fabric: send events via JS thread

Summary: Calling the event emitters on the main thread seems to be problematic, so let's dispatch it via the JS thread. This requires some changes to make "eventTarget" single-use because otherwise the binding would need to synchronize the actual JS call with the act of releasing the target.

Reviewed By: shergin

Differential Revision: D8375291

fbshipit-source-id: bd2b42731176ae209f4a19c232309c163fb1c01b

React/CxxBridge/RCTCxxBridge.mm

@@ -188,6 +188,11 @@ struct RCTInstanceCallback : public InstanceCallback {
   return (JSGlobalContextRef)(_reactInstance ? _reactInstance->getJavaScriptContext() : nullptr);
 }
 
+- (std::shared_ptr<MessageQueueThread>)jsMessageThread
+{
+  return _jsMessageThread;
+}
+
 - (BOOL)isInspectable
 {
   return _reactInstance ? _reactInstance->isInspectable() : NO;

ReactCommon/fabric/core/events/EventDispatcher.h

@@ -30,8 +30,6 @@ public:
 
   virtual EventTarget createEventTarget(const InstanceHandle &instanceHandle) const = 0;
 
-  virtual void releaseEventTarget(const EventTarget &eventTarget) const = 0;
-
   /*
    * Dispatches "raw" event using some event-delivery infrastructure.
    */

ReactCommon/fabric/core/events/EventEmitter.cpp

@@ -17,9 +17,7 @@ EventEmitter::EventEmitter(const InstanceHandle &instanceHandle, const Tag &tag,
   tag_(tag),
   eventDispatcher_(eventDispatcher) {}
 
-EventEmitter::~EventEmitter() {
+EventEmitter::~EventEmitter() {}
-  releaseEventTargetIfNeeded();
-}
 
 void EventEmitter::dispatchEvent(
   const std::string &type,
@@ -31,7 +29,7 @@ void EventEmitter::dispatchEvent(
     return;
   }
 
-  createEventTargetIfNeeded();
+  EventTarget eventTarget = createEventTarget();
 
   // Mixing `target` into `payload`.
   assert(payload.isObject());
@@ -39,31 +37,13 @@ void EventEmitter::dispatchEvent(
   extendedPayload.merge_patch(payload);
 
   // TODO(T29610783): Reconsider using dynamic dispatch here.
-  eventDispatcher->dispatchEvent(eventTarget_, type, extendedPayload, priority);
+  eventDispatcher->dispatchEvent(eventTarget, type, extendedPayload, priority);
 }
 
-void EventEmitter::createEventTargetIfNeeded() const {
+EventTarget EventEmitter::createEventTarget() const {
-  std::lock_guard<std::mutex> lock(mutex_);
-
-  if (eventTarget_) {
-    return;
-  }
-
   auto &&eventDispatcher = eventDispatcher_.lock();
   assert(eventDispatcher);
-  eventTarget_ = eventDispatcher->createEventTarget(instanceHandle_);
+  return eventDispatcher->createEventTarget(instanceHandle_);
-}
-
-void EventEmitter::releaseEventTargetIfNeeded() const {
-  std::lock_guard<std::mutex> lock(mutex_);
-
-  if (!eventTarget_) {
-    return;
-  }
-
-  auto &&eventDispatcher = eventDispatcher_.lock();
-  assert(eventDispatcher);
-  eventDispatcher->releaseEventTarget(eventTarget_);
 }
 
 } // namespace react

ReactCommon/fabric/core/events/EventEmitter.h

@@ -48,14 +48,11 @@ protected:
 
 private:
 
-  void createEventTargetIfNeeded() const;
+  EventTarget createEventTarget() const;
-  void releaseEventTargetIfNeeded() const;
 
   InstanceHandle instanceHandle_;
   Tag tag_;
   std::weak_ptr<const EventDispatcher> eventDispatcher_;
-  mutable EventTarget eventTarget_ {nullptr};
-  mutable std::mutex mutex_;
 };
 
 } // namespace react

ReactCommon/fabric/uimanager/FabricUIManager.cpp

@@ -98,10 +98,6 @@ void FabricUIManager::setDispatchEventFunction(std::function<DispatchEventFuncti
   dispatchEventFunction_ = dispatchEventFunction;
 }
 
-void FabricUIManager::setReleaseEventTargetFunction(std::function<ReleaseEventTargetFunction> releaseEventTargetFunction) {
-  releaseEventTargetFunction_ = releaseEventTargetFunction;
-}
-
 void FabricUIManager::setReleaseEventHandlerFunction(std::function<ReleaseEventHandlerFunction> releaseEventHandlerFunction) {
   releaseEventHandlerFunction_ = releaseEventHandlerFunction;
 }
@@ -119,10 +115,6 @@ void FabricUIManager::dispatchEvent(const EventTarget &eventTarget, const std::s
   );
 }
 
-void FabricUIManager::releaseEventTarget(const EventTarget &eventTarget) const {
-  releaseEventTargetFunction_(eventTarget);
-}
-
 SharedShadowNode FabricUIManager::createNode(int tag, std::string viewName, int rootTag, folly::dynamic props, InstanceHandle instanceHandle) {
   isLoggingEnabled && LOG(INFO) << "FabricUIManager::createNode(tag: " << tag << ", name: " << viewName << ", rootTag: " << rootTag << ", props: " << props << ")";
 

ReactCommon/fabric/uimanager/FabricUIManager.h

@@ -20,7 +20,6 @@ namespace react {
 
 using CreateEventTargetFunction = EventTarget (InstanceHandle instanceHandle);
 using DispatchEventFunction = void (EventHandler eventHandler, EventTarget eventTarget, std::string type, folly::dynamic payload);
-using ReleaseEventTargetFunction = void (EventTarget eventTarget);
 using ReleaseEventHandlerFunction = void (EventHandler eventHandler);
 
 class FabricUIManager {
@@ -46,14 +45,12 @@ public:
    */
   void setCreateEventTargetFunction(std::function<CreateEventTargetFunction> createEventTargetFunction);
   void setDispatchEventFunction(std::function<DispatchEventFunction> dispatchEventFunction);
-  void setReleaseEventTargetFunction(std::function<ReleaseEventTargetFunction> releaseEventTargetFunction);
   void setReleaseEventHandlerFunction(std::function<ReleaseEventHandlerFunction> releaseEventHandlerFunction);
 
 #pragma mark - Native-facing Interface
 
   EventTarget createEventTarget(const InstanceHandle &instanceHandle) const;
   void dispatchEvent(const EventTarget &eventTarget, const std::string &type, const folly::dynamic &payload) const;
-  void releaseEventTarget(const EventTarget &eventTarget) const;
 
 #pragma mark - JavaScript/React-facing Interface
 
@@ -75,7 +72,6 @@ private:
   EventHandler eventHandler_;
   std::function<CreateEventTargetFunction> createEventTargetFunction_;
   std::function<DispatchEventFunction> dispatchEventFunction_;
-  std::function<ReleaseEventTargetFunction> releaseEventTargetFunction_;
   std::function<ReleaseEventHandlerFunction> releaseEventHandlerFunction_;
 };
 

ReactCommon/fabric/uimanager/SchedulerEventDispatcher.cpp

@@ -30,16 +30,13 @@ EventTarget SchedulerEventDispatcher::createEventTarget(const InstanceHandle &in
   return uiManager_->createEventTarget(instanceHandle);
 }
 
-void SchedulerEventDispatcher::releaseEventTarget(const EventTarget &eventTarget) const {
-  uiManager_->releaseEventTarget(eventTarget);
-}
-
 void SchedulerEventDispatcher::dispatchEvent(
   const EventTarget &eventTarget,
   const std::string &type,
   const folly::dynamic &payload,
   const EventPriority &priority
 ) const {
+  // TODO: Schedule the event based on priority.
   uiManager_->dispatchEvent(eventTarget, normalizeEventType(type), payload);
 }
 

ReactCommon/fabric/uimanager/SchedulerEventDispatcher.h

@@ -33,8 +33,6 @@ public:
 
   EventTarget createEventTarget(const InstanceHandle &instanceHandle) const override;
 
-  void releaseEventTarget(const EventTarget &eventTarget) const override;
-
   void dispatchEvent(
     const EventTarget &eventTarget,
     const std::string &type,