Dont measure single flex grow+shrink child

Reviewed By: gkassabli

Differential Revision: D4147298

fbshipit-source-id: 51152e57eff8e322a833a6d698c30f8c5e2dcc35

React/CSSLayout/CSSLayout.c

@@ -259,7 +259,8 @@ static void _CSSNodeMarkDirty(const CSSNodeRef node) {
}

void CSSNodeSetMeasureFunc(const CSSNodeRef node, CSSMeasureFunc measureFunc) {
  CSS_ASSERT(CSSNodeChildCount(node) == 0, "Cannot set measure function: Nodes with measure functions cannot have children.");
  CSS_ASSERT(CSSNodeChildCount(node) == 0,
             "Cannot set measure function: Nodes with measure functions cannot have children.");
  node->measure = measureFunc;
}

@@ -269,7 +270,8 @@ CSSMeasureFunc CSSNodeGetMeasureFunc(const CSSNodeRef node) {

void CSSNodeInsertChild(const CSSNodeRef node, const CSSNodeRef child, const uint32_t index) {
  CSS_ASSERT(child->parent == NULL, "Child already has a parent, it must be removed first.");
  CSS_ASSERT(node->measure == NULL, "Cannot add child: Nodes with measure functions cannot have children.");
  CSS_ASSERT(node->measure == NULL,
             "Cannot add child: Nodes with measure functions cannot have children.");
  CSSNodeListInsert(&node->children, child, index);
  child->parent = node;
  _CSSNodeMarkDirty(node);
@@ -1367,6 +1369,26 @@ static void layoutNodeImpl(const CSSNodeRef node,
  const float availableInnerMainDim = isMainAxisRow ? availableInnerWidth : availableInnerHeight;
  const float availableInnerCrossDim = isMainAxisRow ? availableInnerHeight : availableInnerWidth;

  // If there is only one child with flexGrow + flexShrink it means we can set the
  // computedFlexBasis to 0 instead of measuring and shrinking / flexing the child to exactly
  // match the remaining space
  CSSNodeRef singleFlexChild = NULL;
  if ((isMainAxisRow && widthMeasureMode != CSSMeasureModeUndefined) ||
      (!isMainAxisRow && heightMeasureMode != CSSMeasureModeUndefined)) {
    for (uint32_t i = 0; i < childCount; i++) {
      const CSSNodeRef child = CSSNodeGetChild(node, i);
      if (singleFlexChild) {
        if (isFlex(child)) {
          // There is already a flexible child, abort.
          singleFlexChild = NULL;
          break;
        }
      } else if (CSSNodeStyleGetFlexGrow(child) > 0 && CSSNodeStyleGetFlexShrink(child) > 0) {
        singleFlexChild = child;
      }
    }
  }

  // STEP 3: DETERMINE FLEX BASIS FOR EACH ITEM
  for (uint32_t i = 0; i < childCount; i++) {
    const CSSNodeRef child = CSSNodeListGet(node->children, i);
@@ -1391,13 +1413,17 @@ static void layoutNodeImpl(const CSSNodeRef node,
      currentAbsoluteChild = child;
      child->nextChild = NULL;
    } else {
      computeChildFlexBasis(node,
                            child,
                            availableInnerWidth,
                            widthMeasureMode,
                            availableInnerHeight,
                            heightMeasureMode,
                            direction);
      if (child == singleFlexChild) {
        child->layout.computedFlexBasis = 0;
      } else {
        computeChildFlexBasis(node,
                              child,
                              availableInnerWidth,
                              widthMeasureMode,
                              availableInnerHeight,
                              heightMeasureMode,
                              direction);
      }
    }
  }

@@ -2133,17 +2159,17 @@ static inline bool newMeasureSizeIsStricterAndStillValid(CSSMeasureMode sizeMode
}

bool CSSNodeCanUseCachedMeasurement(const CSSMeasureMode widthMode,
                                           const float width,
                                           const CSSMeasureMode heightMode,
                                           const float height,
                                           const CSSMeasureMode lastWidthMode,
                                           const float lastWidth,
                                           const CSSMeasureMode lastHeightMode,
                                           const float lastHeight,
                                           const float lastComputedWidth,
                                           const float lastComputedHeight,
                                           const float marginRow,
                                           const float marginColumn) {
                                    const float width,
                                    const CSSMeasureMode heightMode,
                                    const float height,
                                    const CSSMeasureMode lastWidthMode,
                                    const float lastWidth,
                                    const CSSMeasureMode lastHeightMode,
                                    const float lastHeight,
                                    const float lastComputedWidth,
                                    const float lastComputedHeight,
                                    const float marginRow,
                                    const float marginColumn) {
  if (lastComputedHeight < 0 || lastComputedWidth < 0) {
    return false;
  }
@@ -2161,19 +2187,16 @@ bool CSSNodeCanUseCachedMeasurement(const CSSMeasureMode widthMode,
      newMeasureSizeIsStricterAndStillValid(
          widthMode, width - marginRow, lastWidthMode, lastWidth, lastComputedWidth);

  const bool heightIsCompatible = hasSameHeightSpec ||
                                  newSizeIsExactAndMatchesOldMeasuredSize(heightMode,
                                                                          height - marginColumn,
                                                                          lastComputedHeight) ||
                                  oldSizeIsUnspecifiedAndStillFits(heightMode,
  const bool heightIsCompatible =
      hasSameHeightSpec || newSizeIsExactAndMatchesOldMeasuredSize(heightMode,
                                                                   height - marginColumn,
                                                                   lastHeightMode,
                                                                   lastComputedHeight) ||
                                  newMeasureSizeIsStricterAndStillValid(heightMode,
                                                                        height - marginColumn,
                                                                        lastHeightMode,
                                                                        lastHeight,
                                                                        lastComputedHeight);
      oldSizeIsUnspecifiedAndStillFits(heightMode,
                                       height - marginColumn,
                                       lastHeightMode,
                                       lastComputedHeight) ||
      newMeasureSizeIsStricterAndStillValid(
          heightMode, height - marginColumn, lastHeightMode, lastHeight, lastComputedHeight);

  return widthIsCompatible && heightIsCompatible;
}