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Re: Disabling a button based on validity

From: Erik Bruchez <erik@bruchez.org>
Date: Fri, 28 Oct 2005 14:00:07 +0200
Message-ID: <436212C7.1070601@bruchez.org>
To: www-forms@w3.org

David Landwehr wrote:
> Hi Erik,
> 
> The reason you get the xforms-valid and xforms-invalid whenever a bound
> instance node changes is because an author might use that event to
> provide a message saying this field is invalid. If the processor only
> sends the event on a change in validity you would get such a dialog for
> the first change to invalid, but if the user changes the value again he
> would not get the message but the node would still be invalid.
> 
> The usecase discussed in this mail thread seems to be a very common
> scenario and should be dealt with by the specification. I don't think it
> should be done by changing the way events are dispatched at the moment
> as it is to tedius to implement the functionality with counters. Also
> that method might not reflect the true validity of the instance as it
> only reflects the validaty of any bound node in the UI.
> 
> I believe that the validity function in XPath could be used to solve
> this usecase (which is properly why formsPlayer has implemented it and
> exforms.org has an extension function for it), however depending on the
> formulation of the function it might also be tedious. E.g. in our
> current usecase you would like to have the validity with regards to a
> relevant subtree not for single nodes.

David,

Thanks for the precisions. I agree with your assessment: I don't think 
it is necessary to revise the way events are dispatched, at least not 
just to implement this use case; counters or setters are not an ideal 
solution; the functionality should IMO follow the semantics of 
xforms:submission, i.e. the property should reflect whether the instance 
or subset thereof (single-node binding) can be submitted or not as per 
section 11.1.

BTW I don't see a exf:valid() function in exforms.org: only 
exf:relevant(), exf:readonly(), and exf:required(). I noticed this a few 
days ago and was going to comment about it. Now isn't there a problem 
with such a function, as revalidation occurs after the other MIPs have 
been computed, and if, for example, you decide that an xforms:submit 
control must be relevant under the condition that a node is valid, then 
at the moment the relevant MIP is evaluated, revalidation hasn't yet 
occurred?

-Erik
Received on Friday, 28 October 2005 12:00:17 GMT

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