well, it's not stateChange. It's really assure that the state is set accordingly.

or to put it another way: 2 different topics can have the same showCatalog state, but we want this event to trigger anyway, because we want to assure that showCatalog is taken into account (possibly overwriting what the user did to the catalog accordion).

I had originally a watch on a showCatalog global variable, but it didn't trigger in this case (new topic with same state), that's why I had to use messaging.