Layout marker metadata

Summary:
@public

Adds marker meta data to `YGMarkerLayout`: the number of measures, and the numbers of layouts for all nodes in the tree.

Reviewed By: SidharthGuglani

Differential Revision: D13838975

fbshipit-source-id: d575c26a3d5a4f0b66834eb6bedecadc3f3ca265

yoga/YGMarker.h

@@ -18,7 +18,8 @@ typedef YG_ENUM_BEGIN(YGMarker){
 } YG_ENUM_END(YGMarker);
 
 typedef struct {
-  int unused;
+  int layouts;
+  int measures;
 } YGMarkerLayoutData;
 
 typedef union {
@@ -54,6 +55,15 @@ struct MarkerData<YGMarkerLayout> {
 };
 
 } // namespace detail
+
+template <YGMarker M>
+typename detail::MarkerData<M>::type* data(YGMarkerData) = delete;
+
+template <>
+inline YGMarkerLayoutData* data<YGMarkerLayout>(YGMarkerData d) {
+  return d.layout;
+}
+
 } // namespace marker
 } // namespace yoga
 } // namespace facebook

yoga/Yoga.cpp

@@ -2685,6 +2685,8 @@ static void YGNodelayoutImpl(
       "availableHeight is indefinite so heightMeasureMode must be "
       "YGMeasureModeUndefined");
 
+  (performLayout ? layoutMarkerData.layouts : layoutMarkerData.measures) += 1;
+
   // Set the resolved resolution in the node's layout.
   const YGDirection direction = node->resolveDirection(ownerDirection);
   node->setLayoutDirection(direction);