facepalm I missed to overriding of the event(QEvent *event) inside my special label AND I also missed to subscribe the label to the gesture that is I had to add grabGesture(fftType) in the label's constructor. Now I can capture data and evaluate it in a state-wise fashion (for example storing event.pos() in a list and then going through that list to see if a gesture might have been caught or not).

@juanki Gracias!

Can you show your class and its implementation ?