Publish event when visiting nodes during layout

Summary:
@public

Publish an event when visiting nodes during layouts.

Reviewed By: SidharthGuglani

Differential Revision: D15206965

fbshipit-source-id: c201f084b1d4186bc64560b8033be965f2549236

yoga/Yoga.cpp

@@ -3667,6 +3667,9 @@ bool YGLayoutNodeInternal(
     const YGConfigRef config,
     YGMarkerLayoutData& layoutMarkerData,
     void* const layoutContext) {
+#ifdef YG_ENABLE_EVENTS
+  Event::publish<Event::NodeLayout>(node);
+#endif
   YGLayout* layout = &node->getLayout();
 
   gDepth++;

yoga/events.h

@@ -15,7 +15,7 @@ namespace facebook {
 namespace yoga {
 
 struct Event {
-  enum Type { NodeAllocation, NodeDeallocation };
+  enum Type { NodeAllocation, NodeDeallocation, NodeLayout };
   class Data;
   using Subscriber = void(const YGNode&, Type, Data);