QQmlApplicationEngine::quit and QGuiApplication::quit

[tilsitt]

Hi,

I found an issue with the following code:

@
MyApplication::MyApplication(int& _argc, char** _argv):
QGuiApplication(_argc, _argv)
{
QQmlApplicationEngine *engine = new QQmlApplicationEngine(
QUrl("qrc:/my.qml"),
this
);

connect(
    engine, &QQmlApplicationEngine :: quit,
    this, &QGuiApplication :: quit
);

}
@

"Qt.quit()":http://qt-project.org/doc/qt-5/qml-qtqml-qt.html#quit-method is called in my QML, and I checked QQmlApplicationEngine::quit was effectively emitted, but the application doesn't quit. I ended up with the following workaround:

@
connect(
engine, &QQmlApplicationEngine :: quit,
engine, &QQmlApplicationEngine :: deleteLater
);
connect(
engine, &QQmlApplicationEngine :: destroyed,
this, &QGuiApplication :: quit
);
@

This version is working: QQmlApplicationEngine::quit schedules engine's deletion which exits the application. It seems QGuiApplication::quit doesn't work if the application has an alive QQmlApplicationEngine child. Did anybody experience something like that?

[SGaist]

Hi,

What happens if you have something like

@
int main(int argc, char *argv[])
{
QGuiApplication app(argc, argv);
QQmlApplicationEngine engine(QUrl("qrc:/my.qml"));
connect(engine, &QQmlApplicationEngine :: quit,
&app, &QGuiApplication :: quit);

return app.exec();
}
@

[tilsitt]

Yes, it's working. I tried your version while using again the application as parent for the QML engine: the application became persistent again, so it's really to link the objects that seems to be the source of this "bug".

[SGaist]

I can't tell if it's a bug, untested scenario or expected behavior. You should have a look at the "bug report system":http://bugreports.qt-project.org to see if someone already wrote about that

[Phrogz]

Under Qt 5.9 I had to modify the connect() call by @SGaist to:

QObject::connect(&engine, &QQmlApplicationEngine::quit, &app, &QGuiApplication::quit);