Currently the mitkDisplayVectorInteractor checks the buttonState of the incoming stateEvent in order to determine whether <ALT> has been pressed or not. Depending on this state, an internal bool-flag is set.

However, as it might be possible to define a different modifier-key, this explicit check is a problem, as the wrong buttonState is checked.

The solution is to move this logic into the actual statemachine. An additional action can be defined that causes the DisplayVectorInteractorScroll to correctly set the bool-flag.