Fabric: Controlling DifferentiatorMode via ReactNativeConfig

Summary:
Now we can control the differentiator mode via MC.

Changelog: [Internal] Fabric-specific internal change.

Reviewed By: fkgozali

Differential Revision: D20978857

fbshipit-source-id: 13264948762f02f874d8d051c873d378062d6db4

React/Fabric/Mounting/RCTMountingManager.h

@@ -26,6 +26,8 @@ NS_ASSUME_NONNULL_BEGIN
 @property (nonatomic, weak) id<RCTMountingManagerDelegate> delegate;
 @property (nonatomic, strong) RCTComponentViewRegistry *componentViewRegistry;
 
+@property (atomic, assign) BOOL useModernDifferentiatorMode;
+
 /**
  * Schedule a mounting transaction to be performed on the main thread.
  * Can be called from any thread.

React/Fabric/Mounting/RCTMountingManager.mm

@@ -266,7 +266,10 @@ static void RNPerformMountInstructions(
   SystraceSection s("-[RCTMountingManager performTransaction:]");
   RCTAssertMainQueue();
 
-  auto transaction = mountingCoordinator->pullTransaction(DifferentiatorMode::Classic);
+  auto differentiatorMode =
+      self.useModernDifferentiatorMode ? DifferentiatorMode::OptimizedMoves : DifferentiatorMode::Classic;
+
+  auto transaction = mountingCoordinator->pullTransaction(differentiatorMode);
   if (!transaction.has_value()) {
     return;
   }

React/Fabric/RCTSurfacePresenter.mm

@@ -24,6 +24,7 @@
 #import <React/RCTUtils.h>
 
 #import <react/components/root/RootShadowNode.h>
+#import <react/config/ReactNativeConfig.h>
 #import <react/core/LayoutConstraints.h>
 #import <react/core/LayoutContext.h>
 #import <react/uimanager/ComponentDescriptorFactory.h>
@@ -299,6 +300,12 @@ static inline LayoutContext RCTGetLayoutContext()
   RCTScheduler *scheduler = [[RCTScheduler alloc] initWithToolbox:toolbox];
   scheduler.delegate = self;
 
+  auto reactNativeConfig = _contextContainer->at<std::shared_ptr<ReactNativeConfig const>>("ReactNativeConfig");
+  if (reactNativeConfig) {
+    _mountingManager.useModernDifferentiatorMode =
+        reactNativeConfig->getBool("react_fabric:enabled_optimized_moves_differ_ios");
+  }
+
   return scheduler;
 }