Simplify bitfields (#1393)

Summary:
X-link: https://github.com/facebook/react-native/pull/39485

Pull Request resolved: https://github.com/facebook/yoga/pull/1393

These were previously packed into structs to allow zero initializing all the flags at once without needing a ctor. C++ 20 has in-class member initializer support for bitfields, which makes these look more like normal member variables.

Setting enum values is a bit jank right now, due to relying on C enums which are effectively int32_t, along with GCC `-Wconversion` being a bit aggressive in needing to explicitly mask. I have some ideas to fix this later (e.g. using scoped enums internally).

bypass-github-export-checks

Changelog:
[General][Breaking] - Require C++ 20 when including renderer headers

Reviewed By: sammy-SC

Differential Revision: D49265967

fbshipit-source-id: 6ab935a866196df06e742c821f3af88eb4d18e1a

yoga/node/Node.cpp

@@ -23,15 +23,17 @@ Node::Node(const yoga::Config* config) : config_{config} {
   yoga::assertFatal(
       config != nullptr, "Attempting to construct Node with null config");
 
-  flags_.hasNewLayout = true;
   if (config->useWebDefaults()) {
     useWebDefaults();
   }
 }
 
 Node::Node(Node&& node) {
+  hasNewLayout_ = node.hasNewLayout_;
+  isReferenceBaseline_ = node.isReferenceBaseline_;
+  isDirty_ = node.isDirty_;
+  nodeType_ = node.nodeType_;
   context_ = node.context_;
-  flags_ = node.flags_;
   measureFunc_ = node.measureFunc_;
   baselineFunc_ = node.baselineFunc_;
   printFunc_ = node.printFunc_;
@@ -271,10 +273,10 @@ void Node::setConfig(yoga::Config* config) {
 }
 
 void Node::setDirty(bool isDirty) {
-  if (isDirty == flags_.isDirty) {
+  if (isDirty == isDirty_) {
     return;
   }
-  flags_.isDirty = isDirty;
+  isDirty_ = isDirty;
   if (isDirty && dirtiedFunc_) {
     dirtiedFunc_(this);
   }
@@ -473,7 +475,7 @@ void Node::cloneChildrenIfNeeded() {
 }
 
 void Node::markDirtyAndPropagate() {
-  if (!flags_.isDirty) {
+  if (!isDirty_) {
     setDirty(true);
     setLayoutComputedFlexBasis(FloatOptional());
     if (owner_) {
@@ -483,7 +485,7 @@ void Node::markDirtyAndPropagate() {
 }
 
 void Node::markDirtyAndPropagateDownwards() {
-  flags_.isDirty = true;
+  isDirty_ = true;
   for_each(children_.begin(), children_.end(), [](Node* childNode) {
     childNode->markDirtyAndPropagateDownwards();
   });