[QUESTION]: Reloading QQuickWindow content without window recreation

[akontsevich]

https://stackoverflow.com/q/53601421/630169

For qml file with Item element as root of qml scene:

Item {
...
}

it is possible to preview qml file content with QQuickView without window recreation - see slightly modified and simplified qmlscene code:

QQmlEngine engine;
QPointer<QQmlComponent> component = new QQmlComponent(&engine);
QQuickWindow *window = nullptr;
auto qxView = new QQuickView(&engine, nullptr);

...

// Call this slot on file update (for example by QFileSystemWatcher signal)
updatePreview()
{
    // Recreate Qml Component
    engine.clearComponentCache();
    component = new QQmlComponent(&engine);
    component->loadUrl(url);
    QObject *topLevel = component->create();
    
    // Recreate Quick Window
    window = qobject_cast<QQuickWindow *>(topLevel);
    if (window) {
        engine.setIncubationController(window->incubationController());
    } else {
        QQuickItem *contentItem = qobject_cast<QQuickItem *>(topLevel);
        if (contentItem) {
            window = qobject_cast<QQuickWindow *>(qxView);
            qxView->setContent(url, component, contentItem);
        }
    }
}

For such qml file structure window become nullptr on Quick Window recreation and execution goes to else path of if statement. And there we use single QQuickView instance - qxView, just modifying its content without full reloading and recreation.

However if qml file contains ApplicationWindow as root item of the scene:

ApplicationWindow {
...
}

execution goes by the 1st variant of Quick Window recreation:

engine.setIncubationController(window->incubationController());

and new QQuickWindow instance created which takes much more time and force us to destroy and close previous one.

Is it possible analogous to QQuickView reload scene content for QQuickWindow without full window recreation? Thanks!