for experimentation: configurable measure cache size

Summary:
@public

Allows to limit the number of measure cache entries used. This is purely for experimentation.

The measure cache uses about half of every `YGNode`. Reducing its size would allow us to reduce resident memory used by Yoga.

Reviewed By: SidharthGuglani

Differential Revision: D14279027

fbshipit-source-id: e0d22138230bee7fb129c193eb6e4085de02a36e

yoga/Yoga.cpp

@@ -28,6 +28,15 @@ __forceinline const float fmaxf(const float a, const float b) {
 using namespace facebook::yoga;
 using detail::Log;
 
+namespace {
+size_t usedMeasureCacheEntries = YG_MAX_CACHED_RESULT_COUNT;
+}
+
+void YGSetUsedCachedEntries(size_t n) {
+  usedMeasureCacheEntries =
+      n == 0 || n > YG_MAX_CACHED_RESULT_COUNT ? YG_MAX_CACHED_RESULT_COUNT : n;
+}
+
 #ifdef ANDROID
 static int YGAndroidLog(
     const YGConfigRef config,
@@ -3871,7 +3880,7 @@ bool YGLayoutNodeInternal(
         layoutMarkerData.maxMeasureCache =
             layout->nextCachedMeasurementsIndex + 1;
       }
-      if (layout->nextCachedMeasurementsIndex == YG_MAX_CACHED_RESULT_COUNT) {
+      if (layout->nextCachedMeasurementsIndex == usedMeasureCacheEntries) {
         if (gPrintChanges) {
           Log::log(node, YGLogLevelVerbose, nullptr, "Out of cache entries!\n");
         }

yoga/Yoga.h

@@ -411,6 +411,8 @@ WIN_EXPORT float YGRoundValueToPixelGrid(
     const bool forceCeil,
     const bool forceFloor);
 
+void YGSetUsedCachedEntries(size_t);
+
 YG_EXTERN_C_END
 
 #ifdef __cplusplus