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From Jason Johnston <coc...@lojjic.net>
Subject Re: CForms: where and how to specify the suggestion-list?
Date Thu, 22 Sep 2005 14:18:26 GMT
Sylvain Wallez wrote:
> Hi all,
> 
> I'm currently working on adding a "Cocoon suggest" feature to CForms 
> fields based on Scriptaculous [1]. This requires to associate an URL to 
> the field to fetch the suggestion list using Ajax requests when the user 
> inputs something.
> 
> Question is: where and how do we specify this? Is this a concern of the 
> form definition, or a particular styling of the field?
> 
> Concretely, should it be
>  <fd:field id="foo">
>    <fd:suggestion-list url="foo-suggest">
>  </fd:field>
> or
>  <ft:widget id="foo">
>    <fi:styling suggest-href="foo-suggest">
>  </ft:widget>
> 
> It seems more natural at first to add this to the definition, but the 
> url attribute must define an externally addressable url providing markup 
> suited to the particular implementation of the suggestion (in the 
> current case, it's a <li> with special classes). It is therefore more 
> related to the view. Also, we may consider that the simple fact that we 
> want to autocomplete is a view concern.
> 
> Hmm...
> 
> Another solution would be for the suggestion list in the definition to 
> be given using the same syntax as <fd:selection-list> and have a 
> system-provided default pipeline to render the list:
> 
>  <fd:field id="foo">
>    <fd:suggestion-list src="cocoon:/foo-suggestion-list"/>
>    <!-- or use whatever implementation of selection list you want -->
>  </fd:field>
> 
> This will automatically generate a
>  <fi:styling suggest-href="_cforms-suggest-foo"/>
> 
> which will be answered to in the sitemap with something like:
>  <map:match pattern="_cforms-suggest-*">
>    <map:generate type="jx" 
> src="resource://org/apache/cocoon/forms/system/generate-suggest-list.xml"/>
>    <map:transform 
> src="resource://org/apache/cocoon/forms/system/list2html.xsl"/>
>    <map:serialize type="xml"/>
>  </map:match>
> 
> This approach still allows to specify the suggest-href only in the view 
> for cases where it's considered as being a view-only concern, and it 
> also allows to specify different renderings of the suggestion list by 
> catching the "_cforms-suggest-xxxx" pattern before the generic 
> "_cforms-suggest-*".
> 
> WDYT?

I don't understand why we need a whole separate pipeline for generating 
and rendering the suggestion list.  Is responding to an AJAX request for 
a suggestion list any different really than any other CForms AJAX 
request?  The pipeline used by Form.showForm() already has the 
capability (if set up for AJAX) to whittle down the widgets' XML to just 
what needs to be updated and transform it into the final view format. 
It seems that's everything we would need.

Put more concretely:

The suggestion list would be declared in the form definition, just like 
a suggestion list.  We could even possibly reuse all the existing 
SelectionListBuilders to create the suggestion lists.  The difference 
between the two would be that the selection list is always

Auto-suggest would be turned on in the view with a suggest="true" 
styling attribute, much like the ajax="true" attribute on the 
form-template element.  When this attribute is present, the XSLT adds 
the appropriate onkeypress listener, which sends an AJAX request to the 
continuation consisting only of that field's name-value pair and a 
special parameter (cocoon-ajax-suggest or similar) indicating the desire 
to get a suggestion list back.

The form model interprets this request by generating the appropriate 
suggestions into the XML, surrounded by a special BrowserUpdate element 
such as <bu:suggest/>.  All the rest of the XML gets removed by the 
BrowserUpdate transformer (just like any other AJAX request), and the 
resulting snippet is transformed by the field-styling XSLT into the 
final format expected by the view.  The client-side script takes this 
response and renders it into a suggestion popup.

I think this is closest to your last suggested solution above, in that 
it can use any of the existing selection-list builders, but it 
eliminates the need for a specialized pipeline.  Seems cleaner to me, 
though I'm not sure about performance impact.  Just another possibility.

--Jason



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