qtwebkit | Qt Webkit - WebKit is an open source web browser engine

So I finally found the solution myself. From what I understand, the reason you cannot find QtWebEngine in the Raspberry Pi OS repositories, is that the Pi OS is made to run on all Raspberry Pi's, including Pi 1 and Pi 2, which have an ARMv6 and ARMv7 CPU architecture respectively. The WebEngine module however is platform dependend and not tested, compiled and distributed for ARMv6/7 anymore, so they won't release it in the repositories for Raspberry Pi OS. Luckily though, the Raspberry Pi 3 that I use has ARMv8, so it is possible to install QtWebEngine from Debian repositories, which offer QtWebEngine for exactly that architecture. Here is how:

Open your sources.list file

The code you sample uses QtWebKit, not Qt WebEngine. If you have installed pyqtwebengine then use the following code:

There are various problems in your question and its code, based on wrong assumptions.

1. while QWebEnginePage is not technically a widget, it behaves as such, so, just like any UI element, it cannot be created nor accessed from external threads (including using QRunnable);
2. The given QUrl is invalid for this purpose: a web "browser" always uses absolute paths, including when loading local files. While file:report.html is an acceptable QUrl for local Qt file access, it is not a valid address from the point of view of the browser: if you try to write that path in your web browser, it won't work, even if the file is in the path of the browser executable.
   You can use QDir or QFileInfo to build the absolute path:
   • QUrl.fromLocalFile(QDir.current().absoluteFilePath('report.html'))
   • QFileInfo('report.html').absoluteFilePath()
3. The loadFinished signal doesn't work for setHtml because that function doesn't "load" anything: it just sets the page content. Loading, in terms of web browser, means both setting the content and finishing its [down]loading;
4. Printing must be queued on the same printer, as it's not possible to access a printer concurrently; since the pdf printer is obviously an abstract printer, it belongs to the web page object;

So, the solution is to not use QRunnable, but properly manage printing.
Then, you either create a QWebEnginePage for each document you need to print, or you use a unique QWebEnginePage and queue each loading and printing.

In either case, the provided QUrl must have a proper absolute path.

Obviously, there are differences.
The second option requires very limited resources, but complete queueing obviously means that the process is sequential, so it might take a lot of time.
The first option requires much more system resources (imagine it as having an opened tab for each document, and each web rendering is very CPU/RAM demanding, even if it's not displayed), but has the benefit of faster printing: since loading and printing are asynchronous you can actually process dozens of pages in a very short time interval.

A possible and safer solution is to create a system that limitates the concurrent number of pages and printing processes, and queues the remaining as soon as every printing is completed.

Finally, both QTextDocument and QPrinter are thread safe, so there's no problem in using them in a QRunnable, and they are not synchronous if you properly create a QRunnable that is being executed for each printing (which is one of the main purposes of QRunnable: being able to run it more than once). The only difference is that QTextDocument has a limited HTML support.

I fixed this issue by doing the following actions:

• removing the library sudo apt-get remove libgl-dev that was needed for GL/gl.h file
• installed the libraries sudo apt install mesa-common-dev libglu1-mesa-dev that fixes the missing dependencies GL/gl.h file.
• running in project the following commands qmake ; make clean; make -j8; node-gyp rebuild;
• After this, npm install command finished succesfully

This problem was caused because the incorrect path for Libs and Cflags were not pointing to right installation folder.

I solved this issue by going to the directory: ${QT_HOME}/gcc_64/lib/pkgconfig directory and modified the files (Qt5WebKit.pc, Qt5WebKitWidgets.pc)by adding the description like below:

• Qt5WebKit.pc

I solved this issue by going to the directory: ${QT_HOME}/gcc_64/lib/pkgconfig directory and modified the files (Qt5WebKit.pc, Qt5WebKitWidgets.pc)by adding the description like below:

• Qt5WebKit.pc

To use QtWebkit you have to install the package python3-pyqt5.qtwebkit. On the other hand, the main change from Qt4 to Qt5 was the reorganization of the modules, and that happened with QtWebKit that was divided into QtWebKit and QtWebkitWidgets, so QWebView belongs to the last sub-module:

You have to use QWebEnginePage so the tasks are asynchronous as I obtained from the HTML, also QtWebEngine does not use QNetworkRequest so you must use QWebEngineHttpRequest:

In the case of QtWebkit you must intercept the request using a QNetworkAccessManager and resend a custom QNetworkReply.