Modify RCTTouchableComponentViewProtocol to get touch event emitter at point

Summary:
This diff includes two changes:
1. Even though `RCTViewComponentView` conforms to `RCTTouchableComponentViewProtocol`, it never implemented this protocol. This diff makes the correction.
2. Make the necessary changes to `RCTSurfaceTouchHandler` required by the changes in `RCTTouchableComponentViewProtocol`. This means modifying the `ActiveTouch` struct to hold `SharedTouchEventEmitter`s. It also means passing in the touch point to the `componentView`'s `touchEventEmitterAtPoint` method.

Reviewed By: shergin

Differential Revision: D9696909

fbshipit-source-id: 3d4a833f7dbae6d0238a0807eb2220250ccbae3d

React/Fabric/Mounting/ComponentViews/View/RCTViewComponentView.h

@@ -13,13 +13,14 @@
 #import <fabric/core/Props.h>
 #import <fabric/components/view/ViewEventEmitter.h>
 #import <fabric/events/EventEmitter.h>
+#import <React/RCTTouchableComponentViewProtocol.h>
 
 NS_ASSUME_NONNULL_BEGIN
 
 /**
  * UIView class for <View> component.
  */
-@interface RCTViewComponentView : UIView <RCTComponentViewProtocol> {
+@interface RCTViewComponentView : UIView <RCTComponentViewProtocol, RCTTouchableComponentViewProtocol> {
 @protected
   facebook::react::LayoutMetrics _layoutMetrics;
   facebook::react::SharedProps _props;

React/Fabric/Mounting/ComponentViews/View/RCTViewComponentView.mm

@@ -449,7 +449,7 @@ static RCTBorderStyle RCTBorderStyleFromBorderStyle(BorderStyle borderStyle) {
   return YES;
 }
 
-- (SharedEventEmitter)touchEventEmitter
+- (SharedTouchEventEmitter)touchEventEmitterAtPoint:(CGPoint)point
 {
   return _eventEmitter;
 }

React/Fabric/RCTSurfaceTouchHandler.mm

@@ -8,11 +8,11 @@
 #import "RCTSurfaceTouchHandler.h"
 
 #import <UIKit/UIGestureRecognizerSubclass.h>
-#import <fabric/components/view/ViewEventEmitter.h>
 #import <React/RCTUtils.h>
 #import <React/RCTViewComponentView.h>
 
 #import "RCTConversions.h"
+#import "RCTTouchableComponentViewProtocol.h"
 
 using namespace facebook::react;
 
@@ -46,10 +46,6 @@ private:
   int lastIndex;
 };
 
-@protocol RCTTouchableComponentViewProtocol <NSObject>
-  - (SharedViewEventEmitter)touchEventEmitter;
-@end
-
 typedef NS_ENUM(NSInteger, RCTTouchEventType) {
   RCTTouchEventTypeTouchStart,
   RCTTouchEventTypeTouchMove,
@@ -59,7 +55,7 @@ typedef NS_ENUM(NSInteger, RCTTouchEventType) {
 
 struct ActiveTouch {
   Touch touch;
-  SharedViewEventEmitter eventEmitter;
+  SharedTouchEventEmitter eventEmitter;
 
   struct Hasher {
     size_t operator()(const ActiveTouch &activeTouch) const {
@@ -95,8 +91,8 @@ static ActiveTouch CreateTouchWithUITouch(UITouch *uiTouch, UIView *rootComponen
 
   ActiveTouch activeTouch = {};
 
-  if ([componentView respondsToSelector:@selector(touchEventEmitter)]) {
-    activeTouch.eventEmitter = [(id<RCTTouchableComponentViewProtocol>)componentView touchEventEmitter];
+  if ([componentView respondsToSelector:@selector(touchEventEmitterAtPoint:)]) {
+    activeTouch.eventEmitter = [(id<RCTTouchableComponentViewProtocol>)componentView touchEventEmitterAtPoint:[uiTouch locationInView:componentView]];
     activeTouch.touch.target = (Tag)componentView.tag;
   }
 
@@ -217,7 +213,7 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithTarget:(id)target action:(SEL)action
 {
   TouchEvent event = {};
   std::unordered_set<ActiveTouch, ActiveTouch::Hasher, ActiveTouch::Comparator> changedActiveTouches = {};
-  std::unordered_set<SharedViewEventEmitter> uniqueEventEmitter = {};
+  std::unordered_set<SharedTouchEventEmitter> uniqueEventEmitter = {};
   BOOL isEndishEventType = eventType == RCTTouchEventTypeTouchEnd || eventType == RCTTouchEventTypeTouchCancel;
 
   for (UITouch *touch in touches) {

React/Fabric/RCTTouchableComponentViewProtocol.h

@@ -0,0 +1,13 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import <UIKit/UIKit.h>
+#import <fabric/components/view/TouchEventEmitter.h>
+
+@protocol RCTTouchableComponentViewProtocol <NSObject>
+- (facebook::react::SharedTouchEventEmitter)touchEventEmitterAtPoint:(CGPoint)point;
+@end