[Seaside] nested LiveCallbacks

Michel Bany m.bany at wanadoo.fr
Fri Oct 28 08:16:45 UTC 2005

Juan Burella a écrit :

>            Using this version it works in a different way but not 
> completely right. When the second list is selected everything works 
> fine, but then the first one is selected, it disappears leaving only 
> the second and the third visible.
I think I can see what's wrong.

The original implementation of live update allowed for updating only one 
area of the html document.
With you test case you need to live-update two areas, provinceSelector 
and citySelector,
therefore the original implementation cannot work.

The implementation in Seaside2.5b8-mb.14 allows you to live-update an 
arbitrary number of
areas of the html document. For detecting all the areas, i.e. all the 
html tags with the id= attribute,
the new implementation uses the DOM feature of XMLHttpRequest. However, 
this DOM feature
is very strict and requires that the html produced by the live update 
blocks is clean XML. That's why
the new implementation sets the content-type to 'text/xml; 
charset=utf-8' and replaces all occurences
of   with  

Your test case introduces an additional difficulty. The html produced by 
the first live update callback
creates something that contains 
The occurence of the ampersand (&_k=) makes this html unclean XML that 
cannot be parsed
by XMLHttpRequest and the live update Javascript degrades into 
displaying whatever is received
rather than selectively updating the document. Not sure I am explaining 
this well.

I tried to have the ampersand encoded so that the html creates something 
With this encoding the html created becomes compliant with XML and is 
properly parsed by XMLHttpRequest.
However, this does not work because the browser does not decode "&" 
back to an ampersand
before sending the URL to Seaside and Seaside gets lost.

Ideas welcome.

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