From a410ef97f6bb735da2946cc9ac7712c821e3bc41 Mon Sep 17 00:00:00 2001
From: Nick Gerleman <ngerlem@meta.com>
Date: Tue, 5 Sep 2023 09:02:19 -0700
Subject: [PATCH] Only disable throttling when scrollEventThrottle isn't set
 (#39293)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/39293

This QE is meant to change behavior to not throttle if `scrollEventThrottle` isn't set, but it's actually disabling throttling entirely.

This changes the gating to instead change the initialization path to set `_scrollEventThrottle = 0` when the QE is set.

`_scrollEventThrottle` is already set to zero when the `scrollEventThrottle` prop is removed/set to null, as the default value in ScrollViewProps.

Changelog: [internal]

Reviewed By: sammy-SC

Differential Revision: D48968754

fbshipit-source-id: c46c7f5093a60e326267c2e5f2f86dc2d545ac7f
---
 .../ScrollView/RCTScrollViewComponentView.mm             | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/packages/react-native/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm b/packages/react-native/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm
index 1896eb96e07..504b0ef147a 100644
--- a/packages/react-native/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm
+++ b/packages/react-native/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm
@@ -134,7 +134,11 @@ static void RCTSendScrollEventForNativeAnimations_DEPRECATED(UIScrollView *scrol
 
     [self.scrollViewDelegateSplitter addDelegate:self];
 
-    _scrollEventThrottle = INFINITY;
+    if (CoreFeatures::disableScrollEventThrottleRequirement) {
+      _scrollEventThrottle = 0;
+    } else {
+      _scrollEventThrottle = INFINITY;
+    }
   }
 
   return self;
@@ -447,8 +451,7 @@ static void RCTSendScrollEventForNativeAnimations_DEPRECATED(UIScrollView *scrol
   }
 
   NSTimeInterval now = CACurrentMediaTime();
-  if (CoreFeatures::disableScrollEventThrottleRequirement || (_lastScrollEventDispatchTime == 0) ||
-      (now - _lastScrollEventDispatchTime > _scrollEventThrottle)) {
+  if ((_lastScrollEventDispatchTime == 0) || (now - _lastScrollEventDispatchTime > _scrollEventThrottle)) {
     _lastScrollEventDispatchTime = now;
     if (_eventEmitter) {
       static_cast<const ScrollViewEventEmitter &>(*_eventEmitter).onScroll([self _scrollViewMetrics]);