableOnDemandGC();
-            Application.lowMemory += GC.Collect;
-            
+
             base.OnEnable();
             
             D.assert(_wrapper == null);

com.unity.uiwidgets/Runtime/foundation/debug.cs

         public static bool debugCheckIntrinsicSizes = false;
 
         public static bool debugPrintMouseHoverEvents = false;
-        
-        static bool debugEnableAtRuntimeInternal = false;
 
         public static HSVColor debugCurrentRepaintColor =
             HSVColor.fromAHSV(0.4f, 60.0f, 1.0f, 1.0f);
             }
         }
 #else
-        public static bool enableDebug => debugEnableAtRuntimeInternal;
+        public static bool enableDebug => UIWidgetsGlobalConfiguration.EnableDebugAtRuntime;
 #endif
 
         public static void _debugDrawDoubleRect(Canvas canvas, Rect outerRect, Rect innerRect, Color color) { 

com.unity.uiwidgets/Runtime/scheduler/binding.cs

         static readonly TimeSpan _coolDownDelay = new TimeSpan(0, 0, 0, 0, 200);
         static Timer frameCoolDownTimer = null;
         
-        //disable auto adjust framerate by default
-        public static bool MEnableAutoAdjustFramerate = false;
-
         public void scheduleFrame() {
             if (hasScheduledFrame || !framesEnabled) {
                 return;
             Window.instance.scheduleFrame();
             hasScheduledFrame = true;
 
+#if !UNITY_EDITOR
+#endif
+#if !UNITY_EDITOR
-            if (!MEnableAutoAdjustFramerate) {
+            if (!UIWidgetsGlobalConfiguration.EnableAutoAdjustFramerate) {
                 return;
             }
             
         void onFrameRateCoolDown() {
             OnDemandRendering.renderFrameInterval = defaultMaxRenderFrameInterval;
         }
+#endif
 
         public void scheduleForcedFrame() {
             if (!framesEnabled) {
             Window.instance.scheduleFrame();
             hasScheduledFrame = true;
 
+#if !UNITY_EDITOR
+#endif
         }
 
         public void scheduleWarmUpFrame() {

com.unity.uiwidgets/Runtime/engine/UIWidgetsGlobalConfiguration.cs

+namespace Unity.UIWidgets.engine {
+    public static class UIWidgetsGlobalConfiguration {
+        //disable auto adjust framerate by default
+        public static bool EnableAutoAdjustFramerate = false;
+
+        //enable incremental gc by default
+        public static bool EnableIncrementalGC = true;
+        
+        //disable debug at runtime by default
+        public static bool EnableDebugAtRuntime = false;
+    }
+}