source: trunk/src/gui/graphicsview/qgridlayoutengine.cpp@ 58

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#include "qglobal.h"

#ifndef QT_NO_GRAPHICSVIEW

#include <math.h>

#include "qgraphicslayoutitem.h"
#include "qgridlayoutengine_p.h"
#include "qstyleoption.h"
#include "qvarlengtharray.h"

#include <QtDebug>

QT_BEGIN_NAMESPACE

template <typename T>
static void insertOrRemoveItems(QVector<T> &items, int index, int delta)
{
    int count = items.count();
    if (index < count) {
        if (delta > 0) {
            items.insert(index, delta, T());
        } else if (delta < 0) {
            items.remove(index, qMin(-delta, count - index));
        }
    }
}

static qreal growthFactorBelowPreferredSize(qreal desired, qreal sumAvailable, qreal sumDesired)
{
    Q_ASSERT(sumDesired != 0.0);
    return desired * ::pow(sumAvailable / sumDesired, desired / sumDesired);
}

static qreal fixedDescent(qreal descent, qreal ascent, qreal targetSize)
{
    if (descent < 0.0)
        return -1.0;

    Q_ASSERT(descent >= 0.0);
    Q_ASSERT(ascent >= 0.0);
    Q_ASSERT(targetSize >= ascent + descent);

    qreal extra = targetSize - (ascent + descent);
    return descent + (extra / 2.0);
}

static qreal compare(const QGridLayoutBox &box1, const QGridLayoutBox &box2, int which)
{
    qreal size1 = box1.q_sizes(which);
    qreal size2 = box2.q_sizes(which);

    if (which == MaximumSize) {
        return size2 - size1;
    } else {
        return size1 - size2;
    }
}

void QGridLayoutBox::add(const QGridLayoutBox &other, int stretch, qreal spacing)
{
    Q_ASSERT(q_minimumDescent < 0.0);

    q_minimumSize += other.q_minimumSize + spacing;
    q_preferredSize += other.q_preferredSize + spacing;
    q_maximumSize += ((stretch == 0) ? other.q_preferredSize : other.q_maximumSize) + spacing;
}

void QGridLayoutBox::combine(const QGridLayoutBox &other)
{
    q_minimumDescent = qMax(q_minimumDescent, other.q_minimumDescent);
    q_minimumAscent = qMax(q_minimumAscent, other.q_minimumAscent);

    q_minimumSize = qMax(q_minimumAscent + q_minimumDescent,
                         qMax(q_minimumSize, other.q_minimumSize));
    qreal maxMax;
    if (q_maximumSize == FLT_MAX && other.q_maximumSize != FLT_MAX)
        maxMax = other.q_maximumSize;
    else if (other.q_maximumSize == FLT_MAX && q_maximumSize != FLT_MAX)
        maxMax = q_maximumSize;
    else
        maxMax = qMax(q_maximumSize, other.q_maximumSize);

    q_maximumSize = qMax(q_minimumSize, maxMax);
    q_preferredSize = qBound(q_minimumSize, qMax(q_preferredSize, other.q_preferredSize),
                             q_maximumSize);
}

void QGridLayoutBox::normalize()
{
    q_maximumSize = qMax(qreal(0.0), q_maximumSize);
    q_minimumSize = qBound(qreal(0.0), q_minimumSize, q_maximumSize);
    q_preferredSize = qBound(q_minimumSize, q_preferredSize, q_maximumSize);
    q_minimumDescent = qMin(q_minimumDescent, q_minimumSize);

    Q_ASSERT((q_minimumDescent < 0.0) == (q_minimumAscent < 0.0));
}

#ifdef QT_DEBUG
void QGridLayoutBox::dump(int indent) const
{
    qDebug("%*sBox (%g <= %g <= %g [%g/%g])", indent, "", q_minimumSize, q_preferredSize,
           q_maximumSize, q_minimumAscent, q_minimumDescent);
}
#endif

bool operator==(const QGridLayoutBox &box1, const QGridLayoutBox &box2)
{
    for (int i = 0; i < NSizes; ++i) {
        if (box1.q_sizes(i) != box2.q_sizes(i))
            return false;
    }
    return box1.q_minimumDescent == box2.q_minimumDescent
           && box1.q_minimumAscent == box2.q_minimumAscent;
}

void QGridLayoutRowData::reset(int count)
{
    ignore.fill(false, count);
    boxes.fill(QGridLayoutBox(), count);
    multiCellMap.clear();
    stretches.fill(0, count);
    spacings.fill(0.0, count);
    hasIgnoreFlag = false;
}

void QGridLayoutRowData::distributeMultiCells()
{
    MultiCellMap::const_iterator i = multiCellMap.constBegin();
    for (; i != multiCellMap.constEnd(); ++i) {
        int start = i.key().first;
        int span = i.key().second;
        int end = start + span;
        const QGridLayoutBox &box = i.value().q_box;
        int stretch = i.value().q_stretch;

        QGridLayoutBox totalBox = this->totalBox(start, end);
        QVarLengthArray<QGridLayoutBox> extras(span);
        QVarLengthArray<qreal> dummy(span);
        QVarLengthArray<qreal> newSizes(span);

        for (int j = 0; j < NSizes; ++j) {
            qreal extra = compare(totalBox, box, j);
            if (extra > 0.0) {
                calculateGeometries(start, end, totalBox.q_sizes(j), dummy.data(), newSizes.data(),
                                    0, totalBox);

                for (int k = 0; k < span; ++k)
                    extras[k].q_sizes(j) = newSizes[k];
            }
        }

        for (int k = 0; k < span; ++k) {
            boxes[start + k].combine(extras[k]);
            stretches[start + k] = qMax(stretches[start + k], stretch);
        }
    }
    multiCellMap.clear();
}

void QGridLayoutRowData::calculateGeometries(int start, int end, qreal targetSize, qreal *positions,
                                             qreal *sizes, qreal *descents,
                                             const QGridLayoutBox &totalBox)
{
    Q_ASSERT(end > start);

    targetSize = qBound(totalBox.q_minimumSize, targetSize, totalBox.q_maximumSize);

    int n = end - start;
    QVarLengthArray<qreal> newSizes(n);
    QVarLengthArray<qreal> factors(n);
    qreal sumFactors = 0.0;
    int sumStretches = 0;
    qreal sumAvailable;

    for (int i = 0; i < n; ++i) {
        if (stretches[start + i] > 0)
            sumStretches += stretches[start + i];
    }

    if (targetSize < totalBox.q_preferredSize) {
        stealBox(start, end, MinimumSize, positions, sizes);

        sumAvailable = targetSize - totalBox.q_minimumSize;
        if (sumAvailable > 0.0) {
            qreal sumDesired = totalBox.q_preferredSize - totalBox.q_minimumSize;

            for (int i = 0; i < n; ++i) {
                if (ignore.testBit(start + i)) {
                    factors[i] = 0.0;
                    continue;
                }

                const QGridLayoutBox &box = boxes.at(start + i);
                qreal desired = box.q_preferredSize - box.q_minimumSize;
                factors[i] = growthFactorBelowPreferredSize(desired, sumAvailable, sumDesired);
                sumFactors += factors[i];
            }

            for (int i = 0; i < n; ++i) {
                Q_ASSERT(sumFactors > 0.0);
                qreal delta = sumAvailable * factors[i] / sumFactors;
                newSizes[i] = sizes[i] + delta;
            }
        }
    } else {
        stealBox(start, end, PreferredSize, positions, sizes);

        sumAvailable = targetSize - totalBox.q_preferredSize;
        if (sumAvailable > 0.0) {
            bool somethingHasAMaximumSize = false;

            qreal sumPreferredSizes = 0.0;
            for (int i = 0; i < n; ++i)
                sumPreferredSizes += sizes[i];

            for (int i = 0; i < n; ++i) {
                if (ignore.testBit(start + i)) {
                    newSizes[i] = 0.0;
                    factors[i] = 0.0;
                    continue;
                }

                const QGridLayoutBox &box = boxes.at(start + i);
                qreal desired = box.q_maximumSize - box.q_preferredSize;
                if (desired == 0.0) {
                    newSizes[i] = sizes[i];
                    factors[i] = 0.0;
                } else {
                    Q_ASSERT(desired > 0.0);

                    int stretch = stretches[start + i];
                    if (sumStretches == 0) {
                        if (hasIgnoreFlag) {
                            factors[i] = (stretch < 0) ? 1.0 : 0.0;
                        } else {
                            factors[i] = (stretch < 0) ? sizes[i] : 0.0;                        
                        }
                    } else if (stretch == sumStretches) {
                        factors[i] = 1.0;
                    } else if (stretch <= 0) {
                        factors[i] = 0.0;
                    } else {
                        qreal ultimatePreferredSize;
                        qreal ultimateSumPreferredSizes;
                        qreal x = ((stretch * sumPreferredSizes)
                                   - (sumStretches * box.q_preferredSize))
                                  / (sumStretches - stretch);
                        if (x >= 0.0) {
                            ultimatePreferredSize = box.q_preferredSize + x;
                            ultimateSumPreferredSizes = sumPreferredSizes + x;
                        } else {
                            ultimatePreferredSize = box.q_preferredSize;
                            ultimateSumPreferredSizes = (sumStretches * box.q_preferredSize)
                                                        / stretch;
                        }

                        /*
                            We multiply these by 1.5 to give some space for a smooth transition
                            (at the expense of the stretch factors, which are not fully respected
                            during the transition).
                        */
                        ultimatePreferredSize = ultimatePreferredSize * 3 / 2;
                        ultimateSumPreferredSizes = ultimateSumPreferredSizes * 3 / 2;

                        qreal ultimateFactor = (stretch * ultimateSumPreferredSizes
                                                / sumStretches)
                                               - (box.q_preferredSize);
                        qreal transitionalFactor = sumAvailable
                                                   * (ultimatePreferredSize - box.q_preferredSize)
                                                   / (ultimateSumPreferredSizes
                                                      - sumPreferredSizes);

                        qreal alpha = qMin(sumAvailable,
                                           ultimateSumPreferredSizes - sumPreferredSizes);
                        qreal beta = ultimateSumPreferredSizes - sumPreferredSizes;

                        factors[i] = ((alpha * ultimateFactor)
                                      + ((beta - alpha) * transitionalFactor)) / beta;
                    }
                    sumFactors += factors[i];
                    if (desired < sumAvailable)
                        somethingHasAMaximumSize = true;

                    newSizes[i] = -1.0;
                }
            }

            bool keepGoing = somethingHasAMaximumSize;
            while (keepGoing) {
                keepGoing = false;

                for (int i = 0; i < n; ++i) {
                    if (newSizes[i] >= 0.0)
                        continue;

                    const QGridLayoutBox &box = boxes.at(start + i);
                    qreal avail = sumAvailable * factors[i] / sumFactors;
                    if (sizes[i] + avail >= box.q_maximumSize) {
                        newSizes[i] = box.q_maximumSize;
                        sumAvailable -= box.q_maximumSize - sizes[i];
                        sumFactors -= factors[i];
                        keepGoing = (sumAvailable > 0.0);
                        if (!keepGoing)
                            break;
                    }
                }
            }

            for (int i = 0; i < n; ++i) {
                if (newSizes[i] < 0.0) {
                    qreal delta = (sumFactors == 0.0) ? 0.0
                                                      : sumAvailable * factors[i] / sumFactors;
                    newSizes[i] = sizes[i] + delta;
                }
            }
        }
    }

    if (sumAvailable > 0) {
        qreal offset = 0;
        for (int i = 0; i < n; ++i) {
            qreal delta = newSizes[i] - sizes[i];
            positions[i] += offset;
            sizes[i] += delta;
            offset += delta;
        }

#if 0 // some "pixel allocation"
        int surplus = targetSize - (positions[n - 1] + sizes[n - 1]);
        Q_ASSERT(surplus >= 0 && surplus <= n);

        int prevSurplus = -1;
        while (surplus > 0 && surplus != prevSurplus) {
            prevSurplus = surplus;

            int offset = 0;
            for (int i = 0; i < n; ++i) {
                const QGridLayoutBox &box = boxes.at(start + i);
                int delta = (!ignore.testBit(start + i) && surplus > 0
                             && factors[i] > 0 && sizes[i] < box.q_maximumSize)
                    ? 1 : 0;

                positions[i] += offset;
                sizes[i] += delta;
                offset += delta;
                surplus -= delta;
            }
        }
        Q_ASSERT(surplus == 0);
#endif
    }

    if (descents) {
        for (int i = 0; i < n; ++i) {
            if (ignore.testBit(start + i))
                continue;
            const QGridLayoutBox &box = boxes.at(start + i);
            descents[i] = fixedDescent(box.q_minimumDescent, box.q_minimumAscent, sizes[i]);
        }
    }
}

QGridLayoutBox QGridLayoutRowData::totalBox(int start, int end) const
{
    QGridLayoutBox result;
    if (start < end) {
        result.q_maximumSize = 0.0;
        qreal nextSpacing = 0.0;
        for (int i = start; i < end; ++i) {
            result.add(boxes.at(i), stretches.at(i), nextSpacing);
            nextSpacing = spacings.at(i);
        }
    }
    return result;
}

void QGridLayoutRowData::stealBox(int start, int end, int which, qreal *positions, qreal *sizes)
{
    qreal offset = 0.0;
    qreal nextSpacing = 0.0;

    for (int i = start; i < end; ++i) {
        qreal avail = 0.0;

        if (!ignore.testBit(i)) {
            const QGridLayoutBox &box = boxes.at(i);
            avail = box.q_sizes(which);
            offset += nextSpacing;
            nextSpacing = spacings.at(i);
        }

        *positions++ = offset;
        *sizes++ = avail;
        offset += avail;
    }
}

#ifdef QT_DEBUG
void QGridLayoutRowData::dump(int indent) const
{
    qDebug("%*sData", indent, "");

    for (int i = 0; i < ignore.count(); ++i) {
        qDebug("%*s Row %d (stretch %d, spacing %g)", indent, "", i, stretches.at(i),
               spacings.at(i));
        if (ignore.testBit(i))
            qDebug("%*s  Ignored", indent, "");
        boxes.at(i).dump(indent + 2);
    }

    MultiCellMap::const_iterator it = multiCellMap.constBegin();
    while (it != multiCellMap.constEnd()) {
        qDebug("%*s Multi-cell entry <%d, %d> (stretch %d)", indent, "", it.key().first,
               it.key().second, it.value().q_stretch);
        it.value().q_box.dump(indent + 2);
    }
}
#endif

QGridLayoutItem::QGridLayoutItem(QGridLayoutEngine *engine, QGraphicsLayoutItem *layoutItem,
                                 int row, int column, int rowSpan, int columnSpan,
                                 Qt::Alignment alignment)
    : q_engine(engine), q_layoutItem(layoutItem), q_alignment(alignment)
{
    q_firstRows[Hor] = column;
    q_firstRows[Ver] = row;
    q_rowSpans[Hor] = columnSpan;
    q_rowSpans[Ver] = rowSpan;
    q_stretches[Hor] = -1;
    q_stretches[Ver] = -1;

    q_engine->addItem(this);
}

int QGridLayoutItem::firstRow(Qt::Orientation orientation) const
{
    return q_firstRows[orientation == Qt::Vertical];
}

int QGridLayoutItem::firstColumn(Qt::Orientation orientation) const
{
    return q_firstRows[orientation == Qt::Horizontal];
}

int QGridLayoutItem::lastRow(Qt::Orientation orientation) const
{
    return firstRow(orientation) + rowSpan(orientation) - 1;
}

int QGridLayoutItem::lastColumn(Qt::Orientation orientation) const
{
    return firstColumn(orientation) + columnSpan(orientation) - 1;
}

int QGridLayoutItem::rowSpan(Qt::Orientation orientation) const
{
    return q_rowSpans[orientation == Qt::Vertical];
}

int QGridLayoutItem::columnSpan(Qt::Orientation orientation) const
{
    return q_rowSpans[orientation == Qt::Horizontal];
}

void QGridLayoutItem::setFirstRow(int row, Qt::Orientation orientation)
{
    q_firstRows[orientation == Qt::Vertical] = row;
}

void QGridLayoutItem::setRowSpan(int rowSpan, Qt::Orientation orientation)
{
    q_rowSpans[orientation == Qt::Vertical] = rowSpan;
}

int QGridLayoutItem::stretchFactor(Qt::Orientation orientation) const
{
    int stretch = q_stretches[orientation == Qt::Vertical];
    if (stretch >= 0)
        return stretch;

    QSizePolicy::Policy policy = sizePolicy(orientation);

    if (policy & QSizePolicy::ExpandFlag) {
        return 1;
    } else if (policy & QSizePolicy::GrowFlag) {
        return -1;  // because we max it up
    } else {
        return 0;
    }
}

void QGridLayoutItem::setStretchFactor(int stretch, Qt::Orientation orientation)
{
    Q_ASSERT(stretch >= 0); // ### deal with too big stretches
    q_stretches[orientation == Qt::Vertical] = stretch;
}

QSizePolicy::Policy QGridLayoutItem::sizePolicy(Qt::Orientation orientation) const
{
    QSizePolicy sizePolicy(q_layoutItem->sizePolicy());
    return (orientation == Qt::Horizontal) ? sizePolicy.horizontalPolicy()
                                           : sizePolicy.verticalPolicy();
}

QSizePolicy::ControlTypes QGridLayoutItem::controlTypes(LayoutSide /* side */) const
{
    return q_layoutItem->sizePolicy().controlType();
}

QSizeF QGridLayoutItem::sizeHint(Qt::SizeHint which, const QSizeF &constraint) const
{
    return q_layoutItem->effectiveSizeHint(which, constraint);
}

QGridLayoutBox QGridLayoutItem::box(Qt::Orientation orientation, qreal constraint) const
{
    QGridLayoutBox result;
    QSizePolicy::Policy policy = sizePolicy(orientation);

    if (orientation == Qt::Horizontal) {
        QSizeF constraintSize(-1.0, constraint);

        result.q_preferredSize = sizeHint(Qt::PreferredSize, constraintSize).width();

        if (policy & QSizePolicy::ShrinkFlag) {
            result.q_minimumSize = sizeHint(Qt::MinimumSize, constraintSize).width();
        } else {
            result.q_minimumSize = result.q_preferredSize;
        }

        if (policy & (QSizePolicy::GrowFlag | QSizePolicy::ExpandFlag)) {
            result.q_maximumSize = sizeHint(Qt::MaximumSize, constraintSize).width();
        } else {
            result.q_maximumSize = result.q_preferredSize;
        }
    } else {
        QSizeF constraintSize(constraint, -1.0);

        result.q_preferredSize = sizeHint(Qt::PreferredSize, constraintSize).height();

        if (policy & QSizePolicy::ShrinkFlag) {
            result.q_minimumSize = sizeHint(Qt::MinimumSize, constraintSize).height();
        } else {
            result.q_minimumSize = result.q_preferredSize;
        }

        if (policy & (QSizePolicy::GrowFlag | QSizePolicy::ExpandFlag)) {
            result.q_maximumSize = sizeHint(Qt::MaximumSize, constraintSize).height();
        } else {
            result.q_maximumSize = result.q_preferredSize;
        }

        result.q_minimumDescent = sizeHint(Qt::MinimumDescent, constraintSize).height();
        if (result.q_minimumDescent >= 0.0)
            result.q_minimumAscent = result.q_minimumSize - result.q_minimumDescent;
    }
    if (policy & QSizePolicy::IgnoreFlag)
        result.q_preferredSize = result.q_minimumSize;

    return result;
}

QRectF QGridLayoutItem::geometryWithin(qreal x, qreal y, qreal width, qreal height,
                                       qreal rowDescent) const
{
    rowDescent = -1.0; // ### This disables the descent

    QGridLayoutBox vBox = box(Qt::Vertical);
    if (vBox.q_minimumDescent < 0.0 || rowDescent < 0.0) {
        qreal cellWidth = width;
        qreal cellHeight = height;

        QSizeF size = effectiveMaxSize().boundedTo(QSizeF(cellWidth, cellHeight));
        width = size.width();
        height = size.height();
        
        Qt::Alignment align = q_engine->effectiveAlignment(this);
        switch (align & Qt::AlignHorizontal_Mask) {
        case Qt::AlignHCenter:
            x += (cellWidth - width)/2;
            break;
        case Qt::AlignRight:
            x += cellWidth - width;
            break;
        default:
            break;
        }
        switch (align & Qt::AlignVertical_Mask) {
        case Qt::AlignVCenter:
            y += (cellHeight - height)/2;
            break;
        case Qt::AlignBottom:
            y += cellHeight - height;
            break;
        default:
            break;
        }
        return QRectF(x, y, width, height);
    } else {
        qreal descent = vBox.q_minimumDescent;
        qreal ascent = vBox.q_minimumSize - descent;
        return QRectF(x, y + height - rowDescent - ascent, width, ascent + descent);
    }
}

void QGridLayoutItem::setGeometry(const QRectF &rect)
{
    q_layoutItem->setGeometry(rect);
}

void QGridLayoutItem::transpose()
{
    qSwap(q_firstRows[Hor], q_firstRows[Ver]);
    qSwap(q_rowSpans[Hor], q_rowSpans[Ver]);
    qSwap(q_stretches[Hor], q_stretches[Ver]);
}

void QGridLayoutItem::insertOrRemoveRows(int row, int delta, Qt::Orientation orientation)
{
    int oldFirstRow = firstRow(orientation);
    if (oldFirstRow >= row) {
        setFirstRow(oldFirstRow + delta, orientation);
    } else if (lastRow(orientation) >= row) {
        setRowSpan(rowSpan(orientation) + delta, orientation);
    }
}
/*!
    \internal
    returns the effective maximumSize, will take the sizepolicy into
    consideration. (i.e. if sizepolicy does not have QSizePolicy::Grow, then
    maxSizeHint will be the preferredSize)
    Note that effectiveSizeHint does not take sizePolicy into consideration,
    (since it only evaluates the hints, as the name implies)
*/
QSizeF QGridLayoutItem::effectiveMaxSize() const
{
    QSizeF size;
    bool vGrow = (sizePolicy(Qt::Vertical) & QSizePolicy::GrowFlag) == QSizePolicy::GrowFlag;
    bool hGrow = (sizePolicy(Qt::Horizontal) & QSizePolicy::GrowFlag) == QSizePolicy::GrowFlag;
    if (!vGrow || !hGrow) {
        QSizeF pref = layoutItem()->effectiveSizeHint(Qt::PreferredSize);
        if (!vGrow)
            size.setHeight(pref.height());
        if (!hGrow)
            size.setWidth(pref.width());
    }

    if (!size.isValid()) {
        QSizeF maxSize = layoutItem()->effectiveSizeHint(Qt::MaximumSize);
        if (size.width() == -1)
            size.setWidth(maxSize.width());
        if (size.height() == -1)
            size.setHeight(maxSize.height());
    }
    return size;
}

#ifdef QT_DEBUG
void QGridLayoutItem::dump(int indent) const
{
    qDebug("%*s%p (%d, %d) %d x %d", indent, "", q_layoutItem, firstRow(), firstColumn(),
           rowSpan(), columnSpan());

    if (q_stretches[Hor] >= 0)
        qDebug("%*s Horizontal stretch: %d", indent, "", q_stretches[Hor]);
    if (q_stretches[Ver] >= 0)
        qDebug("%*s Vertical stretch: %d", indent, "", q_stretches[Ver]);
    if (q_alignment != 0)
        qDebug("%*s Alignment: %x", indent, "", uint(q_alignment));
    qDebug("%*s Horizontal size policy: %x Vertical size policy: %x",
        indent, "", sizePolicy(Qt::Horizontal), sizePolicy(Qt::Vertical));
}
#endif

void QGridLayoutRowInfo::insertOrRemoveRows(int row, int delta)
{
    count += delta;
    
    insertOrRemoveItems(stretches, row, delta);
    insertOrRemoveItems(spacings, row, delta);
    insertOrRemoveItems(alignments, row, delta);
    insertOrRemoveItems(boxes, row, delta);
}

#ifdef QT_DEBUG
void QGridLayoutRowInfo::dump(int indent) const
{
    qDebug("%*sInfo (count: %d)", indent, "", count);
    for (int i = 0; i < count; ++i) {
        QString message;

        if (stretches.value(i).value() >= 0)
            message += QString::fromAscii(" stretch %1").arg(stretches.value(i).value());
        if (spacings.value(i).value() >= 0.0)
            message += QString::fromAscii(" spacing %1").arg(spacings.value(i).value());
        if (alignments.value(i) != 0)
            message += QString::fromAscii(" alignment %1").arg(int(alignments.value(i)), 16);

        if (!message.isEmpty() || boxes.value(i) != QGridLayoutBox()) {
            qDebug("%*s Row %d:%s", indent, "", i, qPrintable(message));
            if (boxes.value(i) != QGridLayoutBox())
                boxes.value(i).dump(indent + 1);
        }
    }
}
#endif

QGridLayoutEngine::QGridLayoutEngine()
{
    m_visualDirection = Qt::LeftToRight;
    invalidate();
}

int QGridLayoutEngine::rowCount(Qt::Orientation orientation) const
{
    return q_infos[orientation == Qt::Vertical].count;
}

int QGridLayoutEngine::columnCount(Qt::Orientation orientation) const
{
    return q_infos[orientation == Qt::Horizontal].count;
}

int QGridLayoutEngine::itemCount() const
{
    return q_items.count();
}

QGridLayoutItem *QGridLayoutEngine::itemAt(int index) const
{
    Q_ASSERT(index >= 0 && index < itemCount());
    return q_items.at(index);
}

int QGridLayoutEngine::effectiveFirstRow(Qt::Orientation orientation) const
{
    ensureEffectiveFirstAndLastRows();
    return q_cachedEffectiveFirstRows[orientation == Qt::Vertical];
}

int QGridLayoutEngine::effectiveLastRow(Qt::Orientation orientation) const
{
    ensureEffectiveFirstAndLastRows();
    return q_cachedEffectiveLastRows[orientation == Qt::Vertical];
}

void QGridLayoutEngine::setSpacing(qreal spacing, Qt::Orientations orientations)
{
    Q_ASSERT(spacing >= 0.0);
    if (orientations & Qt::Horizontal)
        q_defaultSpacings[Hor].setUserValue(spacing);
    if (orientations & Qt::Vertical)
        q_defaultSpacings[Ver].setUserValue(spacing);

    invalidate();
}

qreal QGridLayoutEngine::spacing(const QLayoutStyleInfo &styleInfo, Qt::Orientation orientation) const
{
    if (q_defaultSpacings[orientation == Qt::Vertical].isDefault()) {
        QStyle *style = styleInfo.style();
        QStyleOption option;
        option.initFrom(styleInfo.widget());
        qreal defaultSpacing = (qreal)style->pixelMetric(orientation == Qt::Vertical ? QStyle::PM_LayoutVerticalSpacing
                                               : QStyle::PM_LayoutHorizontalSpacing, &option, styleInfo.widget());
        q_defaultSpacings[orientation == Qt::Vertical].setCachedValue(defaultSpacing);
    }
    return q_defaultSpacings[orientation == Qt::Vertical].value();
}

void QGridLayoutEngine::setRowSpacing(int row, qreal spacing, Qt::Orientation orientation)
{
    Q_ASSERT(row >= 0);

    QGridLayoutRowInfo &rowInfo = q_infos[orientation == Qt::Vertical];
    if (row >= rowInfo.spacings.count())
        rowInfo.spacings.resize(row + 1);
    if (spacing >= 0)
        rowInfo.spacings[row].setUserValue(spacing);
    else
        rowInfo.spacings[row] = QLayoutParameter<qreal>();
    invalidate();
}

qreal QGridLayoutEngine::rowSpacing(int row, Qt::Orientation orientation) const
{
    QLayoutParameter<qreal> spacing = q_infos[orientation == Qt::Vertical].spacings.value(row);
    if (!spacing.isDefault())
        return spacing.value();
    return q_defaultSpacings[orientation == Qt::Vertical].value();
}

void QGridLayoutEngine::setRowStretchFactor(int row, int stretch, Qt::Orientation orientation)
{
    Q_ASSERT(row >= 0);
    Q_ASSERT(stretch >= 0);

    maybeExpandGrid(row, -1, orientation);

    QGridLayoutRowInfo &rowInfo = q_infos[orientation == Qt::Vertical];
    if (row >= rowInfo.stretches.count())
        rowInfo.stretches.resize(row + 1);
    rowInfo.stretches[row].setUserValue(stretch);
}

int QGridLayoutEngine::rowStretchFactor(int row, Qt::Orientation orientation) const
{
    QStretchParameter stretch = q_infos[orientation == Qt::Vertical].stretches.value(row);
    if (!stretch.isDefault())
        return stretch.value();
    return 0;
}

void QGridLayoutEngine::setStretchFactor(QGraphicsLayoutItem *layoutItem, int stretch,
                                         Qt::Orientation orientation)
{
    Q_ASSERT(stretch >= 0);

    if (QGridLayoutItem *item = findLayoutItem(layoutItem))
        item->setStretchFactor(stretch, orientation);
}

int QGridLayoutEngine::stretchFactor(QGraphicsLayoutItem *layoutItem, Qt::Orientation orientation) const
{
    if (QGridLayoutItem *item = findLayoutItem(layoutItem))
        return item->stretchFactor(orientation);
    return 0;
}

void QGridLayoutEngine::setRowSizeHint(Qt::SizeHint which, int row, qreal size,
                                       Qt::Orientation orientation)
{
    Q_ASSERT(row >= 0);
    Q_ASSERT(size >= 0.0);

    maybeExpandGrid(row, -1, orientation);

    QGridLayoutRowInfo &rowInfo = q_infos[orientation == Qt::Vertical];
    if (row >= rowInfo.boxes.count())
        rowInfo.boxes.resize(row + 1);
    rowInfo.boxes[row].q_sizes(which) = size;
}

qreal QGridLayoutEngine::rowSizeHint(Qt::SizeHint which, int row, Qt::Orientation orientation) const
{
    return q_infos[orientation == Qt::Vertical].boxes.value(row).q_sizes(which);
}

void QGridLayoutEngine::setRowAlignment(int row, Qt::Alignment alignment,
                                        Qt::Orientation orientation)
{
    Q_ASSERT(row >= 0);

    maybeExpandGrid(row, -1, orientation);

    QGridLayoutRowInfo &rowInfo = q_infos[orientation == Qt::Vertical];
    if (row >= rowInfo.alignments.count())
        rowInfo.alignments.resize(row + 1);
    rowInfo.alignments[row] = alignment;
}

Qt::Alignment QGridLayoutEngine::rowAlignment(int row, Qt::Orientation orientation) const
{
    Q_ASSERT(row >= 0);
    return q_infos[orientation == Qt::Vertical].alignments.value(row);
}

void QGridLayoutEngine::setAlignment(QGraphicsLayoutItem *layoutItem, Qt::Alignment alignment)
{
    if (QGridLayoutItem *item = findLayoutItem(layoutItem))
        item->setAlignment(alignment);
    invalidate();
}

Qt::Alignment QGridLayoutEngine::alignment(QGraphicsLayoutItem *layoutItem) const
{
    if (QGridLayoutItem *item = findLayoutItem(layoutItem))
        return item->alignment();
    return 0;
}

Qt::Alignment QGridLayoutEngine::effectiveAlignment(const QGridLayoutItem *layoutItem) const
{
    Qt::Alignment align = layoutItem->alignment();
    if (!(align & Qt::AlignVertical_Mask)) {
        // no vertical alignment, respect the row alignment
        int y = layoutItem->firstRow();
        align |= (rowAlignment(y, Qt::Vertical) & Qt::AlignVertical_Mask);
    }
    if (!(align & Qt::AlignHorizontal_Mask)) {
        // no horizontal alignment, respect the column alignment
        int x = layoutItem->firstColumn();
        align |= (rowAlignment(x, Qt::Horizontal) & Qt::AlignHorizontal_Mask);
    }
    return align;
}

void QGridLayoutEngine::addItem(QGridLayoutItem *item)
{
    maybeExpandGrid(item->lastRow(), item->lastColumn());

    q_items.append(item);

    for (int i = item->firstRow(); i <= item->lastRow(); ++i) {
        for (int j = item->firstColumn(); j <= item->lastColumn(); ++j) {
            if (itemAt(i, j))
                qWarning("QGridLayoutEngine::addItem: Cell (%d, %d) already taken", i, j);
            setItemAt(i, j, item);
        }
    }
}

void QGridLayoutEngine::removeItem(QGridLayoutItem *item)
{
    Q_ASSERT(q_items.contains(item));

    invalidate();

    for (int i = item->firstRow(); i <= item->lastRow(); ++i) {
        for (int j = item->firstColumn(); j <= item->lastColumn(); ++j) {
            if (itemAt(i, j) == item)
                setItemAt(i, j, 0);
        }
    }

    q_items.removeAll(item);
}

QGridLayoutItem *QGridLayoutEngine::findLayoutItem(QGraphicsLayoutItem *layoutItem) const
{
    for (int i = q_items.count() - 1; i >= 0; --i) {
        QGridLayoutItem *item = q_items.at(i);
        if (item->layoutItem() == layoutItem)
            return item;
    }
    return 0;
}

QGridLayoutItem *QGridLayoutEngine::itemAt(int row, int column, Qt::Orientation orientation) const
{
    if (orientation == Qt::Horizontal)
        qSwap(row, column);
    if (uint(row) >= uint(rowCount()) || uint(column) >= uint(columnCount()))
        return 0;
    return q_grid.at((row * internalGridColumnCount()) + column);
}

void QGridLayoutEngine::invalidate()
{
    q_cachedEffectiveFirstRows[Hor] = -1;
    q_cachedEffectiveFirstRows[Ver] = -1;
    q_cachedEffectiveLastRows[Hor] = -1;
    q_cachedEffectiveLastRows[Ver] = -1;
    q_cachedDataForStyleInfo.invalidate();
    q_cachedSize = QSizeF();
}

static void visualRect(QRectF *geom, Qt::LayoutDirection dir, const QRectF &contentsRect)
{
    if (dir == Qt::RightToLeft)
        geom->moveRight(contentsRect.right() - (geom->left() - contentsRect.left()));
}

void QGridLayoutEngine::setGeometries(const QLayoutStyleInfo &styleInfo,
                                      const QRectF &contentsGeometry)
{
    if (rowCount() < 1 || columnCount() < 1)
        return;

    ensureGeometries(styleInfo, contentsGeometry.size());

    for (int i = q_items.count() - 1; i >= 0; --i) {
        QGridLayoutItem *item = q_items.at(i);

        qreal x = q_xx[item->firstColumn()];
        qreal y = q_yy[item->firstRow()];
        qreal width = q_widths[item->lastColumn()];
        qreal height = q_heights[item->lastRow()];

        if (item->columnSpan() != 1)
            width += q_xx[item->lastColumn()] - x;
        if (item->rowSpan() != 1)
            height += q_yy[item->lastRow()] - y;

        QRectF geom = item->geometryWithin(contentsGeometry.x() + x, contentsGeometry.y() + y,
                                               width, height, q_descents[item->lastRow()]);
        visualRect(&geom, visualDirection(), contentsGeometry);
        item->setGeometry(geom);
    }
}

// ### candidate for deletion
QRectF QGridLayoutEngine::cellRect(const QLayoutStyleInfo &styleInfo,
                                   const QRectF &contentsGeometry, int row, int column, int rowSpan,
                                   int columnSpan) const
{
    if (uint(row) >= uint(rowCount()) || uint(column) >= uint(columnCount())
            || rowSpan < 1 || columnSpan < 1)
        return QRectF();

    ensureGeometries(styleInfo, contentsGeometry.size());

    int lastColumn = qMax(column + columnSpan, columnCount()) - 1;
    int lastRow = qMax(row + rowSpan, rowCount()) - 1;

    qreal x = q_xx[column];
    qreal y = q_yy[row];
    qreal width = q_widths[lastColumn];
    qreal height = q_heights[lastRow];

    if (columnSpan != 1)
        width += q_xx[lastColumn] - x;
    if (rowSpan != 1)
        height += q_yy[lastRow] - y;

    return QRectF(contentsGeometry.x() + x, contentsGeometry.y() + y, width, height);
}

QSizeF QGridLayoutEngine::sizeHint(const QLayoutStyleInfo &styleInfo, Qt::SizeHint which,
                                   const QSizeF & /* constraint */) const
{
    ensureColumnAndRowData(styleInfo);

    switch (which) {
    case Qt::MinimumSize:
        return QSizeF(q_totalBoxes[Hor].q_minimumSize, q_totalBoxes[Ver].q_minimumSize);
    case Qt::PreferredSize:
        return QSizeF(q_totalBoxes[Hor].q_preferredSize, q_totalBoxes[Ver].q_preferredSize);
    case Qt::MaximumSize:
        return QSizeF(q_totalBoxes[Hor].q_maximumSize, q_totalBoxes[Ver].q_maximumSize);
    case Qt::MinimumDescent:
        return QSizeF(-1.0, q_totalBoxes[Hor].q_minimumDescent);    // ### doesn't work
    default:
        break;
    }
    return QSizeF();
} 

QSizePolicy::ControlTypes QGridLayoutEngine::controlTypes(LayoutSide side) const
{
    Qt::Orientation orientation = (side == Top || side == Bottom) ? Qt::Vertical : Qt::Horizontal;
    int row = (side == Top || side == Left) ? effectiveFirstRow(orientation)
                                            : effectiveLastRow(orientation);
    QSizePolicy::ControlTypes result = 0;

    for (int column = columnCount(orientation) - 1; column >= 0; --column) {
        if (QGridLayoutItem *item = itemAt(row, column, orientation))
            result |= item->controlTypes(side);
    }
    return result;
}

void QGridLayoutEngine::transpose()
{
    invalidate();

    for (int i = q_items.count() - 1; i >= 0; --i)
        q_items.at(i)->transpose();

    qSwap(q_defaultSpacings[Hor], q_defaultSpacings[Ver]);
    qSwap(q_infos[Hor], q_infos[Ver]);

    regenerateGrid();
}

void QGridLayoutEngine::setVisualDirection(Qt::LayoutDirection direction)
{
    m_visualDirection = direction;
}

Qt::LayoutDirection QGridLayoutEngine::visualDirection() const
{
    return m_visualDirection;
}

#ifdef QT_DEBUG
void QGridLayoutEngine::dump(int indent) const
{
    qDebug("%*sEngine", indent, "");

    qDebug("%*s Items (%d)", indent, "", q_items.count());
    int i;
    for (i = 0; i < q_items.count(); ++i)
        q_items.at(i)->dump(indent + 2);

    qDebug("%*s Grid (%d x %d)", indent, "", internalGridRowCount(),
           internalGridColumnCount());
    for (int row = 0; row < internalGridRowCount(); ++row) {
        QString message = QLatin1String("[ ");
        for (int column = 0; column < internalGridColumnCount(); ++column) {
            message += QString::number(q_items.indexOf(itemAt(row, column))).rightJustified(3);
            message += QLatin1String(" ");
        }
        message += QLatin1String("]");
        qDebug("%*s  %s", indent, "", qPrintable(message));
    }

    if (q_defaultSpacings[Hor].value() >= 0.0 || q_defaultSpacings[Ver].value() >= 0.0)
        qDebug("%*s Default spacings: %g %g", indent, "", q_defaultSpacings[Hor].value(),
               q_defaultSpacings[Ver].value());

    qDebug("%*s Column and row info", indent, "");
    q_infos[Hor].dump(indent + 2);
    q_infos[Ver].dump(indent + 2);

    qDebug("%*s Column and row data", indent, "");
    q_columnData.dump(indent + 2);
    q_rowData.dump(indent + 2);

    qDebug("%*s Geometries output", indent, "");
    for (int pass = 0; pass < 2; ++pass) {
        QVector<qreal> &cellPos = q_yy;
        QString message;
        for (i = 0; i < cellPos.count(); ++i) {
            message += QLatin1String((message.isEmpty() ? "[" : ", "));
            message += QString::number(cellPos.at(i));
        }
        message += QLatin1String("]");
        qDebug("%*s %s %s", indent, "", (pass == 0 ? "rows:" : "columns:"), qPrintable(message));
        cellPos = q_xx;
    }
}
#endif

void QGridLayoutEngine::maybeExpandGrid(int row, int column, Qt::Orientation orientation)
{
    invalidate();   // ### move out of here?

    if (orientation == Qt::Horizontal)
        qSwap(row, column);

    if (row < rowCount() && column < columnCount())
        return;

    int oldGridRowCount = internalGridRowCount();
    int oldGridColumnCount = internalGridColumnCount();

    q_infos[Ver].count = qMax(row + 1, rowCount());
    q_infos[Hor].count = qMax(column + 1, columnCount());

    int newGridRowCount = internalGridRowCount();
    int newGridColumnCount = internalGridColumnCount();

    int newGridSize = newGridRowCount * newGridColumnCount;
    if (newGridSize != q_grid.count()) {
        q_grid.resize(newGridSize);

        if (newGridColumnCount != oldGridColumnCount) {
            for (int i = oldGridRowCount - 1; i >= 1; --i) {
                for (int j = oldGridColumnCount - 1; j >= 0; --j) {
                    int oldIndex = (i * oldGridColumnCount) + j;
                    int newIndex = (i * newGridColumnCount) + j;

                    Q_ASSERT(newIndex > oldIndex);
                    q_grid[newIndex] = q_grid[oldIndex];
                    q_grid[oldIndex] = 0;
                }
            }
        }
    }
}

void QGridLayoutEngine::regenerateGrid()
{
    q_grid.fill(0);

    for (int i = q_items.count() - 1; i >= 0; --i) {
        QGridLayoutItem *item = q_items.at(i);

        for (int j = item->firstRow(); j <= item->lastRow(); ++j) {
            for (int k = item->firstColumn(); k <= item->lastColumn(); ++k) {
                setItemAt(j, k, item);
            }
        }
    }
}

void QGridLayoutEngine::setItemAt(int row, int column, QGridLayoutItem *item)
{
    Q_ASSERT(row >= 0 && row < rowCount());
    Q_ASSERT(column >= 0 && column < columnCount());
    q_grid[(row * internalGridColumnCount()) + column] = item;
}

void QGridLayoutEngine::insertOrRemoveRows(int row, int delta, Qt::Orientation orientation)
{
    int oldRowCount = rowCount(orientation);
    Q_ASSERT(uint(row) <= uint(oldRowCount));

    invalidate();

    // appending rows (or columns) is easy
    if (row == oldRowCount && delta > 0) {
        maybeExpandGrid(oldRowCount + delta - 1, -1, orientation);
        return;
    }

    q_infos[orientation == Qt::Vertical].insertOrRemoveRows(row, delta);

    for (int i = q_items.count() - 1; i >= 0; --i)
        q_items.at(i)->insertOrRemoveRows(row, delta, orientation);

    q_grid.resize(internalGridRowCount() * internalGridColumnCount());
    regenerateGrid();
}

void QGridLayoutEngine::fillRowData(QGridLayoutRowData *rowData, const QLayoutStyleInfo &styleInfo,
                                    Qt::Orientation orientation) const
{
    const int ButtonMask = QSizePolicy::ButtonBox | QSizePolicy::PushButton;
    const QGridLayoutRowInfo &rowInfo = q_infos[orientation == Qt::Vertical];
    const QGridLayoutRowInfo &columnInfo = q_infos[orientation == Qt::Horizontal];
    LayoutSide top = (orientation == Qt::Vertical) ? Top : Left;
    LayoutSide bottom = (orientation == Qt::Vertical) ? Bottom : Right;

    QStyle *style = styleInfo.style();
    QStyleOption option;
    option.initFrom(styleInfo.widget());

    const QLayoutParameter<qreal> &defaultSpacing = q_defaultSpacings[orientation == Qt::Vertical];
    qreal innerSpacing = 0.0;
    if (style)
        innerSpacing = (qreal)style->pixelMetric(orientation == Qt::Vertical ? QStyle::PM_LayoutVerticalSpacing
                                                       : QStyle::PM_LayoutHorizontalSpacing,
                           &option, styleInfo.widget());
    if (innerSpacing >= 0.0)
        defaultSpacing.setCachedValue(innerSpacing);

    for (int row = 0; row < rowInfo.count; ++row) {
        bool rowIsEmpty = true;
        bool rowIsIdenticalToPrevious = (row > 0);

        for (int column = 0; column < columnInfo.count; ++column) {
            QGridLayoutItem *item = itemAt(row, column, orientation);

            if (rowIsIdenticalToPrevious && item != itemAt(row - 1, column, orientation))
                rowIsIdenticalToPrevious = false;

            if (item)
                rowIsEmpty = false;
        }

        if ((rowIsEmpty || rowIsIdenticalToPrevious)
                && rowInfo.spacings.value(row).isDefault()
                && rowInfo.stretches.value(row).isDefault()
                && rowInfo.boxes.value(row) == QGridLayoutBox())
            rowData->ignore.setBit(row, true);

        if (rowInfo.spacings.value(row).isUser()) {
            rowData->spacings[row] = rowInfo.spacings.at(row).value();
        } else if (!defaultSpacing.isDefault()) {
            rowData->spacings[row] = defaultSpacing.value();
        }

        rowData->stretches[row] = rowInfo.stretches.value(row).value();
    }

    struct RowAdHocData {
        int q_row;
        unsigned int q_hasButtons : 8;
        unsigned int q_hasNonButtons : 8;

        inline RowAdHocData() : q_row(-1), q_hasButtons(false), q_hasNonButtons(false) {}
        inline void init(int row) {
            this->q_row = row;
            q_hasButtons = false;
            q_hasNonButtons = false;
        }
        inline bool hasOnlyButtons() const { return q_hasButtons && !q_hasNonButtons; }
        inline bool hasOnlyNonButtons() const { return q_hasNonButtons && !q_hasButtons; }
    };
    RowAdHocData lastRowAdHocData;
    RowAdHocData nextToLastRowAdHocData;
    RowAdHocData nextToNextToLastRowAdHocData;

    rowData->hasIgnoreFlag = false;
    for (int row = 0; row < rowInfo.count; ++row) {
        if (rowData->ignore.testBit(row))
            continue;

        QGridLayoutBox &rowBox = rowData->boxes[row];
        if (option.state & QStyle::State_Window) {
            nextToNextToLastRowAdHocData = nextToLastRowAdHocData;
            nextToLastRowAdHocData = lastRowAdHocData;
            lastRowAdHocData.init(row);
        }

        bool userRowStretch = rowInfo.stretches.value(row).isUser();
        int &rowStretch = rowData->stretches[row];

        bool hasIgnoreFlag = true;
        for (int column = 0; column < columnInfo.count; ++column) {
            QGridLayoutItem *item = itemAt(row, column, orientation);
            if (item) {
                int itemRow = item->firstRow(orientation);
                int itemColumn = item->firstColumn(orientation);

                if (itemRow == row && itemColumn == column) {
                    int itemStretch = item->stretchFactor(orientation);
                    if (!(item->sizePolicy(orientation) & QSizePolicy::IgnoreFlag))
                        hasIgnoreFlag = false;
                    int itemRowSpan = item->rowSpan(orientation);

                    int effectiveRowSpan = 1;
                    for (int i = 1; i < itemRowSpan; ++i) {
                        if (!rowData->ignore.testBit(i))
                            ++effectiveRowSpan;
                    }

                    QGridLayoutBox *box;
                    if (effectiveRowSpan == 1) {
                        box = &rowBox;
                        if (!userRowStretch)
                            rowStretch = qMax(rowStretch, itemStretch);
                    } else {
                        QGridLayoutMultiCellData &multiCell =
                                rowData->multiCellMap[qMakePair(row, effectiveRowSpan)];
                        box = &multiCell.q_box;
                        multiCell.q_stretch = itemStretch;
                    }
                    box->combine(item->box(orientation));

                    if (effectiveRowSpan == 1) {
                        QSizePolicy::ControlTypes controls = item->controlTypes(top);
                        if (controls & ButtonMask)
                            lastRowAdHocData.q_hasButtons = true;
                        if (controls & ~ButtonMask)
                            lastRowAdHocData.q_hasNonButtons = true;
                    }
                }
            }
        }
        if (row < rowInfo.boxes.count()) {
            QGridLayoutBox rowBoxInfo = rowInfo.boxes.at(row);
            rowBoxInfo.normalize();
            rowBox.q_minimumSize = qMax(rowBox.q_minimumSize, rowBoxInfo.q_minimumSize);
            rowBox.q_maximumSize = qMax(rowBox.q_minimumSize,
                                        (rowBoxInfo.q_maximumSize != FLT_MAX ?
                                        rowBoxInfo.q_maximumSize : rowBox.q_maximumSize));
            rowBox.q_preferredSize = qBound(rowBox.q_minimumSize,
                                            qMax(rowBox.q_preferredSize, rowBoxInfo.q_preferredSize),
                                            rowBox.q_maximumSize);
        }
        if (hasIgnoreFlag)
            rowData->hasIgnoreFlag = true;
    }

    /*
        Heuristic: Detect button boxes that don't use QSizePolicy::ButtonBox.
        This is somewhat ad hoc but it usually does the trick.
    */
    bool lastRowIsButtonBox = (lastRowAdHocData.hasOnlyButtons()
                               && nextToLastRowAdHocData.hasOnlyNonButtons());
    bool lastTwoRowsIsButtonBox = (lastRowAdHocData.hasOnlyButtons()
                                   && nextToLastRowAdHocData.hasOnlyButtons()
                                   && nextToNextToLastRowAdHocData.hasOnlyNonButtons()
                                   && orientation == Qt::Vertical);

    if (defaultSpacing.isDefault()) {
        int prevRow = -1;
        for (int row = 0; row < rowInfo.count; ++row) {
            if (rowData->ignore.testBit(row))
                continue;

            if (prevRow != -1 && !rowInfo.spacings.value(prevRow).isUser()) {
                qreal &rowSpacing = rowData->spacings[prevRow];
                for (int column = 0; column < columnInfo.count; ++column) {
                    QGridLayoutItem *item1 = itemAt(prevRow, column, orientation);
                    QGridLayoutItem *item2 = itemAt(row, column, orientation);

                    if (item1 && item2 && item1 != item2) {
                        QSizePolicy::ControlTypes controls1 = item1->controlTypes(bottom);
                        QSizePolicy::ControlTypes controls2 = item2->controlTypes(top);

                        if (controls2 & QSizePolicy::PushButton) {
                            if ((row == nextToLastRowAdHocData.q_row && lastTwoRowsIsButtonBox)
                                    || (row == lastRowAdHocData.q_row && lastRowIsButtonBox)) {
                                controls2 &= ~QSizePolicy::PushButton;
                                controls2 |= QSizePolicy::ButtonBox;
                            }
                        }

                        qreal spacing = style->combinedLayoutSpacing(controls1, controls2,
                                                                     orientation, &option,
                                                                     styleInfo.widget());
                        if (orientation == Qt::Horizontal) {
                            qreal width1 = rowData->boxes.at(prevRow).q_minimumSize;
                            qreal width2 = rowData->boxes.at(row).q_minimumSize;
                            QRectF rect1 = item1->geometryWithin(0.0, 0.0, width1, FLT_MAX, -1.0);
                            QRectF rect2 = item2->geometryWithin(0.0, 0.0, width2, FLT_MAX, -1.0);
                            spacing -= (width1 - (rect1.x() + rect1.width())) + rect2.x();
                        } else {
                            const QGridLayoutBox &box1 = rowData->boxes.at(prevRow);
                            const QGridLayoutBox &box2 = rowData->boxes.at(row);
                            qreal height1 = box1.q_minimumSize;
                            qreal height2 = box2.q_minimumSize;
                            qreal rowDescent1 = fixedDescent(box1.q_minimumDescent,
                                                             box1.q_minimumAscent, height1);
                            qreal rowDescent2 = fixedDescent(box2.q_minimumDescent,
                                                             box2.q_minimumAscent, height2);
                            QRectF rect1 = item1->geometryWithin(0.0, 0.0, FLT_MAX, height1,
                                                                 rowDescent1);
                            QRectF rect2 = item2->geometryWithin(0.0, 0.0, FLT_MAX, height2,
                                                                 rowDescent2);
                            spacing -= (height1 - (rect1.y() + rect1.height())) + rect2.y();
                        }
                        rowSpacing = qMax(spacing, rowSpacing);
                    }
                }
            }
            prevRow = row;
        }
    } else if (lastRowIsButtonBox || lastTwoRowsIsButtonBox) {
        /*
            Even for styles that define a uniform spacing, we cheat a
            bit and use the window margin as the spacing. This
            significantly improves the look of dialogs.
        */
        int prevRow = lastRowIsButtonBox ? nextToLastRowAdHocData.q_row
                                         : nextToNextToLastRowAdHocData.q_row;
        if (!defaultSpacing.isUser() && !rowInfo.spacings.value(prevRow).isUser()) {
            qreal windowMargin = style->pixelMetric(orientation == Qt::Vertical
                                                          ? QStyle::PM_LayoutBottomMargin
                                                          : QStyle::PM_LayoutRightMargin,
                                                  &option, styleInfo.widget());

            qreal &rowSpacing = rowData->spacings[prevRow];
            rowSpacing = qMax(windowMargin, rowSpacing);
        }
    }
}

void QGridLayoutEngine::ensureEffectiveFirstAndLastRows() const
{
    if (q_cachedEffectiveFirstRows[Hor] == -1 && !q_items.isEmpty()) {
        int rowCount = this->rowCount();
        int columnCount = this->columnCount();

        q_cachedEffectiveFirstRows[Ver] = rowCount;
        q_cachedEffectiveFirstRows[Hor] = columnCount;
        q_cachedEffectiveLastRows[Ver] = -1;
        q_cachedEffectiveLastRows[Hor] = -1;

        for (int i = q_items.count() - 1; i >= 0; --i) {
            const QGridLayoutItem *item = q_items.at(i);

            for (int j = 0; j < NOrientations; ++j) {
                Qt::Orientation orientation = (j == Hor) ? Qt::Horizontal : Qt::Vertical;
                if (item->firstRow(orientation) < q_cachedEffectiveFirstRows[j])
                    q_cachedEffectiveFirstRows[j] = item->firstRow(orientation);
                if (item->lastRow(orientation) > q_cachedEffectiveLastRows[j])
                    q_cachedEffectiveLastRows[j] = item->lastRow(orientation);
            }
        }
    }
}

void QGridLayoutEngine::ensureColumnAndRowData(const QLayoutStyleInfo &styleInfo) const
{
    if (q_cachedDataForStyleInfo == styleInfo)
        return;

    q_columnData.reset(columnCount());
    q_rowData.reset(rowCount());

    fillRowData(&q_columnData, styleInfo, Qt::Horizontal);
    fillRowData(&q_rowData, styleInfo, Qt::Vertical);

    q_columnData.distributeMultiCells();
    q_rowData.distributeMultiCells();

    q_totalBoxes[Hor] = q_columnData.totalBox(0, columnCount());
    q_totalBoxes[Ver] = q_rowData.totalBox(0, rowCount());

    q_cachedDataForStyleInfo = styleInfo;
}

void QGridLayoutEngine::ensureGeometries(const QLayoutStyleInfo &styleInfo,
                                         const QSizeF &size) const
{
    ensureColumnAndRowData(styleInfo);
    if (q_cachedSize == size)
        return;

    q_xx.resize(columnCount());
    q_yy.resize(rowCount());
    q_widths.resize(columnCount());
    q_heights.resize(rowCount());
    q_descents.resize(rowCount());
    q_columnData.calculateGeometries(0, columnCount(), size.width(), q_xx.data(), q_widths.data(),
                                     0, q_totalBoxes[Hor]);
    q_rowData.calculateGeometries(0, rowCount(), size.height(), q_yy.data(), q_heights.data(),
                                  q_descents.data(), q_totalBoxes[Ver]);

    q_cachedSize = size;
}

QT_END_NAMESPACE
        
#endif //QT_NO_GRAPHICSVIEW