Yes that is correct. Every of the 8 custom gestures defines its own set of data in addition to the QGestureState, which is set by the according gesture recognizer.
I now implemented an abstract superclass for all these gestures with a method getGestureData(). This method basically wraps all the data in a QMap<QString,QVariant> to make a general gesture treatment possible. The custom event GestureEvent now takes gesture type, the Qt::GestureState and the mentioned gesture data map.
It was a little bit circumstantial, but now it works.
Thanks again,
Malte