Fabric: Introducting EventBeat::setFailCallback

Summary: In some cases we have to have a way to notify a EventBeat consumer that the beat cannot be (and will not be) delivered, so we introducing special API for that.

Reviewed By: mdvacca

Differential Revision: D10081503

fbshipit-source-id: 4c5a392d32572f426e3744bdba797efcd29b8cb4

ReactCommon/fabric/events/EventBeat.cpp

@@ -34,5 +34,9 @@ void EventBeat::setBeatCallback(const BeatCallback &beatCallback) {
   beatCallback_ = beatCallback;
 }
 
+void EventBeat::setFailCallback(const FailCallback &failCallback) {
+  failCallback_ = failCallback;
+}
+
 } // namespace react
 } // namespace facebook

ReactCommon/fabric/events/EventBeat.h

@@ -24,6 +24,7 @@ public:
   virtual ~EventBeat() = default;
 
   using BeatCallback = std::function<void()>;
+  using FailCallback = std::function<void()>;
 
   /*
    * Communicates to the Beat that a consumer is waiting for the coming beat.
@@ -44,11 +45,19 @@ public:
   virtual void induce() const;
 
   /*
-   * Sets a callback function.
+   * Sets the beat callback function.
    * The callback is must be called on the proper thread.
    */
   void setBeatCallback(const BeatCallback &beatCallback);
 
+  /*
+   * Sets the fail callback function.
+   * Called in case if the beat cannot be performed anymore because of
+   * some external circumstances (e.g. execution thread is beling destructed).
+   * The callback can be called on any thread.
+   */
+  void setFailCallback(const FailCallback &failCallback);
+
 protected:
   /*
    * Should be used by sublasses to send a beat.
@@ -57,6 +66,7 @@ protected:
   void beat() const;
 
   BeatCallback beatCallback_;
+  FailCallback failCallback_;
   mutable std::atomic<bool> isRequested_ {false};
 };