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Re: Using the same handler to observe multiple different events

From: Erik Bruchez <ebruchez@orbeon.com>
Date: Tue, 17 Apr 2007 16:42:27 +0800
Message-ID: <46248873.3070909@orbeon.com>
To: www-forms@w3.org


ev:listener is good and yes, XForms implementations are supposed to 
support it, but my opinion is that it is heavy for this particular use case.

I was suggesting back a while ago that XML Events should support lists 
of space-separated event names. You would then write:

   <xf:action ev:event="some-event some-other-event">

This would be a much more concise syntax, and it is easy to understand.


Aaron Reed wrote:
> Hi John,
> Using ev:listener is how I would reuse handlers.  No reason that an 
> ev:listener can't work in XForms.
> To clarify actions if you had:
> <xf:trigger>
>   <xf:label>handle some-other-event</xf:label>
>   <xf:action id="handler2" ev:event="DOMActivate" 
> ev:observer="observer2" ev:handler="#handler">
>     <xf:message level="modal">DOMActivate happened</xf:message>
>   </xf:action>
> </xf:trigger>
> and you have another action with id="handler", then when the trigger is 
> clicked, the above action would not process its contents (and thus the 
> above message would not be shown) since it is actually only specifying 
> what the actual handler would be, not acting as a handler itself.  But 
> whatever actions appear in xf:action with @id="handler" would be processed.
> I hope that this helps,
> --Aaron
> Clark, John wrote:
>> I am interested in reusing event handlers, and I was wondering if the 
>> combination of Xforms (1.1) and XML Events allows this.  For example, 
>> say I have an event handler (an `xf:action` element) that looks like 
>> this:
>>   <xf:action ev:event="some-event" ev:observer="observer1"
>>              id="handler">
>>     <!-- Potentially complex handler logic here -->
>>   </xf:action>
>> If I want the same handler logic to also respond to a second event 
>> (and potentially at a different observer location), I would like to 
>> not have to take the na´ve approach and duplicate the entire action.  
>> The XML Events specification gives us one tool, the `ev:listener` 
>> element.  "Reregistering" the above handler might look like:
>>   <ev:listener event="some-other-event" observer="observer2"
>>                handler="#handler"/>
>> Is the `ev:listener` element allowed in XForms, however?  Also, how 
>> would the use of the relative reference in `handler="#handler"` 
>> interact with IDREF resolution in XForms[0]?  If the `ev:listener` 
>> element is not allowed in XForms, then another possibility is to use 
>> the `ev:handler` attribute, which might look like this:
>>   <xf:action ev:event="some-other-event" ev:observer="observer2"
>>              ev:handler="#handler"/>
>> The same question about IDREF resolution applies here, though.  Also, 
>> the spec says that the `action` element "causes its child actions to 
>> be invoked in the order that they are specified in the document"[1]; 
>> does that allow for pointing at a different handler?
>> [0] http://www.w3.org/TR/2007/WD-xforms11-20070222/#idref-resolve
>> [1] http://www.w3.org/TR/2007/WD-xforms11-20070222/#action-action
>> Thanks, and take care,
>>     John L. Clark  |  Systems Analyst
>>                    |  Cardio-Thoracic Surgery Research
>>  Cleveland Clinic  |  9500 Euclid Ave.   |  Cleveland, OH 44195
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Received on Tuesday, 17 April 2007 08:42:46 UTC

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