WebEngine Widgets Html2Pdf Example

Converts web pages to PDF documents using Qt WebEngine.

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Publié le 26 janvier 2024 - Mis à jour le 26 janvier 2024

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WebEngine Widgets Html2Pdf Example▲

Html2Pdf demonstrates how to use Qt WebEngine to implement a command-line application for converting web pages into PDF documents.

Running the Example▲

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

The Conversion Process▲

In order to convert a web page into a PDF document we need to:

Create a QWebEngineView.
Tell the QWebEngineView to begin loading the target URL and wait for it to finish.
Tell the QWebEngineView to begin converting the loaded page into a PDF file and again wait for it to finish.
Once the conversion is finished, exit the program.

This process is encapsulated in the Html2PdfConverter class:

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#include &lt;QApplication&gt;
#include &lt;QCommandLineParser&gt;
#include &lt;QFile&gt;
#include &lt;QTextStream&gt;
#include &lt;QWebEngineView&gt;

#include &lt;functional&gt;

using namespace std;
using namespace std::placeholders;

class Html2PdfConverter : public QObject
{
    Q_OBJECT
public:
    explicit Html2PdfConverter(QString inputPath, QString outputPath);
    int run();

private slots:
    void loadFinished(bool ok);
    void pdfPrintingFinished(const QString &amp;filePath, bool success);

private:
    QString m_inputPath;
    QString m_outputPath;
    QScopedPointer&lt;QWebEngineView&gt; m_view;
};

In the constructor we create the QWebEngineView and connect to its QWebEngineView::loadFinished and QWebEngineView::pdfPrintingFinished signals:

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Html2PdfConverter::Html2PdfConverter(QString inputPath, QString outputPath)
    : m_inputPath(move(inputPath))
    , m_outputPath(move(outputPath))
    , m_view(new QWebEngineView)
{
    connect(m_view.data(), &amp;QWebEngineView::loadFinished,
            this, &amp;Html2PdfConverter::loadFinished);
    connect(m_view.data(), &amp;QWebEngineView::pdfPrintingFinished,
            this, &amp;Html2PdfConverter::pdfPrintingFinished);
}

The run() method will trigger the conversion process by asking QWebEnginePage to start loading the target URL. We then enter the main event loop:

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int Html2PdfConverter::run()
{
    m_view-&gt;load(QUrl::fromUserInput(m_inputPath));
    return QApplication::exec();
}

After the loading is finished we begin PDF generation. We ask the QWebEnginePage::printToPdf method to write the output directly to disk:

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void Html2PdfConverter::loadFinished(bool ok)
{
    if (!ok) {
        QTextStream(stderr)
            &lt;&lt; tr("failed to load URL '%1'").arg(m_inputPath) &lt;&lt; "\n";
        QCoreApplication::exit(1);
        return;
    }

    m_view-&gt;printToPdf(m_outputPath);
}

Once we receive the signal that the PDF conversion has finished, all that remains is to report potential errors and exit the program:

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void Html2PdfConverter::pdfPrintingFinished(const QString &amp;filePath, bool success)
{
    if (!success) {
        QTextStream(stderr)
            &lt;&lt; tr("failed to print to output file '%1'").arg(filePath) &lt;&lt; "\n";
        QCoreApplication::exit(1);
    } else {
        QCoreApplication::quit();
    }
}

The Main Function▲

Our main function is responsible for setting up a QApplication and parsing command line arguments:

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int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QCoreApplication::setOrganizationName("QtExamples");
    QCoreApplication::setApplicationName("html2pdf");
    QCoreApplication::setApplicationVersion(QT_VERSION_STR);

    QCommandLineParser parser;
    parser.setApplicationDescription(
        QCoreApplication::translate("main", "Converts the web page INPUT into the PDF file OUTPUT."));
    parser.addHelpOption();
    parser.addVersionOption();
    parser.addPositionalArgument(
        QCoreApplication::translate("main", "INPUT"),
        QCoreApplication::translate("main", "Input URL for PDF conversion."));
    parser.addPositionalArgument(
        QCoreApplication::translate("main", "OUTPUT"),
        QCoreApplication::translate("main", "Output file name for PDF conversion."));

    parser.process(QCoreApplication::arguments());

    const QStringList requiredArguments = parser.positionalArguments();
    if (requiredArguments.size() != 2)
        parser.showHelp(1);

    Html2PdfConverter converter(requiredArguments.at(0), requiredArguments.at(1));
    return converter.run();
}

Note that to use Qt WebEngine Widgets we need to create a QApplication and not a QCoreApplication, even though this is a command line application.

Example project▲

Example project @ code.qt.io

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