Remove unused native iOS sticky headers implementation

Summary:
Remove the native iOS sticky headers implementation that has been replaced by the js Animated one. Also remove a line in JS that made sure we passed null to native so it did not use the native implementation.

**Test plan**
Made sure there were no more mentions of sticky / header in native ScrollView related code.
Tested that sticky headers still work :o
Closes https://github.com/facebook/react-native/pull/12696

Differential Revision: D4657391

Pulled By: ericvicenti

fbshipit-source-id: 16324a45ca4ce5cd143293c61394a0fa7ad0c4a1

Libraries/Components/ScrollView/ScrollView.js

@@ -670,7 +670,6 @@ const ScrollView = React.createClass({
       scrollEventThrottle: hasStickyHeaders ? 1 : this.props.scrollEventThrottle,
       sendMomentumEvents: (this.props.onMomentumScrollBegin || this.props.onMomentumScrollEnd) ?
         true : false,
-      stickyHeaderIndices: null,
     };
 
     const { decelerationRate } = this.props;

React/Views/RCTScrollView.h

@@ -46,7 +46,6 @@
 @property (nonatomic, assign) BOOL centerContent;
 @property (nonatomic, assign) int snapToInterval;
 @property (nonatomic, copy) NSString *snapToAlignment;
-@property (nonatomic, copy) NSIndexSet *stickyHeaderIndices;
 
 // NOTE: currently these event props are only declared so we can export the
 // event names to JS - we don't call the blocks directly because scroll events

React/Views/RCTScrollView.m

@@ -23,9 +23,6 @@
 #import "RCTRefreshControl.h"
 #endif
 
-CGFloat const ZINDEX_DEFAULT = 0;
-CGFloat const ZINDEX_STICKY_HEADER = 50;
-
 @interface RCTScrollEvent : NSObject <RCTEvent>
 
 - (instancetype)initWithEventName:(NSString *)eventName
@@ -137,11 +134,10 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
 /**
  * Include a custom scroll view subclass because we want to limit certain
  * default UIKit behaviors such as textFields automatically scrolling
- * scroll views that contain them and support sticky headers.
+ * scroll views that contain them.
  */
 @interface RCTCustomScrollView : UIScrollView<UIGestureRecognizerDelegate>
 
-@property (nonatomic, copy) NSIndexSet *stickyHeaderIndices;
 @property (nonatomic, assign) BOOL centerContent;
 #if !TARGET_OS_TV
 @property (nonatomic, strong) RCTRefreshControl *rctRefreshControl;
@@ -151,9 +147,6 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
 
 
 @implementation RCTCustomScrollView
-{
-  __weak UIView *_dockedHeaderView;
-}
 
 - (instancetype)initWithFrame:(CGRect)frame
 {
@@ -281,98 +274,6 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
   super.contentOffset = contentOffset;
 }
 
-- (void)dockClosestSectionHeader
-{
-  UIView *contentView = [self contentView];
-  CGFloat scrollTop = self.bounds.origin.y + self.contentInset.top;
-
-#if !TARGET_OS_TV
-  // If the RefreshControl is refreshing, remove it's height so sticky headers are
-  // positioned properly when scrolling down while refreshing.
-  if (_rctRefreshControl != nil && _rctRefreshControl.refreshing) {
-    scrollTop -= _rctRefreshControl.frame.size.height;
-  }
-#endif
-
-  // Find the section headers that need to be docked
-  __block UIView *previousHeader = nil;
-  __block UIView *currentHeader = nil;
-  __block UIView *nextHeader = nil;
-  NSUInteger subviewCount = contentView.reactSubviews.count;
-  [_stickyHeaderIndices enumerateIndexesWithOptions:0 usingBlock:
-   ^(NSUInteger idx, BOOL *stop) {
-
-    // If the subviews are out of sync with the sticky header indices don't
-    // do anything.
-    if (idx >= subviewCount) {
-      *stop = YES;
-      return;
-    }
-
-    UIView *header = contentView.reactSubviews[idx];
-
-    // If nextHeader not yet found, search for docked headers
-    if (!nextHeader) {
-      CGFloat height = header.bounds.size.height;
-      CGFloat top = header.center.y - height * header.layer.anchorPoint.y;
-      if (top > scrollTop) {
-        nextHeader = header;
-      } else {
-        previousHeader = currentHeader;
-        currentHeader = header;
-      }
-    }
-
-    // Reset transforms for header views
-    header.transform = CGAffineTransformIdentity;
-    header.layer.zPosition = ZINDEX_DEFAULT;
-
-  }];
-
-  // If no docked header, bail out
-  if (!currentHeader) {
-    return;
-  }
-
-  // Adjust current header to hug the top of the screen
-  CGFloat currentFrameHeight = currentHeader.bounds.size.height;
-  CGFloat currentFrameTop = currentHeader.center.y - currentFrameHeight * currentHeader.layer.anchorPoint.y;
-  CGFloat yOffset = scrollTop - currentFrameTop;
-  if (nextHeader) {
-    // The next header nudges the current header out of the way when it reaches
-    // the top of the screen
-    CGFloat nextFrameHeight = nextHeader.bounds.size.height;
-    CGFloat nextFrameTop = nextHeader.center.y - nextFrameHeight * nextHeader.layer.anchorPoint.y;
-    CGFloat overlap = currentFrameHeight - (nextFrameTop - scrollTop);
-    yOffset -= MAX(0, overlap);
-  }
-  currentHeader.transform = CGAffineTransformMakeTranslation(0, yOffset);
-  currentHeader.layer.zPosition = ZINDEX_STICKY_HEADER;
-  _dockedHeaderView = currentHeader;
-
-  if (previousHeader) {
-    // The previous header sits right above the currentHeader's initial position
-    // so it scrolls away nicely once the currentHeader has locked into place
-    CGFloat previousFrameHeight = previousHeader.bounds.size.height;
-    CGFloat targetCenter = currentFrameTop - previousFrameHeight * (1.0 - previousHeader.layer.anchorPoint.y);
-    yOffset = targetCenter - previousHeader.center.y;
-    previousHeader.transform = CGAffineTransformMakeTranslation(0, yOffset);
-    previousHeader.layer.zPosition = ZINDEX_STICKY_HEADER;
-  }
-}
-
-- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
-{
-  if (_dockedHeaderView && [self pointInside:point withEvent:event]) {
-    CGPoint convertedPoint = [_dockedHeaderView convertPoint:point fromView:self];
-    UIView *hitView = [_dockedHeaderView hitTest:convertedPoint withEvent:event];
-    if (hitView) {
-      return hitView;
-    }
-  }
-  return [super hitTest:point withEvent:event];
-}
-
 static inline BOOL isRectInvalid(CGRect rect) {
   return isnan(rect.origin.x) || isinf(rect.origin.x) ||
     isnan(rect.origin.y) || isinf(rect.origin.y) ||
@@ -524,18 +425,6 @@ static inline void RCTApplyTranformationAccordingLayoutDirection(UIView *view, U
   _scrollView.centerContent = centerContent;
 }
 
-- (NSIndexSet *)stickyHeaderIndices
-{
-  return _scrollView.stickyHeaderIndices;
-}
-
-- (void)setStickyHeaderIndices:(NSIndexSet *)headerIndices
-{
-  RCTAssert(_scrollView.contentSize.width <= self.frame.size.width,
-           @"sticky headers are not supported with horizontal scrolled views");
-  _scrollView.stickyHeaderIndices = headerIndices;
-}
-
 - (void)setClipsToBounds:(BOOL)clipsToBounds
 {
   super.clipsToBounds = clipsToBounds;
@@ -699,7 +588,6 @@ RCT_SCROLL_EVENT_HANDLER(scrollViewDidZoom, onScroll)
 
 - (void)scrollViewDidScroll:(UIScrollView *)scrollView
 {
-  [_scrollView dockClosestSectionHeader];
   [self updateClippedSubviews];
 
   NSTimeInterval now = CACurrentMediaTime();
@@ -962,26 +850,6 @@ RCT_SCROLL_EVENT_HANDLER(scrollViewDidZoom, onScroll)
     _scrollView.contentSize = contentSize;
     _scrollView.contentOffset = newOffset;
   }
-
-  if (RCT_DEBUG) {
-    // Validate that sticky headers are not out of range.
-    NSUInteger subviewCount = _scrollView.contentView.reactSubviews.count;
-    NSUInteger lastIndex = NSNotFound;
-    if (_scrollView.stickyHeaderIndices != nil) {
-      lastIndex = _scrollView.stickyHeaderIndices.lastIndex;
-    }
-    if (lastIndex != NSNotFound && lastIndex >= subviewCount) {
-      RCTLogWarn(@"Sticky header index %zd was outside the range {0, %zd}",
-                 lastIndex, subviewCount);
-    }
-  }
-}
-
-- (void)didSetProps:(NSArray<NSString *> *)changedProps
-{
-  if ([changedProps containsObject:@"stickyHeaderIndices"]) {
-    [_scrollView dockClosestSectionHeader];
-  }
 }
 
 // Note: setting several properties of UIScrollView has the effect of

React/Views/RCTScrollViewManager.m

@@ -67,7 +67,6 @@ RCT_EXPORT_VIEW_PROPERTY(scrollsToTop, BOOL)
 #endif
 RCT_EXPORT_VIEW_PROPERTY(showsHorizontalScrollIndicator, BOOL)
 RCT_EXPORT_VIEW_PROPERTY(showsVerticalScrollIndicator, BOOL)
-RCT_EXPORT_VIEW_PROPERTY(stickyHeaderIndices, NSIndexSet)
 RCT_EXPORT_VIEW_PROPERTY(scrollEventThrottle, NSTimeInterval)
 RCT_EXPORT_VIEW_PROPERTY(zoomScale, CGFloat)
 RCT_EXPORT_VIEW_PROPERTY(contentInset, UIEdgeInsets)