Don't receive touches in RCTRootView

Reviewed By: mmmulani, majak

Differential Revision: D4104319

fbshipit-source-id: 70731b72e087710ccbc32024a596583640b94d04

Author: javache

React/Base/RCTRootView.h

@@ -135,6 +135,18 @@ extern NSString *const RCTContentDidAppearNotification;
  */
 - (void)cancelTouches;
 
+/**
+ * When set, any touches on the RCTRootView that are not matched up to any of the child
+ * views will be passed to siblings of the RCTRootView. See -[UIView hitTest:withEvent:]
+ * for details on iOS hit testing.
+ *
+ * Enable this to support a semi-transparent RN view that occupies the whole screen but
+ * has visible content below it that the user can interact with.
+ *
+ * The default value is NO.
+ */
+@property (nonatomic, assign) BOOL passThroughTouches;
+
 /**
  * Timings for hiding the loading view after the content has loaded. Both of
  * these values default to 0.25 seconds.

React/Base/RCTRootView.m

@@ -40,6 +40,7 @@ @interface RCTRootContentView : RCTView <RCTInvalidating>
 
 @property (nonatomic, readonly) BOOL contentHasAppeared;
 @property (nonatomic, readonly, strong) RCTTouchHandler *touchHandler;
+@property (nonatomic, assign) BOOL passThroughTouches;
 
 - (instancetype)initWithFrame:(CGRect)frame
                        bridge:(RCTBridge *)bridge
@@ -125,6 +126,16 @@ - (void)setBackgroundColor:(UIColor *)backgroundColor
   _contentView.backgroundColor = backgroundColor;
 }
 
+- (BOOL)passThroughTouches
+{
+  return _contentView.passThroughTouches;
+}
+
+- (void)setPassThroughTouches:(BOOL)passThroughTouches
+{
+  _contentView.passThroughTouches = passThroughTouches;
+}
+
 - (UIViewController *)reactViewController
 {
   return _reactViewController ?: [super reactViewController];
@@ -259,6 +270,16 @@ - (void)layoutSubviews
   };
 }
 
+- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
+{
+  // The root view itself should never receive touches
+  UIView *hitView = [super hitTest:point withEvent:event];
+  if (self.passThroughTouches && hitView == self) {
+    return nil;
+  }
+  return hitView;
+}
+
 - (void)setAppProperties:(NSDictionary *)appProperties
 {
   RCTAssertMainQueue();
@@ -382,6 +403,16 @@ - (UIColor *)backgroundColor
   return _backgroundColor;
 }
 
+- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
+{
+  // The root content view itself should never receive touches
+  UIView *hitView = [super hitTest:point withEvent:event];
+  if (_passThroughTouches && hitView == self) {
+    return nil;
+  }
+  return hitView;
+}
+
 - (void)invalidate
 {
   if (self.userInteractionEnabled) {