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

You can run the example from:

• Qt Creator

  Open the Welcome mode and select the example from Examples. For more information, see Qt Creator: Tutorial: Build and run.

• Qt Extension for Visual Studio Code

  Run the Qt: Open Qt examples command from the Command Palette, and select the example from the list. For more information, see Qt Extension for Visual Studio Code: Tutorial: Build and run.

The Conversion Process

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

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

This process is encapsulated in the Html2PdfConverter class:

 #include <QApplication>
 #include <QCommandLineParser>
 #include <QFile>
 #include <QTextStream>
 #include <QWebEngineView>

 #include <functional>
 #include <utility>

 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 &filePath, bool success);

 private:
     QString m_inputPath;
     QString m_outputPath;
     QScopedPointer<QWebEngineView> m_view;
 };

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

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

 int Html2PdfConverter::run()
 {
     m_view->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:

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

     m_view->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:

 void Html2PdfConverter::pdfPrintingFinished(const QString &filePath, bool success)
 {
     if (!success) {
         QTextStream(stderr)
             << tr("failed to print to output file '%1'").arg(filePath) << "\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:

 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 @ code.qt.io