Scrollview updatedChildFrames data controlled by prop

Summary: Optimize ScrollView by adding flag "DEPRECATED_sendUpdatedChildFrames" to gate whether updatedChildFrames data is computed and propagated on scroll events.  The frame data is used in ListView by the onChangeVisibleRows prop.  When this prop is not defined, unnecessary computation in ScrollView should not be performed.

Reviewed By: sahrens

Differential Revision: D5174898

fbshipit-source-id: e3eaed8760b76becf14dfeb00122bdebdaeae4ef

Libraries/Components/ScrollView/ScrollView.js

@@ -388,6 +388,15 @@ const ScrollView = React.createClass({
       'always',
       'never',
     ]),
+    /**
+     * When true, ScrollView will emit updateChildFrames data in scroll events,
+     * otherwise will not compute or emit child frame data.  This only exists
+     * to support legacy issues, `onLayout` should be used instead to retrieve
+     * frame data.
+     * The default value is false.
+     * @platform ios
+     */
+    DEPRECATED_sendUpdatedChildFrames: PropTypes.bool,
   },
 
   mixins: [ScrollResponder.Mixin],
@@ -682,6 +691,9 @@ const ScrollView = React.createClass({
         this.props.alwaysBounceVertical :
         !this.props.horizontal;
 
+    const DEPRECATED_sendUpdatedChildFrames =
+      !!this.props.DEPRECATED_sendUpdatedChildFrames;
+
     const baseStyle = this.props.horizontal ? styles.baseHorizontal : styles.baseVertical;
     const props = {
       ...this.props,
@@ -710,6 +722,7 @@ const ScrollView = React.createClass({
       scrollEventThrottle: hasStickyHeaders ? 1 : this.props.scrollEventThrottle,
       sendMomentumEvents: (this.props.onMomentumScrollBegin || this.props.onMomentumScrollEnd) ?
         true : false,
+      DEPRECATED_sendUpdatedChildFrames,
     };
 
     const { decelerationRate } = this.props;

Libraries/Lists/ListView/ListView.js

@@ -508,6 +508,7 @@ var ListView = React.createClass({
       ref: this._setScrollComponentRef,
       onContentSizeChange: this._onContentSizeChange,
       onLayout: this._onLayout,
+      DEPRECATED_sendUpdatedChildFrames: props.onChangeVisibleRows !== undefined,
     }, header, bodyComponents, footer);
   },
 

React/Views/RCTScrollView.h

@@ -42,6 +42,7 @@
 
 @property (nonatomic, assign) UIEdgeInsets contentInset;
 @property (nonatomic, assign) BOOL automaticallyAdjustContentInsets;
+@property (nonatomic, assign) BOOL DEPRECATED_sendUpdatedChildFrames;
 @property (nonatomic, assign) NSTimeInterval scrollEventThrottle;
 @property (nonatomic, assign) BOOL centerContent;
 @property (nonatomic, assign) int snapToInterval;

React/Views/RCTScrollView.m

@@ -109,7 +109,6 @@ - (BOOL)canCoalesce
 - (RCTScrollEvent *)coalesceWithEvent:(RCTScrollEvent *)newEvent
 {
   NSArray<NSDictionary *> *updatedChildFrames = [_userData[@"updatedChildFrames"] arrayByAddingObjectsFromArray:newEvent->_userData[@"updatedChildFrames"]];
-
   if (updatedChildFrames) {
     NSMutableDictionary *userData = [newEvent->_userData mutableCopy];
     userData[@"updatedChildFrames"] = updatedChildFrames;
@@ -338,6 +337,7 @@ - (instancetype)initWithEventDispatcher:(RCTEventDispatcher *)eventDispatcher
     _scrollView.delegate = self;
     _scrollView.delaysContentTouches = NO;
     _automaticallyAdjustContentInsets = YES;
+    _DEPRECATED_sendUpdatedChildFrames = NO;
     _contentInset = UIEdgeInsetsZero;
     _contentSize = CGSizeZero;
     _lastClippedToRect = CGRectNull;
@@ -587,9 +587,7 @@ - (void)removeScrollListener:(NSObject<UIScrollViewDelegate> *)scrollListener
 - (void)scrollViewDidScroll:(UIScrollView *)scrollView
 {
   [self updateClippedSubviews];
-
   NSTimeInterval now = CACurrentMediaTime();
-
   /**
    * TODO: this logic looks wrong, and it may be because it is. Currently, if _scrollEventThrottle
    * is set to zero (the default), the "didScroll" event is only sent once per scroll, instead of repeatedly
@@ -599,16 +597,18 @@ - (void)scrollViewDidScroll:(UIScrollView *)scrollView
   if (_allowNextScrollNoMatterWhat ||
       (_scrollEventThrottle > 0 && _scrollEventThrottle < (now - _lastScrollDispatchTime))) {
 
-    // Calculate changed frames
-    NSArray<NSDictionary *> *childFrames = [self calculateChildFramesData];
-
-    // Dispatch event
-    RCT_SEND_SCROLL_EVENT(onScroll, (@{@"updatedChildFrames": childFrames}));
+    if (_DEPRECATED_sendUpdatedChildFrames) {
+      // Calculate changed frames
+      RCT_SEND_SCROLL_EVENT(onScroll, (@{@"updatedChildFrames": [self calculateChildFramesData]}));
+    } else {
+      RCT_SEND_SCROLL_EVENT(onScroll, nil);
+    }
 
     // Update dispatch time
     _lastScrollDispatchTime = now;
     _allowNextScrollNoMatterWhat = NO;
   }
+
   RCT_FORWARD_SCROLL_EVENT(scrollViewDidScroll:scrollView);
 }
 

React/Views/RCTScrollViewManager.m

@@ -80,6 +80,7 @@ - (UIView *)view
 RCT_EXPORT_VIEW_PROPERTY(onMomentumScrollBegin, RCTDirectEventBlock)
 RCT_EXPORT_VIEW_PROPERTY(onMomentumScrollEnd, RCTDirectEventBlock)
 RCT_EXPORT_VIEW_PROPERTY(onScrollAnimationEnd, RCTDirectEventBlock)
+RCT_EXPORT_VIEW_PROPERTY(DEPRECATED_sendUpdatedChildFrames, BOOL)
 
 // overflow is used both in css-layout as well as by react-native. In css-layout
 // we always want to treat overflow as scroll but depending on what the overflow