Both Arvid and Stefan have implemented ways to signal zoom changes to
applications. I don't think that either is better as such, but I don't
think that there should be two of them:
I suppose that if I had to choose, I would say that the second one
seems more 'natural' as it fits in with the other ICMERH methods like
'selectionChanged' and 'coordinatesChanged'. Also, that
ICDKChangeListener is a quite general - and probably underused -
mechanism for indicating changes to the model.