An example puzzle me, please help

[wysota]

It can do the same thing.

Because you are not using anything Q_PROPERTY offers. If I have a car and I don't use the wipes, I can take them off and say the car still behaves as it did before. Q_PROPERTY is an extra functionality that you are simply not using at the time.

Please read about Q_PROPERTY and meta-object system in Qt Assistant. It's a wide topic, impossible to cover in a forum thread.