如何将 QWebEngineView 渲染到打印机？

Question

My goal: I would like to be able to store a HTML page taken from the qrc as a PDF file using qt 5.6.1.

Limitations:

• I can't use the QWebEnginePage::print nor QWebEnginePage::printToPdf methods since they have been added in versions 5.8 and 5.7 respectively
• Using QTextDocument instead is not an option, since I need a full HTML support, not just the limited subset the QTextDocument offers

The problem: The code below indeed shows the page on the screen, then the doc.pdf is created, which means that the page has been loaded without errors, but when I open the created PDF file a blank page is shown.

Any ideas what I am doing wrong or missing?

#include "MainWindow.h"
#include "ui_MainWindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    QWebEngineView *view = new QWebEngineView(this);

    setCentralWidget(view);

    QFile file(":/print.htm");
    QString str;

    if (file.open(QFile::ReadOnly | QFile::Text))
    {
        str.append(file.readAll());
        view->setHtml(str);
        file.close();
    }

    connect(view, &QWebEngineView::loadFinished, this, &MainWindow::on_loadFinished);
}

void MainWindow::on_loadFinished(bool ok)
{
    if (ok)
    {
        QPrinter printer(QPrinter::HighResolution);

        printer.setOutputFormat(QPrinter::PdfFormat);
        printer.setPageSize(QPageSize(QPageSize::A4));
        printer.setPageOrientation(QPageLayout::Portrait);
        printer.setColorMode(QPrinter::GrayScale);
        printer.setOutputFileName("doc.pdf");

        static_cast<QWebEngineView *>(sender())->render(&printer);
    }
}

Answer 1

As mentioned in my comment, it seems to me that updating is the only/best solution, because Qt 5.6 does not support printing a QWebEngineView :

References:

• Qt mailing list :

  1. How can I print a QWebEngineView content ?? with QWebView I only need to call the print method

  Printing with Chromium is surprisingly difficult to implement, but we aim to support printing to PDF in Qt 5.7:

• Qt forum :

  Looking at this and this it seems we wont have it in Qt 5.5 too.

Alternative: using the old QtWebKit

One can still use the print method from the deprecated QWebView class (which is replaced by QWebEngineView ) if you build Qt from source (or use an older Qt version, for example Qt 5.5) as mentioned in the Release Notes of Qt 5.6 :

With Qt 5.6 the following modules are no longer part of the release packages, but users can still build them from source:

• Qt WebKit

Note that I do not recommend this alternative, only use it if you are not able to update to the latest Qt version