printpreview.cpp Example File
^{demos/textedit/printpreview.cpp}

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 #include "printpreview.h"

 #include <QAbstractScrollArea>
 #include <QPrintDialog>
 #include <QPrinter>
 #include <QToolBar>
 #include <QAction>
 #include <QTextFormat>
 #include <QMouseEvent>
 #include <QTextFrame>
 #include <QTextDocument>
 #include <QAbstractTextDocumentLayout>
 #include <QScrollBar>
 #include <QPainter>
 #include <QDebug>
 #include <QPageSetupDialog>
 #include <QStatusBar>

 #ifdef Q_WS_MAC
 const QString rsrcPath = ":/images/mac";
 #else
 const QString rsrcPath = ":/images/win";
 #endif

 static inline int inchesToPixels(float inches, QPaintDevice *device)
 {
     return qRound(inches * device->logicalDpiY());
 }

 static inline qreal mmToInches(double mm)
 {
     return mm*0.039370147;
 }

 class PreviewView : public QAbstractScrollArea
 {
     Q_OBJECT
 public:
     PreviewView(QTextDocument *document, PrintPreview *printPrev);

     inline void updateLayout() { resizeEvent(0); viewport()->update(); }

 public slots:
     void zoomIn();
     void zoomOut();

 protected:
     virtual void paintEvent(QPaintEvent *e);
     virtual void resizeEvent(QResizeEvent *);
     virtual void mousePressEvent(QMouseEvent *e);
     virtual void mouseMoveEvent(QMouseEvent *e);
     virtual void mouseReleaseEvent(QMouseEvent *e);

 private:
     void paintPage(QPainter *painter, int page);
     QTextDocument *doc;
     qreal scale;
     int interPageSpacing;
     QPoint mousePressPos;
     QPoint scrollBarValuesOnMousePress;
     PrintPreview *printPreview;
 };

 PreviewView::PreviewView(QTextDocument *document, PrintPreview *printPrev)
     : printPreview(printPrev)
 {
     verticalScrollBar()->setSingleStep(20);
     horizontalScrollBar()->setSingleStep(20);

     viewport()->setBackgroundRole(QPalette::Dark);

     doc = document;
     scale = 1.0;
     interPageSpacing = 30;
 }

 void PreviewView::zoomIn()
 {
     scale += 0.2;
     resizeEvent(0);
     viewport()->update();
 }

 void PreviewView::zoomOut()
 {
     scale -= 0.2;
     resizeEvent(0);
     viewport()->update();
 }

 void PreviewView::paintEvent(QPaintEvent *)
 {
     QPainter p(viewport());

     p.translate(-horizontalScrollBar()->value(), -verticalScrollBar()->value());
     p.translate(interPageSpacing, interPageSpacing);

     const int pages = doc->pageCount();
     for (int i = 0; i < pages; ++i) {
         p.save();
         p.scale(scale, scale);

         paintPage(&p, i);

         p.restore();
         p.translate(0, interPageSpacing + printPreview->paperSize.height() * scale);
     }
 }

 void PreviewView::paintPage(QPainter *painter, int page)
 {
     const QSizeF pgSize = doc->pageSize();

     QColor col(Qt::black);

     painter->setPen(col);
     painter->setBrush(Qt::white);
     painter->drawRect(QRectF(QPointF(0, 0), printPreview->paperSize));
     painter->setBrush(Qt::NoBrush);

     col = col.light();
     painter->drawLine(QLineF(printPreview->paperSize.width(), 1,
                              printPreview->paperSize.width(), printPreview->paperSize.height() - 1));

     col = col.light();
     painter->drawLine(QLineF(printPreview->paperSize.width(), 2,
                              printPreview->paperSize.width(), printPreview->paperSize.height() - 2));

     QRectF docRect(QPointF(0, page * pgSize.height()), pgSize);
     QAbstractTextDocumentLayout::PaintContext ctx;
     ctx.clip = docRect;

     // don't use the system palette text as default text color, on HP/UX
     // for example that's white, and white text on white paper doesn't
     // look that nice
     ctx.palette.setColor(QPalette::Text, Qt::black);

     painter->translate(0, - page * pgSize.height());

     painter->translate(printPreview->pageTopLeft);
     painter->setClipRect(docRect);//.translated(printPreview->pageTopLeft));
     doc->documentLayout()->draw(painter, ctx);
 }

 void PreviewView::resizeEvent(QResizeEvent *)
 {
     const QSize viewportSize = viewport()->size();

     QSize docSize;
     docSize.setWidth(qRound(printPreview->paperSize.width() * scale + 2 * interPageSpacing));
     const int pageCount = doc->pageCount();
     docSize.setHeight(qRound(pageCount * printPreview->paperSize.height() * scale + (pageCount + 1) * interPageSpacing));

     horizontalScrollBar()->setRange(0, docSize.width() - viewportSize.width());
     horizontalScrollBar()->setPageStep(viewportSize.width());

     verticalScrollBar()->setRange(0, docSize.height() - viewportSize.height());
     verticalScrollBar()->setPageStep(viewportSize.height());
 }

 void PreviewView::mousePressEvent(QMouseEvent *e)
 {
     mousePressPos = e->pos();
     scrollBarValuesOnMousePress.rx() = horizontalScrollBar()->value();
     scrollBarValuesOnMousePress.ry() = verticalScrollBar()->value();
     e->accept();
 }

 void PreviewView::mouseMoveEvent(QMouseEvent *e)
 {
     if (mousePressPos.isNull()) {
         e->ignore();
         return;
     }

     horizontalScrollBar()->setValue(scrollBarValuesOnMousePress.x() - e->pos().x() + mousePressPos.x());
     verticalScrollBar()->setValue(scrollBarValuesOnMousePress.y() - e->pos().y() + mousePressPos.y());
     horizontalScrollBar()->update();
     verticalScrollBar()->update();
     e->accept();
 }

 void PreviewView::mouseReleaseEvent(QMouseEvent *e)
 {
     mousePressPos = QPoint();
     e->accept();
 }

 PrintPreview::PrintPreview(const QTextDocument *document, QWidget *parent)
     : QMainWindow(parent), printer(QPrinter::HighResolution)
 {
     setWindowTitle(tr("TextEdit Demo - Print Preview"));

     printer.setFullPage(true);
     doc = document->clone();

     view = new PreviewView(doc, this);
     setCentralWidget(view);
     resize(800, 600);

     doc->setUseDesignMetrics(true);
     doc->documentLayout()->setPaintDevice(view->viewport());

     // add a nice 2 cm margin
     const qreal margin = inchesToPixels(mmToInches(20), this);
     QTextFrameFormat fmt = doc->rootFrame()->frameFormat();
     fmt.setMargin(margin);
     doc->rootFrame()->setFrameFormat(fmt);

     setup();

     QFont f(doc->defaultFont());
     f.setPointSize(10);
     doc->setDefaultFont(f);

     QToolBar *tb = addToolBar(tr("Print"));
     tb->setToolButtonStyle(Qt::ToolButtonTextUnderIcon);

     QAction *a;
     a = new QAction(/*QIcon(rsrcPath + "/fileprint.png"),*/ tr("&Print..."), this);
     a->setShortcut(Qt::CTRL + Qt::Key_P);
     connect(a, SIGNAL(triggered()), this, SLOT(print()));
     tb->addAction(a);

     a = new QAction(this);
     a->setText(tr("Page Setup..."));
     connect(a, SIGNAL(triggered()), this, SLOT(pageSetup()));
     tb->addAction(a);

     tb->addSeparator();

     a = new QAction(QIcon(rsrcPath + "/zoomin.png"), tr("Zoom In"), this);
     connect(a, SIGNAL(triggered()), view, SLOT(zoomIn()));
     tb->addAction(a);

     a = new QAction(QIcon(rsrcPath + "/zoomout.png"), tr("Zoom Out"), this);
     connect(a, SIGNAL(triggered()), view, SLOT(zoomOut()));
     tb->addAction(a);

     tb->addSeparator();

     a = new QAction(this);
     a->setText(tr("&Close"));
     connect(a, SIGNAL(triggered()), this, SLOT(close()));
     tb->addAction(a);

     statusBar()->setSizeGripEnabled(true);
 }

 void PrintPreview::setup()
 {
     QSizeF page = printer.pageRect().size();
     paperSize = printer.paperRect().size();
     paperSize.rwidth() *= qreal(view->logicalDpiX()) / printer.logicalDpiX();
     paperSize.rheight() *= qreal(view->logicalDpiY()) / printer.logicalDpiY();

     pageTopLeft = printer.pageRect().topLeft();
     pageTopLeft.rx() *= qreal(view->logicalDpiX()) / printer.logicalDpiX();
     pageTopLeft.ry() *= qreal(view->logicalDpiY()) / printer.logicalDpiY();

     page.setWidth(page.width() * view->logicalDpiX() / printer.logicalDpiX());
     page.setHeight(page.height() * view->logicalDpiY() / printer.logicalDpiY());

     // add a nice 2 cm margin
     const qreal margin = inchesToPixels(mmToInches(20), this);
     QTextFrameFormat fmt = doc->rootFrame()->frameFormat();
     fmt.setMargin(margin);
     doc->rootFrame()->setFrameFormat(fmt);

     doc->setPageSize(page);
 }

 PrintPreview::~PrintPreview()
 {
     delete doc;
 }

 void PrintPreview::print()
 {
     QPrintDialog *dlg = new QPrintDialog(&printer, this);
     if (dlg->exec() == QDialog::Accepted) {
         doc->print(&printer);
     }
     delete dlg;
 }

 void PrintPreview::pageSetup()
 {
     QPageSetupDialog dlg(&printer, this);
     if (dlg.exec() == QDialog::Accepted) {
         setup();
         view->updateLayout();
     }
 }

 #include "printpreview.moc"