Jakob Petsovits commented on merge request !368 at Plasma / PowerDevil

But.. I did a little research and learned that I can call Q_INVOKABLE functions from within QML. This does seem like a valid reason to me, or is it still preferable to use signals to call functions from the QML side?

You can use Q_INVOKABLE to call C++ functions from QML. But in this case, isn't it the other way round, where you want something from C++ to invoke a QML function? Q_INVOKABLE (and also Q_SLOTS) won't help much in this direction.