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Re: comment on description xf:dispatch in XForms 1.1

From: C. M. Sperberg-McQueen <cmsmcq@blackmesatech.com>
Date: Tue, 31 Jul 2012 10:54:01 -0600
Cc: "C. M. Sperberg-McQueen" <cmsmcq@blackmesatech.com>, "www-forms-editor@w3.org" <www-forms-editor@w3.org>
Message-Id: <2CAA8939-62FF-40A1-8A6F-58E567DA9D3B@blackmesatech.com>
To: Nick Van den Bleeken <Nick.Van.den.Bleeken@inventivegroup.com>
Thank you; this is very helpful (both your explanation and your
pointer to the XML Events spec, which I have never looked at 
properly.

I don't think it's a good idea to repeat in the XForms spec all
the details given in the XML Events spec, but here is one reader
who would benefit if the XForms spec gave a little more of
an overview of the event-handling model -- perhaps a paragraph
or two added to section 4.1 would do the trick.  (The idea would
be to provide enough orientation to allow the reader to understand
some important concepts -- such as the distinction relevant
here between handler and observer -- and to know where to 
go for more details.)

I realize that it's very hard for people steeped in a spec to write 
high-level overviews that work well for novices and for people 
who don't already know what the overview is saying.  So I apologize
for not offering specific wording.  Perhaps after I spend some time
with the XML Events spec I will be able to come back and propose
wording.
 
Michael

On Jul 31, 2012, at 12:15 AM, Nick Van den Bleeken wrote:

> When you ommit the ev:observer element you are listening to your parent element for events. See [1]
> 
> The following piece of markup attaches an event listener to xf:group with ID g for event my-event:
> <xf:group id="g">
>    <xf:action id="a" ev:event="my-event">
>      <xf:message level="modal">Hi, mom.</xf:message>
>    </xf:action>
>  </xf:group>
> 
> Is equivalent to:
> 
> <xf:group id="g">
>    <xf:action id="a" ev:event="my-event" ev:observer="g">
>      <xf:message level="modal">Hi, mom.</xf:message>
>    </xf:action>
>  </xf:group>
> 
> 
> And can also be written as:
> 
> <xf:group id="g">
>    ....
> </xf:group>
> ....
> <xf:action id="a" ev:event="my-event" ev:observer="g">
>   <xf:message level="modal">Hi, mom.</xf:message>
> </xf:action>
> 
> Regards,
> 
> Nick Van den Bleeken
> 
> 
> 1: http://www.w3.org/TR/2003/REC-xml-events-20031014/Overview.html#section-attributedefaulting
> ________________________________________
> Van: C. M. Sperberg-McQueen [cmsmcq@blackmesatech.com]
> Verzonden: dinsdag 31 juli 2012 4:56
> Aan: www-forms-editor@w3.org
> CC: C. M. Sperberg-McQueen
> Onderwerp: comment on description xf:dispatch in XForms 1.1
> 
> The description of xf:dispatch in section 10.8
> (http://www.w3.org/TR/xforms11/#action-dispatch) says
> 
>> This action dispatches an XML Event to a specific target element.
> 
> The description of targetid says
> 
>> Author-optional attribute for specifying the reference to the event target.
> 
> Nothing in section 10.8 seems to say what kinds of elements can
> and what kinds of elements cannot usefully serve as the target
> of an event.  (A search for 'event target' turns up no useful
> discussion.)
> 
> Experimentation with XSLTForms showed (eventually) that if I
> wrote
> 
>  <xf:group id="g">
>    <xf:action id="a" ev:event="my-event">
>      <xf:message level="modal">Hi, mom.</xf:message>
>    </xf:action>
>  </xf:group>
> 
> then
> 
>  <xf:dispatch name="my-event" targetid="g"/>
> 
> works as  one might expect.  That is, a message reading
> "Hi, mom!" appears.  But in contrast
> 
>  <xf:dispatch name="my-event" targetid="a"/>
> 
> does not work as one might (and I did) expect.  That is,
> no message appears.
> 
> If this is the expected behavior (I confess that I have not tried
> the example with a different implementation), then perhaps it
> would be helpful to some readers if section 10.8 said something
> about whatever property it is of xf:group and xf:action which
> make one but not the other a suitable target for event
> dispatch.
> 
> If this topic is discussed in the spec, I would be grateful for a
> pointer to the discussion. If it is a consequence of the rules
> for event propagation in DOM2 Events or XML Events, I'd be
> glad to know that, too.
> 
> 
> --
> ****************************************************************
> * C. M. Sperberg-McQueen, Black Mesa Technologies LLC
> * http://www.blackmesatech.com
> * http://cmsmcq.com/mib
> * http://balisage.net
> ****************************************************************
> 
> 
> 
> 
> 
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****************************************************************
* C. M. Sperberg-McQueen, Black Mesa Technologies LLC
* http://www.blackmesatech.com 
* http://cmsmcq.com/mib                 
* http://balisage.net
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Received on Tuesday, 31 July 2012 16:54:30 GMT

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