From cefc5a66f2e4971cbcad25b3b2a31422971909b1 Mon Sep 17 00:00:00 2001
From: Martin Kralik <kralik@fb.com>
Date: Fri, 1 Apr 2016 06:53:08 -0700
Subject: [PATCH] adding coalescing key generation for scroll events

Reviewed By: javache

Differential Revision: D3092857

fb-gh-sync-id: 79a1e235d97d484ee7247f17250759b161bc2c07
fbshipit-source-id: 79a1e235d97d484ee7247f17250759b161bc2c07
---
 React/Views/RCTScrollView.m | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/React/Views/RCTScrollView.m b/React/Views/RCTScrollView.m
index eeb00ab0a79..5440084e6ad 100644
--- a/React/Views/RCTScrollView.m
+++ b/React/Views/RCTScrollView.m
@@ -392,6 +392,8 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
   NSMutableArray<NSValue *> *_cachedChildFrames;
   BOOL _allowNextScrollNoMatterWhat;
   CGRect _lastClippedToRect;
+  uint16_t _coalescingKey;
+  RCTScrollEventType _lastEmittedEventType;
 }
 
 @synthesize nativeScrollDelegate = _nativeScrollDelegate;
@@ -925,11 +927,15 @@ RCT_SET_AND_PRESERVE_OFFSET(setScrollIndicatorInsets, scrollIndicatorInsets, UIE
                      scrollView:(UIScrollView *)scrollView
                        userData:(NSDictionary *)userData
 {
+  if (_lastEmittedEventType != type) {
+    _coalescingKey++;
+    _lastEmittedEventType = type;
+  }
   [_eventDispatcher sendScrollEventWithType:type
                                    reactTag:reactTag
                                  scrollView:scrollView
                                    userData:userData
-                              coalescingKey:0];
+                              coalescingKey:_coalescingKey];
 }
 
 @end