[Chandler-dev] Re: [Dev] collections and notifications

[Andi Vajda]

On Fri, 24 Mar 2006, Katie Capps Parlante wrote:

> I wanted to follow up on this to make sure all is well. If I understand 
> correctly...
>
> - "Item notifications" have been implemented (watchItem), and are 
> synchronous, and this will meet the detail view requirements for item 
> notifications

Yes, within a given view. Changes that occur in other views will be notified 
after refresh, synchronously.

> - Most notifications are synchronous
>   - attribute monitors (which are probably mostly used internally in the 
> repository, to maintain indexes and whatnot)
>   - watchItem
>   - watchKind
>   - watchCollection

Likewise

> - "watchQueue" is asynchronous

Yes, although 'watchQueue' doesn't exist yet, it's still using the old name, I 
haven't changed that one yet.

> A few questions:
> - When does one use "watchQueue" vs "watchCollection"? (Andi has documented 
> this from a bottom up perspective, but how do we explain this  clearly to 
> people writing code at higher layers?)

Indeed...

> - We had talked about deliverNotifications/mapChanges as having become 
> something of a "Frankenstein" in 0.6. At the collections meeting, we 
> theorized that onIdle could just call view.refresh() and that 
> deliverNotifications() could go away, given that all of the "below the line" 
> notifications would be synchronous. Given that watchQueue remains 
> asynchronous for performance reasons, where does that leave us? Are we happy 
> that the current implementation of deliverNotifications() is reasonable? Are 
> we happy with the options/consequences at the app level?

All of what you say above was implemented, actually, except that not all 
notifs below the line are synchronous. The queued notifs are now *always* 
dispatched during refresh() solving the problem of what to do with them when 
no-one polls for them, as is the case when running without a UI.

> - Does Bryan have everything he needs for detail view work (wrt 
> notifications)? If not, what remains?

That is my understanding, Bryan ?

I could still provide more details in some notifications. If this is needed,
please let me know.

Andi..