[CSS Grid Layout] Introduce an explicit type for resolved grid positions

Source/core/rendering/RenderGrid.cpp

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 180 matching lines @@
         return;
     }
 
     RenderBox* newChildBox = toRenderBox(newChild);
     OwnPtr<GridSpan> rowPositions = resolveGridPositionsFromStyle(newChildBox, ForRows);
     OwnPtr<GridSpan> columnPositions = resolveGridPositionsFromStyle(newChildBox, ForColumns);
     if (!rowPositions || !columnPositions) {
         // The new child requires the auto-placement algorithm to run so we need to recompute the grid fully.
         dirtyGrid();
     } else {
-        if (gridRowCount() <= rowPositions->finalPositionIndex || gridColumnCount() <= columnPositions->finalPositionIndex) {
+        if (gridRowCount() <= rowPositions->finalPositionIndex.integerPosition() || gridColumnCount() <= columnPositions->finalPositionIndex.integerPosition()) {
             // FIXME: We could just insert the new child provided we had a primitive to arbitrarily grow the grid.
             dirtyGrid();
         } else {
             insertItemIntoGrid(newChildBox, GridCoordinate(*rowPositions, *columnPositions));
         }
     }
 }
 
 void RenderGrid::removeChild(RenderObject* child)
 {
@@ skipping 203 matching lines @@
             normalizedFractionBreadth = std::max(normalizedFractionBreadth, tracks[trackIndex].m_usedBreadth / trackSize.maxTrackBreadth().flex());
         }
 
         for (size_t i = 0; i < flexibleSizedTracksIndex.size(); ++i) {
             GridIterator iterator(m_grid, direction, flexibleSizedTracksIndex[i]);
             while (RenderBox* gridItem = iterator.nextGridItem()) {
                 const GridCoordinate coordinate = cachedGridCoordinate(gridItem);
                 const GridSpan span = (direction == ForColumns) ? coordinate.columns : coordinate.rows;
 
                 // Do not include already processed items.
-                if (i > 0 && span.initialPositionIndex <= flexibleSizedTracksIndex[i - 1])
+                if (i > 0 && span.initialPositionIndex.integerPosition() <= flexibleSizedTracksIndex[i - 1])
                     continue;
 
                 double itemNormalizedFlexBreadth = computeNormalizedFractionBreadth(tracks, span, direction, maxContentForChild(gridItem, direction, sizingData.columnTracks));
                 normalizedFractionBreadth = std::max(normalizedFractionBreadth, itemNormalizedFlexBreadth);
             }
         }
     }
 
     for (size_t i = 0; i < flexibleSizedTracksIndex.size(); ++i) {
         const size_t trackIndex = flexibleSizedTracksIndex[i];
@@ skipping 44 matching lines @@
 static bool sortByGridNormalizedFlexValue(const GridTrackForNormalization& track1, const GridTrackForNormalization& track2)
 {
     return track1.m_normalizedFlexValue < track2.m_normalizedFlexValue;
 }
 
 double RenderGrid::computeNormalizedFractionBreadth(Vector<GridTrack>& tracks, const GridSpan& tracksSpan, GridTrackSizingDirection direction, LayoutUnit availableLogicalSpace) const
 {
     // |availableLogicalSpace| already accounts for the used breadths so no need to remove it here.
 
     Vector<GridTrackForNormalization> tracksForNormalization;
-    for (size_t i = tracksSpan.initialPositionIndex; i <= tracksSpan.finalPositionIndex; ++i) {
+    for (size_t i = tracksSpan.initialPositionIndex.integerPosition(); i <= tracksSpan.finalPositionIndex.integerPosition(); ++i) {
         const GridTrackSize& trackSize = gridTrackSize(direction, i);
         if (!trackSize.maxTrackBreadth().isFlex())
             continue;
 
         tracksForNormalization.append(GridTrackForNormalization(tracks[i], trackSize.maxTrackBreadth().flex()));
     }
 
     // The function is not called if we don't have <flex> grid tracks
     ASSERT(!tracksForNormalization.isEmpty());
 
@@ skipping 124 matching lines @@
 
         GridTrack& track = (direction == ForColumns) ? sizingData.columnTracks[i] : sizingData.rowTracks[i];
         if (track.m_maxBreadth == infinity)
             track.m_maxBreadth = track.m_usedBreadth;
     }
 }
 
 void RenderGrid::resolveContentBasedTrackSizingFunctionsForItems(GridTrackSizingDirection direction, GridSizingData& sizingData, RenderBox* gridItem, FilterFunction filterFunction, SizingFunction sizingFunction, AccumulatorGetter trackGetter, AccumulatorGrowFunction trackGrowthFunction)
 {
     const GridCoordinate coordinate = cachedGridCoordinate(gridItem);
-    const size_t initialTrackIndex = (direction == ForColumns) ? coordinate.columns.initialPositionIndex : coordinate.rows.initialPositionIndex;
-    const size_t finalTrackIndex = (direction == ForColumns) ? coordinate.columns.finalPositionIndex : coordinate.rows.finalPositionIndex;
+    const size_t initialTrackIndex = (direction == ForColumns) ? coordinate.columns.initialPositionIndex.integerPosition() : coordinate.rows.initialPositionIndex.integerPosition();
+    const size_t finalTrackIndex = (direction == ForColumns) ? coordinate.columns.finalPositionIndex.integerPosition() : coordinate.rows.finalPositionIndex.integerPosition();
 
     sizingData.filteredTracks.shrink(0);
     for (size_t trackIndex = initialTrackIndex; trackIndex <= finalTrackIndex; ++trackIndex) {
         const GridTrackSize& trackSize = gridTrackSize(direction, trackIndex);
         if (!(trackSize.*filterFunction)())
             continue;
 
         GridTrack& track = (direction == ForColumns) ? sizingData.columnTracks[trackIndex] : sizingData.rowTracks[trackIndex];
         sizingData.filteredTracks.append(&track);
     }
@@ skipping 73 matching lines @@
             m_grid[row].grow(oldColumnSize + 1);
     } else {
         const size_t oldRowSize = m_grid.size();
         m_grid.grow(oldRowSize + 1);
         m_grid[oldRowSize].grow(m_grid[0].size());
     }
 }
 
 void RenderGrid::insertItemIntoGrid(RenderBox* child, const GridCoordinate& coordinate)
 {
-    for (size_t row = coordinate.rows.initialPositionIndex; row <= coordinate.rows.finalPositionIndex; ++row) {
-        for (size_t column = coordinate.columns.initialPositionIndex; column <= coordinate.columns.finalPositionIndex; ++column)
+    for (size_t row = coordinate.rows.initialPositionIndex.integerPosition(); row <= coordinate.rows.finalPositionIndex.integerPosition(); ++row) {
+        for (size_t column = coordinate.columns.initialPositionIndex.integerPosition(); column <= coordinate.columns.finalPositionIndex.integerPosition(); ++column)
             m_grid[row][column].append(child);
     }
 
     m_gridItemCoordinate.set(child, coordinate);
 }
 
 void RenderGrid::insertItemIntoGrid(RenderBox* child, size_t rowTrack, size_t columnTrack)
 {
     const GridSpan& rowSpan = resolveGridPositionsFromAutoPlacementPosition(child, ForRows, rowTrack);
     const GridSpan& columnSpan = resolveGridPositionsFromAutoPlacementPosition(child, ForColumns, columnTrack);
@@ skipping 58 matching lines @@
     for (RenderBox* child = firstChildBox(); child; child = child->nextSiblingBox()) {
         populator.collectChild(child);
 
         // This function bypasses the cache (cachedGridCoordinate()) as it is used to build it.
         OwnPtr<GridSpan> rowPositions = resolveGridPositionsFromStyle(child, ForRows);
         OwnPtr<GridSpan> columnPositions = resolveGridPositionsFromStyle(child, ForColumns);
 
         // |positions| is 0 if we need to run the auto-placement algorithm. Our estimation ignores
         // this case as the auto-placement algorithm will grow the grid as needed.
         if (rowPositions)
-            maximumRowIndex = std::max(maximumRowIndex, rowPositions->finalPositionIndex + 1);
+            maximumRowIndex = std::max(maximumRowIndex, rowPositions->finalPositionIndex.integerPosition() + 1);
         if (columnPositions)
-            maximumColumnIndex = std::max(maximumColumnIndex, columnPositions->finalPositionIndex + 1);
+            maximumColumnIndex = std::max(maximumColumnIndex, columnPositions->finalPositionIndex.integerPosition() + 1);
     }
 
     m_grid.grow(maximumRowIndex);
     for (size_t i = 0; i < m_grid.size(); ++i)
         m_grid[i].grow(maximumColumnIndex);
 }
 
 void RenderGrid::placeSpecifiedMajorAxisItemsOnGrid(const Vector<RenderBox*>& autoGridItems)
 {
     for (size_t i = 0; i < autoGridItems.size(); ++i) {
         OwnPtr<GridSpan> majorAxisPositions = resolveGridPositionsFromStyle(autoGridItems[i], autoPlacementMajorAxisDirection());
-        GridIterator iterator(m_grid, autoPlacementMajorAxisDirection(), majorAxisPositions->initialPositionIndex);
+        GridIterator iterator(m_grid, autoPlacementMajorAxisDirection(), majorAxisPositions->initialPositionIndex.integerPosition());
         if (OwnPtr<GridCoordinate> emptyGridArea = iterator.nextEmptyGridArea()) {
-            insertItemIntoGrid(autoGridItems[i], emptyGridArea->rows.initialPositionIndex, emptyGridArea->columns.initialPositionIndex);
+            insertItemIntoGrid(autoGridItems[i], emptyGridArea->rows.initialPositionIndex.integerPosition(), emptyGridArea->columns.initialPositionIndex.integerPosition());
             continue;
         }
 
         growGrid(autoPlacementMinorAxisDirection());
         OwnPtr<GridCoordinate> emptyGridArea = iterator.nextEmptyGridArea();
         ASSERT(emptyGridArea);
-        insertItemIntoGrid(autoGridItems[i], emptyGridArea->rows.initialPositionIndex, emptyGridArea->columns.initialPositionIndex);
+        insertItemIntoGrid(autoGridItems[i], emptyGridArea->rows.initialPositionIndex.integerPosition(), emptyGridArea->columns.initialPositionIndex.integerPosition());
     }
 }
 
 void RenderGrid::placeAutoMajorAxisItemsOnGrid(const Vector<RenderBox*>& autoGridItems)
 {
     for (size_t i = 0; i < autoGridItems.size(); ++i)
         placeAutoMajorAxisItemOnGrid(autoGridItems[i]);
 }
 
 void RenderGrid::placeAutoMajorAxisItemOnGrid(RenderBox* gridItem)
 {
     OwnPtr<GridSpan> minorAxisPositions = resolveGridPositionsFromStyle(gridItem, autoPlacementMinorAxisDirection());
     ASSERT(!resolveGridPositionsFromStyle(gridItem, autoPlacementMajorAxisDirection()));
     size_t minorAxisIndex = 0;
     if (minorAxisPositions) {
-        minorAxisIndex = minorAxisPositions->initialPositionIndex;
+        minorAxisIndex = minorAxisPositions->initialPositionIndex.integerPosition();
         GridIterator iterator(m_grid, autoPlacementMinorAxisDirection(), minorAxisIndex);
         if (OwnPtr<GridCoordinate> emptyGridArea = iterator.nextEmptyGridArea()) {
-            insertItemIntoGrid(gridItem, emptyGridArea->rows.initialPositionIndex, emptyGridArea->columns.initialPositionIndex);
+            insertItemIntoGrid(gridItem, emptyGridArea->rows.initialPositionIndex.integerPosition(), emptyGridArea->columns.initialPositionIndex.integerPosition());
             return;
         }
     } else {
         const size_t endOfMajorAxis = (autoPlacementMajorAxisDirection() == ForColumns) ? gridColumnCount() : gridRowCount();
         for (size_t majorAxisIndex = 0; majorAxisIndex < endOfMajorAxis; ++majorAxisIndex) {
             GridIterator iterator(m_grid, autoPlacementMajorAxisDirection(), majorAxisIndex);
             if (OwnPtr<GridCoordinate> emptyGridArea = iterator.nextEmptyGridArea()) {
-                insertItemIntoGrid(gridItem, emptyGridArea->rows.initialPositionIndex, emptyGridArea->columns.initialPositionIndex);
+                insertItemIntoGrid(gridItem, emptyGridArea->rows.initialPositionIndex.integerPosition(), emptyGridArea->columns.initialPositionIndex.integerPosition());
                 return;
             }
         }
     }
 
     // We didn't find an empty grid area so we need to create an extra major axis line and insert our gridItem in it.
     const size_t columnIndex = (autoPlacementMajorAxisDirection() == ForColumns) ? m_grid[0].size() : minorAxisIndex;
     const size_t rowIndex = (autoPlacementMajorAxisDirection() == ForColumns) ? minorAxisIndex : m_grid.size();
     growGrid(autoPlacementMajorAxisDirection());
     insertItemIntoGrid(gridItem, rowIndex, columnIndex);
@@ skipping 54 matching lines @@
 
         LayoutRect oldChildRect = child->frameRect();
 
         // FIXME: Grid items should stretch to fill their cells. Once we
         // implement grid-{column,row}-align, we can also shrink to fit. For
         // now, just size as if we were a regular child.
         child->layoutIfNeeded();
 
 #ifndef NDEBUG
         const GridCoordinate& coordinate = cachedGridCoordinate(child);
-        ASSERT(coordinate.columns.initialPositionIndex < sizingData.columnTracks.size());
-        ASSERT(coordinate.rows.initialPositionIndex < sizingData.rowTracks.size());
+        ASSERT(coordinate.columns.initialPositionIndex.integerPosition() < sizingData.columnTracks.size());
+        ASSERT(coordinate.rows.initialPositionIndex.integerPosition() < sizingData.rowTracks.size());
 #endif
         child->setLogicalLocation(findChildLogicalPosition(child));
 
         // Keep track of children overflowing their grid area as we might need to paint them even if the grid-area is
         // not visible
         if (child->logicalHeight() > overrideContainingBlockContentLogicalHeight
             || child->logicalWidth() > overrideContainingBlockContentLogicalWidth)
             m_gridItemsOverflowingGridArea.append(child);
 
         // If the child moved, we have to repaint it as well as any floating/positioned
@@ skipping 37 matching lines @@
     if (initialPosition.shouldBeResolvedAgainstOppositePosition() && finalPosition.shouldBeResolvedAgainstOppositePosition()) {
         if (style()->gridAutoFlow() == AutoFlowNone)
             return adoptPtr(new GridSpan(0, 0));
 
         // We can't get our grid positions without running the auto placement algorithm.
         return nullptr;
     }
 
     if (initialPosition.shouldBeResolvedAgainstOppositePosition()) {
         // Infer the position from the final position ('auto / 1' or 'span 2 / 3' case).
-        const size_t finalResolvedPosition = resolveGridPositionFromStyle(finalPosition, finalPositionSide);
+        GridResolvedPosition finalResolvedPosition = resolveGridPositionFromStyle(finalPosition, finalPositionSide);
         return resolveGridPositionAgainstOppositePosition(finalResolvedPosition, initialPosition, initialPositionSide);
     }
 
     if (finalPosition.shouldBeResolvedAgainstOppositePosition()) {
         // Infer our position from the initial position ('1 / auto' or '3 / span 2' case).
-        const size_t initialResolvedPosition = resolveGridPositionFromStyle(initialPosition, initialPositionSide);
+        GridResolvedPosition initialResolvedPosition = resolveGridPositionFromStyle(initialPosition, initialPositionSide);
         return resolveGridPositionAgainstOppositePosition(initialResolvedPosition, finalPosition, finalPositionSide);
     }
 
-    size_t resolvedInitialPosition = resolveGridPositionFromStyle(initialPosition, initialPositionSide);
-    size_t resolvedFinalPosition = resolveGridPositionFromStyle(finalPosition, finalPositionSide);
+    GridResolvedPosition resolvedInitialPosition = resolveGridPositionFromStyle(initialPosition, initialPositionSide);
+    GridResolvedPosition resolvedFinalPosition = resolveGridPositionFromStyle(finalPosition, finalPositionSide);
 
     // If 'grid-after' specifies a line at or before that specified by 'grid-before', it computes to 'span 1'.
-    if (resolvedFinalPosition < resolvedInitialPosition)
-        resolvedFinalPosition = resolvedInitialPosition;
+    if (resolvedFinalPosition.integerPosition() < resolvedInitialPosition.integerPosition())
+        resolvedFinalPosition.setIntegerPosition(resolvedInitialPosition.integerPosition());
 
-    return adoptPtr(new GridSpan(resolvedInitialPosition, resolvedFinalPosition));
+    return adoptPtr(new GridSpan(resolvedInitialPosition.integerPosition(), resolvedFinalPosition.integerPosition()));
 }
 
-size_t RenderGrid::resolveNamedGridLinePositionFromStyle(const GridPosition& position, GridPositionSide side) const
+GridResolvedPosition RenderGrid::resolveNamedGridLinePositionFromStyle(const GridPosition& position, GridPositionSide side) const
 {
     ASSERT(!position.namedGridLine().isNull());
 
     const NamedGridLinesMap& gridLinesNames = (side == ColumnStartSide || side == ColumnEndSide) ? style()->namedGridColumnLines() : style()->namedGridRowLines();
     NamedGridLinesMap::const_iterator it = gridLinesNames.find(position.namedGridLine());
     if (it == gridLinesNames.end()) {
         if (position.isPositive())
-            return 0;
+            return GridResolvedPosition();
         const size_t lastLine = explicitGridSizeForSide(side);
-        return GridPosition::adjustGridPositionForSide(lastLine, side);
+        return GridResolvedPosition::adjustGridPositionForSide(lastLine, side);
     }
 
     size_t namedGridLineIndex;
     if (position.isPositive())
         namedGridLineIndex = std::min<size_t>(position.integerPosition(), it->value.size()) - 1;
     else
         namedGridLineIndex = std::max<int>(it->value.size() - abs(position.integerPosition()), 0);
-    return GridPosition::adjustGridPositionForSide(it->value[namedGridLineIndex], side);
+    return GridResolvedPosition::adjustGridPositionForSide(it->value[namedGridLineIndex], side);
 }
 
-size_t RenderGrid::resolveGridPositionFromStyle(const GridPosition& position, GridPositionSide side) const
+GridResolvedPosition RenderGrid::resolveGridPositionFromStyle(const GridPosition& position, GridPositionSide side) const
 {
     switch (position.type()) {
     case ExplicitPosition: {
         ASSERT(position.integerPosition());
 
         if (!position.namedGridLine().isNull())
             return resolveNamedGridLinePositionFromStyle(position, side);
 
         // Handle <integer> explicit position.
         if (position.isPositive())
-            return GridPosition::adjustGridPositionForSide(position.integerPosition() - 1, side);
+            return GridResolvedPosition::adjustGridPositionForSide(position.integerPosition() - 1, side);
 
         size_t resolvedPosition = abs(position.integerPosition()) - 1;
         const size_t endOfTrack = explicitGridSizeForSide(side);
 
         // Per http://lists.w3.org/Archives/Public/www-style/2013Mar/0589.html, we clamp negative value to the first line.
         if (endOfTrack < resolvedPosition)
-            return 0;
+            return GridResolvedPosition();
 
-        return GridPosition::adjustGridPositionForSide(endOfTrack - resolvedPosition, side);
+        return GridResolvedPosition::adjustGridPositionForSide(endOfTrack - resolvedPosition, side);
     }
     case NamedGridAreaPosition:
     {
         NamedGridAreaMap::const_iterator it = style()->namedGridArea().find(position.namedGridLine());
         // Unknown grid area should have been computed to 'auto' by now.
         ASSERT_WITH_SECURITY_IMPLICATION(it != style()->namedGridArea().end());
         const GridCoordinate& gridAreaCoordinate = it->value;
         switch (side) {
         case ColumnStartSide:
             return gridAreaCoordinate.columns.initialPositionIndex;
         case ColumnEndSide:
             return gridAreaCoordinate.columns.finalPositionIndex;
         case RowStartSide:
             return gridAreaCoordinate.rows.initialPositionIndex;
         case RowEndSide:
-            return gridAreaCoordinate.rows.finalPositionIndex;
+            return GridResolvedPosition(gridAreaCoordinate.rows.finalPositionIndex);
         }
         ASSERT_NOT_REACHED();
-        return 0;
+        return GridResolvedPosition();
     }
     case AutoPosition:
     case SpanPosition:
         // 'auto' and span depend on the opposite position for resolution (e.g. grid-row: auto / 1 or grid-column: span 3 / "myHeader").
         ASSERT_NOT_REACHED();
-        return 0;
+        return GridResolvedPosition();
     }
     ASSERT_NOT_REACHED();
-    return 0;
+    return GridResolvedPosition();
 }
 
-PassOwnPtr<GridSpan> RenderGrid::resolveGridPositionAgainstOppositePosition(size_t resolvedOppositePosition, const GridPosition& position, GridPositionSide side) const
+PassOwnPtr<GridSpan> RenderGrid::resolveGridPositionAgainstOppositePosition(const GridResolvedPosition& resolvedOppositePosition, const GridPosition& position, GridPositionSide side) const
 {
     if (position.isAuto())
         return GridSpan::create(resolvedOppositePosition, resolvedOppositePosition);
 
     ASSERT(position.isSpan());
     ASSERT(position.spanPosition() > 0);
 
     if (!position.namedGridLine().isNull()) {
         // span 2 'c' -> we need to find the appropriate grid line before / after our opposite position.
         return resolveNamedGridLinePositionAgainstOppositePosition(resolvedOppositePosition, position, side);
     }
 
     return GridSpan::createWithSpanAgainstOpposite(resolvedOppositePosition, position, side);
 }
 
-PassOwnPtr<GridSpan> RenderGrid::resolveNamedGridLinePositionAgainstOppositePosition(size_t resolvedOppositePosition, const GridPosition& position, GridPositionSide side) const
+PassOwnPtr<GridSpan> RenderGrid::resolveNamedGridLinePositionAgainstOppositePosition(const GridResolvedPosition& resolvedOppositePosition, const GridPosition& position, GridPositionSide side) const
 {
     ASSERT(position.isSpan());
     ASSERT(!position.namedGridLine().isNull());
     // Negative positions are not allowed per the specification and should have been handled during parsing.
     ASSERT(position.spanPosition() > 0);
 
     const NamedGridLinesMap& gridLinesNames = (side == ColumnStartSide || side == ColumnEndSide) ? style()->namedGridColumnLines() : style()->namedGridRowLines();
     NamedGridLinesMap::const_iterator it = gridLinesNames.find(position.namedGridLine());
 
     // If there is no named grid line of that name, we resolve the position to 'auto' (which is equivalent to 'span 1' in this case).
     // See http://lists.w3.org/Archives/Public/www-style/2013Jun/0394.html.
     if (it == gridLinesNames.end())
         return GridSpan::create(resolvedOppositePosition, resolvedOppositePosition);
 
     return GridSpan::createWithNamedSpanAgainstOpposite(resolvedOppositePosition, position, side, it->value);
 }
 
 LayoutUnit RenderGrid::gridAreaBreadthForChild(const RenderBox* child, GridTrackSizingDirection direction, const Vector<GridTrack>& tracks) const
 {
     const GridCoordinate& coordinate = cachedGridCoordinate(child);
     const GridSpan& span = (direction == ForColumns) ? coordinate.columns : coordinate.rows;
     LayoutUnit gridAreaBreadth = 0;
-    for (size_t trackIndex = span.initialPositionIndex; trackIndex <= span.finalPositionIndex; ++trackIndex)
+    for (size_t trackIndex = span.initialPositionIndex.integerPosition(); trackIndex <= span.finalPositionIndex.integerPosition(); ++trackIndex)
         gridAreaBreadth += tracks[trackIndex].m_usedBreadth;
     return gridAreaBreadth;
 }
 
 void RenderGrid::populateGridPositions(const GridSizingData& sizingData)
 {
     m_columnPositions.resize(sizingData.columnTracks.size() + 1);
     m_columnPositions[0] = borderAndPaddingStart();
     for (size_t i = 0; i < m_columnPositions.size() - 1; ++i)
         m_columnPositions[i + 1] = m_columnPositions[i] + sizingData.columnTracks[i].m_usedBreadth;
 
     m_rowPositions.resize(sizingData.rowTracks.size() + 1);
     m_rowPositions[0] = borderAndPaddingBefore();
     for (size_t i = 0; i < m_rowPositions.size() - 1; ++i)
         m_rowPositions[i + 1] = m_rowPositions[i] + sizingData.rowTracks[i].m_usedBreadth;
 }
 
 LayoutUnit RenderGrid::startOfColumnForChild(const RenderBox* child) const
 {
     const GridCoordinate& coordinate = cachedGridCoordinate(child);
-    LayoutUnit startOfColumn = m_columnPositions[coordinate.columns.initialPositionIndex];
+    LayoutUnit startOfColumn = m_columnPositions[coordinate.columns.initialPositionIndex.integerPosition()];
     // The grid items should be inside the grid container's border box, that's why they need to be shifted.
     // FIXME: This should account for the grid item's <overflow-position>.
     return startOfColumn + marginStartForChild(child);
 }
 
 LayoutUnit RenderGrid::endOfColumnForChild(const RenderBox* child) const
 {
     const GridCoordinate& coordinate = cachedGridCoordinate(child);
-    LayoutUnit startOfColumn = m_columnPositions[coordinate.columns.initialPositionIndex];
+    LayoutUnit startOfColumn = m_columnPositions[coordinate.columns.initialPositionIndex.integerPosition()];
     // The grid items should be inside the grid container's border box, that's why they need to be shifted.
     LayoutUnit columnPosition = startOfColumn + marginStartForChild(child);
 
-    LayoutUnit endOfColumn = m_columnPositions[coordinate.columns.finalPositionIndex + 1];
+    LayoutUnit endOfColumn = m_columnPositions[coordinate.columns.finalPositionIndex.integerPosition() + 1];
     // FIXME: This should account for the grid item's <overflow-position>.
-    return columnPosition + std::max<LayoutUnit>(0, endOfColumn - m_columnPositions[coordinate.columns.initialPositionIndex] - child->logicalWidth());
+    return columnPosition + std::max<LayoutUnit>(0, endOfColumn - m_columnPositions[coordinate.columns.initialPositionIndex.integerPosition()] - child->logicalWidth());
 }
 
 LayoutUnit RenderGrid::columnPositionAlignedWithGridContainerStart(const RenderBox* child) const
 {
     if (style()->isLeftToRightDirection())
         return startOfColumnForChild(child);
 
     return endOfColumnForChild(child);
 }
 
 LayoutUnit RenderGrid::columnPositionAlignedWithGridContainerEnd(const RenderBox* child) const
 {
     if (!style()->isLeftToRightDirection())
         return startOfColumnForChild(child);
 
     return endOfColumnForChild(child);
 }
 
 LayoutUnit RenderGrid::centeredColumnPositionForChild(const RenderBox* child) const
 {
     const GridCoordinate& coordinate = cachedGridCoordinate(child);
-    LayoutUnit startOfColumn = m_columnPositions[coordinate.columns.initialPositionIndex];
-    LayoutUnit endOfColumn = m_columnPositions[coordinate.columns.finalPositionIndex + 1];
+    LayoutUnit startOfColumn = m_columnPositions[coordinate.columns.initialPositionIndex.integerPosition()];
+    LayoutUnit endOfColumn = m_columnPositions[coordinate.columns.finalPositionIndex.integerPosition() + 1];
     LayoutUnit columnPosition = startOfColumn + marginStartForChild(child);
     return columnPosition + std::max<LayoutUnit>(0, endOfColumn - startOfColumn - child->logicalWidth()) / 2;
 }
 
 LayoutUnit RenderGrid::columnPositionForChild(const RenderBox* child) const
 {
     ItemPosition childJustifySelf = child->style()->justifySelf();
     switch (childJustifySelf) {
     case ItemPositionSelfStart:
         // self-start is based on the child's direction. That's why we need to check against the grid container's direction.
@@ skipping 48 matching lines @@
 
     ASSERT_NOT_REACHED();
     return 0;
 }
 
 LayoutUnit RenderGrid::rowPositionForChild(const RenderBox* child) const
 {
     const GridCoordinate& coordinate = cachedGridCoordinate(child);
 
     // The grid items should be inside the grid container's border box, that's why they need to be shifted.
-    LayoutUnit startOfRow = m_rowPositions[coordinate.rows.initialPositionIndex];
+    LayoutUnit startOfRow = m_rowPositions[coordinate.rows.initialPositionIndex.integerPosition()];
     LayoutUnit rowPosition = startOfRow + marginBeforeForChild(child);
 
     // FIXME: This function should account for 'align-self'.
 
     return rowPosition;
 }
 
 LayoutPoint RenderGrid::findChildLogicalPosition(const RenderBox* child) const
 {
     return LayoutPoint(columnPositionForChild(child), rowPositionForChild(child));
@@ skipping 14 matching lines @@
 
 class GridCoordinateSorter {
 public:
     GridCoordinateSorter(RenderGrid* renderer) : m_renderer(renderer) { }
 
     bool operator()(const RenderBox* firstItem, const RenderBox* secondItem) const
     {
         GridCoordinate first = m_renderer->cachedGridCoordinate(firstItem);
         GridCoordinate second = m_renderer->cachedGridCoordinate(secondItem);
 
-        if (first.rows.initialPositionIndex < second.rows.initialPositionIndex)
+        if (first.rows.initialPositionIndex.integerPosition() < second.rows.initialPositionIndex.integerPosition())
             return true;
-        if (first.rows.initialPositionIndex > second.rows.initialPositionIndex)
+        if (first.rows.initialPositionIndex.integerPosition() > second.rows.initialPositionIndex.integerPosition())
             return false;
-        return first.columns.finalPositionIndex < second.columns.finalPositionIndex;
+        return first.columns.finalPositionIndex.integerPosition() < second.columns.finalPositionIndex.integerPosition();
     }
 private:
     RenderGrid* m_renderer;
 };
 
 static inline bool isInSameRowBeforeDirtyArea(const GridCoordinate& coordinate, size_t row, const GridSpan& dirtiedColumns)
 {
-    return coordinate.rows.initialPositionIndex == row && coordinate.columns.initialPositionIndex < dirtiedColumns.initialPositionIndex;
+    return coordinate.rows.initialPositionIndex.integerPosition() == row && coordinate.columns.initialPositionIndex.integerPosition() < dirtiedColumns.initialPositionIndex.integerPosition();
 }
 
 static inline bool isInSameRowAfterDirtyArea(const GridCoordinate& coordinate, size_t row, const GridSpan& dirtiedColumns)
 {
-    return coordinate.rows.initialPositionIndex == row && coordinate.columns.initialPositionIndex >= dirtiedColumns.finalPositionIndex;
+    return coordinate.rows.initialPositionIndex.integerPosition() == row && coordinate.columns.initialPositionIndex.integerPosition() >= dirtiedColumns.finalPositionIndex.integerPosition();
 }
 
 static inline bool rowIsBeforeDirtyArea(const GridCoordinate& coordinate, const GridSpan& dirtiedRows)
 {
-    return coordinate.rows.initialPositionIndex < dirtiedRows.initialPositionIndex;
+    return coordinate.rows.initialPositionIndex.integerPosition() < dirtiedRows.initialPositionIndex.integerPosition();
 }
 
 void RenderGrid::paintChildren(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!gridIsDirty());
 
     LayoutRect localRepaintRect = paintInfo.rect;
     localRepaintRect.moveBy(-paintOffset);
 
     GridSpan dirtiedColumns = dirtiedGridAreas(m_columnPositions, localRepaintRect.x(), localRepaintRect.maxX());
     GridSpan dirtiedRows = dirtiedGridAreas(m_rowPositions, localRepaintRect.y(), localRepaintRect.maxY());
 
     // Sort the overflowing grid items according to their positions in the grid. We collect items during the layout
     // process following DOM's order but we have to paint following grid's.
     std::stable_sort(m_gridItemsOverflowingGridArea.begin(), m_gridItemsOverflowingGridArea.end(), GridCoordinateSorter(this));
 
     OrderIterator paintIterator(this);
     {
         OrderIteratorPopulator populator(paintIterator);
         Vector<RenderBox*>::const_iterator overflowIterator = m_gridItemsOverflowingGridArea.begin();
         Vector<RenderBox*>::const_iterator end = m_gridItemsOverflowingGridArea.end();
 
         for (; overflowIterator != end && rowIsBeforeDirtyArea(cachedGridCoordinate(*overflowIterator), dirtiedRows); ++overflowIterator) {
             if ((*overflowIterator)->frameRect().intersects(localRepaintRect))
                 populator.storeChild(*overflowIterator);
         }
 
-        for (size_t row = dirtiedRows.initialPositionIndex; row < dirtiedRows.finalPositionIndex; ++row) {
+        for (size_t row = dirtiedRows.initialPositionIndex.integerPosition(); row < dirtiedRows.finalPositionIndex.integerPosition(); ++row) {
 
             for (; overflowIterator != end && isInSameRowBeforeDirtyArea(cachedGridCoordinate(*overflowIterator), row, dirtiedColumns); ++overflowIterator) {
                 if ((*overflowIterator)->frameRect().intersects(localRepaintRect))
                     populator.storeChild(*overflowIterator);
             }
 
-            for (size_t column = dirtiedColumns.initialPositionIndex; column < dirtiedColumns.finalPositionIndex; ++column) {
+            for (size_t column = dirtiedColumns.initialPositionIndex.integerPosition(); column < dirtiedColumns.finalPositionIndex.integerPosition(); ++column) {
                 const Vector<RenderBox*, 1>& children = m_grid[row][column];
                 // FIXME: If we start adding spanning children in all grid areas they span, this
                 // would make us paint them several times, which is wrong!
                 for (size_t j = 0; j < children.size(); ++j) {
                     populator.storeChild(children[j]);
                     // Do not paint overflowing grid items twice.
                     if (overflowIterator != end && *overflowIterator == children[j])
                         ++overflowIterator;
                 }
             }
@@ skipping 21 matching lines @@
     if (isOutOfFlowPositioned())
         return "RenderGrid (positioned)";
     if (isAnonymous())
         return "RenderGrid (generated)";
     if (isRelPositioned())
         return "RenderGrid (relative positioned)";
     return "RenderGrid";
 }
 
 } // namespace WebCore