[Dev] Menu items support named dispatch

[John Anderson]

BroadcastEverywhere should be rarely used, and eventually we may 
eliminate it. Typically you should use BroadcastInsideMyEventBoundary, 
which broadcasts to all the blocks inside an event boundary, containing 
the block that sent the event, or 
BroadcastInsideActiveViewEventBoundary, which broadcasts to all the 
blocks inside an event boundary containing the active view. 
BroadcastEverywhere broadcasts to all the blocks that are rendered, 
which is slow (especially during UpdateUIEvents) and doesn't allow 
different parcels to have a different namespace for events.

Let me know if none of the dispatch mechanisms, except 
BroadcastEverywhere, are convenient for you and I'll try to come up with 
an alternate dispatch mechanism.

John

Brendan O'Connor wrote:

>> In our dynamic user interface, where blocks come and go, it's handy 
>> to  have a mechanism that sends an event to whichever block is 
>> available to  handle that event.  For this reason CPIA has had the 
>> ability to dispatch  to events using the event's name.  This is 
>> implemented as an attribute  "eventsForNamedDispatch" on Block.  
>> Essentially, this allows the block  to publish events that it, or its 
>> children blocks, can handle.  This  feature has not been widely used, 
>> until now.
>
>
> Donn, is this in general preferable to using BroadcastEverywhere?  
> More  and more BroadcastEverywhere events are being sent around in 
> the  block-ified main calendar, but they do so because of the reason 
> you're  advocating eventsForNamedDispatch, namely that you can assign 
> an arbitrary  number of listeners and the sender doesn't have to worry 
> about who'  listening ... some notes on  
> http://bugzilla.osafoundation.org/show_bug.cgi?id=3607
>
> Brendan
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