some more perf - use reference instead of copying

Author: intergalacticspacehighway

yoga/algorithm/grid/AutoPlacement.h

@@ -11,7 +11,7 @@
 #include <yoga/node/Node.h>
 #include <vector>
 #include <yoga/style/GridLine.h>
-#include <map>
+#include <unordered_map>
 #include <unordered_set>
 
 namespace facebook::yoga {
@@ -155,7 +155,7 @@ struct AutoPlacement {
     // Step 1: Position anything that's not auto-positioned.
     // In spec level 1, span is always definite. Default is 1.
     // So for grid position to be definite, we need either start or end to be definite.
-    for (auto child: node->getChildren()) {
+    for (const auto& child: node->getChildren()) {
       if (child->style().positionType() == PositionType::Absolute) {
         continue;
       }
@@ -194,8 +194,8 @@ struct AutoPlacement {
 
     // Step 2: Process the items locked to a given row.
     // Definite row positions only, exclude items with definite column positions.
-    std::map<int32_t, int32_t> rowStartToColumnStartCache;
-    for (auto child: node->getChildren()) {
+    std::unordered_map<int32_t, int32_t> rowStartToColumnStartCache;
+    for (const auto& child: node->getChildren()) {
       if (child->style().positionType() == PositionType::Absolute) {
         continue;
       }
@@ -215,9 +215,8 @@ struct AutoPlacement {
         auto rowStart = rowPlacement.start;
         auto rowEnd = rowPlacement.end;
 
-        auto columnStart = rowStartToColumnStartCache.find(rowStart) == 
-          rowStartToColumnStartCache.end() ? 
-          minColumnStart : rowStartToColumnStartCache[rowStart];
+        auto columnStart = rowStartToColumnStartCache.contains(rowStart) ? 
+          rowStartToColumnStartCache[rowStart] : minColumnStart;
 
         auto columnPlacement = GridItemTrackPlacement::resolveLinePlacement(gridItemColumnStart, gridItemColumnEnd, explicitColumnLineCount);
         auto columnSpan = columnPlacement.span;
@@ -234,7 +233,7 @@ struct AutoPlacement {
             child
           };
 
-          for (auto placedItem: gridItemAreas) {
+          for (const auto& placedItem: gridItemAreas) {
             if (gridItemArea.overlaps(placedItem)) {
               columnStart++;
               columnEnd = columnStart + columnSpan;
@@ -255,7 +254,7 @@ struct AutoPlacement {
     // Step 3: Determine the columns in the implicit grid.
     // TODO: we dont need this loop. we can do it in above steps. But keeping it for now, to match the spec.
     auto largestColumnSpan = 1;
-    for (auto child: node->getChildren()) {
+    for (const auto& child: node->getChildren()) {
       if (child->style().positionType() == PositionType::Absolute) {
         continue;
       }
@@ -291,7 +290,7 @@ struct AutoPlacement {
       minColumnStart,
       minRowStart
     };
-    for (auto child: node->getChildren()) {
+    for (const auto& child: node->getChildren()) {
       if (child->style().positionType() == PositionType::Absolute) {
         continue;
       }
@@ -342,7 +341,7 @@ struct AutoPlacement {
             };
             bool hasOverlap = false;
 
-            for (auto placedItem: gridItemAreas) {
+            for (const auto& placedItem: gridItemAreas) {
               if (proposedPlacement.overlaps(placedItem)) {
                 hasOverlap = true;
                 break;
@@ -384,7 +383,7 @@ struct AutoPlacement {
               };
               bool hasOverlap = false;
 
-              for (auto placedItem: gridItemAreas) {
+              for (const auto& placedItem: gridItemAreas) {
                 if (proposedPlacement.overlaps(placedItem)) {
                   hasOverlap = true;
                   break;

yoga/algorithm/grid/GridLayout.cpp

@@ -408,9 +408,7 @@ void calculateGridLayoutInternal(Node* node,
       }
 
       float alignSelfOffset = 0.0f;
-      if (alignSelf == Align::Start) {
-        alignSelfOffset = 0.0f;
-      } else if (alignSelf == Align::End) {
+      if (alignSelf == Align::End) {
         alignSelfOffset = freeSpaceBlockAxis;
       } else if (alignSelf == Align::Center) {
         alignSelfOffset = freeSpaceBlockAxis / 2;

yoga/algorithm/grid/TrackSizing.h

@@ -10,6 +10,8 @@
 #include <yoga/numeric/Comparison.h>
 #include <yoga/style/StyleSizeLength.h>
 #include <unordered_set>
+#include <unordered_map>
+#include <map>
 
 namespace facebook::yoga {
 
@@ -140,6 +142,8 @@ struct TrackSizing {
   // https://www.w3.org/TR/css-grid-1/#algo-spanning-items
   void accomodateSpanningItemsCrossingContentSizedTracks(Dimension dimension) {
     auto& tracks = dimension == Dimension::Width ? columnTracks : rowTracks;
+    // https://en.cppreference.com/w/cpp/container/map.html
+    // we use map here because we want to store span in increasing order, map keys are sorted automatically in ascending order
     std::map<size_t, std::vector<std::pair<GridItemArea, std::vector<GridTrackSize*>>>> itemsGroupedByIncreasingSpan;
     for (auto& item: gridItemAreas) {
       auto spannedTracks = getTracksSpannedByItem(item, tracks, dimension);
@@ -153,7 +157,6 @@ struct TrackSizing {
     auto containerSize = dimension == Dimension::Width ? containerInnerWidth : containerInnerHeight;
     auto sizingMode = dimension == Dimension::Width ? widthSizingMode : heightSizingMode;
 
-    // we need to proceed in increasing order of span, keys are automatically sorted in std::map
     for (const auto& [span, itemsWithTracks] : itemsGroupedByIncreasingSpan) {
       for (const auto& [item, spannedTracks] : itemsWithTracks) {
         std::vector<GridTrackSize*> intrinsicMinimumSizingFunctionTracks;
@@ -248,8 +251,10 @@ struct TrackSizing {
     auto containerSize = dimension == Dimension::Width ? containerInnerWidth : containerInnerHeight;
 
     // 1. Set planned increase to 0 for all affected tracks
-    std::map<GridTrackSize*, float> plannedIncrease;
-    std::map<GridTrackSize*, float> itemIncurredIncrease;
+    std::unordered_map<GridTrackSize*, float> plannedIncrease;
+    std::unordered_map<GridTrackSize*, float> itemIncurredIncrease;
+    plannedIncrease.reserve(affectedTracks.size());
+    itemIncurredIncrease.reserve(affectedTracks.size());
     for (auto& track: affectedTracks) {
       plannedIncrease[track] = 0.0f;
       itemIncurredIncrease[track] = 0.0f;
@@ -356,8 +361,10 @@ struct TrackSizing {
     auto containerSize = dimension == Dimension::Width ? containerInnerWidth : containerInnerHeight;
 
     // 1. Set planned increase to 0 for all affected tracks
-    std::map<GridTrackSize*, float> plannedIncrease;
-    std::map<GridTrackSize*, float> itemIncurredIncrease;
+    std::unordered_map<GridTrackSize*, float> plannedIncrease;
+    std::unordered_map<GridTrackSize*, float> itemIncurredIncrease;
+    plannedIncrease.reserve(affectedTracks.size());
+    itemIncurredIncrease.reserve(affectedTracks.size());
     for (auto& track: affectedTracks) {
       plannedIncrease[track] = 0.0f;
       itemIncurredIncrease[track] = 0.0f;