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# 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"