Marker for measure callbacks

Summary:
@public

Wraps measure callbacks with a marker.

Reviewed By: SidharthGuglani

Differential Revision: D13896745

fbshipit-source-id: d6e14fe93f666b06516be1aef7f8e1bfe45440a7

yoga/YGMarker.h

@@ -15,6 +15,7 @@ typedef struct YGConfig* YGConfigRef;
 
 typedef YG_ENUM_BEGIN(YGMarker){
     YGMarkerLayout,
+    YGMarkerMeasure,
 } YG_ENUM_END(YGMarker);
 
 typedef struct {
@@ -25,8 +26,13 @@ typedef struct {
   int cachedMeasures;
 } YGMarkerLayoutData;
 
+typedef struct {
+  bool _unused;
+} YGMarkerNoData;
+
 typedef union {
   YGMarkerLayoutData* layout;
+  YGMarkerNoData* noData;
 } YGMarkerData;
 
 typedef struct {
@@ -55,16 +61,24 @@ struct MarkerData;
 template <>
 struct MarkerData<YGMarkerLayout> {
   using type = YGMarkerLayoutData;
+  static type*& get(YGMarkerData& d) {
+    return d.layout;
+  }
+};
+
+template <>
+struct MarkerData<YGMarkerMeasure> {
+  using type = YGMarkerNoData;
+  static type*& get(YGMarkerData& d) {
+    return d.noData;
+  }
 };
 
 } // namespace detail
 
 template <YGMarker M>
-typename detail::MarkerData<M>::type* data(YGMarkerData) = delete;
-
-template <>
-inline YGMarkerLayoutData* data<YGMarkerLayout>(YGMarkerData d) {
-  return d.layout;
+typename detail::MarkerData<M>::type* data(YGMarkerData d) {
+  return detail::MarkerData<M>::get(d);
 }
 
 } // namespace marker

yoga/Yoga.cpp

@@ -1688,8 +1688,14 @@ static void YGNodeWithMeasureFuncSetMeasuredDimensions(
         YGDimensionHeight);
   } else {
     // Measure the text under the current constraints.
-    const YGSize measuredSize = node->getMeasure()(
-        node, innerWidth, widthMeasureMode, innerHeight, heightMeasureMode);
+    const YGSize measuredSize = marker::MarkerSection<YGMarkerMeasure>::wrap(
+        node,
+        node->getMeasure(),
+        node,
+        innerWidth,
+        widthMeasureMode,
+        innerHeight,
+        heightMeasureMode);
 
     node->setLayoutMeasuredDimension(
         YGNodeBoundAxis(

yoga/instrumentation.h

@@ -14,15 +14,24 @@ namespace marker {
 
 template <YGMarker MarkerType>
 class MarkerSection {
+private:
+  using Data = detail::MarkerData<MarkerType>;
+
 public:
   MarkerSection(YGNodeRef node) : MarkerSection{node, node->getConfig()} {}
   ~MarkerSection() {
     if (endMarker_) {
-      endMarker_(MarkerType, node_, {&data}, userData_);
+      endMarker_(MarkerType, node_, markerData(&data), userData_);
     }
   }
 
-  typename detail::MarkerData<MarkerType>::type data = {};
+  typename Data::type data = {};
+
+  template <typename Ret, typename... Args>
+  static Ret wrap(YGNodeRef node, Ret (*fn)(Args...), Args... args) {
+    MarkerSection<MarkerType> section{node};
+    return fn(std::forward<Args>(args)...);
+  }
 
 private:
   decltype(YGMarkerCallbacks{}.endMarker) endMarker_;
@@ -34,9 +43,16 @@ private:
   MarkerSection(YGNodeRef node, YGMarkerCallbacks* callbacks)
       : endMarker_{callbacks ? callbacks->endMarker : nullptr},
         node_{node},
-        userData_{callbacks && callbacks->startMarker
-                      ? callbacks->startMarker(MarkerType, node, {&data})
-                      : nullptr} {}
+        userData_{
+            callbacks && callbacks->startMarker
+                ? callbacks->startMarker(MarkerType, node, markerData(&data))
+                : nullptr} {}
+
+  static YGMarkerData markerData(typename Data::type* d) {
+    YGMarkerData markerData = {};
+    Data::get(markerData) = d;
+    return markerData;
+  }
 };
 
 } // namespace marker