[ImageJ-devel] EventBus issues.

[Lee Kamentsky]

Thanks, hope this all helps to get it right.

On 6/30/2011 2:27 PM, Curtis Rueden wrote:
> Hi Grant et. al,
>
> Grant and I discussed this further, and we agree that it is much 
> preferred to avoid depending on or altering the order events are 
> delivered to subscribers. It should always be possible to create 
> additional event types to discriminate more finely, as Lee describes.
>
> So Grant, I propose that we remove the PriorityEventSubscriber stuff 
> we added the other day, to avoid complexifying the events package. 
> What do you think?
>
> -Curtis
>
> On Thu, Jun 23, 2011 at 12:38 PM, Lee Kamentsky 
> <leek at broadinstitute.org <mailto:leek at broadinstitute.org>> wrote:
>
>     IMHO - if you depend on order for events, there's a good chance
>     you're not doing something right. If you depend on order, I'm
>     guessing that a direct function call is the appropriate solution
>     or that you are not properly modeling what is really happening.
>
>     I'm guessing that this has to do with the overlay manager - that
>     you've received an overlay created/deleted event and you don't
>     know whether it's in the overlay manager or not. There are two
>     different events here:
>     * an overlay object was created or deleted
>     * the overlay manager added or removed an overlay
>     so, the code that is experiencing difficulty should respond to the
>     appropriate event. If you have a user interface that shows the
>     overlays in the manager, it's the second event that you want. If I
>     guessed wrong, perhaps it follows the same pattern?
>
>     --Lee
>
>
>     On 6/23/2011 12:58 PM, Grant B. Harris wrote:
>
>         Ooops... My bad.  I thought we were using 1.2... We are
>         already using 1.4.  But we need to change Events framework.
>          I'll take a stab at it today.
>         -- Grant
>
>         On 6/23/2011 12:55 PM, Grant B. Harris wrote:
>
>             I think EventBus can serve us well, but I have run into a
>             serious issue that demands that we move from EventBus
>             version 1.2 to 1.4.
>
>             Because "subscribers are called in the order in which they
>             subscribed", we cannot use the EventBus (1.2) in ways that
>             we need.  If I have a class which is watching things (say
>             a ROI Manager or the Window menu list of open displays)
>             it's behavior depends on when it was subscribed.  I've
>             been working on this for a week and I have not found a way
>             to manage this.  Fortunately I discovered that as of
>             version 1.3 there is a PrioritizedEventSubscriber
>              (http://www.jarvana.com/jarvana/view/org/bushe/eventbus/1.3/eventbus-1.3-javadoc.jar!/org/bushe/swing/event/Prioritized.html
>             <http://www.jarvana.com/jarvana/view/org/bushe/eventbus/1.3/eventbus-1.3-javadoc.jar%21/org/bushe/swing/event/Prioritized.html>)
>              I think this is just what we need.
>
>             (Using this priority mechanism may also eliminate the need
>             for the ObjectsUpdatedEvent that I added last week.)
>
>             EventBus version 1.4 is here:
>             http://mvnrepository.com/artifact/org.bushe/eventbus/1.4
>
>             We will need to change the Events framework a bit to add
>             Prioritized Event Subscription, but otherwise I don't
>             think it will require any refactoring except for the
>             subscribers that need to set priority.
>
>             -- Grant
>
>
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