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

Source/core/rendering/style/GridResolvedPosition.h

Index: Source/core/rendering/style/GridResolvedPosition.h
diff --git a/Source/core/rendering/style/GridResolvedPosition.h b/Source/core/rendering/style/GridResolvedPosition.h
new file mode 100644
index 0000000000000000000000000000000000000000..8005337ad02a7edf8ec57c59bdb0e1bdd28dfd56
--- /dev/null
+++ b/Source/core/rendering/style/GridResolvedPosition.h
@@ -0,0 +1,125 @@
+// 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 {
+
+class GridSpan;
+class RenderBox;
+class RenderStyle;
+
+enum GridPositionSide {
+    ColumnStartSide,
+    ColumnEndSide,
+    RowStartSide,
+    RowEndSide
+};
+
+enum GridTrackSizingDirection {
+    ForColumns,
+    ForRows
+};
+

[Julien - ping for review, 2014/03/21 23:49:27]

Maybe worth adding a class comment that this is an index into the grid array.
It's also a glorified size_t 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)
+    {
+        size_t integerPosition;

[Julien - ping for review, 2014/03/21 23:49:27]

No need to define this variable here. Better just below when you set it.

+
+        ASSERT(position.integerPosition());
+        integerPosition = position.integerPosition() - 1;
+
+        m_integerPosition = adjustGridPositionForSide(integerPosition, side);
+    }
+
+    GridResolvedPosition next() const
+    {
+        return GridResolvedPosition(m_integerPosition + 1);
+    }
+
+    GridResolvedPosition& operator++()
+    {
+        m_integerPosition++;
+        return *this;
+    }
+
+    GridResolvedPosition& operator=(const GridResolvedPosition& other)
+    {
+        m_integerPosition = other.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<(size_t otherIntegerPosition) const
+    {
+        return m_integerPosition < otherIntegerPosition;
+    }
+
+    bool operator<=(size_t otherIntegerPosition) const
+    {
+        return m_integerPosition <= otherIntegerPosition;
+    }
+
+    operator size_t() 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