Source/core/rendering/style/GridCoordinate.h

/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions are
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 *
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 * in the documentation and/or other materials provided with the
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 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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 */

#ifndef GridCoordinate_h
#define GridCoordinate_h

#include "core/rendering/style/GridPosition.h"
#include "wtf/HashMap.h"
#include "wtf/PassOwnPtr.h"
#include "wtf/text/WTFString.h"

namespace WebCore {

// A span in a single direction (either rows or columns). Note that |initialPositionIndex|
// and |finalPositionIndex| are grid areas' indexes, NOT grid lines'. Iterating over the
// span should include both |initialPositionIndex| and |finalPositionIndex| to be correct.
struct GridSpan {
    static PassOwnPtr<GridSpan> create(size_t initialPosition, size_t finalPosition)
    {
        return adoptPtr(new GridSpan(initialPosition, finalPosition));
    }

    static PassOwnPtr<GridSpan> createWithSpanAgainstOpposite(size_t resolvedOppositePosition, const GridPosition& position, GridPositionSide side)
    {
        // 'span 1' is contained inside a single grid track regardless of the direction.
        // That's why the CSS span value is one more than the offset we apply.
        size_t positionOffset = position.spanPosition() - 1;
        if (side == ColumnStartSide || side == RowStartSide) {
            size_t initialResolvedPosition = std::max<int>(0, resolvedOppositePosition - positionOffset);
            return GridSpan::create(initialResolvedPosition, resolvedOppositePosition);
        }

        return GridSpan::create(resolvedOppositePosition, resolvedOppositePosition + positionOffset);
    }

    static PassOwnPtr<GridSpan> createWithNamedSpanAgainstOpposite(size_t resolvedOppositePosition, const GridPosition& position, GridPositionSide side, const Vector<size_t>& gridLines)
    {
        if (side == RowStartSide || side == ColumnStartSide)
            return createWithInitialNamedSpanAgainstOpposite(resolvedOppositePosition, position, gridLines);

        return createWithFinalNamedSpanAgainstOpposite(resolvedOppositePosition, position, gridLines);
    }

    static PassOwnPtr<GridSpan> createWithInitialNamedSpanAgainstOpposite(size_t resolvedOppositePosition, const GridPosition& position, const Vector<size_t>& gridLines)
    {
        // The grid line inequality needs to be strict (which doesn't match the after / end case) because |resolvedOppositePosition|
        // is already converted to an index in our grid representation (ie one was removed from the grid line to account for the side).
        size_t firstLineBeforeOppositePositionIndex = 0;
        const size_t* firstLineBeforeOppositePosition = std::lower_bound(gridLines.begin(), gridLines.end(), resolvedOppositePosition);
        if (firstLineBeforeOppositePosition != gridLines.end())
            firstLineBeforeOppositePositionIndex = firstLineBeforeOppositePosition - gridLines.begin();

        size_t gridLineIndex = std::max<int>(0, firstLineBeforeOppositePositionIndex - position.spanPosition() + 1);
        size_t resolvedGridLinePosition = gridLines[gridLineIndex];
        if (resolvedGridLinePosition > resolvedOppositePosition)
            resolvedGridLinePosition = resolvedOppositePosition;
        return GridSpan::create(resolvedGridLinePosition, resolvedOppositePosition);
    }

    static PassOwnPtr<GridSpan> createWithFinalNamedSpanAgainstOpposite(size_t resolvedOppositePosition, const GridPosition& position, const Vector<size_t>& gridLines)
    {
        size_t firstLineAfterOppositePositionIndex = gridLines.size() - 1;
        const size_t* firstLineAfterOppositePosition = std::upper_bound(gridLines.begin(), gridLines.end(), resolvedOppositePosition);
        if (firstLineAfterOppositePosition != gridLines.end())
            firstLineAfterOppositePositionIndex = firstLineAfterOppositePosition - gridLines.begin();

        size_t gridLineIndex = std::min(gridLines.size() - 1, firstLineAfterOppositePositionIndex + position.spanPosition() - 1);
        size_t resolvedGridLinePosition = GridPosition::adjustGridPositionForAfterEndSide(gridLines[gridLineIndex]);
        if (resolvedGridLinePosition < resolvedOppositePosition)
            resolvedGridLinePosition = resolvedOppositePosition;
        return GridSpan::create(resolvedOppositePosition, resolvedGridLinePosition);
    }

    GridSpan(size_t initialPosition, size_t finalPosition)
        : initialPositionIndex(initialPosition)
        , finalPositionIndex(finalPosition)
    {
        ASSERT(initialPositionIndex <= finalPositionIndex);
    }

    bool operator==(const GridSpan& o) const
    {
        return initialPositionIndex == o.initialPositionIndex && finalPositionIndex == o.finalPositionIndex;
    }

    size_t initialPositionIndex;
    size_t finalPositionIndex;
};

// This represents a grid area that spans in both rows' and columns' direction.
struct GridCoordinate {
    // HashMap requires a default constuctor.
    GridCoordinate()
        : columns(0, 0)
        , rows(0, 0)
    {
    }

    GridCoordinate(const GridSpan& r, const GridSpan& c)
        : columns(c)
        , rows(r)
    {
    }

    bool operator==(const GridCoordinate& o) const
    {
        return columns == o.columns && rows == o.rows;
    }

    bool operator!=(const GridCoordinate& o) const
    {
        return !(*this == o);
    }

    GridSpan columns;
    GridSpan rows;
};

typedef HashMap<String, GridCoordinate> NamedGridAreaMap;

} // namespace WebCore

#endif // GridCoordinate_h