W3C home > Mailing lists > Public > www-forms@w3.org > October 2005

Fw: Disabling a button based on validity

From: <andyh@collegenet.com>
Date: Thu, 27 Oct 2005 12:11:12 -0700
To: www-forms@w3.org
Message-ID: <OFDEC343CD.75FCC3C5-ON882570A7.006953B1-882570A7.006959D7@collegenet.com>


> 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.

Which is why my xforms-(in)valid handlers just set an instance element for
that field to 0 or 1. The event can fire as many times as possible.
There is a completely separate element for counting the number of
valid/invalid fields.

The code I presented below is not that cumbersome. Once you have the
instance and the three binds, you need a single instance data element per
field and two simple event handlers per control.

Use of formsPlayer's fpext:valid function would remove the need for the two
event handlers per control in favor of a bind/@calculate statement.

What I'm finding as I develop more and more complex XForms is to follow a
spreadsheet model and not try to do too much in each "formula". Instead I'm
calculating something to set up a calculation for something higher and so


             Vincent Berger                                                
             fp.com>                                                    To 
             Sent by:                  Erik Bruchez <erik@bruchez.org>     
             www-forms-request                                          cc 
             @w3.org                   www-forms@w3.org                    
                                       Re: Disabling a button based on     
             10/27/2005 10:23          validity                            

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
      higher up the XHTML, to catch all the validation events of a group of

      controls, and incrementing vs. decrementing a counter. This takes
      10-15 lines of extra code, including the extra instance. I think that

      ideally such a functionality should be achieved with a single

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 ?


      So far, we are taking branch #2 in my original question!


      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
      > 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
      > pattern above.
      > Andy
      > [1]


      >              Erik Bruchez

      >              <erik@bruchez.org

      >              >
      >              Sent by:                  www-forms@w3.org

      >              www-forms-request
      >              @w3.org

      >                                        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
      > requirement: disabling a submit button, implemented either with
      > xforms:submit or xforms:trigger, until certain fields have been
      > 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
      > 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
      >     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 19:11:22 UTC

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