PyQt6: can't serialize QWebEngineHistory

[Phil Thompson]

On 22/11/2021 06:08, jimmy at spalge.com wrote:
> I don't seem to be able to serialize QWebEngineHistory objects to a
> QDataStream anymore with PyQt (and Qt) 6.2.0 and 6.2.1. A warning log 
> message
> is printed out and the data steam just has a few null bytes. The 
> message is
> `QVariant::save: unable to save type 'QObject*' (type id: 39)`. It 
> seems
> QVariant isn't seeing the right type? Here are a couple of example 
> programs in
> python and c++ and their output to demonstrate.
> 
> Python:
> 
>     try:
>         from PyQt6.QtCore import QDataStream, QByteArray, QIODevice,
> QVariant, QUrl
>         from PyQt6.QtWebEngineWidgets import QWebEngineView
>         from PyQt6.QtWidgets import QApplication
>     except ImportError:
>         from PyQt5.QtCore import QDataStream, QByteArray, QIODevice,
> QVariant, QUrl
>         from PyQt5.QtWebEngineWidgets import QWebEngineView
>         from PyQt5.QtWidgets import QApplication
> 
>     def serialize(history):
>       data = QByteArray()
>       stream = QDataStream(data, QIODevice.OpenModeFlag.WriteOnly)
>       stream << history
>       print(f"bytes: {len(data)}")
>       print(f"type: {history}")
>       print(f"QVariant type: {QVariant(history).typeName()}")
> 
>     app = QApplication([])
>     view = QWebEngineView()
>     view.loadFinished.connect(lambda: serialize(view.history()))
>     view.load(QUrl("https://example.com/"))
>     view.show();
>     app.exec();
> 
> PyQt5 (and Qt5) output:
> 
>     bytes: 498
>     type: <PyQt5.QtWebEngineWidgets.QWebEngineHistory object at 
> 0x7f785c8cb040>
>     QVariant type: PyQt_PyObject
> 
> PyQt6 (and Qt6) output:
> 
>     QVariant::save: unable to save type 'QObject*' (type id: 39).
>     bytes: 5
>     type: <PyQt6.QtWebEngineCore.QWebEngineHistory object at 
> 0x7f2b7d79bb80>
>     QVariant type: QObject*
> 
> C++:
> 
>     #include <iostream>
>     #include <QApplication>
>     #include <QWebEngineView>
>     #include <QWebEngineHistory>
>     #include <QUrl>
>     #include <QIODevice>
>     #include <QObject>
>     #include <QDebug>
> 
>     void serialize(QWebEngineHistory *history) {
>       QByteArray data;
>       QDataStream stream(&data, QIODevice::WriteOnly);
>       stream << *history;
>       qDebug() << "bytes: " << data.length();
>       qDebug() << "type: " << history;
>     }
> 
>     int main(int argc, char *argv[])
>     {
>         QApplication app(argc, argv);
>         QWebEngineView view;
>         QObject::connect(&view, &QWebEngineView::loadFinished, 
> [&view]() {
>             serialize(view.history());
>         });
>         view.load(QUrl("https://example.com/"));
>         view.show();
>         return app.exec();
>     }
> 
> C++ Qt6 output:
> 
>     bytes: 498
>     type: QWebEngineHistory(0x560d9e171f80)

Should be fixed in the next snapshot.

Thanks,
Phil