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

Source/core/rendering/style/GridResolvedPosition.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef GridResolvedPosition_h
+#define GridResolvedPosition_h
+
+#include "core/rendering/style/GridPosition.h"
+
+namespace WebCore {
+
+struct GridSpan;
+class RenderBox;
+class RenderStyle;
+
+enum GridPositionSide {
+    ColumnStartSide,
+    ColumnEndSide,
+    RowStartSide,
+    RowEndSide
+};
+
+enum GridTrackSizingDirection {
+    ForColumns,
+    ForRows
+};
+
+// This class represents an index into one of the dimensions of the grid array.
+// Wraps a size_t integer just for the purpose of knowing what we manipulate in the grid code.
+class GridResolvedPosition {
+public:
+    static size_t adjustGridPositionForAfterEndSide(size_t resolvedPosition)
+    {
+        return resolvedPosition ? resolvedPosition - 1 : 0;
+    }
+
+    static size_t adjustGridPositionForSide(size_t resolvedPosition, GridPositionSide side)
+    {
+        // An item finishing on the N-th line belongs to the N-1-th cell.
+        if (side == ColumnEndSide || side == RowEndSide)
+            return adjustGridPositionForAfterEndSide(resolvedPosition);
+
+        return resolvedPosition;
+    }
+
+    static GridSpan resolveGridPositionsFromAutoPlacementPosition(const RenderBox&, GridTrackSizingDirection, const GridResolvedPosition&);
+    static PassOwnPtr<GridSpan> resolveGridPositionsFromStyle(const RenderStyle&, const RenderBox&, GridTrackSizingDirection);
+    static GridResolvedPosition resolveNamedGridLinePositionFromStyle(const RenderStyle&, const GridPosition&, GridPositionSide);
+    static GridResolvedPosition resolveGridPositionFromStyle(const RenderStyle&, const GridPosition&, GridPositionSide);
+    static PassOwnPtr<GridSpan> resolveGridPositionAgainstOppositePosition(const RenderStyle&, const GridResolvedPosition& resolvedOppositePosition, const GridPosition&, GridPositionSide);
+    static PassOwnPtr<GridSpan> resolveNamedGridLinePositionAgainstOppositePosition(const RenderStyle&, const GridResolvedPosition& resolvedOppositePosition, const GridPosition&, GridPositionSide);
+
+    GridResolvedPosition(size_t position)
+        : m_integerPosition(position)
+    {
+    }
+
+    GridResolvedPosition(const GridPosition& position, GridPositionSide side)
+    {
+        ASSERT(position.integerPosition());
+        size_t integerPosition = position.integerPosition() - 1;
+
+        m_integerPosition = adjustGridPositionForSide(integerPosition, side);
+    }
+
+    GridResolvedPosition& operator++()
+    {
+        m_integerPosition++;
+        return *this;
+    }
+
+    bool operator==(const GridResolvedPosition& other) const
+    {
+        return m_integerPosition == other.m_integerPosition;
+    }
+
+    bool operator<(const GridResolvedPosition& other) const
+    {
+        return m_integerPosition < other.m_integerPosition;
+    }
+
+    bool operator>(const GridResolvedPosition& other) const
+    {
+        return m_integerPosition > other.m_integerPosition;
+    }
+
+    bool operator<=(const GridResolvedPosition& other) const
+    {
+        return m_integerPosition <= other.m_integerPosition;
+    }
+
+    bool operator>=(const GridResolvedPosition& other) const
+    {
+        return m_integerPosition >= other.m_integerPosition;
+    }
+
+    size_t toInt() const
+    {
+        return m_integerPosition;
+    }
+
+    static size_t explicitGridColumnCount(const RenderStyle&);
+    static size_t explicitGridRowCount(const RenderStyle&);
+
+private:
+
+    static size_t explicitGridSizeForSide(const RenderStyle&, GridPositionSide);
+
+    size_t m_integerPosition;
+};
+
+} // namespace WebCore
+
+#endif // GridResolvedPosition_h