I have problems with a multitouch library, in this case Interact.js, which e.g. generates a pinch / rotate for a target although one of the two pointer events is outside the target when the gesture is started. That doesn't do me any good.
I wonder if it makes sense to rely on a library or to create the 2 gestures, drag and rotate, myself.
In order not to start all over, there is an example for this, i.e. to determine the mathematics of the rotation from the movement of 2 points, I have managed the relevant pointers so far.
Many thanks in advance.