The mitkStepper that is contained in every SliceNavigationController emits a Modified event each time the position is change.
The SliceNavigationController reacts on each modified-event by emitting a GeometrySliceEvent with the updated slice position.

However, the slice position is changed frequently although other actions are performed subsequently and eventually a special event is emitted anyway. We should remove the number of events sent and clean the event-chain to have a simpler and easier to understand code base and to have a clear source of events for depending classes to react on.

Edit
not the same but related / similar: T19284: Display Update with crosshair interaction (Scrolling/..) is inefficient