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From Sylvain Wallez <>
Subject Re: Event handling in form libraries
Date Sat, 03 Sep 2005 16:06:00 GMT
Reinhard Poetz wrote:

> Sylvain Wallez wrote:
>>>  - event handlers in libraries are allowed, but I don't think they
>>>    make sense there (e.g. on-value-changed)
>> Why not? A library may for example contain a group of related widgets 
>> with some interactions between them, e.g. a reusable car selector :-)
> [Moving this discussion between Sylvain, Max and me to cocoon-dev as 
> it's of general interest]
> my wording was bad: I think they would make sense but I think the 
> implementation is a bit difficult or at least this can cause strange 
> errors. Maybe I'm wrong ...
> Here a simple example why I don't think that it can work with simply 
> using the eventhandler code of the library in the form definition.
>  libWidget1 has eventhandler that references libWidget2
>  libWidget2
> FORM DEFINITION (imports above library)
>  myWidget1 extends libWidget1
> What happens now? The form doesn't has a reference to libWidget2. And 
> if it had, how could the reference in the event handler code can work 
> as it probably has a different name than libWidget2 or is reused 
> several times in the form definition.

Good point. We may allow on-change listeners in form libraries only in 
fields that aren't top-level, i.e. part of a group.

Now aren't there any valid use cases where a field has an on-change that 
only acts on itself?


Sylvain Wallez                        Anyware Technologies
Apache Software Foundation Member     Research & Technology Director

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