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

tests/EventsTest.cpp

@@ -0,0 +1,118 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the LICENSE
+ * file in the root directory of this source tree.
+ */
+#include <gtest/gtest.h>
+#include <yoga/Yoga.h>
+#include <yoga/events.h>
+#include <yoga/YGNode.h>
+
+#include <functional>
+#include <memory>
+
+namespace facebook {
+namespace yoga {
+namespace test {
+
+struct EventArgs {
+  const YGNode* node;
+  Event::Type type;
+  std::unique_ptr<void, std::function<void(void*)>> dataPtr;
+
+  template <Event::Type E>
+  const Event::TypedData<E>& data() {
+    return *static_cast<Event::TypedData<E>*>(dataPtr.get());
+  }
+};
+
+struct EventTest : public ::testing::Test {
+  static EventArgs lastEvent;
+  static void SetUpTestCase() noexcept;
+};
+
+TEST_F(EventTest, new_node_has_event) {
+  auto c = YGConfigGetDefault();
+  auto n = YGNodeNew();
+
+  ASSERT_EQ(lastEvent.node, n);
+  ASSERT_EQ(lastEvent.type, Event::NodeAllocation);
+  ASSERT_EQ(lastEvent.data<Event::NodeAllocation>().config, c);
+
+  YGNodeFree(n);
+}
+
+TEST_F(EventTest, new_node_with_config_event) {
+  auto c = YGConfigNew();
+  auto n = YGNodeNewWithConfig(c);
+
+  ASSERT_EQ(lastEvent.node, n);
+  ASSERT_EQ(lastEvent.type, Event::NodeAllocation);
+  ASSERT_EQ(lastEvent.data<Event::NodeAllocation>().config, c);
+
+  YGNodeFree(n);
+  YGConfigFree(c);
+}
+
+TEST_F(EventTest, clone_node_event) {
+  auto c = YGConfigNew();
+  auto n = YGNodeNewWithConfig(c);
+  auto clone = YGNodeClone(n);
+
+  ASSERT_EQ(lastEvent.node, clone);
+  ASSERT_EQ(lastEvent.type, Event::NodeAllocation);
+  ASSERT_EQ(lastEvent.data<Event::NodeAllocation>().config, c);
+
+  YGNodeFree(n);
+  YGNodeFree(clone);
+  YGConfigFree(c);
+}
+
+TEST_F(EventTest, free_node_event) {
+  auto c = YGConfigNew();
+  auto n = YGNodeNewWithConfig(c);
+  YGNodeFree(n);
+
+  ASSERT_EQ(lastEvent.node, n);
+  ASSERT_EQ(lastEvent.type, Event::NodeDeallocation);
+  ASSERT_EQ(lastEvent.data<Event::NodeDeallocation>().config, c);
+
+  YGConfigFree(c);
+}
+
+namespace {
+
+template <Event::Type E>
+EventArgs createArgs(const YGNode& node, const Event::Data& data) {
+  using Data = Event::TypedData<E>;
+  auto deleteData = [](void* x) { delete static_cast<Data*>(x); };
+  return {&node, E, {new Data{data.get<E>()}, deleteData}};
+}
+
+} // namespace
+
+void EventTest::SetUpTestCase() noexcept {
+  static bool isSetup = false;
+  if (isSetup) {
+    return;
+  }
+  isSetup = true;
+
+  Event::subscribe([](const YGNode& node, Event::Type type, Event::Data data) {
+    switch (type) {
+      case Event::NodeAllocation:
+        lastEvent = createArgs<Event::NodeAllocation>(node, data);
+        break;
+      case Event::NodeDeallocation:
+        lastEvent = createArgs<Event::NodeDeallocation>(node, data);
+        break;
+    }
+  });
+}
+
+EventArgs EventTest::lastEvent{};
+
+} // namespace test
+} // namespace yoga
+} // namespace facebook