Tuesday, May 24, 2016

QtWebEngine: Printing to PDF

Among new features in Qt 5.7 for QtWebEngine there is printing to PDF. There are several samples which are available for QtWebEngine you can start from this folder in your Qt installation:

c:\Qt\Qt5.7.0\Examples\Qt-5.7\qtwebengine\webenginewidgets\

We will look at demobrowser sample. Let's start from BrowserMainWindow::slotFilePrintToPDF(). Unfortunately Qt still has problem with QPrintDialog not working on Windows described here:

https://bugreports.qt.io/browse/QTBUG-28822
http://www.qtcentre.org/threads/56992-Printer-problem

So for sample purposes we will remove QPrintDialog and just hardcode filename:

void BrowserMainWindow::slotFilePrintToPDF()
{    
#ifndef QT_NO_PRINTER
    if (!currentTab())
        return;    

    QPrinter printer;
    printer.setOutputFileName("test.pdf");
    if (printer.outputFileName().isEmpty() || 
        !m_printerOutputFileName.isEmpty())
        return;
    m_printerOutputFileName = printer.outputFileName();
    currentTab()->page()->printToPdf(printer.pageLayout(), 
                                     invoke(this, &BrowserMainWindow::slotHandlePdfPrinted));
#endif // QT_NO_PRINTER
}

void BrowserMainWindow::slotHandlePdfPrinted(const QByteArray& result)
{
    if (!result.size())
        return;

    QFile file(m_printerOutputFileName);
    m_printerOutputFileName.clear();
    if (!file.open(QFile::WriteOnly))
        return;
    file.write(result.data(), result.size());
    file.close();
} 

So what was actually added in Qt 5.7?

Two overloads of printToPdf() function for QWebEnginePage are here.

They allow to render page content into a PDF document.

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