title: How to get a return value from QMetaObject::invokeMethod
body: <p>I am calling from my thread the following:</p>
  
  <pre><code>QMetaObject::invokeMethod(pProcessor,
                            "doTask",
                            Qt::QueuedConnection,
                            Q_RETURN_ARG(quint32, taskId),
                            Q_ARG(quint64,   objId),
                            Q_ARG(quint8,    intId),
                            Q_ARG(QString,   name),
                            Q_ARG(QString,   comment)
                            );
  </code></pre>
  
  <p>but it just fails, no matter what I do. If I take out Q_RETURN_ARG(quint32, taskId), the method is invoked, but I need the taskId, which I cannot get.
  Any help is much appreciated.</p>