Add support for ScrollView.onScroll animations

Summary: To enable onScroll animations with Fabric's scrollView on iOS, we dispatch onScroll event to Paper's eventDispatcher as well as to Fabric's one. One we have a proper NativeAnimationDriver in place, we will get rid of this.

Reviewed By: shergin

Differential Revision: D17814260

fbshipit-source-id: f04faf59cdfd4ea5cede513388e30500b4cb2ad5

Author: sammy-SC

React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm

@@ -8,6 +8,8 @@
 #import "RCTScrollViewComponentView.h"
 
 #import <React/RCTAssert.h>
+#import <React/RCTBridge+Private.h>
+#import <React/RCTScrollEvent.h>
 
 #import <react/components/scrollview/ScrollViewComponentDescriptor.h>
 #import <react/components/scrollview/ScrollViewEventEmitter.h>
@@ -20,6 +22,21 @@
 
 using namespace facebook::react;
 
+static void RCTSendPaperScrollEvent_DEPRECATED(UIScrollView *scrollView, NSInteger tag)
+{
+  static uint16_t coalescingKey = 0;
+  RCTScrollEvent *scrollEvent = [[RCTScrollEvent alloc] initWithEventName:@"onScroll"
+                                                                 reactTag:[NSNumber numberWithInt:tag]
+                                                  scrollViewContentOffset:scrollView.contentOffset
+                                                   scrollViewContentInset:scrollView.contentInset
+                                                    scrollViewContentSize:scrollView.contentSize
+                                                          scrollViewFrame:scrollView.frame
+                                                      scrollViewZoomScale:scrollView.zoomScale
+                                                                 userData:nil
+                                                            coalescingKey:coalescingKey];
+  [[RCTBridge currentBridge].eventDispatcher sendEvent:scrollEvent];
+}
+
 @interface RCTScrollViewComponentView () <UIScrollViewDelegate>
 
 @end
@@ -211,6 +228,9 @@ - (void)scrollViewDidScroll:(UIScrollView *)scrollView
   if ((_lastScrollEventDispatchTime == 0) || (now - _lastScrollEventDispatchTime > _scrollEventThrottle)) {
     _lastScrollEventDispatchTime = now;
     std::static_pointer_cast<ScrollViewEventEmitter const>(_eventEmitter)->onScroll([self _scrollViewMetrics]);
+    // Once Fabric implements proper NativeAnimationDriver, this should be removed.
+    // This is just a workaround to allow animations based on onScroll event.
+    RCTSendPaperScrollEvent_DEPRECATED(scrollView, self.tag);
   }
 }
 

React/Modules/RCTUIManager.m

@@ -335,7 +335,22 @@ - (void)registerRootView:(RCTRootContentView *)rootView
 - (NSString *)viewNameForReactTag:(NSNumber *)reactTag
 {
   RCTAssertUIManagerQueue();
-  return _shadowViewRegistry[reactTag].viewName;
+  NSString *name = _shadowViewRegistry[reactTag].viewName;
+  if (name) {
+    return name;
+  }
+  
+  UIView *view = _viewRegistry[reactTag];
+  
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wundeclared-selector"
+
+  if ([view respondsToSelector:@selector(componentViewName_DO_NOT_USE_THIS_IS_BROKEN)]) {
+    return [view performSelector:@selector(componentViewName_DO_NOT_USE_THIS_IS_BROKEN)];
+  }
+
+#pragma clang diagnostic pop
+  return nil;
 }
 
 - (UIView *)viewForReactTag:(NSNumber *)reactTag