[GridNG] Refactor track direction to be contained in track collection

1. Refactoring `NGGridLayoutAlgorithmTrackCollection::SetIterator` to
   allow callers access to the iterator from a const reference/pointer
   to the collection; this change improves the `NGGridLayoutAlgorithm`
   implementation since previously we were not able to pass const
   references to an algorithm track collection as an input parameter
   (because of the non-const restriction imposed by `SetIterator`).

2. Refactoring use of `GridTrackSizingDirection` into track collections;
   several methods in `NGGridLayoutAlgorithm` received both, track
   collection and its respective direction, as parameters. Since the
   direction is already tied to the specified collection, this change
   moves the `GridTrackSizingDirection` into the collection class.

Bug: 1045599
Change-Id: Ibbc7d2d93c5947106b0fe627d67dce2fb24916f2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2573889Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Jacques Newman <janewman@microsoft.com>
Reviewed-by: Kurt Catti-Schmidt <kschmi@microsoft.com>
Commit-Queue: Ethan Jimenez <ethavar@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#833870}

third_party/blink/renderer/core/layout/ng/grid/ng_grid_layout_algorithm.cc

@@ -26,7 +26,7 @@ NGGridLayoutAlgorithm::NGGridLayoutAlgorithm(
 }
 
 scoped_refptr<const NGLayoutResult> NGGridLayoutAlgorithm::Layout() {
-  // Measure Items
+  // Measure items.
   Vector<GridItemData> grid_items;
   Vector<GridItemData> out_of_flow_items;
   ConstructAndAppendGridItems(&grid_items, &out_of_flow_items);
@@ -38,18 +38,14 @@ scoped_refptr<const NGLayoutResult> NGGridLayoutAlgorithm::Layout() {
                                  &algorithm_row_track_collection);
 
   // Cache set indices.
-  CacheItemSetIndices(GridTrackSizingDirection::kForColumns,
-                      &algorithm_column_track_collection, &grid_items);
-  CacheItemSetIndices(GridTrackSizingDirection::kForRows,
-                      &algorithm_row_track_collection, &grid_items);
+  CacheItemSetIndices(algorithm_column_track_collection, &grid_items);
+  CacheItemSetIndices(algorithm_row_track_collection, &grid_items);
 
   // Resolve inline size.
-  ComputeUsedTrackSizes(GridTrackSizingDirection::kForColumns, &grid_items,
-                        &algorithm_column_track_collection);
+  ComputeUsedTrackSizes(&algorithm_column_track_collection, &grid_items);
 
   // Resolve block size.
-  ComputeUsedTrackSizes(GridTrackSizingDirection::kForRows, &grid_items,
-                        &algorithm_row_track_collection);
+  ComputeUsedTrackSizes(&algorithm_row_track_collection, &grid_items);
 
   // Place items.
   LayoutUnit intrinsic_block_size;
@@ -133,14 +129,10 @@ const GridSpan& NGGridLayoutAlgorithm::GridItemData::Span(
 void NGGridLayoutAlgorithm::GridItemData::SetSpan(
     const GridSpan& span,
     GridTrackSizingDirection track_direction) {
-  switch (track_direction) {
-    case kForColumns:
+  if (track_direction == kForColumns)
     resolved_position.columns = span;
-      break;
-    case kForRows:
+  else
     resolved_position.rows = span;
-      break;
-  }
 }
 
 NGGridLayoutAlgorithm::ReorderedGridItems::Iterator::Iterator(
@@ -191,12 +183,11 @@ NGGridLayoutAlgorithm::ReorderedGridItems::end() {
 NGGridLayoutAlgorithmTrackCollection::SetIterator
 NGGridLayoutAlgorithm::GetSetIteratorForItem(
     const GridItemData& item,
-    GridTrackSizingDirection track_direction,
     NGGridLayoutAlgorithmTrackCollection& track_collection) {
   return track_collection.GetSetIterator(
-      (track_direction == kForColumns) ? item.columns_begin_set_index
+      track_collection.IsForColumns() ? item.columns_begin_set_index
                                       : item.rows_begin_set_index,
-      (track_direction == kForColumns) ? item.columns_end_set_index
+      track_collection.IsForColumns() ? item.columns_end_set_index
                                       : item.rows_end_set_index);
 }
 
@@ -423,10 +414,8 @@ void NGGridLayoutAlgorithm::BuildBlockTrackCollections(
   wtf_size_t automatic_column_repetitions = 0;
   wtf_size_t automatic_row_repetitions = 0;
 
-  SetSpecifiedTracks(GridTrackSizingDirection::kForColumns,
-                     automatic_column_repetitions, column_track_collection);
-  SetSpecifiedTracks(GridTrackSizingDirection::kForRows,
-                     automatic_row_repetitions, row_track_collection);
+  SetSpecifiedTracks(automatic_column_repetitions, column_track_collection);
+  SetSpecifiedTracks(automatic_row_repetitions, row_track_collection);
 
   wtf_size_t explicit_column_start;
   wtf_size_t explicit_row_start;
@@ -459,8 +448,8 @@ void NGGridLayoutAlgorithm::BuildAlgorithmTrackCollections(
   DCHECK(row_track_collection);
   DCHECK_NE(child_percentage_size_.inline_size, kIndefiniteSize);
   // Build track collections.
-  NGGridBlockTrackCollection column_block_track_collection;
-  NGGridBlockTrackCollection row_block_track_collection;
+  NGGridBlockTrackCollection column_block_track_collection(kForColumns);
+  NGGridBlockTrackCollection row_block_track_collection(kForRows);
   BuildBlockTrackCollections(grid_items, &column_block_track_collection,
                              &row_block_track_collection);
 
@@ -476,16 +465,17 @@ void NGGridLayoutAlgorithm::BuildAlgorithmTrackCollections(
 }
 
 void NGGridLayoutAlgorithm::SetSpecifiedTracks(
-    GridTrackSizingDirection track_direction,
     wtf_size_t automatic_repetitions,
     NGGridBlockTrackCollection* track_collection) const {
+  DCHECK(track_collection);
   const ComputedStyle& grid_style = Style();
+
   const NGGridTrackList& template_track_list =
-      track_direction == GridTrackSizingDirection::kForColumns
+      track_collection->IsForColumns()
           ? grid_style.GridTemplateColumns().NGTrackList()
           : grid_style.GridTemplateRows().NGTrackList();
   const NGGridTrackList& auto_track_list =
-      track_direction == GridTrackSizingDirection::kForColumns
+      track_collection->IsForColumns()
           ? grid_style.GridAutoColumns().NGTrackList()
           : grid_style.GridAutoRows().NGTrackList();
   track_collection->SetSpecifiedTracks(&template_track_list, &auto_track_list,
@@ -538,27 +528,26 @@ void NGGridLayoutAlgorithm::DetermineExplicitTrackStarts(
 }
 
 void NGGridLayoutAlgorithm::CacheItemSetIndices(
-    GridTrackSizingDirection track_direction,
-    const NGGridLayoutAlgorithmTrackCollection* track_collection,
+    const NGGridLayoutAlgorithmTrackCollection& track_collection,
     Vector<GridItemData>* grid_items) const {
-  DCHECK(track_collection);
   DCHECK(grid_items);
+  const GridTrackSizingDirection track_direction = track_collection.Direction();
+
   for (GridItemData& item : *grid_items) {
-    wtf_size_t first_spanned_range =
-        track_collection->RangeIndexFromTrackNumber(
+    wtf_size_t first_spanned_range = track_collection.RangeIndexFromTrackNumber(
         item.StartLine(track_direction));
-    wtf_size_t last_spanned_range = track_collection->RangeIndexFromTrackNumber(
+    wtf_size_t last_spanned_range = track_collection.RangeIndexFromTrackNumber(
         item.EndLine(track_direction) - 1);
 
     DCHECK_LE(first_spanned_range, last_spanned_range);
     wtf_size_t begin_set_index =
-        track_collection->RangeStartingSetIndex(first_spanned_range);
+        track_collection.RangeStartingSetIndex(first_spanned_range);
     wtf_size_t end_set_index =
-        track_collection->RangeStartingSetIndex(last_spanned_range) +
-        track_collection->RangeSetCount(last_spanned_range);
+        track_collection.RangeStartingSetIndex(last_spanned_range) +
+        track_collection.RangeSetCount(last_spanned_range);
 
     DCHECK_LE(begin_set_index, end_set_index);
-    DCHECK_LE(end_set_index, track_collection->SetCount());
+    DCHECK_LE(end_set_index, track_collection.SetCount());
 
     if (track_direction == kForColumns) {
       item.columns_begin_set_index = begin_set_index;
@@ -571,13 +560,12 @@ void NGGridLayoutAlgorithm::CacheItemSetIndices(
 }
 
 void NGGridLayoutAlgorithm::DetermineGridItemsSpanningIntrinsicOrFlexTracks(
-    GridTrackSizingDirection track_direction,
+    const NGGridLayoutAlgorithmTrackCollection& track_collection,
     Vector<GridItemData>* grid_items,
-    Vector<wtf_size_t>* reordered_item_indices,
-    NGGridLayoutAlgorithmTrackCollection* track_collection) const {
-  DCHECK(grid_items);
-  DCHECK(track_collection);
-  DCHECK(reordered_item_indices);
+    Vector<wtf_size_t>* reordered_item_indices) const {
+  DCHECK(grid_items && reordered_item_indices);
+  const GridTrackSizingDirection track_direction = track_collection.Direction();
+
   auto CompareGridItemsByStartLine = [grid_items, track_direction](
                                          wtf_size_t index_a,
                                          wtf_size_t index_b) -> bool {
@@ -590,9 +578,9 @@ void NGGridLayoutAlgorithm::DetermineGridItemsSpanningIntrinsicOrFlexTracks(
   // At this point we have the grid items sorted by their start line in the
   // respective direction; this is important since we'll process both, the
   // ranges in the track collection and the grid items, incrementally.
-  auto range_spanning_flex_track_iterator = track_collection->RangeIterator();
+  auto range_spanning_flex_track_iterator = track_collection.RangeIterator();
   auto range_spanning_intrinsic_track_iterator =
-      track_collection->RangeIterator();
+      track_collection.RangeIterator();
 
   for (GridItemData& grid_item :
        ReorderedGridItems(*reordered_item_indices, *grid_items)) {
@@ -607,14 +595,14 @@ void NGGridLayoutAlgorithm::DetermineGridItemsSpanningIntrinsicOrFlexTracks(
     while (!range_spanning_intrinsic_track_iterator.IsAtEnd() &&
            (range_spanning_intrinsic_track_iterator.RangeTrackEnd() <
                 grid_item.StartLine(track_direction) ||
-            !track_collection->IsRangeSpanningIntrinsicTrack(
+            !track_collection.IsRangeSpanningIntrinsicTrack(
                 range_spanning_intrinsic_track_iterator.RangeIndex()))) {
       range_spanning_intrinsic_track_iterator.MoveToNextRange();
     }
     while (!range_spanning_flex_track_iterator.IsAtEnd() &&
            (range_spanning_flex_track_iterator.RangeTrackEnd() <
                 grid_item.StartLine(track_direction) ||
-            !track_collection->IsRangeSpanningFlexTrack(
+            !track_collection.IsRangeSpanningFlexTrack(
                 range_spanning_flex_track_iterator.RangeIndex()))) {
       range_spanning_flex_track_iterator.MoveToNextRange();
     }
@@ -640,12 +628,10 @@ void NGGridLayoutAlgorithm::DetermineGridItemsSpanningIntrinsicOrFlexTracks(
 
 // https://drafts.csswg.org/css-grid-1/#algo-track-sizing
 void NGGridLayoutAlgorithm::ComputeUsedTrackSizes(
-    GridTrackSizingDirection track_direction,
-    Vector<GridItemData>* grid_items,
-    NGGridLayoutAlgorithmTrackCollection* track_collection) const {
-  DCHECK(grid_items);
-  DCHECK(track_collection);
-  LayoutUnit content_box_size = (track_direction == kForColumns)
+    NGGridLayoutAlgorithmTrackCollection* track_collection,
+    Vector<GridItemData>* grid_items) const {
+  DCHECK(track_collection && grid_items);
+  LayoutUnit content_box_size = track_collection->IsForColumns()
                                     ? child_percentage_size_.inline_size
                                     : child_percentage_size_.block_size;
 
@@ -694,10 +680,10 @@ void NGGridLayoutAlgorithm::ComputeUsedTrackSizes(
   reordered_item_indices.ReserveInitialCapacity(grid_items->size());
   for (wtf_size_t i = 0; i < grid_items->size(); ++i)
     reordered_item_indices.push_back(i);
-  DetermineGridItemsSpanningIntrinsicOrFlexTracks(
-      track_direction, grid_items, &reordered_item_indices, track_collection);
-  ResolveIntrinsicTrackSizes(track_direction, grid_items,
-                             &reordered_item_indices, track_collection);
+  DetermineGridItemsSpanningIntrinsicOrFlexTracks(*track_collection, grid_items,
+                                                  &reordered_item_indices);
+  ResolveIntrinsicTrackSizes(track_collection, grid_items,
+                             &reordered_item_indices);
 }
 
 // Helpers for the track sizing algorithm.
@@ -1002,12 +988,14 @@ void NGGridLayoutAlgorithm::DistributeExtraSpaceToSets(
 }
 
 void NGGridLayoutAlgorithm::IncreaseTrackSizesToAccommodateGridItems(
-    GridTrackSizingDirection track_direction,
     ReorderedGridItems::Iterator group_begin,
     ReorderedGridItems::Iterator group_end,
     GridItemContributionType contribution_type,
     NGGridLayoutAlgorithmTrackCollection* track_collection) const {
   DCHECK(track_collection);
+  const GridTrackSizingDirection track_direction =
+      track_collection->Direction();
+
   for (auto set_iterator = track_collection->GetSetIterator();
        !set_iterator.IsAtEnd(); set_iterator.MoveToNextSet()) {
     set_iterator.CurrentSet().SetPlannedIncrease(LayoutUnit());
@@ -1033,8 +1021,8 @@ void NGGridLayoutAlgorithm::IncreaseTrackSizesToAccommodateGridItems(
     // know our block size.
     LayoutUnit spanned_tracks_size =
         GridGap(track_direction) * (grid_item->SpanSize(track_direction) - 1);
-    for (auto set_iterator = GetSetIteratorForItem(*grid_item, track_direction,
-                                                   *track_collection);
+    for (auto set_iterator =
+             GetSetIteratorForItem(*grid_item, *track_collection);
          !set_iterator.IsAtEnd(); set_iterator.MoveToNextSet()) {
       NGGridSet& current_set = set_iterator.CurrentSet();
 
@@ -1073,13 +1061,13 @@ void NGGridLayoutAlgorithm::IncreaseTrackSizesToAccommodateGridItems(
 
 // https://drafts.csswg.org/css-grid-1/#algo-content
 void NGGridLayoutAlgorithm::ResolveIntrinsicTrackSizes(
-    GridTrackSizingDirection track_direction,
+    NGGridLayoutAlgorithmTrackCollection* track_collection,
     Vector<GridItemData>* grid_items,
-    Vector<wtf_size_t>* reordered_item_indices,
-    NGGridLayoutAlgorithmTrackCollection* track_collection) const {
-  DCHECK(grid_items);
-  DCHECK(reordered_item_indices);
-  DCHECK(track_collection);
+    Vector<wtf_size_t>* reordered_item_indices) const {
+  DCHECK(grid_items && track_collection && reordered_item_indices);
+  const GridTrackSizingDirection track_direction =
+      track_collection->Direction();
+
   // Reorder grid items to process them as follows:
   //   - First, consider items spanning a single non-flexible track.
   //   - Next, consider items with span size of 2 not spanning a flexible track.
@@ -1121,7 +1109,7 @@ void NGGridLayoutAlgorithm::ResolveIntrinsicTrackSizes(
                  current_group_span_size);
 
     IncreaseTrackSizesToAccommodateGridItems(
-        track_direction, current_group_begin, current_group_end,
+        current_group_begin, current_group_end,
         GridItemContributionType::kForIntrinsicMinimums, track_collection);
 
     // TODO(ethavar): Add remaining stages, mark infinitely growable sets...
@@ -1148,9 +1136,9 @@ void NGGridLayoutAlgorithm::PlaceGridItems(
       GridGap(kForColumns, ChildAvailableSize().inline_size);
   LayoutUnit row_grid_gap = GridGap(kForRows, ChildAvailableSize().block_size);
   Vector<LayoutUnit> column_set_offsets =
-      ComputeSetOffsets(kForColumns, column_grid_gap, column_track_collection);
+      ComputeSetOffsets(column_track_collection, column_grid_gap);
   Vector<LayoutUnit> row_set_offsets =
-      ComputeSetOffsets(kForRows, row_grid_gap, row_track_collection);
+      ComputeSetOffsets(row_track_collection, row_grid_gap);
 
   // Intrinsic block size is based on the final row offset.
   // Because gaps are included in row offsets, subtract out the final gap.
@@ -1164,8 +1152,7 @@ void NGGridLayoutAlgorithm::PlaceGridItems(
   // intrinsic block size.
   if (IsRowGridGapUnresolvable(ChildAvailableSize().block_size)) {
     row_grid_gap = GridGap(kForRows, *intrinsic_block_size);
-    row_set_offsets =
-        ComputeSetOffsets(kForRows, row_grid_gap, row_track_collection);
+    row_set_offsets = ComputeSetOffsets(row_track_collection, row_grid_gap);
   }
 
   for (const GridItemData& grid_item : grid_items) {
@@ -1279,10 +1266,9 @@ LayoutUnit NGGridLayoutAlgorithm::GridGap(
 }
 
 Vector<LayoutUnit> NGGridLayoutAlgorithm::ComputeSetOffsets(
-    GridTrackSizingDirection track_direction,
-    LayoutUnit grid_gap,
-    NGGridLayoutAlgorithmTrackCollection& track_collection) const {
-  LayoutUnit set_offset = track_direction == kForColumns
+    const NGGridLayoutAlgorithmTrackCollection& track_collection,
+    LayoutUnit grid_gap) const {
+  LayoutUnit set_offset = track_collection.IsForColumns()
                               ? BorderScrollbarPadding().inline_start
                               : BorderScrollbarPadding().block_start;
   Vector<LayoutUnit> set_offsets = {set_offset};

third_party/blink/renderer/core/layout/ng/grid/ng_grid_layout_algorithm.h

@@ -122,7 +122,6 @@ class CORE_EXPORT NGGridLayoutAlgorithm
   // in the relevant track collection.
   static NGGridLayoutAlgorithmTrackCollection::SetIterator
   GetSetIteratorForItem(const GridItemData& item,
-                        GridTrackSizingDirection track_direction,
                         NGGridLayoutAlgorithmTrackCollection& track_collection);
 
   // Returns the size that a grid item will distribute across the tracks with an
@@ -149,8 +148,7 @@ class CORE_EXPORT NGGridLayoutAlgorithm
       NGGridLayoutAlgorithmTrackCollection* row_track_collection) const;
 
   // Sets specified track lists on |track_collection|.
-  void SetSpecifiedTracks(GridTrackSizingDirection track_direction,
-                          wtf_size_t automatic_repetitions,
+  void SetSpecifiedTracks(wtf_size_t automatic_repetitions,
                           NGGridBlockTrackCollection* track_collection) const;
   // Determines the explicit column and row track starts.
   void DetermineExplicitTrackStarts(wtf_size_t automatic_column_repetitions,
@@ -164,32 +162,27 @@ class CORE_EXPORT NGGridLayoutAlgorithm
   // "begin" and "end" such that the item spans every set from the respective
   // collection's |sets_| with an index in the range [begin, end).
   void CacheItemSetIndices(
-      GridTrackSizingDirection track_direction,
-      const NGGridLayoutAlgorithmTrackCollection* track_collection,
+      const NGGridLayoutAlgorithmTrackCollection& track_collection,
       Vector<GridItemData>* grid_items) const;
   // For every grid item, determines if it spans a track with an intrinsic or
   // flexible sizing function and caches the answer in its |GridItemData|.
   void DetermineGridItemsSpanningIntrinsicOrFlexTracks(
-      GridTrackSizingDirection track_direction,
+      const NGGridLayoutAlgorithmTrackCollection& track_collection,
       Vector<GridItemData>* grid_items,
-      Vector<wtf_size_t>* reordered_item_indices,
-      NGGridLayoutAlgorithmTrackCollection* track_collection) const;
+      Vector<wtf_size_t>* reordered_item_indices) const;
 
   // Calculates from the min and max track sizing functions the used track size.
   void ComputeUsedTrackSizes(
-      GridTrackSizingDirection track_direction,
-      Vector<GridItemData>* grid_items,
-      NGGridLayoutAlgorithmTrackCollection* track_collection) const;
+      NGGridLayoutAlgorithmTrackCollection* track_collection,
+      Vector<GridItemData>* grid_items) const;
 
   // These methods implement the steps of the algorithm for intrinsic track size
   // resolution defined in https://drafts.csswg.org/css-grid-1/#algo-content.
   void ResolveIntrinsicTrackSizes(
-      GridTrackSizingDirection track_direction,
+      NGGridLayoutAlgorithmTrackCollection* track_collection,
       Vector<GridItemData>* grid_items,
-      Vector<wtf_size_t>* reordered_item_indices,
-      NGGridLayoutAlgorithmTrackCollection* track_collection) const;
+      Vector<wtf_size_t>* reordered_item_indices) const;
   void IncreaseTrackSizesToAccommodateGridItems(
-      GridTrackSizingDirection track_direction,
       ReorderedGridItems::Iterator group_begin,
       ReorderedGridItems::Iterator group_end,
       GridItemContributionType contribution_type,
@@ -220,9 +213,8 @@ class CORE_EXPORT NGGridLayoutAlgorithm
 
   // Calculates inline and block offsets for all tracks.
   Vector<LayoutUnit> ComputeSetOffsets(
-      GridTrackSizingDirection track_direction,
-      LayoutUnit grid_gap,
-      NGGridLayoutAlgorithmTrackCollection& track_collection) const;
+      const NGGridLayoutAlgorithmTrackCollection& track_collection,
+      LayoutUnit grid_gap) const;
 
   // Tests whether the row gap is unresolvable based on its type and the
   // available size.

third_party/blink/renderer/core/layout/ng/grid/ng_grid_layout_algorithm_test.cc

@@ -50,22 +50,18 @@ class NGGridLayoutAlgorithmTest
         &algorithm_row_track_collection_);
 
     // Cache set indices.
-    algorithm.CacheItemSetIndices(GridTrackSizingDirection::kForColumns,
-                                  &algorithm_column_track_collection_,
+    algorithm.CacheItemSetIndices(algorithm_column_track_collection_,
                                   &grid_items_);
-    algorithm.CacheItemSetIndices(GridTrackSizingDirection::kForRows,
-                                  &algorithm_row_track_collection_,
+    algorithm.CacheItemSetIndices(algorithm_row_track_collection_,
                                   &grid_items_);
 
     // Resolve inline size.
-    algorithm.ComputeUsedTrackSizes(GridTrackSizingDirection::kForColumns,
-                                    &grid_items_,
-                                    &algorithm_column_track_collection_);
+    algorithm.ComputeUsedTrackSizes(&algorithm_column_track_collection_,
+                                    &grid_items_);
 
     // Resolve block size.
-    algorithm.ComputeUsedTrackSizes(GridTrackSizingDirection::kForRows,
-                                    &grid_items_,
-                                    &algorithm_row_track_collection_);
+    algorithm.ComputeUsedTrackSizes(&algorithm_row_track_collection_,
+                                    &grid_items_);
   }
 
   NGGridLayoutAlgorithmTrackCollection& TrackCollection(
@@ -116,15 +112,14 @@ class NGGridLayoutAlgorithmTest
   }
 
   void DetermineGridItemsSpanningIntrinsicOrFlexTracks(
-      NGGridLayoutAlgorithm& algorithm,
-      GridTrackSizingDirection track_direction) {
+      const NGGridLayoutAlgorithm& algorithm,
+      const NGGridLayoutAlgorithmTrackCollection& track_collection) {
     Vector<wtf_size_t> reordered_item_indices;
     reordered_item_indices.ReserveInitialCapacity(grid_items_.size());
     for (wtf_size_t i = 0; i < grid_items_.size(); ++i)
       reordered_item_indices.push_back(i);
     algorithm.DetermineGridItemsSpanningIntrinsicOrFlexTracks(
-        track_direction, &grid_items_, &reordered_item_indices,
-        &TrackCollection(track_direction));
+        track_collection, &grid_items_, &reordered_item_indices);
   }
 
   Vector<wtf_size_t> GridItemsSpanningIntrinsicTrack(
@@ -1196,7 +1191,8 @@ TEST_F(NGGridLayoutAlgorithmTest,
   NGGridLayoutAlgorithm algorithm({node, fragment_geometry, space});
   BuildGridItemsAndTrackCollections(algorithm);
 
-  DetermineGridItemsSpanningIntrinsicOrFlexTracks(algorithm, kForColumns);
+  DetermineGridItemsSpanningIntrinsicOrFlexTracks(algorithm,
+                                                  TrackCollection(kForColumns));
   Vector<wtf_size_t> expected_grid_items_spanning_intrinsic_track = {0, 1, 3};
   Vector<wtf_size_t> expected_grid_items_spanning_flex_track = {1};
 
@@ -1212,7 +1208,8 @@ TEST_F(NGGridLayoutAlgorithmTest,
   for (wtf_size_t i = 0; i < actual_items.size(); ++i)
     EXPECT_EQ(expected_grid_items_spanning_flex_track[i], actual_items[i]);
 
-  DetermineGridItemsSpanningIntrinsicOrFlexTracks(algorithm, kForRows);
+  DetermineGridItemsSpanningIntrinsicOrFlexTracks(algorithm,
+                                                  TrackCollection(kForRows));
   expected_grid_items_spanning_intrinsic_track = {1, 2, 3};
   expected_grid_items_spanning_flex_track = {2};
 

third_party/blink/renderer/core/layout/ng/grid/ng_grid_track_collection.cc

@@ -136,6 +136,10 @@ bool NGGridTrackCollectionBase::RangeRepeatIterator::SetRangeIndex(
   return true;
 }
 
+NGGridBlockTrackCollection::NGGridBlockTrackCollection(
+    GridTrackSizingDirection direction)
+    : direction_(direction) {}
+
 void NGGridBlockTrackCollection::SetSpecifiedTracks(
     const NGGridTrackList* explicit_tracks,
     const NGGridTrackList* implicit_tracks,
@@ -481,36 +485,10 @@ NGGridLayoutAlgorithmTrackCollection::Range::Range(
       starting_set_index(starting_set_index),
       is_collapsed(block_track_range.is_collapsed) {}
 
-NGGridLayoutAlgorithmTrackCollection::SetIterator::SetIterator(
-    NGGridLayoutAlgorithmTrackCollection* collection,
-    wtf_size_t begin_set_index,
-    wtf_size_t end_set_index)
-    : collection_(collection),
-      current_set_index_(begin_set_index),
-      end_set_index_(end_set_index) {
-  DCHECK(collection_);
-  DCHECK_LE(current_set_index_, end_set_index_);
-}
-
-bool NGGridLayoutAlgorithmTrackCollection::SetIterator::IsAtEnd() const {
-  DCHECK_LE(current_set_index_, end_set_index_);
-  return current_set_index_ == end_set_index_;
-}
-
-bool NGGridLayoutAlgorithmTrackCollection::SetIterator::MoveToNextSet() {
-  current_set_index_ = std::min(current_set_index_ + 1, end_set_index_);
-  return current_set_index_ < end_set_index_;
-}
-
-NGGridSet& NGGridLayoutAlgorithmTrackCollection::SetIterator::CurrentSet()
-    const {
-  DCHECK_LT(current_set_index_, end_set_index_);
-  return collection_->SetAt(current_set_index_);
-}
-
 NGGridLayoutAlgorithmTrackCollection::NGGridLayoutAlgorithmTrackCollection(
     const NGGridBlockTrackCollection& block_track_collection,
-    bool is_content_box_size_indefinite) {
+    bool is_content_box_size_indefinite)
+    : direction_(block_track_collection.Direction()) {
   for (auto range_iterator = block_track_collection.RangeIterator();
        !range_iterator.IsAtEnd(); range_iterator.MoveToNextRange()) {
     const NGGridBlockTrackCollection::Range& block_track_range =
@@ -602,19 +580,35 @@ NGGridSet& NGGridLayoutAlgorithmTrackCollection::SetAt(wtf_size_t set_index) {
   return sets_[set_index];
 }
 
+const NGGridSet& NGGridLayoutAlgorithmTrackCollection::SetAt(
+    wtf_size_t set_index) const {
+  DCHECK_LT(set_index, SetCount());
+  return sets_[set_index];
+}
+
 NGGridLayoutAlgorithmTrackCollection::SetIterator
 NGGridLayoutAlgorithmTrackCollection::GetSetIterator() {
   return SetIterator(this, 0u, SetCount());
 }
 
+NGGridLayoutAlgorithmTrackCollection::ConstSetIterator
+NGGridLayoutAlgorithmTrackCollection::GetSetIterator() const {
+  return ConstSetIterator(this, 0u, SetCount());
+}
+
 NGGridLayoutAlgorithmTrackCollection::SetIterator
 NGGridLayoutAlgorithmTrackCollection::GetSetIterator(wtf_size_t begin_set_index,
                                                      wtf_size_t end_set_index) {
-  DCHECK_LE(end_set_index, SetCount());
-  DCHECK_LE(begin_set_index, end_set_index);
   return SetIterator(this, begin_set_index, end_set_index);
 }
 
+NGGridLayoutAlgorithmTrackCollection::ConstSetIterator
+NGGridLayoutAlgorithmTrackCollection::GetSetIterator(
+    wtf_size_t begin_set_index,
+    wtf_size_t end_set_index) const {
+  return ConstSetIterator(this, begin_set_index, end_set_index);
+}
+
 wtf_size_t NGGridLayoutAlgorithmTrackCollection::RangeSetCount(
     wtf_size_t range_index) const {
   DCHECK_LT(range_index, RangeCount());

third_party/blink/renderer/core/layout/ng/grid/ng_grid_track_collection.h

@@ -58,13 +58,10 @@ class CORE_EXPORT NGGridTrackCollectionBase {
  protected:
   // Returns the first track number of a range.
   virtual wtf_size_t RangeTrackNumber(wtf_size_t range_index) const = 0;
-
   // Returns the number of tracks in a range.
   virtual wtf_size_t RangeTrackCount(wtf_size_t range_index) const = 0;
-
   // Returns true if the range at the given index is collapsed.
   virtual bool IsRangeCollapsed(wtf_size_t range_index) const = 0;
-
   // Returns the number of track ranges in the collection.
   virtual wtf_size_t RangeCount() const = 0;
 };
@@ -82,6 +79,9 @@ class CORE_EXPORT NGGridBlockTrackCollection
     bool is_collapsed : 1;
   };
 
+  explicit NGGridBlockTrackCollection(
+      GridTrackSizingDirection track_direction = kForColumns);
+
   // Sets the specified, implicit tracks, along with a given auto repeat value.
   void SetSpecifiedTracks(const NGGridTrackList* explicit_tracks,
                           const NGGridTrackList* implicit_tracks,
@@ -98,9 +98,11 @@ class CORE_EXPORT NGGridBlockTrackCollection
   // Returns the range at the given track.
   const Range& RangeAtTrackNumber(wtf_size_t track_number) const;
 
+  GridTrackSizingDirection Direction() const { return direction_; }
+  bool IsForColumns() const { return direction_ == kForColumns; }
+
   const NGGridTrackList& ExplicitTracks() const;
   const NGGridTrackList& ImplicitTracks() const;
-
   String ToString() const;
 
  protected:
@@ -117,6 +119,7 @@ class CORE_EXPORT NGGridBlockTrackCollection
   wtf_size_t ImplicitRepeatSize() const;
 
   bool track_indices_need_sort_ = false;
+  GridTrackSizingDirection direction_;
   wtf_size_t auto_repeat_count_ = 0;
 
   // Stores the specified and implicit tracks specified by SetSpecifiedTracks.
@@ -233,23 +236,51 @@ class CORE_EXPORT NGGridLayoutAlgorithmTrackCollection
     bool is_collapsed : 1;
   };
 
-  // Note that this iterator can alter any set's data.
-  class CORE_EXPORT SetIterator {
+  template <bool is_const>
+  class CORE_EXPORT SetIteratorBase {
    public:
-    SetIterator(NGGridLayoutAlgorithmTrackCollection* collection,
+    using TrackCollectionPtr =
+        typename std::conditional<is_const,
+                                  const NGGridLayoutAlgorithmTrackCollection*,
+                                  NGGridLayoutAlgorithmTrackCollection*>::type;
+    using NGGridSetRef =
+        typename std::conditional<is_const, const NGGridSet&, NGGridSet&>::type;
+
+    SetIteratorBase(TrackCollectionPtr track_collection,
                     wtf_size_t begin_set_index,
-                wtf_size_t end_set_index);
+                    wtf_size_t end_set_index)
+        : track_collection_(track_collection),
+          current_set_index_(begin_set_index),
+          end_set_index_(end_set_index) {
+      DCHECK(track_collection_);
+      DCHECK_LE(current_set_index_, end_set_index_);
+      DCHECK_LE(end_set_index_, track_collection_->SetCount());
+    }
 
-    bool IsAtEnd() const;
-    bool MoveToNextSet();
-    NGGridSet& CurrentSet() const;
+    bool IsAtEnd() const {
+      DCHECK_LE(current_set_index_, end_set_index_);
+      return current_set_index_ == end_set_index_;
+    }
+
+    bool MoveToNextSet() {
+      current_set_index_ = std::min(current_set_index_ + 1, end_set_index_);
+      return current_set_index_ < end_set_index_;
+    }
+
+    NGGridSetRef CurrentSet() const {
+      DCHECK_LT(current_set_index_, end_set_index_);
+      return track_collection_->SetAt(current_set_index_);
+    }
 
    private:
-    NGGridLayoutAlgorithmTrackCollection* collection_;
+    TrackCollectionPtr track_collection_;
     wtf_size_t current_set_index_;
     wtf_size_t end_set_index_;
   };
 
+  using SetIterator = SetIteratorBase<false>;
+  using ConstSetIterator = SetIteratorBase<true>;
+
   NGGridLayoutAlgorithmTrackCollection() = default;
   // |is_content_box_size_indefinite| is used to normalize percentage track
   // sizing functions (see the constructor for |NGGridSet|).
@@ -261,12 +292,16 @@ class CORE_EXPORT NGGridLayoutAlgorithmTrackCollection
   wtf_size_t SetCount() const;
   // Returns a reference to the set located at position |set_index|.
   NGGridSet& SetAt(wtf_size_t set_index);
+  const NGGridSet& SetAt(wtf_size_t set_index) const;
   // Returns an iterator for all the sets contained in this collection.
   SetIterator GetSetIterator();
+  ConstSetIterator GetSetIterator() const;
   // Returns an iterator for every set in this collection's |sets_| located at
   // an index in the interval [begin_set_index, end_set_index).
   SetIterator GetSetIterator(wtf_size_t begin_set_index,
                              wtf_size_t end_set_index);
+  ConstSetIterator GetSetIterator(wtf_size_t begin_set_index,
+                                  wtf_size_t end_set_index) const;
 
   wtf_size_t RangeSetCount(wtf_size_t range_index) const;
   wtf_size_t RangeStartingSetIndex(wtf_size_t range_index) const;
@@ -276,6 +311,9 @@ class CORE_EXPORT NGGridLayoutAlgorithmTrackCollection
   // Returns true if the range contains a set with a flexible sizing function.
   bool IsRangeSpanningFlexTrack(wtf_size_t range_index) const;
 
+  GridTrackSizingDirection Direction() const { return direction_; }
+  bool IsForColumns() const { return direction_ == kForColumns; }
+
  protected:
   // NGGridTrackCollectionBase overrides.
   wtf_size_t RangeTrackNumber(wtf_size_t range_index) const override;
@@ -289,6 +327,8 @@ class CORE_EXPORT NGGridLayoutAlgorithmTrackCollection
       const NGGridTrackList& specified_track_list,
       bool is_content_box_size_indefinite);
 
+  GridTrackSizingDirection direction_;
+
   Vector<Range> ranges_;
   // A vector of every set element that compose the entire collection's ranges;
   // track definitions from the same set are stored in consecutive positions,