W3C home > Mailing lists > Public > www-forms@w3.org > July 2006

Re: Event questions.

From: Mark Birbeck <mark.birbeck@x-port.net>
Date: Fri, 28 Jul 2006 18:09:31 +0100
Message-ID: <640dd5060607281009r112e4e54jcf3fee49f7cf14c8@mail.gmail.com>
To: www-forms@w3.org

Hi Rogelio,

> 1- The latest XForms 1.0 recommendation doesn´t forbid a handler attribute
> in an <action> element,so does it mean that an <action> can be defined with
> a handler attribute pointing to another <action>?
>
> (This can be usefull in order to reuse code).
>
>   Something like that should it work?
>
> ....
>
> <xforms:trigger id="trigger1">
>   <xforms:label>Button1</xforms:label>
>   <xforms:action ev:event="DOMActivate" ev:target="trigger1"
> ev:observer="trigger1" ev:handler="action2"/>
> </xforms:trigger>
> <xforms:trigger>
>   <xforms:label>Button2</xforms:label>
>   <xforms:message id="action2" level="modal" ev:event="DOMActivate"> Hi
> again!!</xforms:message>
>
> </xforms:trigger>
> ......
>
> I mean, when the "Button1" is pressed should the message be shown?

Yes. (Although you would specify @handler="#action2".)


> 2- What is the interpretation of an <action> in terms of XML Events, is it a
> listener or can be always considered like a handler?

Mmm...well, it's sort of both. In DOM 2 Events there isn't much of a
distinction between the two. We have EventListener objects, which are
added to the list of listeners waiting for an event to be fired, and
when the event actually arrives, the handleEvent() method on the
EventListener object is invoked. Since the handleEvent() method is
always 'on' the EventListener object then any reuse of handlers you
might have is outside of the scope of DOM 2 Events, and would be
achieved by making handleEvent() call some other function.

But in XML Events the listener and the handler can be separate.
Elements like xf:setvalue are *always* handlers, but they can also be
listeners if they have @ev:event on them. xf:action is a handler too,
but it's role is simply to invoke the handleEvent() methods of its
children. As with other handlers, whether it is also a listener
depends on whether it has the @ev:event attribute.


> 3- What is the aim of having events in a <model> element, more specifically
> what does this sentence mean?
>
> "Attributes from XML Events are allowed on this element to facilitate
> creating observers"

I don't really know why that's in the spec, since although it's true,
it's no more true for xf:model than it is for any other element. All
it's saying is that you can place attributes from XML Events onto
xf:model, but that doesn't make it an action handler, just a listener.
So you could do this:

  <xf:model ev:event="xforms-submit-error" ev:handler="#allsubmiterrorsgohere">
    ...
  </xf:model>

Regards,

Mark

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Mark Birbeck
CEO
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Received on Friday, 28 July 2006 17:09:43 GMT

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