Publish events for node allocation and deallocation

Summary:
@public

Publish two events, `NodeAllocation` and `NodeDeallocation`, in the same places where the global node counter is changed.

Reviewed By: SidharthGuglani

Differential Revision: D15174858

fbshipit-source-id: 6e4e9add88513b9e987189ca5035d76da2a1de55

yoga/Yoga.cpp

@@ -13,6 +13,7 @@
 #include "YGNode.h"
 #include "YGNodePrint.h"
 #include "Yoga-internal.h"
+#include "events.h"
 #include "instrumentation.h"
 #ifdef _MSC_VER
 #include <float.h>
@@ -213,6 +214,9 @@ WIN_EXPORT YGNodeRef YGNodeNewWithConfig(const YGConfigRef config) {
   YGAssertWithConfig(
       config, node != nullptr, "Could not allocate memory for node");
   gNodeInstanceCount++;
+#ifdef YG_ENABLE_EVENTS
+  Event::publish<Event::NodeAllocation>(node, {config});
+#endif
 
   if (config->useWebDefaults) {
     node->getStyle().flexDirection() = YGFlexDirectionRow;
@@ -238,6 +242,9 @@ YGNodeRef YGNodeClone(YGNodeRef oldNode) {
       node != nullptr,
       "Could not allocate memory for node");
   gNodeInstanceCount++;
+#ifdef YG_ENABLE_EVENTS
+  Event::publish<Event::NodeAllocation>(node, {node->getConfig()});
+#endif
   node->setOwner(nullptr);
   return node;
 }
@@ -284,6 +291,9 @@ void YGNodeFree(const YGNodeRef node) {
   }
 
   node->clearChildren();
+#ifdef YG_ENABLE_EVENTS
+  Event::publish<Event::NodeDeallocation>(node, {node->getConfig()});
+#endif
   delete node;
   gNodeInstanceCount--;
 }

yoga/events.cpp

@@ -8,6 +8,8 @@
 #include <memory>
 #include <stdexcept>
 
+#include <iostream>
+
 namespace facebook {
 namespace yoga {
 

yoga/events.h

@@ -15,7 +15,7 @@ namespace facebook {
 namespace yoga {
 
 struct Event {
-  enum Type {};
+  enum Type { NodeAllocation, NodeDeallocation };
   class Data;
   using Subscriber = void(const YGNode&, Type, Data);
 
@@ -51,5 +51,15 @@ private:
   static void publish(const YGNode&, Type, const Data&);
 };
 
+template <>
+struct Event::TypedData<Event::NodeAllocation> {
+  YGConfig* config;
+};
+
+template <>
+struct Event::TypedData<Event::NodeDeallocation> {
+  YGConfig* config;
+};
+
 } // namespace yoga
 } // namespace facebook