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Re: Disabling a button based on validity

From: Vincent Berger <vincent.berger@afp.com>
Date: Thu, 27 Oct 2005 19:23:25 +0200
To: Erik Bruchez <erik@bruchez.org>
Cc: www-forms@w3.org
Message-Id: <1130433805.29596.120.camel@genepi>
Hi Erik,

Le mardi 25 octobre 2005 à 18:49 +0200, Erik Bruchez a écrit :

> Thanks Andy. It makes sense, and unfortunately (for you and I) falls 
> into the category "here is a way, but it's really a dirty hack" ;-)
> 
> We have done exactly the same things by placing a single event handler 
> higher up the XHTML, to catch all the validation events of a group of 
> controls, and incrementing vs. decrementing a counter. This takes about 
> 10-15 lines of extra code, including the extra instance. I think that 
> ideally such a functionality should be achieved with a single attribute.


This extra-code is not so easy to do for me. And furthermore difficult
since David Landwehr
show me that an event 'xforms-invalid' is dispatched when an invalid
data is changed to a still invalid value.

In the first extra-code I´ve done, the counter was incremented in the
case above ... and it´s wrong of course.
My second extra-code works but is too dirty to be written there.

Shall I see yours, please ?

vinzo.




> 
> So far, we are taking branch #2 in my original question!
> 
> -Erik
> 
> andyh@collegenet.com wrote:
> > 
> > 
> > 
> > 
> > Erik,
> > 
> > This is what we do...
> > 
> > We have an errors instance:
> > 
> > <xf:instance id="iErrors">
> >       <errors xmlns="">
> >             <total>0</total>
> >             <fields>
> >                   <field id="USERNAME">0</field>
> >                   <field id="FIRST_NAME">0</field>
> >                   <field id="LAST_NAME">0</field>
> >                   <field id="EMAIL_ADDRESS">0</field>
> >                   <field id="PASSWORD">0</field>
> >             </fields>
> >             <save/>
> >             <nosave/>
> >       </errors>
> > </xf:instance>
> > 
> > <xf:bind nodeset="/errors/total" calculate="sum(../fields/field)"/>
> > <xf:bind id="bndSave" nodeset="/errors/save" relevant="../total = 0" />
> > <xf:bind id="bndNoSave" nodeset="/errors/nosave" relevant="../total &gt; 0"
> > />
> > 
> > that records the state of each field we need to validate.
> > 
> > Each of those controls have event handlers for xforms-valid and
> > xforms-invalid to set the error count to 0 or 1 respectively.
> > eg.
> > 
> > <xf:input ref="USERNAME" class="SmallTextField" id="f001">
> >       <xf:label>Username:</xf:label>
> >       <xf:alert>Please supply a unique username</xf:alert>
> >       <xf:setvalue model="mErrors"
> > ref="instance('iErrors')/fields/field[@id = 'USERNAME']" value="1"
> > ev:event="xforms-invalid"/>
> >       <xf:setvalue model="mErrors"
> > ref="instance('iErrors')/fields/field[@id = 'USERNAME']" value="0"
> > ev:event="xforms-valid"/>
> > </xf:input>
> > 
> > Finally we have two trigger elements bound to bndSave and bndNoSave. Our
> > styling hides non-relevant controls so only one of these buttons is visible
> > at any point in time. The bndNoSave version has the HTML attribute
> > disabled="disabled" on it so that the button truly looks disabled.
> > 
> > 
> > Now formsPlayer has just introduced an XPath extension function
> > fpext:valid(node-set) [1] that returns true or false of whether a node is
> > valid or not, and this could be used in calculations instead of the event
> > pattern above.
> > 
> > 
> > Andy
> > 
> > [1] http://www.xforms-wiki.com/bin/view/Main/XformsXpathFunctionsExtension
> > 
> > 
> > 
> > 
> >                                                                            
> >              Erik Bruchez                                                  
> >              <erik@bruchez.org                                             
> >              >                                                          To 
> >              Sent by:                  www-forms@w3.org                    
> >              www-forms-request                                          cc 
> >              @w3.org                                                       
> >                                                                    Subject 
> >                                        Disabling a button based on         
> >              10/25/2005 08:32          validity                            
> >              AM                                                            
> >                                                                            
> >                                                                            
> >                                                                            
> >                                                                            
> >                                                                            
> > 
> > 
> > 
> > 
> > 
> > All,
> > 
> > I am having trouble figuring out the solution to an extremely basic UI
> > requirement: disabling a submit button, implemented either with
> > xforms:submit or xforms:trigger, until certain fields have been filled
> > out correctly by the user.
> > 
> > Of course, you could leave the button always enabled. Upon XForms
> > submission, if the submitted instance is not valid or has missing
> > required fields, submission will fail, throw an xforms-submit-error,
> > and you can notify the user of the failure. But from a usability
> > perspective, this is usually a bad solution.
> > 
> > So these are my questions:
> > 
> > 1. How do people address this UI requirement today with XForms? Is
> >     there a way of doing this purely based on the XForms 1.0
> >     specification? If not, are there workarounds? For example, we have
> >     played with counting xforms-valid and xforms-invalid events,
> >     clearly a quite heavy solution.
> > 
> > 2. If the answer to #1 above is "no" or "here is a way, but it's
> >     really a dirty hack":
> > 
> >     2.1. Is the WG working on addressing this? (I should talk with
> >          Sebastian but it doesn't hurt to ask this publicly.)
> > 
> >     2.2. Are there extensions suggested or implemented by existing
> >          XForms engines that address this?
> > 
> > Thanks,
> > 
> > -Erik
> > 
> > 
> > 
> 
> 

-- 
Vincent Berger <vincent.berger@afp.com>
Agence France-Presse

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Received on Thursday, 27 October 2005 17:21:21 GMT

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