rework on generationCount

yoga/YGLayout.h

@@ -22,12 +22,12 @@ struct YGLayout {
   bool doesLegacyStretchFlagAffectsLayout : 1;
   bool hadOverflow : 1;
 
-  uint16_t computedFlexBasisGeneration = 0;
+  uint8_t computedFlexBasisGeneration = 0;
   YGFloatOptional computedFlexBasis = {};
 
   // Instead of recomputing the entire layout every single time, we cache some
   // information to break early when nothing changed
-  uint16_t generationCount = 0;
+  uint8_t generationCount = 0;
   YGDirection lastOwnerDirection = (YGDirection) -1;
 
   uint32_t nextCachedMeasurementsIndex = 0;

yoga/YGNode.cpp

@@ -190,7 +190,7 @@ void YGNode::setLayoutPosition(float position, int index) {
 }
 
 void YGNode::setLayoutComputedFlexBasisGeneration(
-    uint16_t computedFlexBasisGeneration) {
+    uint8_t computedFlexBasisGeneration) {
   layout_.computedFlexBasisGeneration = computedFlexBasisGeneration;
 }
 

yoga/YGNode.h

@@ -240,7 +240,7 @@ struct YGNode {
   void setLayoutLastOwnerDirection(YGDirection direction);
   void setLayoutComputedFlexBasis(const YGFloatOptional computedFlexBasis);
   void setLayoutComputedFlexBasisGeneration(
-      uint16_t computedFlexBasisGeneration);
+      uint8_t computedFlexBasisGeneration);
   void setLayoutMeasuredDimension(float measuredDimension, int index);
   void setLayoutHadOverflow(bool hadOverflow);
   void setLayoutDimension(float dimension, int index);

yoga/Yoga.cpp

@@ -1007,6 +1007,8 @@ bool YGNodeLayoutGetDidLegacyStretchFlagAffectLayout(const YGNodeRef node) {
   return node->getLayout().doesLegacyStretchFlagAffectsLayout;
 }
 
+std::atomic<uint8_t> gCurrentGenerationCount(0);
+
 bool YGLayoutNodeInternal(
     const YGNodeRef node,
     const float availableWidth,
@@ -1020,7 +1022,7 @@ bool YGLayoutNodeInternal(
     const char* reason,
     const YGConfigRef config,
     const uint32_t depth,
-    const uint16_t generationCount);
+    const uint8_t generationCount);
 
 static void YGNodePrintInternal(
     const YGNodeRef node,
@@ -1261,7 +1263,7 @@ static void YGNodeComputeFlexBasisForChild(
     const YGDirection direction,
     const YGConfigRef config,
     const uint32_t depth,
-    const uint16_t generationCount) {
+    const uint8_t generationCount) {
   const YGFlexDirection mainAxis =
       YGResolveFlexDirection(node->getStyle().flexDirection, direction);
   const bool isMainAxisRow = YGFlexDirectionIsRow(mainAxis);
@@ -1454,7 +1456,7 @@ static void YGNodeAbsoluteLayoutChild(
     const YGDirection direction,
     const YGConfigRef config,
     const uint32_t depth,
-    const uint16_t generationCount) {
+    const uint8_t generationCount) {
   const YGFlexDirection mainAxis =
       YGResolveFlexDirection(node->getStyle().flexDirection, direction);
   const YGFlexDirection crossAxis = YGFlexDirectionCross(mainAxis, direction);
@@ -1878,7 +1880,7 @@ static float YGNodeComputeFlexBasisForChildren(
     const YGConfigRef config,
     bool performLayout,
     const uint32_t depth,
-    const uint16_t generationCount) {
+    const uint8_t generationCount) {
   float totalOuterFlexBasis = 0.0f;
   YGNodeRef singleFlexChild = nullptr;
   YGVector children = node->getChildren();
@@ -2058,7 +2060,7 @@ static float YGDistributeFreeSpaceSecondPass(
     const bool performLayout,
     const YGConfigRef config,
     const uint32_t depth,
-    const uint16_t generationCount) {
+    const uint8_t generationCount) {
   float childFlexBasis = 0;
   float flexShrinkScaledFactor = 0;
   float flexGrowFactor = 0;
@@ -2355,7 +2357,7 @@ static void YGResolveFlexibleLength(
     const bool performLayout,
     const YGConfigRef config,
     const uint32_t depth,
-    const uint16_t generationCount) {
+    const uint8_t generationCount) {
   const float originalFreeSpace = collectedFlexItemsValues.remainingFreeSpace;
   // First pass: detect the flex items whose min/max constraints trigger
   YGDistributeFreeSpaceFirstPass(
@@ -2679,7 +2681,7 @@ static void YGNodelayoutImpl(
     const bool performLayout,
     const YGConfigRef config,
     const uint32_t depth,
-    const uint16_t generationCount) {
+    const uint8_t generationCount) {
   YGAssertWithNode(
       node,
       YGFloatIsUndefined(availableWidth)
@@ -3719,7 +3721,7 @@ bool YGLayoutNodeInternal(
     const char* reason,
     const YGConfigRef config,
     uint32_t depth,
-    const uint16_t generationCount) {
+    const uint8_t generationCount) {
   YGLayout* layout = &node->getLayout();
 
 #if PRINT_CHANGES
@@ -4045,12 +4047,10 @@ void YGNodeCalculateLayout(
     const float ownerWidth,
     const float ownerHeight,
     const YGDirection ownerDirection) {
-  uint16_t generationCount = 0;
-
   // Increment the generation count. This will force the recursive routine to
   // visit all dirty nodes at least once. Subsequent visits will be skipped if
   // the input parameters don't change.
-  generationCount++;
+  gCurrentGenerationCount++;
   node->resolveDimension();
   float width = YGUndefined;
   YGMeasureMode widthMeasureMode = YGMeasureModeUndefined;
@@ -4109,7 +4109,7 @@ void YGNodeCalculateLayout(
           "initial",
           node->getConfig(),
           0, // tree root
-          generationCount)) {
+          gCurrentGenerationCount)) {
     node->setPosition(
         node->getLayout().direction, ownerWidth, ownerHeight, ownerWidth);
     YGRoundToPixelGrid(node, node->getConfig()->pointScaleFactor, 0.0f, 0.0f);
@@ -4136,7 +4136,7 @@ void YGNodeCalculateLayout(
     originalNode->resolveDimension();
     // Recursively mark nodes as dirty
     originalNode->markDirtyAndPropogateDownwards();
-    generationCount++;
+    gCurrentGenerationCount++;
     // Rerun the layout, and calculate the diff
     originalNode->setAndPropogateUseLegacyFlag(false);
     if (YGLayoutNodeInternal(
@@ -4152,7 +4152,7 @@ void YGNodeCalculateLayout(
             "initial",
             originalNode->getConfig(),
             0, // tree root
-            generationCount)) {
+            gCurrentGenerationCount)) {
       originalNode->setPosition(
           originalNode->getLayout().direction,
           ownerWidth,