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#include "qprintpreviewwidget.h"
#include "private/qwidget_p.h"
#include <private/qprinter_p.h>

#include <QtCore/qmath.h>
#include <QtWidgets/qboxlayout.h>
#include <QtWidgets/qgraphicsitem.h>
#include <QtWidgets/qgraphicsview.h>
#include <QtWidgets/qscrollbar.h>
#include <QtWidgets/qstyleoption.h>

QT_BEGIN_NAMESPACE

namespace {
class PageItem : public QGraphicsItem
{
public:
    PageItem(int _pageNum, const QPicture* _pagePicture, QSize _paperSize, QRect _pageRect)
        : pageNum(_pageNum), pagePicture(_pagePicture),
          paperSize(_paperSize), pageRect(_pageRect)
    {
        qreal border = qMax(paperSize.height(), paperSize.width()) / 25;
        brect = QRectF(QPointF(-border, -border),
                       QSizeF(paperSize)+QSizeF(2*border, 2*border));
        setCacheMode(DeviceCoordinateCache);
    }

    QRectF boundingRect() const override
    { return brect; }

    inline int pageNumber() const
    { return pageNum; }

    void paint(QPainter *painter, const QStyleOptionGraphicsItem *item, QWidget *widget) override;

private:
    int pageNum;
    const QPicture* pagePicture;
    QSize paperSize;
    QRect pageRect;
    QRectF brect;
};

void PageItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    Q_UNUSED(widget);

#if 0
    // Draw item bounding rect, for debugging
    painter->save();
    painter->setPen(QPen(Qt::red, 0));
    painter->setBrush(Qt::NoBrush);
    painter->drawRect(QRectF(-border()+1.0, -border()+1.0, boundingRect().width()-2, boundingRect().height()-2));
    painter->restore();
#endif

    QRectF paperRect(0,0, paperSize.width(), paperSize.height());

    // Draw shadow
    painter->setClipRect(option->exposedRect);
    qreal shWidth = paperRect.width()/100;
    QRectF rshadow(paperRect.topRight() + QPointF(0, shWidth),
                   paperRect.bottomRight() + QPointF(shWidth, 0));
    QLinearGradient rgrad(rshadow.topLeft(), rshadow.topRight());
    rgrad.setColorAt(0.0, QColor(0,0,0,255));
    rgrad.setColorAt(1.0, QColor(0,0,0,0));
    painter->fillRect(rshadow, QBrush(rgrad));
    QRectF bshadow(paperRect.bottomLeft() + QPointF(shWidth, 0),
                   paperRect.bottomRight() + QPointF(0, shWidth));
    QLinearGradient bgrad(bshadow.topLeft(), bshadow.bottomLeft());
    bgrad.setColorAt(0.0, QColor(0,0,0,255));
    bgrad.setColorAt(1.0, QColor(0,0,0,0));
    painter->fillRect(bshadow, QBrush(bgrad));
    QRectF cshadow(paperRect.bottomRight(),
                   paperRect.bottomRight() + QPointF(shWidth, shWidth));
    QRadialGradient cgrad(cshadow.topLeft(), shWidth, cshadow.topLeft());
    cgrad.setColorAt(0.0, QColor(0,0,0,255));
    cgrad.setColorAt(1.0, QColor(0,0,0,0));
    painter->fillRect(cshadow, QBrush(cgrad));

    painter->setClipRect(paperRect & option->exposedRect);
    painter->fillRect(paperRect, Qt::white);
    if (!pagePicture)
        return;
    painter->drawPicture(pageRect.topLeft(), *pagePicture);

    // Effect: make anything drawn in the margins look washed out.
    QPainterPath path;
    path.addRect(paperRect);
    path.addRect(pageRect);
    painter->setPen(QPen(Qt::NoPen));
    painter->setBrush(QColor(255, 255, 255, 180));
    painter->drawPath(path);

#if 0
    // Draw frame around paper.
    painter->setPen(QPen(Qt::black, 0));
    painter->setBrush(Qt::NoBrush);
    painter->drawRect(paperRect);
#endif

    // todo: drawtext "Page N" below paper
}

class GraphicsView : public QGraphicsView
{
    Q_OBJECT
public:
    GraphicsView(QWidget* parent = 0)
        : QGraphicsView(parent)
    {
#ifdef Q_OS_MAC
        setFrameStyle(QFrame::NoFrame);
#endif
    }
signals:
    void resized();

protected:
    void resizeEvent(QResizeEvent* e) override
    {
        {
            const QSignalBlocker blocker(verticalScrollBar()); // Don't change page, QTBUG-14517
            QGraphicsView::resizeEvent(e);
        }
        emit resized();
    }

    void showEvent(QShowEvent* e) override
    {
        QGraphicsView::showEvent(e);
        emit resized();
    }
};

} // anonymous namespace

class QPrintPreviewWidgetPrivate : public QWidgetPrivate
{
    Q_DECLARE_PUBLIC(QPrintPreviewWidget)
public:
    QPrintPreviewWidgetPrivate()
        : scene(0), curPage(1),
          viewMode(QPrintPreviewWidget::SinglePageView),
          zoomMode(QPrintPreviewWidget::FitInView),
          zoomFactor(1), initialized(false), fitting(true)
    {}

    // private slots
    void _q_fit(bool doFitting = false);
    void _q_updateCurrentPage();

    void init();
    void populateScene();
    void layoutPages();
    void generatePreview();
    void setCurrentPage(int pageNumber);
    void zoom(qreal zoom);
    void setZoomFactor(qreal zoomFactor);
    int calcCurrentPage();

    GraphicsView *graphicsView;
    QGraphicsScene *scene;

    int curPage;
    QList<const QPicture *> pictures;
    QList<QGraphicsItem *> pages;

    QPrintPreviewWidget::ViewMode viewMode;
    QPrintPreviewWidget::ZoomMode zoomMode;
    qreal zoomFactor;
    bool ownPrinter;
    QPrinter* printer;
    bool initialized;
    bool fitting;
};

void QPrintPreviewWidgetPrivate::_q_fit(bool doFitting)
{
    Q_Q(QPrintPreviewWidget);

    if (curPage < 1 || curPage > pages.count())
        return;

    if (!doFitting && !fitting)
        return;

    if (doFitting && fitting) {
        QRect viewRect = graphicsView->viewport()->rect();
        if (zoomMode == QPrintPreviewWidget::FitInView) {
            const QList<QGraphicsItem*> containedItems = graphicsView->items(viewRect, Qt::ContainsItemBoundingRect);
            for (QGraphicsItem* item : containedItems) {
                PageItem* pg = static_cast<PageItem*>(item);
                if (pg->pageNumber() == curPage)
                    return;
            }
        }

        int newPage = calcCurrentPage();
        if (newPage != curPage)
            curPage = newPage;
    }

    QRectF target = pages.at(curPage-1)->sceneBoundingRect();
    if (viewMode == QPrintPreviewWidget::FacingPagesView) {
        // fit two pages
        if (curPage % 2)
            target.setLeft(target.left() - target.width());
        else
            target.setRight(target.right() + target.width());
    } else if (viewMode == QPrintPreviewWidget::AllPagesView) {
        target = scene->itemsBoundingRect();
    }

    if (zoomMode == QPrintPreviewWidget::FitToWidth) {
        QTransform t;
        qreal scale = graphicsView->viewport()->width() / target.width();
        t.scale(scale, scale);
        graphicsView->setTransform(t);
        if (doFitting && fitting) {
            QRectF viewSceneRect = graphicsView->viewportTransform().mapRect(graphicsView->viewport()->rect());
            viewSceneRect.moveTop(target.top());
            graphicsView->ensureVisible(viewSceneRect); // Nah...
        }
    } else {
        graphicsView->fitInView(target, Qt::KeepAspectRatio);
        if (zoomMode == QPrintPreviewWidget::FitInView) {
            int step = qRound(graphicsView->matrix().mapRect(target).height());
            graphicsView->verticalScrollBar()->setSingleStep(step);
            graphicsView->verticalScrollBar()->setPageStep(step);
        }
    }

    zoomFactor = graphicsView->transform().m11() * (float(printer->logicalDpiY()) / q->logicalDpiY());
    emit q->previewChanged();
}

void QPrintPreviewWidgetPrivate::_q_updateCurrentPage()
{
    Q_Q(QPrintPreviewWidget);

    if (viewMode == QPrintPreviewWidget::AllPagesView)
        return;

    int newPage = calcCurrentPage();
    if (newPage != curPage) {
        curPage = newPage;
        emit q->previewChanged();
    }
}

int QPrintPreviewWidgetPrivate::calcCurrentPage()
{
    int maxArea = 0;
    int newPage = curPage;
    QRect viewRect = graphicsView->viewport()->rect();
    const QList<QGraphicsItem*> items = graphicsView->items(viewRect);
    for (auto *item : items) {
        PageItem* pg = static_cast<PageItem*>(item);
        QRect overlap = graphicsView->mapFromScene(pg->sceneBoundingRect()).boundingRect() & viewRect;
        int area = overlap.width() * overlap.height();
        if (area > maxArea) {
            maxArea = area;
            newPage = pg->pageNumber();
        } else if (area == maxArea && pg->pageNumber() < newPage) {
            newPage = pg->pageNumber();
        }
    }
    return newPage;
}

void QPrintPreviewWidgetPrivate::init()
{
    Q_Q(QPrintPreviewWidget);

    graphicsView = new GraphicsView;
    graphicsView->setInteractive(false);
    graphicsView->setDragMode(QGraphicsView::ScrollHandDrag);
    graphicsView->setViewportUpdateMode(QGraphicsView::SmartViewportUpdate);
    QObject::connect(graphicsView->verticalScrollBar(), SIGNAL(valueChanged(int)),
                     q, SLOT(_q_updateCurrentPage()));
    QObject::connect(graphicsView, SIGNAL(resized()), q, SLOT(_q_fit()));

    scene = new QGraphicsScene(graphicsView);
    scene->setBackgroundBrush(Qt::gray);
    graphicsView->setScene(scene);

    QVBoxLayout *layout = new QVBoxLayout;
    q->setLayout(layout);
    layout->setContentsMargins(0, 0, 0, 0);
    layout->addWidget(graphicsView);
}

void QPrintPreviewWidgetPrivate::populateScene()
{
    // remove old pages
    for (auto *page : qAsConst(pages))
        scene->removeItem(page);
    qDeleteAll(pages);
    pages.clear();

    QSize paperSize = printer->pageLayout().fullRectPixels(printer->resolution()).size();
    QRect pageRect = printer->pageLayout().paintRectPixels(printer->resolution());

    int page = 1;
    for (auto *picture : qAsConst(pictures)) {
        PageItem* item = new PageItem(page++, picture, paperSize, pageRect);
        scene->addItem(item);
        pages.append(item);
    }
}

void QPrintPreviewWidgetPrivate::layoutPages()
{
    int numPages = pages.count();
    if (numPages < 1)
        return;

    int numPagePlaces = numPages;
    int cols = 1; // singleMode and default
    if (viewMode == QPrintPreviewWidget::AllPagesView) {
        if (printer->orientation() == QPrinter::Portrait)
            cols = qCeil(qSqrt((float) numPages));
        else
            cols = qFloor(qSqrt((float) numPages));
        cols += cols % 2;  // Nicer with an even number of cols
    }
    else if (viewMode == QPrintPreviewWidget::FacingPagesView) {
        cols = 2;
        numPagePlaces += 1;
    }
    int rows = qCeil(qreal(numPagePlaces) / cols);

    qreal itemWidth = pages.at(0)->boundingRect().width();
    qreal itemHeight = pages.at(0)->boundingRect().height();
    int pageNum = 1;
    for (int i = 0; i < rows && pageNum <= numPages; i++) {
        for (int j = 0; j < cols && pageNum <= numPages; j++) {
            if (!i && !j && viewMode == QPrintPreviewWidget::FacingPagesView) {
                // Front page doesn't have a facing page
                continue;
            } else {
                pages.at(pageNum-1)->setPos(QPointF(j*itemWidth, i*itemHeight));
                pageNum++;
            }
        }
    }
    scene->setSceneRect(scene->itemsBoundingRect());
}

void QPrintPreviewWidgetPrivate::generatePreview()
{
    //### If QPrinter::setPreviewMode() becomes public, handle the
    //### case that we have been constructed with a printer that
    //### _already_ has been preview-painted to, so we should
    //### initially just show the pages it already contains, and not
    //### emit paintRequested() until the user changes some parameter

    Q_Q(QPrintPreviewWidget);
    printer->d_func()->setPreviewMode(true);
    emit q->paintRequested(printer);
    printer->d_func()->setPreviewMode(false);
    pictures = printer->d_func()->previewPages();
    populateScene(); // i.e. setPreviewPrintedPictures() e.l.
    layoutPages();
    curPage = qBound(1, curPage, pages.count());
    if (fitting)
        _q_fit();
    emit q->previewChanged();
}

void QPrintPreviewWidgetPrivate::setCurrentPage(int pageNumber)
{
    if (pageNumber < 1 || pageNumber > pages.count())
        return;

    int lastPage = curPage;
    curPage = pageNumber;

    if (lastPage != curPage && lastPage > 0 && lastPage <= pages.count()) {
        if (zoomMode != QPrintPreviewWidget::FitInView) {
            QScrollBar *hsc = graphicsView->horizontalScrollBar();
            QScrollBar *vsc = graphicsView->verticalScrollBar();
            QPointF pt = graphicsView->transform().map(pages.at(curPage-1)->pos());
            vsc->setValue(int(pt.y()) - 10);
            hsc->setValue(int(pt.x()) - 10);
        } else {
            graphicsView->centerOn(pages.at(curPage-1));
        }
    }
}

void QPrintPreviewWidgetPrivate::zoom(qreal zoom)
{
    zoomFactor *= zoom;
    graphicsView->scale(zoom, zoom);
}

void QPrintPreviewWidgetPrivate::setZoomFactor(qreal _zoomFactor)
{
    Q_Q(QPrintPreviewWidget);
    zoomFactor = _zoomFactor;
    graphicsView->resetTransform();
    int dpi_y = q->logicalDpiY();
    int printer_dpi_y = printer->logicalDpiY();
    graphicsView->scale(zoomFactor*(dpi_y/float(printer_dpi_y)),
                        zoomFactor*(dpi_y/float(printer_dpi_y)));
}

///////////////////////////////////////

/*!
    \class QPrintPreviewWidget
    \since 4.4

    \brief The QPrintPreviewWidget class provides a widget for
    previewing page layouts for printer output.

    \ingroup printing
    \inmodule QtPrintSupport

    QPrintPreviewDialog uses a QPrintPreviewWidget internally, and the
    purpose of QPrintPreviewWidget is to make it possible to embed the
    preview into other widgets. It also makes it possible to build a different
    user interface around it than the default one provided with QPrintPreviewDialog.

    Using QPrintPreviewWidget is straightforward:

    \list 1
    \li Create the QPrintPreviewWidget

    Construct the QPrintPreviewWidget either by passing in an
    existing QPrinter object, or have QPrintPreviewWidget create a
    default constructed QPrinter object for you.

    \li Connect the paintRequested() signal to a slot.

    When the widget needs to generate a set of preview pages, a
    paintRequested() signal will be emitted from the widget. Connect a
    slot to this signal, and draw onto the QPrinter passed in as a
    signal parameter. Call QPrinter::newPage(), to start a new
    page in the preview.

    \endlist

    \sa QPrinter, QPrintDialog, QPageSetupDialog, QPrintPreviewDialog
*/


/*!
    \enum QPrintPreviewWidget::ViewMode

    This enum is used to describe the view mode of the preview widget.

    \value SinglePageView   A mode where single pages in the preview
                            is viewed.

    \value FacingPagesView  A mode where the facing pages in the preview
                            is viewed.

    \value AllPagesView     A view mode where all the pages in the preview
                            is viewed.
*/

/*!
    \enum QPrintPreviewWidget::ZoomMode

    This enum is used to describe zoom mode of the preview widget.

    \value CustomZoom  The zoom is set to a custom zoom value.

    \value FitToWidth  This mode fits the current page to the width of the view.

    \value FitInView   This mode fits the current page inside the view.

*/

/*!
    Constructs a QPrintPreviewWidget based on \a printer and with \a
    parent as the parent widget. The widget flags \a flags are passed on
    to the QWidget constructor.

    \sa QWidget::setWindowFlags()
*/
QPrintPreviewWidget::QPrintPreviewWidget(QPrinter *printer, QWidget *parent, Qt::WindowFlags flags)
    : QWidget(*new QPrintPreviewWidgetPrivate, parent, flags)
{
    Q_D(QPrintPreviewWidget);
    d->printer = printer;
    d->ownPrinter = false;
    d->init();
}

/*!
    \overload

    This will cause QPrintPreviewWidget to create an internal, default
    constructed QPrinter object, which will be used to generate the
    preview.
*/
QPrintPreviewWidget::QPrintPreviewWidget(QWidget *parent, Qt::WindowFlags flags)
    : QWidget(*new QPrintPreviewWidgetPrivate, parent, flags)
{
    Q_D(QPrintPreviewWidget);
    d->printer = new QPrinter;
    d->ownPrinter = true;
    d->init();
}


/*!
    Destroys the QPrintPreviewWidget.
*/
QPrintPreviewWidget::~QPrintPreviewWidget()
{
    Q_D(QPrintPreviewWidget);
    if (d->ownPrinter)
        delete d->printer;
}

/*!
    Returns the current view mode. The default view mode is SinglePageView.
*/
QPrintPreviewWidget::ViewMode QPrintPreviewWidget::viewMode() const
{
    Q_D(const QPrintPreviewWidget);
    return d->viewMode;
}

/*!
    Sets the view mode to \a mode. The default view mode is
    SinglePageView.
*/
void QPrintPreviewWidget::setViewMode(ViewMode mode)
{
    Q_D(QPrintPreviewWidget);
    d->viewMode = mode;
    d->layoutPages();
    if (d->viewMode == AllPagesView) {
        d->graphicsView->fitInView(d->scene->itemsBoundingRect(), Qt::KeepAspectRatio);
        d->fitting = false;
        d->zoomMode = QPrintPreviewWidget::CustomZoom;
        d->zoomFactor = d->graphicsView->transform().m11() * (float(d->printer->logicalDpiY()) / logicalDpiY());
        emit previewChanged();
    } else {
        d->fitting = true;
        d->_q_fit();
    }
}

/*!
    Returns the current orientation of the preview. This value is
    obtained from the QPrinter object associated with the preview.
*/
QPrinter::Orientation QPrintPreviewWidget::orientation() const
{
    Q_D(const QPrintPreviewWidget);
    return d->printer->orientation();
}

/*!
    Sets the current orientation to \a orientation. This value will be
    set on the QPrinter object associated with the preview.
*/
void QPrintPreviewWidget::setOrientation(QPrinter::Orientation orientation)
{
    Q_D(QPrintPreviewWidget);
    d->printer->setOrientation(orientation);
    d->generatePreview();
}

/*!
    Prints the preview to the printer associated with the preview.
*/
void QPrintPreviewWidget::print()
{
    Q_D(QPrintPreviewWidget);
    // ### make use of the generated pages
    emit paintRequested(d->printer);
}

/*!
    Zooms the current view in by \a factor. The default value for \a
    factor is 1.1, which means the view will be scaled up by 10%.
*/
void QPrintPreviewWidget::zoomIn(qreal factor)
{
    Q_D(QPrintPreviewWidget);
    d->fitting = false;
    d->zoomMode = QPrintPreviewWidget::CustomZoom;
    d->zoom(factor);
}

/*!
    Zooms the current view out by \a factor. The default value for \a
    factor is 1.1, which means the view will be scaled down by 10%.
*/
void QPrintPreviewWidget::zoomOut(qreal factor)
{
    Q_D(QPrintPreviewWidget);
    d->fitting = false;
    d->zoomMode = QPrintPreviewWidget::CustomZoom;
    d->zoom(1/factor);
}

/*!
    Returns the zoom factor of the view.
*/
qreal QPrintPreviewWidget::zoomFactor() const
{
    Q_D(const QPrintPreviewWidget);
    return d->zoomFactor;
}

/*!
    Sets the zoom factor of the view to \a factor. For example, a
    value of 1.0 indicates an unscaled view, which is approximately
    the size the view will have on paper. A value of 0.5 will halve
    the size of the view, while a value of 2.0 will double the size of
    the view.
*/
void QPrintPreviewWidget::setZoomFactor(qreal factor)
{
    Q_D(QPrintPreviewWidget);
    d->fitting = false;
    d->zoomMode = QPrintPreviewWidget::CustomZoom;
    d->setZoomFactor(factor);
}

/*!
    \since 4.6
    Returns the number of pages in the preview.
*/
int QPrintPreviewWidget::pageCount() const
{
    Q_D(const QPrintPreviewWidget);
    return d->pages.size();
}

/*!
    Returns the currently viewed page in the preview.
*/
int QPrintPreviewWidget::currentPage() const
{
    Q_D(const QPrintPreviewWidget);
    return d->curPage;
}

/*!
    Sets the current page in the preview. This will cause the view to
    skip to the beginning of \a page.
*/
void QPrintPreviewWidget::setCurrentPage(int page)
{
    Q_D(QPrintPreviewWidget);
    d->setCurrentPage(page);
}

/*!
    This is a convenience function and is the same as calling \c
    {setZoomMode(QPrintPreviewWidget::FitToWidth)}.
*/
void QPrintPreviewWidget::fitToWidth()
{
    setZoomMode(FitToWidth);
}

/*!
    This is a convenience function and is the same as calling \c
    {setZoomMode(QPrintPreviewWidget::FitInView)}.
*/
void QPrintPreviewWidget::fitInView()
{
    setZoomMode(FitInView);
}

/*!
    Sets the zoom mode to \a zoomMode. The default zoom mode is FitInView.

    \sa zoomMode(), viewMode(), setViewMode()
*/
void QPrintPreviewWidget::setZoomMode(QPrintPreviewWidget::ZoomMode zoomMode)
{
    Q_D(QPrintPreviewWidget);
    d->zoomMode = zoomMode;
    if (d->zoomMode == FitInView || d->zoomMode == FitToWidth) {
        d->fitting = true;
        d->_q_fit(true);
    } else {
        d->fitting = false;
    }
}

/*!
    Returns the current zoom mode.

    \sa setZoomMode(), viewMode(), setViewMode()
*/
QPrintPreviewWidget::ZoomMode QPrintPreviewWidget::zoomMode() const
{
    Q_D(const QPrintPreviewWidget);
    return d->zoomMode;
}

/*!
    This is a convenience function and is the same as calling \c
    {setOrientation(QPrinter::Landscape)}.
*/
void QPrintPreviewWidget::setLandscapeOrientation()
{
    setOrientation(QPrinter::Landscape);
}

/*!
    This is a convenience function and is the same as calling \c
    {setOrientation(QPrinter::Portrait)}.
*/
void QPrintPreviewWidget::setPortraitOrientation()
{
    setOrientation(QPrinter::Portrait);
}

/*!
    This is a convenience function and is the same as calling \c
    {setViewMode(QPrintPreviewWidget::SinglePageView)}.
*/
void QPrintPreviewWidget::setSinglePageViewMode()
{
    setViewMode(SinglePageView);
}

/*!
    This is a convenience function and is the same as calling \c
    {setViewMode(QPrintPreviewWidget::FacingPagesView)}.
*/
void QPrintPreviewWidget::setFacingPagesViewMode()
{
    setViewMode(FacingPagesView);
}

/*!
    This is a convenience function and is the same as calling \c
    {setViewMode(QPrintPreviewWidget::AllPagesView)}.
*/
void QPrintPreviewWidget::setAllPagesViewMode()
{
    setViewMode(AllPagesView);
}


/*!
    This function updates the preview, which causes the
    paintRequested() signal to be emitted.
*/
void QPrintPreviewWidget::updatePreview()
{
    Q_D(QPrintPreviewWidget);
    d->initialized = true;
    d->generatePreview();
    d->graphicsView->updateGeometry();
}

/*! \reimp
*/
void QPrintPreviewWidget::setVisible(bool visible)
{
    Q_D(QPrintPreviewWidget);
    if (visible && !d->initialized)
        updatePreview();
    QWidget::setVisible(visible);
}

/*!
    \fn void QPrintPreviewWidget::paintRequested(QPrinter *printer)

    This signal is emitted when the preview widget needs to generate a
    set of preview pages. \a printer is the printer associated with
    this preview widget.
*/

/*!
    \fn void QPrintPreviewWidget::previewChanged()

    This signal is emitted whenever the preview widget has changed
    some internal state, such as the orientation.
*/


QT_END_NAMESPACE

#include "moc_qprintpreviewwidget.cpp"
#include "qprintpreviewwidget.moc"