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

Source/core/rendering/RenderGrid.cpp

Index: Source/core/rendering/RenderGrid.cpp
diff --git a/Source/core/rendering/RenderGrid.cpp b/Source/core/rendering/RenderGrid.cpp
index 43f3a7013874d2c8cf75cbc9a28ab06503d80c9d..33a32181a69a10335356b5a3bd52cd009bc34856 100644
--- a/Source/core/rendering/RenderGrid.cpp
+++ b/Source/core/rendering/RenderGrid.cpp
@@ -197,7 +197,7 @@ void RenderGrid::addChild(RenderObject* newChild, RenderObject* beforeChild)
         // 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 {
@@ -680,8 +680,8 @@ void RenderGrid::growGrid(GridTrackSizingDirection direction)
 
 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; row <= coordinate.rows.finalPositionIndex.integerPosition(); ++row) {
+        for (size_t column = coordinate.columns.initialPositionIndex; column <= coordinate.columns.finalPositionIndex.integerPosition(); ++column)
             m_grid[row][column].append(child);
     }
 
@@ -760,9 +760,9 @@ void RenderGrid::populateExplicitGridAndOrderIterator()
         // |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);
@@ -933,27 +933,27 @@ PassOwnPtr<GridSpan> RenderGrid::resolveGridPositionsFromStyle(const RenderBox*
 
     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;
+        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());
 
@@ -961,9 +961,9 @@ size_t RenderGrid::resolveNamedGridLinePositionFromStyle(const GridPosition& pos
     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;
@@ -971,10 +971,10 @@ size_t RenderGrid::resolveNamedGridLinePositionFromStyle(const GridPosition& pos
         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: {
@@ -985,16 +985,16 @@ size_t RenderGrid::resolveGridPositionFromStyle(const GridPosition& position, Gr
 
         // 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:
     {
@@ -1004,28 +1004,28 @@ size_t RenderGrid::resolveGridPositionFromStyle(const GridPosition& position, Gr
         const GridCoordinate& gridAreaCoordinate = it->value;
         switch (side) {
         case ColumnStartSide:
-            return gridAreaCoordinate.columns.initialPositionIndex;
+            return GridResolvedPosition(gridAreaCoordinate.columns.initialPositionIndex);
         case ColumnEndSide:
-            return gridAreaCoordinate.columns.finalPositionIndex;
+            return GridResolvedPosition(gridAreaCoordinate.columns.finalPositionIndex);
         case RowStartSide:
-            return gridAreaCoordinate.rows.initialPositionIndex;
+            return GridResolvedPosition(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);
@@ -1041,7 +1041,7 @@ PassOwnPtr<GridSpan> RenderGrid::resolveGridPositionAgainstOppositePosition(size
     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());
@@ -1064,7 +1064,7 @@ LayoutUnit RenderGrid::gridAreaBreadthForChild(const RenderBox* child, GridTrack
     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; trackIndex <= span.finalPositionIndex.integerPosition(); ++trackIndex)
         gridAreaBreadth += tracks[trackIndex].m_usedBreadth;
     return gridAreaBreadth;
 }
@@ -1130,8 +1130,8 @@ void RenderGrid::paintChildren(PaintInfo& paintInfo, const LayoutPoint& paintOff
     {
         OrderIteratorPopulator populator(paintIterator);
 
-        for (size_t row = dirtiedRows.initialPositionIndex; row < dirtiedRows.finalPositionIndex; ++row) {
-            for (size_t column = dirtiedColumns.initialPositionIndex; column < dirtiedColumns.finalPositionIndex; ++column) {
+        for (size_t row = dirtiedRows.initialPositionIndex; row < dirtiedRows.finalPositionIndex.integerPosition(); ++row) {
+            for (size_t column = dirtiedColumns.initialPositionIndex; 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!