[news.eclipse.technology.equinox] Re: Separating concerns...

[Mel Martinez <melm@xxxxxxxxxx>]

Jeff McAffer wrote:
> see
> http://dev.eclipse.org/viewcvs/indextech.cgi/~checkout~/equinox-home/dynamic
> Plugins/registryDelta.html
>
> This details the kind of thing one would see when the registry changes.  The
> API class does not capture all of this.
>
> I don't see that there is much in having a mechanism specifically for
> extensions and extension points.  By telling people the whole picture they
> can batch changes, understand the context better and in general do a better
> job of handling the changes.  Of course, if they are truly only interested
> in particular kinds of changes they can just ignore all others.

There are two things here:

1) the granularity of the event object.  I have no great problem if it 
contains a delta for the registry as a whole (unless that starts to 
become a large thing to calculate), although I wonder at the value for 
the out-of-context information for a given listener when the listener 
could always just interrogate the registry to get the state of the 
larger context.
2) the granularity of the messaging.  Are you saying that for every 
registry event you would prefer to broadcast that to every listener? 
Doesn't that become problematic in the hypothetical 5000 plugin case? 
If there are only two or three plugins that are actually affected by an 
event, it is really inefficient to make 5000 calls that each have to 
examine the delta to see if it is of concern before no-op'ing.  One 
badly written plugin could slow up the processing of EVERY event!  Maybe 
I'm misunderstanding you here.

My preference would be to send deltas to just the parties that are 
registered to listen for events on that registry item.

Mel