[IGSTK-Developers] (no subject)

[Sandnes Torleif]

Hi Everybody.

I am currently on paternity leave and will be back at work in early August, but will try to 
keep myself updated on the development of IGSTK and maybe post some comments from time to time. 

I see from the last minutes that there will be a refactoring of the event hierarchy.
It looks like the new hierarchy will be a great improvement on the old one. It makes sense to
separate error events from normal events, and I agree that the multiple-inheritance approach
maybe would be a bit of an overkill. 

Error handling in IGSTK applications is an issue I have found it somewhat hard to get a grip on 
(as an app. developer). I have some comments and questions based on my experiences:

1. For an app.developer that is working on a specific component I understand that he can just create
   a subscriber for igstkErrorEvent and add that to the component. He will then get all ErrorEvents 
   that component emits. Also, it is possible to create a subscriber for igstkErrorEvents and add this 
   to all components So with this approach we can have one subscriber that registers with all 
   components for error events and have this observe all errorevents if that is desireable.
2. What kind of load will error events have? It would be nice with a descriptive error message. 
   Not necessarily meant for the user of the software, but something that makes sense for the developer. 
   And maybe it would be possible to attach information about where the error originated?
3. Is it feasible to have one class for each error event that may arise? Would it be better to 
   let one class represent a set of similar errors and add an enumerated value describing the exact error?
4. In any case, it should be clearly documented (doxygen) which events a component may emit in response to
   requests.
5. What happens when an error occurs in a component and no observer is observing this kind of error?
   Would it be justifiable to throw an exception in these cases? If I Remember Correctly such errors will
   be silently ignored if not observed. 
6. There should definitely be an example in IGSTK that demonstrates how to do proper error handling. 
   This would be of great help to new users.

Regards,

Torleif