C++ GridPosition类代码示例

GridPosition StyleBuilderConverter::convertGridPosition(StyleResolverState&, CSSValue* value)
{
    // We accept the specification's grammar:
    // 'auto' | [ <integer> || <custom-ident> ] | [ span && [ <integer> || <custom-ident> ] ] | <custom-ident>

    GridPosition position;

    if (value->isPrimitiveValue()) {
        CSSPrimitiveValue* primitiveValue = toCSSPrimitiveValue(value);
        // We translate <custom-ident> to <string> during parsing as it
        // makes handling it more simple.
        if (primitiveValue->isString()) {
            position.setNamedGridArea(primitiveValue->getStringValue());
            return position;
        }

        ASSERT(primitiveValue->getValueID() == CSSValueAuto);
        return position;
    }

    CSSValueList* values = toCSSValueList(value);
    ASSERT(values->length());

    bool isSpanPosition = false;
    // The specification makes the <integer> optional, in which case it default to '1'.
    int gridLineNumber = 1;
    String gridLineName;

    CSSValueListIterator it = values;
    CSSPrimitiveValue* currentValue = toCSSPrimitiveValue(it.value());
    if (currentValue->getValueID() == CSSValueSpan) {
        isSpanPosition = true;
        it.advance();
        currentValue = it.hasMore() ? toCSSPrimitiveValue(it.value()) : 0;
    }

    if (currentValue && currentValue->isNumber()) {
        gridLineNumber = currentValue->getIntValue();
        it.advance();
        currentValue = it.hasMore() ? toCSSPrimitiveValue(it.value()) : 0;
    }

    if (currentValue && currentValue->isString()) {
        gridLineName = currentValue->getStringValue();
        it.advance();
    }

    ASSERT(!it.hasMore());
    if (isSpanPosition)
        position.setSpanPosition(gridLineNumber, gridLineName);
    else
        position.setExplicitPosition(gridLineNumber, gridLineName);

    return position;
}

static int resolveNamedGridLinePositionFromStyle(const RenderStyle& gridContainerStyle, const GridPosition& position, GridPositionSide side, unsigned autoRepeatTracksCount)
{
    ASSERT(!position.namedGridLine().isNull());

    unsigned lastLine = explicitGridSizeForSide(gridContainerStyle, side, autoRepeatTracksCount);
    NamedLineCollection linesCollection(gridContainerStyle, position.namedGridLine(), directionFromSide(side), lastLine, autoRepeatTracksCount);

    if (position.isPositive())
        return lookAheadForNamedGridLine(0, std::abs(position.integerPosition()), lastLine, linesCollection);
    return lookBackForNamedGridLine(lastLine, std::abs(position.integerPosition()), lastLine, linesCollection);
}

static GridSpan resolveNamedGridLinePositionAgainstOppositePosition(const RenderStyle& gridContainerStyle, int oppositeLine, const GridPosition& position, GridPositionSide side, unsigned autoRepeatTracksCount)
{
    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);

    unsigned lastLine = explicitGridSizeForSide(gridContainerStyle, side, autoRepeatTracksCount);
    NamedLineCollection linesCollection(gridContainerStyle, position.namedGridLine(), directionFromSide(side), lastLine, autoRepeatTracksCount);
    return definiteGridSpanWithNamedLineSpanAgainstOpposite(oppositeLine, position, side, lastLine, linesCollection);
}

static GridSpan definiteGridSpanWithNamedLineSpanAgainstOpposite(int oppositeLine, const GridPosition& position, GridPositionSide side, unsigned lastLine, NamedLineCollection& linesCollection)
{
    int start, end;
    if (side == RowStartSide || side == ColumnStartSide) {
        start = lookBackForNamedGridLine(oppositeLine - 1, position.spanPosition(), lastLine, linesCollection);
        end = oppositeLine;
    } else {
        start = oppositeLine;
        end = lookAheadForNamedGridLine(oppositeLine + 1, position.spanPosition(), lastLine, linesCollection);
    }

    return GridSpan::untranslatedDefiniteGridSpan(start, end);
}

PassOwnPtr<GridSpan> GridResolvedPosition::resolveGridPositionAgainstOppositePosition(const RenderStyle& gridContainerStyle, const GridResolvedPosition& resolvedOppositePosition, const GridPosition& position, GridPositionSide side)
{
    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(gridContainerStyle, resolvedOppositePosition, position, side);
    }

    return GridSpan::createWithSpanAgainstOpposite(resolvedOppositePosition, position, side);
}

unsigned GridPositionsResolver::spanSizeForAutoPlacedItem(const RenderStyle& gridContainerStyle, const RenderBox& gridItem, GridTrackSizingDirection direction)
{
    GridPosition initialPosition, finalPosition;
    adjustGridPositionsFromStyle(gridContainerStyle, gridItem, direction, initialPosition, finalPosition);

    // This method will only be used when both positions need to be resolved against the opposite one.
    ASSERT(initialPosition.shouldBeResolvedAgainstOppositePosition() && finalPosition.shouldBeResolvedAgainstOppositePosition());

    if (initialPosition.isAuto() && finalPosition.isAuto())
        return 1;

    GridPosition position = initialPosition.isSpan() ? initialPosition : finalPosition;
    ASSERT(position.isSpan());

    ASSERT(position.spanPosition());
    return position.spanPosition();
}

GridSpan GridResolvedPosition::resolveGridPositionAgainstOppositePosition(const ComputedStyle& gridContainerStyle, const GridResolvedPosition& resolvedOppositePosition, const GridPosition& position, GridPositionSide side)
{
    if (position.isAuto()) {
        if ((side == ColumnStartSide || side == RowStartSide) && resolvedOppositePosition.toInt())
            return GridSpan::definiteGridSpan(resolvedOppositePosition.prev(), resolvedOppositePosition);
        return GridSpan::definiteGridSpan(resolvedOppositePosition, resolvedOppositePosition.next());
    }

    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(gridContainerStyle, resolvedOppositePosition, position, side);
    }

    return GridSpan::definiteGridSpanWithSpanAgainstOpposite(resolvedOppositePosition, position, side);
}

static int resolveGridPositionFromStyle(const RenderStyle& gridContainerStyle, const GridPosition& position, GridPositionSide side, unsigned autoRepeatTracksCount)
{
    switch (position.type()) {
    case ExplicitPosition: {
        ASSERT(position.integerPosition());

        if (!position.namedGridLine().isNull())
            return resolveNamedGridLinePositionFromStyle(gridContainerStyle, position, side, autoRepeatTracksCount);

        // Handle <integer> explicit position.
        if (position.isPositive())
            return position.integerPosition() - 1;

        unsigned resolvedPosition = std::abs(position.integerPosition()) - 1;
        const unsigned endOfTrack = explicitGridSizeForSide(gridContainerStyle, side, autoRepeatTracksCount);

        return endOfTrack - resolvedPosition;
    }
    case NamedGridAreaPosition:
    {
        // First attempt to match the grid area's edge to a named grid area: if there is a named line with the name
        // ''<custom-ident>-start (for grid-*-start) / <custom-ident>-end'' (for grid-*-end), contributes the first such
        // line to the grid item's placement.
        String namedGridLine = position.namedGridLine();
        ASSERT(!position.namedGridLine().isNull());

        unsigned lastLine = explicitGridSizeForSide(gridContainerStyle, side, autoRepeatTracksCount);
        NamedLineCollection implicitLines(gridContainerStyle, implicitNamedGridLineForSide(namedGridLine, side), directionFromSide(side), lastLine, autoRepeatTracksCount);
        if (implicitLines.hasNamedLines())
            return implicitLines.firstPosition();

        // Otherwise, if there is a named line with the specified name, contributes the first such line to the grid
        // item's placement.
        NamedLineCollection explicitLines(gridContainerStyle, namedGridLine, directionFromSide(side), lastLine, autoRepeatTracksCount);
        if (explicitLines.hasNamedLines())
            return explicitLines.firstPosition();

        ASSERT(!NamedLineCollection::isValidNamedLineOrArea(namedGridLine, gridContainerStyle, side));
        // If none of the above works specs mandate to assume that all the lines in the implicit grid have this name.
        return lastLine + 1;
    }
    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;
    }
    ASSERT_NOT_REACHED();
    return 0;
}

static GridSpan resolveGridPositionAgainstOppositePosition(const RenderStyle& gridContainerStyle, int oppositeLine, const GridPosition& position, GridPositionSide side, unsigned autoRepeatTracksCount)
{
    if (position.isAuto()) {
        if (isStartSide(side))
            return GridSpan::untranslatedDefiniteGridSpan(oppositeLine - 1, oppositeLine);
        return GridSpan::untranslatedDefiniteGridSpan(oppositeLine, oppositeLine + 1);
    }

    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(gridContainerStyle, oppositeLine, position, side, autoRepeatTracksCount);
    }

    // '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.
    unsigned positionOffset = position.spanPosition();
    if (isStartSide(side))
        return GridSpan::untranslatedDefiniteGridSpan(oppositeLine - positionOffset, oppositeLine);

    return GridSpan::untranslatedDefiniteGridSpan(oppositeLine, oppositeLine + positionOffset);
}

GridResolvedPosition GridResolvedPosition::resolveGridPositionFromStyle(const RenderStyle& gridContainerStyle, const GridPosition& position, GridPositionSide side)
{
    switch (position.type()) {
    case ExplicitPosition: {
        ASSERT(position.integerPosition());

        if (!position.namedGridLine().isNull())
            return resolveNamedGridLinePositionFromStyle(gridContainerStyle, position, side);

        // Handle <integer> explicit position.
        if (position.isPositive())
            return adjustGridPositionForSide(position.integerPosition() - 1, side);

        size_t resolvedPosition = abs(position.integerPosition()) - 1;
        const size_t endOfTrack = explicitGridSizeForSide(gridContainerStyle, 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 GridResolvedPosition(0);

        return adjustGridPositionForSide(endOfTrack - resolvedPosition, side);
    }
    case NamedGridAreaPosition:
    {
        NamedGridAreaMap::const_iterator it = gridContainerStyle.namedGridArea().find(position.namedGridLine());
        // Unknown grid area should have been computed to 'auto' by now.
        ASSERT_WITH_SECURITY_IMPLICATION(it != gridContainerStyle.namedGridArea().end());
        const GridCoordinate& gridAreaCoordinate = it->value;
        switch (side) {
        case ColumnStartSide:
            return gridAreaCoordinate.columns.resolvedInitialPosition;
        case ColumnEndSide:
            return gridAreaCoordinate.columns.resolvedFinalPosition;
        case RowStartSide:
            return gridAreaCoordinate.rows.resolvedInitialPosition;
        case RowEndSide:
            return GridResolvedPosition(gridAreaCoordinate.rows.resolvedFinalPosition);
        }
        ASSERT_NOT_REACHED();
        return GridResolvedPosition(0);
    }
    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 GridResolvedPosition(0);
    }
    ASSERT_NOT_REACHED();
    return GridResolvedPosition(0);
}

PassOwnPtr<GridSpan> GridResolvedPosition::resolveGridPositionsFromStyle(const RenderStyle& gridContainerStyle, const RenderBox& gridItem, GridTrackSizingDirection direction)
{
    GridPosition initialPosition = (direction == ForColumns) ? gridItem.style()->gridColumnStart() : gridItem.style()->gridRowStart();
    const GridPositionSide initialPositionSide = (direction == ForColumns) ? ColumnStartSide : RowStartSide;
    GridPosition finalPosition = (direction == ForColumns) ? gridItem.style()->gridColumnEnd() : gridItem.style()->gridRowEnd();
    const GridPositionSide finalPositionSide = (direction == ForColumns) ? ColumnEndSide : RowEndSide;

    // We must handle the placement error handling code here instead of in the StyleAdjuster because we don't want to
    // overwrite the specified values.
    if (initialPosition.isSpan() && finalPosition.isSpan())
        finalPosition.setAutoPosition();

    if (initialPosition.isNamedGridArea() && !gridContainerStyle.namedGridArea().contains(initialPosition.namedGridLine()))
        initialPosition.setAutoPosition();

    if (finalPosition.isNamedGridArea() && !gridContainerStyle.namedGridArea().contains(finalPosition.namedGridLine()))
        finalPosition.setAutoPosition();

    if (initialPosition.shouldBeResolvedAgainstOppositePosition() && finalPosition.shouldBeResolvedAgainstOppositePosition()) {
        if (gridContainerStyle.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).
        GridResolvedPosition finalResolvedPosition = resolveGridPositionFromStyle(gridContainerStyle, finalPosition, finalPositionSide);
        return resolveGridPositionAgainstOppositePosition(gridContainerStyle, finalResolvedPosition, initialPosition, initialPositionSide);
    }

    if (finalPosition.shouldBeResolvedAgainstOppositePosition()) {
        // Infer our position from the initial position ('1 / auto' or '3 / span 2' case).
        GridResolvedPosition initialResolvedPosition = resolveGridPositionFromStyle(gridContainerStyle, initialPosition, initialPositionSide);
        return resolveGridPositionAgainstOppositePosition(gridContainerStyle, initialResolvedPosition, finalPosition, finalPositionSide);
    }

    GridResolvedPosition resolvedInitialPosition = resolveGridPositionFromStyle(gridContainerStyle, initialPosition, initialPositionSide);
    GridResolvedPosition resolvedFinalPosition = resolveGridPositionFromStyle(gridContainerStyle, 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;

    return adoptPtr(new GridSpan(resolvedInitialPosition, resolvedFinalPosition));
}

void GridResolvedPosition::initialAndFinalPositionsFromStyle(const RenderStyle& gridContainerStyle, const RenderBox& gridItem, GridTrackSizingDirection direction, GridPosition& initialPosition, GridPosition& finalPosition)
{
    initialPosition = (direction == ForColumns) ? gridItem.style()->gridColumnStart() : gridItem.style()->gridRowStart();
    finalPosition = (direction == ForColumns) ? gridItem.style()->gridColumnEnd() : gridItem.style()->gridRowEnd();
    GridPositionSide initialPositionSide = calculateInitialPositionSide(direction);
    GridPositionSide finalPositionSide = calculateFinalPositionSide(direction);

    // We must handle the placement error handling code here instead of in the StyleAdjuster because we don't want to
    // overwrite the specified values.
    if (initialPosition.isSpan() && finalPosition.isSpan())
        finalPosition.setAutoPosition();

    // Try to early detect the case of non existing named grid lines. This way we could assume later that
    // GridResolvedPosition::resolveGrisPositionFromStyle() always return a valid resolved position.
    if (initialPosition.isNamedGridArea() && !isValidNamedLineOrArea(initialPosition.namedGridLine(), gridContainerStyle, initialPositionSide))
        initialPosition.setAutoPosition();

    if (finalPosition.isNamedGridArea() && !isValidNamedLineOrArea(finalPosition.namedGridLine(), gridContainerStyle, finalPositionSide))
        finalPosition.setAutoPosition();

    // If the grid item has an automatic position and a grid span for a named line in a given dimension, instead treat the grid span as one.
    if (initialPosition.isAuto() && finalPosition.isSpan() && !finalPosition.namedGridLine().isNull())
        finalPosition.setSpanPosition(1, String());
    if (finalPosition.isAuto() && initialPosition.isSpan() && !initialPosition.namedGridLine().isNull())
        initialPosition.setSpanPosition(1, String());
}