Add support for context-aware cloning functions

Summary:
@public

Context-aware cloning functions are an internal Yoga feature that will be used for Yoga’s JNI code.

It will be possible to specify a context when calculating layout, which will be passed on to cloning functions. This will be a private feature.

Reviewed By: SidharthGuglani

Differential Revision: D14149470

fbshipit-source-id: 1d11106e65f9d872d10f191763da001f8d158a61

tests/YGConfigTest.cpp

@@ -32,7 +32,7 @@ TEST_F(ConfigCloningTest, uses_values_provided_by_cloning_callback) {
   config->setCloneNodeCallback(cloneNode);
 
   YGNode node{}, owner{};
-  auto clone = config->cloneNode(&node, &owner, 0);
+  auto clone = config->cloneNode(&node, &owner, 0, nullptr);
 
   ASSERT_EQ(clone, &clonedNode);
 }
@@ -43,12 +43,21 @@ TEST_F(
   config->setCloneNodeCallback(doNotClone);
 
   YGNode node{}, owner{};
-  auto clone = config->cloneNode(&node, &owner, 0);
+  auto clone = config->cloneNode(&node, &owner, 0, nullptr);
 
   ASSERT_NE(clone, nullptr);
   YGNodeFree(clone);
 }
 
+TEST_F(ConfigCloningTest, can_clone_with_context) {
+  config->setCloneNodeCallback([](YGNodeRef, YGNodeRef, int, void* context) {
+    return (YGNodeRef) context;
+  });
+
+  YGNode node{}, owner{}, clone{};
+  ASSERT_EQ(config->cloneNode(&node, &owner, 0, &clone), &clone);
+}
+
 void ConfigCloningTest::SetUp() {
   config = {YGConfigNew(), YGConfigFree};
 }

yoga/YGConfig.cpp

@@ -25,10 +25,16 @@ void YGConfig::log(
   }
 }
 
-YGNodeRef YGConfig::cloneNode(YGNodeRef node, YGNodeRef owner, int childIndex) {
+YGNodeRef YGConfig::cloneNode(
+    YGNodeRef node,
+    YGNodeRef owner,
+    int childIndex,
+    void* cloneContext) {
   YGNodeRef clone = nullptr;
-  if (cloneNodeCallback_ != nullptr) {
+  if (cloneNodeCallback_.noContext != nullptr) {
-    clone = cloneNodeCallback_(node, owner, childIndex);
+    clone = cloneNodeUsesContext_
+        ? cloneNodeCallback_.withContext(node, owner, childIndex, cloneContext)
+        : cloneNodeCallback_.noContext(node, owner, childIndex);
   }
   if (clone == nullptr) {
     clone = YGNodeClone(node);

yoga/YGConfig.h

@@ -17,13 +17,22 @@ struct YGConfig {
       void* context,
       const char* format,
       va_list args);
+  using CloneWithContextFn = YGNodeRef (*)(
+      YGNodeRef node,
+      YGNodeRef owner,
+      int childIndex,
+      void* cloneContext);
 
 private:
-  YGCloneNodeFunc cloneNodeCallback_ = nullptr;
+  union {
+    CloneWithContextFn withContext;
+    YGCloneNodeFunc noContext;
+  } cloneNodeCallback_;
   union {
     LogWithContextFn withContext;
     YGLogger noContext;
   } logger_;
+  bool cloneNodeUsesContext_;
   bool loggerUsesContext_;
 
 public:
@@ -51,8 +60,20 @@ public:
     setLogger(YGLogger{nullptr});
   }
 
-  YGNodeRef cloneNode(YGNodeRef node, YGNodeRef owner, int childIndex);
+  YGNodeRef cloneNode(
+      YGNodeRef node,
+      YGNodeRef owner,
+      int childIndex,
+      void* cloneContext);
   void setCloneNodeCallback(YGCloneNodeFunc cloneNode) {
-    cloneNodeCallback_ = cloneNode;
+    cloneNodeCallback_.noContext = cloneNode;
+    cloneNodeUsesContext_ = false;
+  }
+  void setCloneNodeCallback(CloneWithContextFn cloneNode) {
+    cloneNodeCallback_.withContext = cloneNode;
+    cloneNodeUsesContext_ = true;
+  }
+  void setCloneNodeCallback(std::nullptr_t) {
+    setCloneNodeCallback(YGCloneNodeFunc{nullptr});
   }
 };

yoga/YGNode.cpp

@@ -385,8 +385,8 @@ void YGNode::clearChildren() {
 
 // Other Methods
 
-void YGNode::cloneChildrenIfNeeded() {
+void YGNode::cloneChildrenIfNeeded(void* cloneContext) {
-  iterChildrenAfterCloningIfNeeded([](YGNodeRef) {});
+  iterChildrenAfterCloningIfNeeded([](YGNodeRef, void*) {}, cloneContext);
 }
 
 void YGNode::markDirtyAndPropogate() {

yoga/YGNode.h

@@ -146,16 +146,16 @@ public:
   // Applies a callback to all children, after cloning them if they are not
   // owned.
   template <typename T>
-  void iterChildrenAfterCloningIfNeeded(T callback) {
+  void iterChildrenAfterCloningIfNeeded(T callback, void* cloneContext) {
     int i = 0;
     for (YGNodeRef& child : children_) {
       if (child->getOwner() != this) {
-        child = config_->cloneNode(child, this, i);
+        child = config_->cloneNode(child, this, i, cloneContext);
         child->setOwner(this);
       }
       i += 1;
 
-      callback(child);
+      callback(child, cloneContext);
     }
   }
 
@@ -335,7 +335,7 @@ public:
   bool removeChild(YGNodeRef child);
   void removeChild(uint32_t index);
 
-  void cloneChildrenIfNeeded();
+  void cloneChildrenIfNeeded(void*);
   void markDirtyAndPropogate();
   float resolveFlexGrow();
   float resolveFlexShrink();

yoga/Yoga.cpp

@@ -1789,13 +1789,16 @@ static bool YGNodeFixedSizeSetMeasuredDimensions(
   return false;
 }
 
-static void YGZeroOutLayoutRecursivly(const YGNodeRef node) {
+static void YGZeroOutLayoutRecursivly(
+    const YGNodeRef node,
+    void* layoutContext) {
   node->getLayout() = {};
   node->setLayoutDimension(0, 0);
   node->setLayoutDimension(0, 1);
   node->setHasNewLayout(true);
 
-  node->iterChildrenAfterCloningIfNeeded(YGZeroOutLayoutRecursivly);
+  node->iterChildrenAfterCloningIfNeeded(
+      YGZeroOutLayoutRecursivly, layoutContext);
 }
 
 static float YGNodeCalculateAvailableInnerDim(
@@ -1877,7 +1880,7 @@ static float YGNodeComputeFlexBasisForChildren(
   for (auto child : children) {
     child->resolveDimension();
     if (child->getStyle().display == YGDisplayNone) {
-      YGZeroOutLayoutRecursivly(child);
+      YGZeroOutLayoutRecursivly(child, layoutContext);
       child->setHasNewLayout(true);
       child->setDirty(false);
       continue;
@@ -2751,7 +2754,7 @@ static void YGNodelayoutImpl(
 
   // At this point we know we're going to perform work. Ensure that each child
   // has a mutable copy.
-  node->cloneChildrenIfNeeded();
+  node->cloneChildrenIfNeeded(layoutContext);
   // Reset layout flags, as they could have changed.
   node->setLayoutHadOverflow(false);