Move node cloning to YGConfig

Summary:
@public

Encapsulates node cloning within `YGConfig`.
This is necessary for allowing for context-aware cloning functions, which will ultimately allow for removal of weak global JNI references.

Reviewed By: shergin

Differential Revision: D14132608

fbshipit-source-id: 0dec114c8e172b1e34a4b7fd146c43f13c151ade

tests/YGConfigTest.cpp

@@ -0,0 +1,60 @@
+/**
+ * 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.
+ */
+// @Generated by gentest/gentest.rb from gentest/fixtures/YGDisplayTest.html
+
+#include <gtest/gtest.h>
+#include <yoga/Yoga.h>
+#include <yoga/YGConfig.h>
+#include <yoga/YGNode.h>
+
+#include <functional>
+#include <memory>
+
+struct ConfigCloningTest : public ::testing::Test {
+  std::unique_ptr<YGConfig, std::function<void(YGConfig*)>> config;
+  void SetUp() override;
+  void TearDown() override;
+
+  static YGNode clonedNode;
+  static YGNodeRef cloneNode(YGNodeRef, YGNodeRef, int) {
+    return &clonedNode;
+  }
+  static YGNodeRef doNotClone(YGNodeRef, YGNodeRef, int) {
+    return nullptr;
+  }
+};
+
+TEST_F(ConfigCloningTest, uses_values_provided_by_cloning_callback) {
+  config->setCloneNodeCallback(cloneNode);
+
+  YGNode node{}, owner{};
+  auto clone = config->cloneNode(&node, &owner, 0);
+
+  ASSERT_EQ(clone, &clonedNode);
+}
+
+TEST_F(
+    ConfigCloningTest,
+    falls_back_to_regular_cloning_if_callback_returns_null) {
+  config->setCloneNodeCallback(doNotClone);
+
+  YGNode node{}, owner{};
+  auto clone = config->cloneNode(&node, &owner, 0);
+
+  ASSERT_NE(clone, nullptr);
+  YGNodeFree(clone);
+}
+
+void ConfigCloningTest::SetUp() {
+  config = {YGConfigNew(), YGConfigFree};
+}
+
+void ConfigCloningTest::TearDown() {
+  config.reset();
+}
+
+YGNode ConfigCloningTest::clonedNode = {};

yoga/YGConfig.cpp

@@ -6,7 +6,7 @@
  */
 #include "YGConfig.h"
 
-YGConfig::YGConfig(YGLogger logger) {
+YGConfig::YGConfig(YGLogger logger) : cloneNodeCallback_{nullptr} {
   logger_.noContext = logger;
   loggerUsesContext_ = false;
 }
@@ -24,3 +24,14 @@ void YGConfig::log(
     logger_.noContext(config, node, logLevel, format, args);
   }
 }
+
+YGNodeRef YGConfig::cloneNode(YGNodeRef node, YGNodeRef owner, int childIndex) {
+  YGNodeRef clone = nullptr;
+  if (cloneNodeCallback_ != nullptr) {
+    clone = cloneNodeCallback_(node, owner, childIndex);
+  }
+  if (clone == nullptr) {
+    clone = YGNodeClone(node);
+  }
+  return clone;
+}

yoga/YGConfig.h

@@ -19,6 +19,7 @@ struct YGConfig {
       va_list args);
 
 private:
+  YGCloneNodeFunc cloneNodeCallback_ = nullptr;
   union {
     LogWithContextFn withContext;
     YGLogger noContext;
@@ -31,7 +32,6 @@ public:
   bool shouldDiffLayoutWithoutLegacyStretchBehaviour = false;
   bool printTree = false;
   float pointScaleFactor = 1.0f;
-  YGCloneNodeFunc cloneNodeCallback = nullptr;
   std::array<bool, facebook::yoga::enums::count<YGExperimentalFeature>()>
       experimentalFeatures = {};
   void* context = nullptr;
@@ -50,4 +50,9 @@ public:
   void setLogger(std::nullptr_t) {
     setLogger(YGLogger{nullptr});
   }
+
+  YGNodeRef cloneNode(YGNodeRef node, YGNodeRef owner, int childIndex);
+  void setCloneNodeCallback(YGCloneNodeFunc cloneNode) {
+    cloneNodeCallback_ = cloneNode;
+  }
 };

yoga/YGNode.cpp

@@ -404,16 +404,9 @@ void YGNode::cloneChildrenIfNeeded() {
     return;
   }
 
-  const YGCloneNodeFunc cloneNodeCallback = config_->cloneNodeCallback;
   for (uint32_t i = 0; i < childCount; ++i) {
     const YGNodeRef oldChild = children_[i];
-    YGNodeRef newChild = nullptr;
-    if (cloneNodeCallback) {
-      newChild = cloneNodeCallback(oldChild, this, i);
-    }
-    if (newChild == nullptr) {
-      newChild = YGNodeClone(oldChild);
-    }
+    YGNodeRef newChild = config_->cloneNode(oldChild, this, i);
     replaceChild(newChild, i);
     newChild->setOwner(this);
   }

yoga/Yoga.cpp

@@ -425,8 +425,6 @@ void YGNodeRemoveChild(const YGNodeRef owner, const YGNodeRef excludedChild) {
   // Otherwise we have to clone the node list except for the child we're trying
   // to delete. We don't want to simply clone all children, because then the
   // host will need to free the clone of the child that was just deleted.
-  const YGCloneNodeFunc cloneNodeCallback =
-      owner->getConfig()->cloneNodeCallback;
   uint32_t nextInsertIndex = 0;
   for (uint32_t i = 0; i < childCount; i++) {
     const YGNodeRef oldChild = owner->getChild(i);
@@ -437,13 +435,8 @@ void YGNodeRemoveChild(const YGNodeRef owner, const YGNodeRef excludedChild) {
       owner->markDirtyAndPropogate();
       continue;
     }
-    YGNodeRef newChild = nullptr;
-    if (cloneNodeCallback) {
-      newChild = cloneNodeCallback(oldChild, owner, nextInsertIndex);
-    }
-    if (newChild == nullptr) {
-      newChild = YGNodeClone(oldChild);
-    }
+    YGNodeRef newChild =
+        owner->getConfig()->cloneNode(oldChild, owner, nextInsertIndex);
     owner->replaceChild(newChild, nextInsertIndex);
     newChild->setOwner(owner);
 
@@ -4293,7 +4286,7 @@ void* YGConfigGetContext(const YGConfigRef config) {
 void YGConfigSetCloneNodeFunc(
     const YGConfigRef config,
     const YGCloneNodeFunc callback) {
-  config->cloneNodeCallback = callback;
+  config->setCloneNodeCallback(callback);
 }
 
 static void YGTraverseChildrenPreOrder(