src/gui/kernel/qlayout.cpp

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/****************************************************************************
**
** Copyright (C) 1992-2006 Trolltech ASA. All rights reserved.
**
** This file is part of the QtGui module of the Qt Toolkit.
**
** This file may be used under the terms of the GNU General Public
** License version 2.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of
** this file.  Please review the following information to ensure GNU
** General Public Licensing requirements will be met:
** http://www.trolltech.com/products/qt/opensource.html
**
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://www.trolltech.com/products/qt/licensing.html or contact the
** sales department at sales@trolltech.com.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
**
****************************************************************************/

#include "qlayout.h"

#include "qapplication.h"
#include "qlayoutengine_p.h"
#include "qmenubar.h"
#include "qtoolbar.h"
#include "qevent.h"
#include "qstyle.h"
#include "qvariant.h"
#include "qwidget_p.h"
#include "qlayout_p.h"

static int menuBarHeightForWidth(QWidget *menubar, int w)
{
    if (menubar && !menubar->isHidden() && !menubar->isWindow())
        return menubar->heightForWidth(qMax(w, menubar->minimumWidth()));
    return 0;
}

QLayout::QLayout(QWidget *parent)
    : QObject(*new QLayoutPrivate, parent)
{
    if (!parent)
        return;
    parent->setLayout(this);
}

QLayout::QLayout()
    : QObject(*new QLayoutPrivate, 0)
{
}


QLayout::QLayout(QLayoutPrivate &dd, QLayout *lay, QWidget *w)
    : QObject(dd, lay ? static_cast<QObject*>(lay) : static_cast<QObject*>(w))
{
   Q_D(QLayout);
     if (lay) {
        lay->addItem(this);
    } else if (w) {
        if (w->layout()) {
            qWarning("QLayout: Attempting to add QLayout \"%s\" to %s \"%s\", which"
                     " already has a layout",
                     qPrintable(QObject::objectName()), w->metaObject()->className(),
                     w->objectName().toLocal8Bit().data());
            setParent(0);
        } else {
            d->topLevel = true;
            w->d_func()->layout = this;
            invalidate();
        }
    }
}

QLayoutPrivate::QLayoutPrivate()
    : QObjectPrivate(), insideSpacing(-1), outsideBorder(-1), topLevel(false), enabled(true),
      activated(true), autoNewChild(false), constraint(QLayout::SetDefaultConstraint)
      , menubar(0)
{
}




#ifdef QT3_SUPPORT

QLayout::QLayout(QWidget *parent, int margin, int spacing, const char *name)
    : QObject(*new QLayoutPrivate,parent)
{
    Q_D(QLayout);
     setObjectName(QString::fromAscii(name));
    d->outsideBorder = margin;
    if (spacing < 0)
        d->insideSpacing = margin;
    else
        d->insideSpacing = spacing;
    if (parent) {
        if (parent->layout()) {
            qWarning("QLayout \"%s\" added to %s \"%s\", which already has a layout",
                     QObject::objectName().toLocal8Bit().data(), parent->metaObject()->className(),
                     parent->objectName().toLocal8Bit().data());
            parent->layout()->setParent(0);
        } else {
            d->topLevel = true;
            parent->d_func()->layout = this;
            invalidate();
        }
    }
}

QLayout::QLayout(QLayout *parentLayout, int spacing, const char *name)
    : QObject(*new QLayoutPrivate,parentLayout)

{
    Q_D(QLayout);
    setObjectName(QString::fromAscii(name));
    d->insideSpacing = spacing;
    parentLayout->addItem(this);
}

QLayout::QLayout(int spacing, const char *name)
    : QObject(*new QLayoutPrivate, 0)
{
    Q_D(QLayout);
    setObjectName(QString::fromAscii(name));
    d->insideSpacing = spacing;
}

void QLayout::setAutoAdd(bool a) { Q_D(QLayout); d->autoNewChild = a; }

bool QLayout::autoAdd() const { Q_D(const QLayout); return d->autoNewChild; }
#endif


void QLayout::addWidget(QWidget *w)
{
    addChildWidget(w);
    addItem(new QWidgetItem(w));
}



bool QLayout::setAlignment(QWidget *w, Qt::Alignment alignment)
{
    int i = 0;
    QLayoutItem *item = itemAt(i);
    while (item) {
        if (item->widget() == w) {
            item->setAlignment(alignment);
            invalidate();
            return true;
        }
        ++i;
        item = itemAt(i);
    }
    return false;
}

bool QLayout::setAlignment(QLayout *l, Qt::Alignment alignment)
{
    int i = 0;
    QLayoutItem *item = itemAt(i);
    while (item) {
        if (item->layout() == l) {
            item->setAlignment(alignment);
            invalidate();
            return true;
        }
        ++i;
        item = itemAt(i);
    }
    return false;
}

int QLayout::margin() const
{
    Q_D(const QLayout);
    if ( d->outsideBorder >= 0 )
        return d->outsideBorder;
    if (!d->topLevel)
        return 0;
    QWidget *pw = parentWidget();
    if (pw)
        return pw->style()->pixelMetric(
            (pw->isWindow() || (pw->windowType() == Qt::SubWindow))
            ? QStyle::PM_DefaultTopLevelMargin
            : QStyle::PM_DefaultChildMargin
            );
    return 0;
}


int QLayout::spacing() const
{
    Q_D(const QLayout);
    if (d->insideSpacing >=0) {
        return d->insideSpacing;
    } else if (d->topLevel) {
        QWidget *pw = parentWidget();
        if (pw)
            return pw->style()->pixelMetric(QStyle::PM_DefaultLayoutSpacing);
        else
            return QApplication::style()->pixelMetric(QStyle::PM_DefaultLayoutSpacing);
    } else if (parent()) {
        return static_cast<QLayout*>(parent())->spacing();
    } else {
        return -1; //this is a layout that hasn't been inserted yet
    }
}

#ifdef QT3_SUPPORT
bool QLayout::isTopLevel() const
{
    Q_D(const QLayout);
    return d->topLevel;
}
#endif

void QLayout::setMargin(int margin)
{
    Q_D(QLayout);
    d->outsideBorder = margin;
    invalidate();
}


void QLayout::setSpacing(int spacing)
{
    Q_D(QLayout);
    d->insideSpacing = spacing;
    invalidate();
}

QWidget *QLayout::parentWidget() const
{
    Q_D(const QLayout);
    if (!d->topLevel) {
        if (parent()) {
            QLayout *parentLayout = ::qobject_cast<QLayout*>(parent());
            Q_ASSERT(parentLayout);
            return parentLayout->parentWidget();
        } else {
            return 0;
        }
    } else {
        Q_ASSERT(parent() && parent()->isWidgetType());
        return static_cast<QWidget *>(parent());
    }
}

bool QLayout::isEmpty() const
{
    int i = 0;
    QLayoutItem *item = itemAt(i);
    while (item) {
        if (!item->isEmpty())
            return false;
        ++i;
        item = itemAt(i);
    }
    return true;
}

void QLayout::setGeometry(const QRect &r)
{
    Q_D(QLayout);
    d->rect = r;
}

QRect QLayout::geometry() const
{
    Q_D(const QLayout);
    return d->rect;
}

void QLayout::invalidate()
{
    Q_D(QLayout);
    d->rect = QRect();
    update();
}

static bool removeWidgetRecursively(QLayoutItem *li, QWidget *w)
{
    QLayout *lay = li->layout();
    if (!lay)
        return false;
    int i = 0;
    QLayoutItem *child;
    while ((child = lay->itemAt(i))) {
        if (child->widget() == w) {
            delete lay->takeAt(i);
            lay->invalidate();
            return true;
        } else if (removeWidgetRecursively(child, w)) {
            return true;
        } else {
            ++i;
        }
    }
    return false;
}


void QLayoutPrivate::doResize(const QSize &r)
{
    Q_Q(QLayout);
    int mbh = menuBarHeightForWidth(menubar, r.width());
    QWidget *mw = q->parentWidget();
    QRect rect = mw->testAttribute(Qt::WA_LayoutOnEntireRect) ? mw->rect() : mw->contentsRect();
    rect.setTop(rect.top() + mbh);
    q->setGeometry(rect);
#ifndef QT_NO_MENUBAR
    if (menubar)
        menubar->setGeometry(0,0,r.width(), mbh);
#endif
}


void QLayout::widgetEvent(QEvent *e)
{
    Q_D(QLayout);
    if (!d->enabled)
        return;

    switch (e->type()) {
    case QEvent::Resize:
        if (d->activated) {
            QResizeEvent *r = (QResizeEvent *)e;
            d->doResize(r->size());
        } else {
            activate();
        }
        break;
    case QEvent::ChildRemoved:
        {
            QChildEvent *c = (QChildEvent *)e;
            if (c->child()->isWidgetType()) {
                QWidget *w = (QWidget *)c->child();
#ifndef QT_NO_MENUBAR
                if (w == d->menubar)
                    d->menubar = 0;
#endif
                removeWidgetRecursively(this, w);
            }
        }
        break;
#ifdef QT3_SUPPORT
    case QEvent::ChildInserted:
        if (d->topLevel && d->autoNewChild) {
            QChildEvent *c = (QChildEvent *)e;
            if (c->child()->isWidgetType()) {
                QWidget *w = (QWidget *)c->child();
                if (!w->isWindow()) {
#if !defined(QT_NO_MENUBAR) && !defined(QT_NO_TOOLBAR)
                    if (qobject_cast<QMenuBar*>(w) && !::qobject_cast<QToolBar*>(w->parentWidget())) {
                        d->menubar = (QMenuBar *)w;
                        invalidate();
                    } else
#endif
                        addItem(new QWidgetItem(w));
                }
            }
        }
        break;
    case QEvent::LayoutHint:
        d->activated = false;
        // fall through
#endif
    case QEvent::LayoutRequest:
        activate();
        break;
    default:
        break;
    }
}

void QLayout::childEvent(QChildEvent *e)
{
    Q_D(QLayout);
    if (!d->enabled)
        return;

    if (e->type() == QEvent::ChildRemoved) {
        QChildEvent *c = (QChildEvent*)e;
        int i = 0;

        QLayoutItem *item;
        while ((item = itemAt(i))) {
            if (item == static_cast<QLayout*>(c->child())) {
                takeAt(i);
                invalidate();
                break;
            } else {
                ++i;
            }
        }
    }
}

int QLayout::totalHeightForWidth(int w) const
{
    Q_D(const QLayout);
    int side=0, top=0;
    if (d->topLevel) {
        QWidget *parent = parentWidget();
        parent->ensurePolished();
        QWidgetPrivate *wd = parent->d_func();
        side += wd->leftmargin + wd->rightmargin;
        top += wd->topmargin + wd->bottommargin;
    }
    int h = heightForWidth(w - side) + top;
#ifndef QT_NO_MENUBAR
    h += menuBarHeightForWidth(d->menubar, w);
#endif
    return h;
}

QSize QLayout::totalMinimumSize() const
{
    Q_D(const QLayout);
    int side=0, top=0;
    if (d->topLevel) {
        QWidget *pw = parentWidget();
        pw->ensurePolished();
        QWidgetPrivate *wd = pw->d_func();
        side += wd->leftmargin + wd->rightmargin;
        top += wd->topmargin + wd->bottommargin;
    }

    QSize s = minimumSize();
#ifndef QT_NO_MENUBAR
    top += menuBarHeightForWidth(d->menubar, s.width() + side);
#endif
    return s + QSize(side, top);
}

QSize QLayout::totalSizeHint() const
{
    Q_D(const QLayout);
    int side=0, top=0;
    if (d->topLevel) {
        QWidget *pw = parentWidget();
        pw->ensurePolished();
        QWidgetPrivate *wd = pw->d_func();
        side += wd->leftmargin + wd->rightmargin;
        top += wd->topmargin + wd->bottommargin;
    }

    QSize s = sizeHint();
    if (hasHeightForWidth())
        s.setHeight(heightForWidth(s.width() + side));
#ifndef QT_NO_MENUBAR
    top += menuBarHeightForWidth(d->menubar, s.width());
#endif
    return s + QSize(side, top);
}

QSize QLayout::totalMaximumSize() const
{
    Q_D(const QLayout);
    int side=0, top=0;
    if (d->topLevel) {
        QWidget *pw = parentWidget();
        pw->ensurePolished();
        QWidgetPrivate *wd = pw->d_func();
        side += wd->leftmargin + wd->rightmargin;
        top += wd->topmargin + wd->bottommargin;
    }

    QSize s = maximumSize();
#ifndef QT_NO_MENUBAR
    top += menuBarHeightForWidth(d->menubar, s.width());
#endif

    if (d->topLevel)
        s = QSize(qMin(s.width() + side, QLAYOUTSIZE_MAX),
                   qMin(s.height() + top, QLAYOUTSIZE_MAX));
    return s;
}

QLayout::~QLayout()
{
    Q_D(QLayout);
    /*
      This function may be called during the QObject destructor,
      when the parent no longer is a QWidget.
    */
    if (d->topLevel && parent() && parent()->isWidgetType() &&
         ((QWidget*)parent())->layout() == this)
        ((QWidget*)parent())->d_func()->layout = 0;
}

#ifdef QT3_SUPPORT

void QLayout::deleteAllItems()
{
    QLayoutItem *l;
    while ((l = takeAt(0)))
        delete l;
}
#endif

void QLayout::addChildLayout(QLayout *l)
{
    if (l->parent()) {
        qWarning("QLayout::addChildLayout: layout \"%s\" already has a parent",
                 l->objectName().toLocal8Bit().data());
        return;
    }
    l->setParent(this);

    if (QWidget *mw = parentWidget()) {
        l->d_func()->reparentChildWidgets(mw);
    }

}

#ifdef QT_DEBUG
static bool layoutDebug()
{
    static int checked_env = -1;
    if(checked_env == -1)
        checked_env = !!qgetenv("QT_LAYOUT_DEBUG").toInt();

    return checked_env;
}
#endif

void QLayoutPrivate::reparentChildWidgets(QWidget *mw)
{
    Q_Q(QLayout);
    int n =  q->count();

#ifndef QT_NO_MENUBAR
    if (menubar && menubar->parentWidget() != mw) {
        menubar->setParent(mw);
    }
#endif
    for (int i = 0; i < n; ++i) {
        QLayoutItem *item = q->itemAt(i);
        if (QWidget *w = item->widget()) {
            QWidget *pw = w->parentWidget();
#ifdef QT_DEBUG
            if (pw && pw != mw && layoutDebug()) {
                qWarning("QLayout::addChildLayout: widget %s \"%s\" in wrong parent; moved to correct parent",
                         w->metaObject()->className(), w->objectName().toLocal8Bit().data());
            }
#endif
            if (pw != mw)
                w->setParent(mw);
        } else if (QLayout *l = item->layout()) {
            l->d_func()->reparentChildWidgets(mw);
        }
    }
}

void QLayout::addChildWidget(QWidget *w)
{
    QWidget *mw = parentWidget();
    QWidget *pw = w->parentWidget();

    //Qt::WA_LaidOut is never reset. It only means that the widget at some point has
    //been in a layout.
    if (pw && w->testAttribute(Qt::WA_LaidOut)) {
        QLayout *l = pw->layout();
        if (l && removeWidgetRecursively(l, w)) {
#ifdef QT_DEBUG
            if (layoutDebug())
                qWarning("QLayout::addChildWidget: %s \"%s\" is already in a layout; moved to new layout",
                         w->metaObject()->className(), w->objectName().toLocal8Bit().data());
#endif
        }
    }
    if (pw && mw && pw != mw) {
#ifdef QT_DEBUG
            if (layoutDebug())
                qWarning("QLayout::addChildWidget: %s \"%s\" in wrong parent; moved to correct parent",
                         w->metaObject()->className(), w->objectName().toLocal8Bit().data());
#endif
        pw = 0;
    }
    bool needShow = mw && mw->isVisible() && !(w->isHidden() && w->testAttribute(Qt::WA_WState_ExplicitShowHide));
    if (!pw && mw)
        w->setParent(mw);
    w->setAttribute(Qt::WA_LaidOut);
    if (needShow)
        QMetaObject::invokeMethod(w, "_q_showIfNotHidden", Qt::QueuedConnection); //show later
}

#ifdef QT3_SUPPORT

void QLayout::freeze(int w, int h)
{
    Q_D(QLayout);
    if (!d->topLevel)
        return;
    if (w <= 0 || h <= 0) {
        QSize s = totalSizeHint();
        w = s.width();
        h = s.height();
    }
    setSizeConstraint(SetNoConstraint); // layout will not change min/max size
    QWidget *parent = parentWidget();
    if (parent)
        parent->setFixedSize(w, h);
}

#endif







void QLayout::setMenuBar(QWidget *widget)
{
    Q_D(QLayout);
    if (widget)
        addChildWidget(widget);
    d->menubar = widget;
}

QWidget *QLayout::menuBar() const
{
    Q_D(const QLayout);
    return d->menubar;
}


QSize QLayout::minimumSize() const
{
    return QSize(0, 0);
}

QSize QLayout::maximumSize() const
{
    return QSize(QLAYOUTSIZE_MAX, QLAYOUTSIZE_MAX);
}

Qt::Orientations QLayout::expandingDirections() const
{
    return Qt::Horizontal | Qt::Vertical;
}

void QLayout::activateRecursiveHelper(QLayoutItem *item)
{
    item->invalidate();
    QLayout *layout = item->layout();
    if (layout) {
        QLayoutItem *child;
        int i=0;
        while ((child = layout->itemAt(i++)))
            activateRecursiveHelper(child);
        layout->d_func()->activated = true;
    }
}

void QLayout::update()
{
    QLayout *layout = this;
    while (layout && layout->d_func()->activated) {
        layout->d_func()->activated = false;
        if (layout->d_func()->topLevel) {
            Q_ASSERT(layout->parent()->isWidgetType());
            QWidget *mw = static_cast<QWidget*>(layout->parent());
            if (mw->isVisible())
                QApplication::postEvent(mw, new QEvent(QEvent::LayoutRequest));
            break;
        }
        layout = static_cast<QLayout*>(layout->parent());
    }
}

bool QLayout::activate()
{
    Q_D(QLayout);
    if (!d->enabled || !parent())
        return false;
    if (!d->topLevel)
        return static_cast<QLayout*>(parent())->activate();
    if (d->activated)
        return false;
    QWidget *mw = static_cast<QWidget*>(parent());
    if (mw == 0) {
        qWarning("QLayout::activate: %s \"%s\" does not have a main widget",
                 QObject::metaObject()->className(), QObject::objectName().toLocal8Bit().data());
        return false;
    }
    activateRecursiveHelper(this);

    QWidgetPrivate *md = mw->d_func();
    uint explMin = md->extra ? md->extra->explicitMinSize : 0;

    switch (d->constraint) {
    case SetFixedSize:
        // will trigger resize
        mw->setFixedSize(totalSizeHint());
        break;
    case SetMinimumSize:
        mw->setMinimumSize(totalMinimumSize());
        break;
    case SetMaximumSize:
        mw->setMaximumSize(totalMaximumSize());
        break;
    case SetMinAndMaxSize:
        mw->setMinimumSize(totalMinimumSize());
        mw->setMaximumSize(totalMaximumSize());
        break;
    case SetDefaultConstraint: {
        bool widthSet = explMin & Qt::Horizontal;
        bool heightSet = explMin & Qt::Vertical;
        if (mw->isWindow()) {
            QSize ms = totalMinimumSize();
            if (widthSet)
                ms.setWidth(mw->minimumSize().width());
            if (heightSet)
                ms.setHeight(mw->minimumSize().height());
            if ((!heightSet || !widthSet) && hasHeightForWidth()) {
                int h = minimumHeightForWidth(ms.width());
                if (h > ms.height()) {
                    if (!heightSet)
                        ms.setHeight(0);
                    if (!widthSet)
                        ms.setWidth(0);
                }
            }
            mw->setMinimumSize(ms);
        } else if (!widthSet || !heightSet) {
            QSize ms = mw->minimumSize();
            if (!widthSet)
                ms.setWidth(0);
            if (!heightSet)
                ms.setHeight(0);
            mw->setMinimumSize(ms);
        }
        break;
    }
    case SetNoConstraint:
        break;
    }

    d->doResize(mw->size());

    if (md->extra)
        md->extra->explicitMinSize = explMin;
    // ideally only if sizeHint() or sizePolicy() has changed
    mw->updateGeometry();
    return true;
}

int QLayout::indexOf(QWidget *widget) const
{
    int i = 0;
    QLayoutItem *item = itemAt(i);
    while (item) {
        if (item->widget() == widget)
            return i;
        ++i;
        item = itemAt(i);
    }
    return -1;
}


void QLayout::setSizeConstraint(SizeConstraint constraint)
{
    Q_D(QLayout);
    if (constraint == d->constraint)
        return;

    d->constraint = constraint;
    invalidate();
}

QLayout::SizeConstraint QLayout::sizeConstraint() const
{
    Q_D(const QLayout);
    return d->constraint;
}

QRect QLayout::alignmentRect(const QRect &r) const
{
    QSize s = sizeHint();
    Qt::Alignment a = alignment();

    /*
      This is a hack to obtain the real maximum size, not
      QSize(QLAYOUTSIZE_MAX, QLAYOUTSIZE_MAX), the value consistently
      returned by QLayoutItems that have an alignment.
    */
    QLayout *that = const_cast<QLayout *>(this);
    that->setAlignment(0);
    QSize ms = that->maximumSize();
    that->setAlignment(a);

    if ((expandingDirections() & Qt::Horizontal) ||
         !(a & Qt::AlignHorizontal_Mask)) {
        s.setWidth(qMin(r.width(), ms.width()));
    }
    if ((expandingDirections() & Qt::Vertical) ||
         !(a & Qt::AlignVertical_Mask)) {
        s.setHeight(qMin(r.height(), ms.height()));
    } else if (hasHeightForWidth()) {
        int hfw = heightForWidth(s.width());
        if (hfw < s.height())
            s.setHeight(qMin(hfw, ms.height()));
    }

    int x = r.x();
    int y = r.y();

    if (a & Qt::AlignBottom)
        y += (r.height() - s.height());
    else if (!(a & Qt::AlignTop))
        y += (r.height() - s.height()) / 2;

    QWidget *parent = parentWidget();
    a = QStyle::visualAlignment(parent ? parent->layoutDirection() : QApplication::layoutDirection(), a);
    if (a & Qt::AlignRight)
        x += (r.width() - s.width());
    else if (!(a & Qt::AlignLeft))
        x += (r.width() - s.width()) / 2;

    return QRect(x, y, s.width(), s.height());
}

void QLayout::removeWidget(QWidget *widget)
{
    int i = 0;
    QLayoutItem *child;
    while ((child = itemAt(i))) {
        if (child->widget() == widget) {
            delete takeAt(i);
            invalidate();
        } else {
            ++i;
        }
    }
}

void QLayout::removeItem(QLayoutItem *item)
{
    int i = 0;
    QLayoutItem *child;
    while ((child = itemAt(i))) {
        if (child == item) {
            takeAt(i);
            invalidate();
        } else {
            ++i;
        }
    }
}

void QLayout::setEnabled(bool enable)
{
    Q_D(QLayout);
    d->enabled = enable;
}

bool QLayout::isEnabled() const
{
    Q_D(const QLayout);
    return d->enabled;
}

QSize QLayout::closestAcceptableSize(const QWidget *widget, const QSize &size)
{
    QSize result = size.boundedTo(qSmartMaxSize(widget));
    result = result.expandedTo(qSmartMinSize(widget));
    QLayout *l = widget->layout();
    if (l && l->hasHeightForWidth() && result.height() < l->minimumHeightForWidth(result.width()) ) {
        QSize current = widget->size();
        int currentHfw =  l->minimumHeightForWidth(current.width());
        int newHfw = l->minimumHeightForWidth(result.width());
        if (current.height() < currentHfw || currentHfw == newHfw) {
            //handle the constant hfw case and the vertical-only case, as well as the
            // current-size-is-not-correct case
            result.setHeight(newHfw);
        } else {
            // binary search; assume hfw is decreasing ###

            int maxw = qMax(widget->width(),result.width());
            int maxh = qMax(widget->height(), result.height());
            int minw = qMin(widget->width(),result.width());
            int minh = qMin(widget->height(), result.height());

            int minhfw = l->minimumHeightForWidth(minw);
            int maxhfw = l->minimumHeightForWidth(maxw);
            while (minw < maxw) {
                if (minhfw > maxh) { //assume decreasing
                    minw = maxw - (maxw-minw)/2;
                    minhfw = l->minimumHeightForWidth(minw);
                } else if (maxhfw < minh ) { //assume decreasing
                    maxw = minw + (maxw-minw)/2;
                    maxhfw = l->minimumHeightForWidth(maxw);
                } else  {
                    break;
                }
            }
            result = result.expandedTo(QSize(minw, minhfw));
        }
    }
    return result;
}

#ifndef QT_NO_DATASTREAM

QDataStream &operator<<(QDataStream &stream, const QSizePolicy &policy)
{
    stream << policy.data;
    return stream;
}

QDataStream &operator>>(QDataStream &stream, QSizePolicy &policy)
{
    stream >> policy.data;
    return stream;
}
#endif

---