Minor display: contents optimizations

yoga/algorithm/CalculateLayout.cpp

@@ -540,7 +540,7 @@ static float computeFlexBasisForChildren(
     const uint32_t generationCount) {
   float totalOuterFlexBasis = 0.0f;
   YGNodeRef singleFlexChild = nullptr;
-  const auto& children = node->getLayoutChildren();
+  auto children = node->getLayoutChildren();
   SizingMode sizingModeMainDim =
       isRow(mainAxis) ? widthSizingMode : heightSizingMode;
   // If there is only one child with flexGrow + flexShrink it means we can set

yoga/algorithm/FlexLine.cpp

@@ -29,8 +29,7 @@ FlexLine calculateFlexLine(
   float totalFlexGrowFactors = 0.0f;
   float totalFlexShrinkScaledFactors = 0.0f;
   size_t numberOfAutoMargins = 0;
-  size_t endOfLineIndex = iterator.index();
-  size_t firstElementInLineIndex = iterator.index();
+  yoga::Node* firstElementInLine = nullptr;
 
   float sizeConsumedIncludingMinConstraint = 0;
   const Direction direction = node->resolveDirection(ownerDirection);
@@ -40,33 +39,31 @@ FlexLine calculateFlexLine(
   const float gap =
       node->style().computeGapForAxis(mainAxis, availableInnerMainDim);
 
+  const auto childrenEnd = node->getLayoutChildren().end();
   // Add items to the current line until it's full or we run out of items.
-  for (; iterator != node->getLayoutChildren().end();
-       iterator++, endOfLineIndex = iterator.index()) {
+  for (; iterator != childrenEnd; iterator++) {
     auto child = *iterator;
     if (child->style().display() == Display::None ||
         child->style().positionType() == PositionType::Absolute) {
-      if (firstElementInLineIndex == endOfLineIndex) {
-        // We haven't found the first contributing element in the line yet.
-        firstElementInLineIndex++;
-      }
       continue;
     }
 
+    if (firstElementInLine == nullptr) {
+      firstElementInLine = child;
+    }
+
     if (child->style().flexStartMarginIsAuto(mainAxis, ownerDirection)) {
       numberOfAutoMargins++;
     }
     if (child->style().flexEndMarginIsAuto(mainAxis, ownerDirection)) {
       numberOfAutoMargins++;
     }
 
-    const bool isFirstElementInLine =
-        (endOfLineIndex - firstElementInLineIndex) == 0;
-
     child->setLineIndex(lineCount);
     const float childMarginMainAxis =
         child->style().computeMarginForAxis(mainAxis, availableInnerWidth);
-    const float childLeadingGapMainAxis = isFirstElementInLine ? 0.0f : gap;
+    const float childLeadingGapMainAxis =
+        child == firstElementInLine ? 0.0f : gap;
     const float flexBasisWithMinAndMaxConstraints =
         boundAxisWithinMinAndMax(
             child,
@@ -117,7 +114,6 @@ FlexLine calculateFlexLine(
   return FlexLine{
       .itemsInFlow = std::move(itemsInFlow),
       .sizeConsumed = sizeConsumed,
-      .endOfLineIndex = endOfLineIndex,
       .numberOfAutoMargins = numberOfAutoMargins,
       .layout = FlexLineRunningLayout{
           totalFlexGrowFactors,

yoga/algorithm/FlexLine.h

@@ -49,9 +49,6 @@ struct FlexLine {
   // the flexible children.
   const float sizeConsumed{0.0f};
 
-  // The index of the first item beyond the current line.
-  const size_t endOfLineIndex{0};
-
   // Number of edges along the line flow with an auto margin.
   const size_t numberOfAutoMargins{0};
 

yoga/algorithm/PixelGrid.cpp

@@ -124,7 +124,7 @@ void roundLayoutResultsToPixelGrid(
         Dimension::Height);
   }
 
-  for (yoga::Node* child : node->getLayoutChildren()) {
+  for (yoga::Node* child : node->getChildren()) {
     roundLayoutResultsToPixelGrid(child, absoluteNodeLeft, absoluteNodeTop);
   }
 }

yoga/node/LayoutableChildren.h

@@ -4,10 +4,12 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  */
+
 #pragma once
 
 #include <cstdint>
-#include <vector>
+#include <forward_list>
+#include <utility>
 
 #include <yoga/enums/Display.h>
 
@@ -18,7 +20,6 @@ class Node;
 template <typename T>
 class LayoutableChildren {
  public:
-  using Backtrack = std::vector<std::pair<const T*, size_t>>;
   struct Iterator {
     using iterator_category = std::input_iterator_tag;
     using difference_type = std::ptrdiff_t;
@@ -30,18 +31,13 @@ class LayoutableChildren {
 
     Iterator(const T* node, size_t childIndex)
         : node_(node), childIndex_(childIndex) {}
-    Iterator(const T* node, size_t childIndex, Backtrack&& backtrack)
-        : node_(node),
-          childIndex_(childIndex),
-          backtrack_(std::move(backtrack)) {}
 
     T* operator*() const {
       return node_->getChild(childIndex_);
     }
 
     Iterator& operator++() {
       next();
-      currentNodeIndex_++;
       return *this;
     }
 
@@ -51,10 +47,6 @@ class LayoutableChildren {
       return tmp;
     }
 
-    size_t index() const {
-      return currentNodeIndex_;
-    }
-
     friend bool operator==(const Iterator& a, const Iterator& b) {
       return a.node_ == b.node_ && a.childIndex_ == b.childIndex_;
     }
@@ -68,16 +60,16 @@ class LayoutableChildren {
       if (childIndex_ + 1 >= node_->getChildCount()) {
         // if the current node has no more children, try to backtrack and
         // visit its successor
-        if (backtrack_.empty()) {
+        if (backtrack_.empty()) [[likely]] {
           // if there are no nodes to backtrack to, the last node has been
           // visited
           *this = Iterator{};
         } else {
           // pop and restore the latest backtrack entry
-          const auto back = backtrack_.back();
-          backtrack_.pop_back();
+          const auto& back = backtrack_.front();
           node_ = back.first;
           childIndex_ = back.second;
+          backtrack_.pop_front();
 
           // go to the next node
           next();
@@ -87,7 +79,10 @@ class LayoutableChildren {
         ++childIndex_;
         // skip all display: contents nodes, possibly going deeper into the
         // tree
-        skipContentsNodes();
+        if (node_->getChild(childIndex_)->style().display() ==
+            Display::Contents) [[unlikely]] {
+          skipContentsNodes();
+        }
       }
     }
 
@@ -99,7 +94,7 @@ class LayoutableChildren {
         // if it has display: contents set, it shouldn't be returned but its
         // children should in its place push the current node and child index
         // so that the current state can be restored when backtracking
-        backtrack_.push_back({node_, childIndex_});
+        backtrack_.push_front({node_, childIndex_});
         // traverse the child
         node_ = currentNode;
         childIndex_ = 0;
@@ -117,8 +112,7 @@ class LayoutableChildren {
 
     const T* node_{nullptr};
     size_t childIndex_{0};
-    size_t currentNodeIndex_{0};
-    Backtrack backtrack_;
+    std::forward_list<std::pair<const T*, size_t>> backtrack_;
 
     friend LayoutableChildren;
   };
@@ -133,7 +127,10 @@ class LayoutableChildren {
   Iterator begin() const {
     if (node_->getChildCount() > 0) {
       auto result = Iterator(node_, 0);
-      result.skipContentsNodes();
+      if (node_->getChild(0)->style().display() == Display::Contents)
+          [[unlikely]] {
+        result.skipContentsNodes();
+      }
       return result;
     } else {
       return Iterator{};