Add flag to do granular state updates in scroll views in iOS

Differential Revision: D45916675

fbshipit-source-id: f6d0722db658c5d744a8b9fa8b17c5736603b9f6

Author: rubennorte

packages/react-native/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm

@@ -437,7 +437,7 @@ - (BOOL)touchesShouldCancelInContentView:(__unused UIView *)view
 
 - (void)scrollViewDidScroll:(UIScrollView *)scrollView
 {
-  if (!_isUserTriggeredScrolling) {
+  if (!_isUserTriggeredScrolling || CoreFeatures::enableGranularScrollViewStateUpdatesIOS) {
     [self _updateStateWithContentOffset];
   }
 

packages/react-native/React/Fabric/RCTSurfacePresenter.mm

@@ -276,6 +276,10 @@ - (RCTScheduler *)_createScheduler
     CoreFeatures::disableTransactionCommit = true;
   }
 
+  if (reactNativeConfig && reactNativeConfig->getBool("react_fabric:enable_granular_scroll_view_state_updates_ios")) {
+    CoreFeatures::enableGranularScrollViewStateUpdatesIOS = true;
+  }
+
   auto componentRegistryFactory =
       [factory = wrapManagedObject(_mountingManager.componentViewRegistry.componentViewFactory)](
           EventDispatcher::Weak const &eventDispatcher, ContextContainer::Shared const &contextContainer) {

packages/react-native/ReactCommon/react/renderer/core/CoreFeatures.cpp

@@ -16,5 +16,6 @@ bool CoreFeatures::useNativeState = false;
 bool CoreFeatures::cacheLastTextMeasurement = false;
 bool CoreFeatures::cancelImageDownloadsOnRecycle = false;
 bool CoreFeatures::disableTransactionCommit = false;
+bool CoreFeatures::enableGranularScrollViewStateUpdatesIOS = false;
 
 } // namespace facebook::react

packages/react-native/ReactCommon/react/renderer/core/CoreFeatures.h

@@ -48,6 +48,10 @@ class CoreFeatures {
   // [CATransaction end] This feature flag disables it to measure its impact in
   // production.
   static bool disableTransactionCommit;
+
+  // When enabled, RCTScrollViewComponentView will trigger ShadowTree state
+  // updates for all changes in scroll position.
+  static bool enableGranularScrollViewStateUpdatesIOS;
 };
 
 } // namespace facebook::react