@panch said:

Would you then restrict the signals/slots to only GUI-related information passing? As a proper way of developing Qt applications, I mean...

QNetworkAccessManager emits signals to tell the world that a download has completed. QSerialPort emits signals to tell the world that some data has been received. QMediaPlayer emits signals to tell the world that its playback status has changed.

These show that signals and slots are "proper" for developing all kinds of things, not just GUIs.