[ImageJ-devel] EventBus issues.

[Lee Kamentsky]

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)  
>> 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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