From 19387925170ac3c7a776c1eaaf3268a2f59d137b Mon Sep 17 00:00:00 2001
From: David Aurelio <davidaurelio@fb.com>
Date: Mon, 20 May 2019 10:37:59 -0700
Subject: [PATCH] `YGNode`: Field for web defaults

Summary:
In order to remove the config pointer from nodes, we have to keep track of whether the node is using web defaults.
This information fits into one bit that we can place in padding (i.e. no extra memory needed).

This allows us to get rid of config usage withing `YGNode` with some exceptions:

- `iterChildrenAfterCloningIfNeeded` -- this function will simply receive the configuration, or the cloning callback.
- `setAndPropogateUseLegacyFlag` -- will be removed in D15316863
- in `YGNode::reset` -- will go away utomatically once we remove the config pointer

Reviewed By: SidharthGuglani

Differential Revision: D15391536

fbshipit-source-id: 0fa0d0805c6862bd741fe4a7d9b637ed534f56a4
---
 yoga/YGNode.cpp | 24 +++++++++++++++---------
 yoga/YGNode.h   | 23 ++++++++++++++++++++---
 yoga/Yoga.cpp   |  7 +------
 3 files changed, 36 insertions(+), 18 deletions(-)

diff --git a/yoga/YGNode.cpp b/yoga/YGNode.cpp
index 2c68d607..172da871 100644
--- a/yoga/YGNode.cpp
+++ b/yoga/YGNode.cpp
@@ -22,6 +22,7 @@ YGNode::YGNode(YGNode&& node) {
   measureUsesContext_ = node.measureUsesContext_;
   baselineUsesContext_ = node.baselineUsesContext_;
   printUsesContext_ = node.printUsesContext_;
+  useWebDefaults_ = node.useWebDefaults_;
   measure_ = node.measure_;
   baseline_ = node.baseline_;
   print_ = node.print_;
@@ -38,6 +39,13 @@ YGNode::YGNode(YGNode&& node) {
   }
 }
 
+YGNode::YGNode(const YGNode& node, YGConfigRef config) : YGNode{node} {
+  config_ = config;
+  if (config->useWebDefaults) {
+    useWebDefaults();
+  }
+}
+
 void YGNode::print(void* printContext) {
   if (print_.noContext != nullptr) {
     if (printUsesContext_) {
@@ -349,7 +357,7 @@ YGValue YGNode::resolveFlexBasisPtr() const {
     return flexBasis;
   }
   if (!style_.flex().isUndefined() && style_.flex().unwrap() > 0.0f) {
-    return config_->useWebDefaults ? YGValueAuto : YGValueZero;
+    return useWebDefaults_ ? YGValueAuto : YGValueZero;
   }
   return YGValueAuto;
 }
@@ -425,11 +433,11 @@ float YGNode::resolveFlexShrink() const {
   if (!style_.flexShrink().isUndefined()) {
     return style_.flexShrink().unwrap();
   }
-  if (!config_->useWebDefaults && !style_.flex().isUndefined() &&
+  if (!useWebDefaults_ && !style_.flex().isUndefined() &&
       style_.flex().unwrap() < 0.0f) {
     return -style_.flex().unwrap();
   }
-  return config_->useWebDefaults ? kWebDefaultFlexShrink : kDefaultFlexShrink;
+  return useWebDefaults_ ? kWebDefaultFlexShrink : kDefaultFlexShrink;
 }
 
 bool YGNode::isNodeFlexible() {
@@ -581,11 +589,9 @@ void YGNode::reset() {
 
   clearChildren();
 
-  auto config = getConfig();
-  *this = YGNode{};
-  if (config->useWebDefaults) {
-    style_.flexDirection() = YGFlexDirectionRow;
-    style_.alignContent() = YGAlignStretch;
+  auto webDefaults = useWebDefaults_;
+  *this = YGNode{getConfig()};
+  if (webDefaults) {
+    useWebDefaults();
   }
-  setConfig(config);
 }
diff --git a/yoga/YGNode.h b/yoga/YGNode.h
index bbd1b703..d368bde0 100644
--- a/yoga/YGNode.h
+++ b/yoga/YGNode.h
@@ -13,6 +13,8 @@
 #include "YGStyle.h"
 #include "Yoga-internal.h"
 
+YGConfigRef YGConfigGetDefault();
+
 struct YGNode {
   using MeasureWithContextFn =
       YGSize (*)(YGNode*, float, YGMeasureMode, float, YGMeasureMode, void*);
@@ -28,6 +30,7 @@ private:
   bool measureUsesContext_ : 1;
   bool baselineUsesContext_ : 1;
   bool printUsesContext_ : 1;
+  bool useWebDefaults_ : 1;
   uint8_t reserved_ = 0;
   union {
     YGMeasureFunc noContext;
@@ -58,6 +61,12 @@ private:
   void setMeasureFunc(decltype(measure_));
   void setBaselineFunc(decltype(baseline_));
 
+  void useWebDefaults() {
+    useWebDefaults_ = true;
+    style_.flexDirection() = YGFlexDirectionRow;
+    style_.alignContent() = YGAlignStretch;
+  }
+
   // DANGER DANGER DANGER!
   // If the the node assigned to has children, we'd either have to deallocate
   // them (potentially incorrect) or ignore them (danger of leaks). Only ever
@@ -68,8 +77,8 @@ private:
   using CompactValue = facebook::yoga::detail::CompactValue;
 
 public:
-  YGNode() : YGNode{nullptr} {}
-  explicit YGNode(const YGConfigRef newConfig)
+  YGNode() : YGNode{YGConfigGetDefault()} {}
+  explicit YGNode(const YGConfigRef config)
       : hasNewLayout_{true},
         isReferenceBaseline_{false},
         isDirty_{false},
@@ -77,7 +86,12 @@ public:
         measureUsesContext_{false},
         baselineUsesContext_{false},
         printUsesContext_{false},
-        config_{newConfig} {};
+        useWebDefaults_{config->useWebDefaults},
+        config_{config} {
+    if (useWebDefaults_) {
+      useWebDefaults();
+    }
+  };
   ~YGNode() = default; // cleanup of owner/children relationships in YGNodeFree
 
   YGNode(YGNode&&);
@@ -86,6 +100,9 @@ public:
   // Should we remove this?
   YGNode(const YGNode& node) = default;
 
+  // for RB fabric
+  YGNode(const YGNode& node, YGConfigRef config);
+
   // assignment means potential leaks of existing children, or alternatively
   // freeing unowned memory, double free, or freeing stack memory.
   YGNode& operator=(const YGNode&) = delete;
diff --git a/yoga/Yoga.cpp b/yoga/Yoga.cpp
index f7322980..bcca9795 100644
--- a/yoga/Yoga.cpp
+++ b/yoga/Yoga.cpp
@@ -210,18 +210,13 @@ void YGNodeMarkDirtyAndPropogateToDescendants(const YGNodeRef node) {
 int32_t gConfigInstanceCount = 0;
 
 WIN_EXPORT YGNodeRef YGNodeNewWithConfig(const YGConfigRef config) {
-  const YGNodeRef node = new YGNode();
+  const YGNodeRef node = new YGNode{config};
   YGAssertWithConfig(
       config, node != nullptr, "Could not allocate memory for node");
 #ifdef YG_ENABLE_EVENTS
   Event::publish<Event::NodeAllocation>(node, {config});
 #endif
 
-  if (config->useWebDefaults) {
-    node->getStyle().flexDirection() = YGFlexDirectionRow;
-    node->getStyle().alignContent() = YGAlignStretch;
-  }
-  node->setConfig(config);
   return node;
 }