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From Jason Johnston <coc...@lojjic.net>
Subject Re: [cforms] fi:validation-errors in AJAX mode
Date Thu, 04 Aug 2005 13:35:21 GMT
Sylvain Wallez wrote:
> Jason Johnston wrote:
> 
>> Sylvain Wallez wrote:
>>
>>> Ugo Cei wrote:
>>>
>>>> Looks good to me. AFAIK, Ajax support works only with the template 
>>>> macros, so it might not make sense to add this feature to the 
>>>> transformer also. What is the orientation of the community towards 
>>>> the transformer/macros ambiguity? I'd like to have just one 
>>>> recommended implementation of this, so if macros are the way to go, 
>>>> what about deprecating the forms transformer? 
>>>
>>> Well, macros are more powerful because they allow to do more than 
>>> templating with the widgets. A straightforward example is conditional 
>>> templating, e.g. displaying "There are now contacts" rather than an 
>>> empty table. This is not possible with a transformer, unless we add 
>>> an expression language and some control structures which will make it 
>>> yet another programming-language-in-XML...
>>>
>>> OTOH, the transformer is useful when JXTG is not a option e.g. when 
>>> the generator is an XSP...
>>
>> IIUC you can also use JX as a transformer, so wouldn't that cover this 
>> case?
> 
> Because you should really avoid using JXTransformer if you want a 
> responsive application: this transformer basically feeds the JX 
> generator with the incoming SAX stream, meaning the template is full 
> reparsed and recompiled at each execution, which is highly inefficient.
> 
> IMO, we should make this very prominent in the doc and discourage such 
> usage, or even deprecate this transformer.
> 
>> Anyway... to Ugo's question, I believe (correct me if I'm wrong) that 
>> AJAX works regardless of whether the template is interpreted by JX or 
>> the FormsTemplateTransformer, since it's the widgets themselves that 
>> signal whether or not they have been updated by wrapping their SAX 
>> output in a <bu:replace>.
> 
> Exactly.

Getting more familiar with this code, it actually looks like I was wrong 
about where the bu:replace gets created.  I thought it was done in the 
widget's generateSaxFragment method, but it actually is done in the 
template layer.  And it looks like it's only implemented so far in the 
JX macros, not in FormsTemplateTransformer.  So it looks like Ugo was right.

The only AJAX-related code I can find in the Widget (formmodel) classes 
is in AbstractWidget.generateSaxFragment(), where it creates an 
fi:placeholder if the widget is invisible.  It seems odd to me to have 
this here, perhaps it would better belong in the template layer as well.

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