A DESCRIPTION OF THE PROBLEM :
If the applikation is in window mode and the window is not in the upper left corner of the screen, then you're getting no or wrong scroll events.

The reason for this is that in the ScrollGestureRecognizer the absolute x and y coordinates are passed on to generate the scroll events. But the methods which are called with the absolute coordinates expect relative coordinates.

This is the reason why the scroll events in fullscreen mode or if the window is in the upper left corner of the screen work, because then the absolute and relative coordinates are the same.