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Re: Removing a Control from the taborder

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Norman Peelman wrote:

> Thomas 'PointedEars' Lahn wrote:
>> Norman Peelman wrote:
>>>     Consider this, the tabindex controls the tab order of the form
>>> elements with a range of 0 - 32767. That means to remove a form element
>>> from the tabindex it must not be in that range. "-1" is not in that
>>> range, nor is "-32767" or anything in between for that matter. You could
>>> simply throw (insert) a minus sign in front of a form element to disable
>>> it, even via scripting (simply multiply the tabindex by -1 to toggle).
>>
>> Your logic is flawed.  The HTML 4.01 Specification is definitive about
>> this: values for the `tabindex' attribute outside the specified range are
>> *invalid*.  It is specified accordingly in W3C DOM Level 2 HTML:
> 
>    Invalid, thereby causing the tabindex to be ignored.

No, not necessarily.  That is the fallacy.  The type of the `tabindex' 
attribute in HTML 4.01 is the SGML type NUMBER [1a], and that type does not 
include values containing the `-' (U+002D HYPHEN-MINUS) character [2].  
There is no standard on handling invalid documents (only a non-normative 
recommendation for HTML 4.01 documents [1b]; HTML5 would become the first 
version of HTML to fix that [3]).  A conforming HTML 4.01 parser is free to 
interpret invalid markup as it sees fit (which is done, as evident by 
comparing results of other invalid markup in MSHTML-based and Gecko-based 
browsers alone).  For example, one parser, but not another (i.e., one 
browser, but not another), could reasonably normalize a value out of range 
to one in range – 0 – which would include the element in the tab order after 
all other elements that have a proper `tabindex' attribute set [1c].  

On top of inconsistent results with HTML user agents, the W3C Markup 
Validator and other properly working markup validators will report such an 
attribute value as a *syntax error* [4a].  While validation is not a mark of 
quality in itself [4b], failure of a document to validate, for dubious 
reasons such as this, certainly raises doubt about the competence of the 
document's author, which usually also is to the disadvantage of enterprises 
making and publishing the corresponding website.

Deliberately using invalid markup will make it harder for the 
author/programmer to find other, potentially more serious, accidental syntax 
errors in the document by using markup validation.  For example, think about 
a document where several such invalid elements as you propose are generated 
by a server-side application in a loop. 

There is also no guarantee that, in order to avoid an invalid document, 
assigning afterwards a negative Number value to the `tabIndex' attribute 
property of the corresponding DOM object would work; but there is strong 
indication that it would not work.  W3C DOM Level 2 HTML, which applies to 
HTML 4.01 and XHTML 1.0 documents [5a], specifies that property to be an 
implementation of the `tabIndex' IDL attribute of the HTMLInputElement 
interface (a.o.) whose values must correspond to the HTML 4.01 specification 
of the markup attribute [5b, 5c].

Your approach is positively harmful to all involved (enterprise, document 
author, script developer, and visitor).  IOW, it is a Really Bad Idea.


HTH

PointedEars
___________
[1a] <http://www.w3.org/TR/1999/REC-html401-19991224/interact/forms.html
      #h-17.4>,
     <http://www.w3.org/TR/1999/REC-html401-19991224/sgml/dtd.html>,
     <http://www.w3.org/TR/1999/REC-html401-19991224/strict.dtd>
[1b] <http://www.w3.org/TR/1999/REC-html401-19991224/appendix/notes.html
      #h-B.1>
[1c] <http://www.w3.org/TR/1999/REC-html401-19991224/interact/forms.html
      #adef-tabindex>
[2]  <http://www.w3.org/MarkUp/SGML/productions.html#prod56>
[3]  <http://www.w3.org/TR/html5/editing.html#sequential-focus-navigation-
      and-the-tabindex-attribute>
[4a] <http://validator.w3.org/#validate_by_input+with_options>,
     type `<input tabindex="-1">', select "Validate HTML fragment" (which
     by default selects "Use Doctype: HTML 4.01", select "Check".
[4b] <http://validator.w3.org/docs/help.html#validandquality>
[5a] <http://www.w3.org/TR/2003/REC-DOM-Level-2-HTML-20030109/>
[5b] <http://www.w3.org/TR/2003/REC-DOM-Level-2-HTML-20030109/ecma-script
      binding.html>
[5c] <http://www.w3.org/TR/2003/REC-DOM-Level-2-
      HTML-20030109/html.html#ID-62176355>
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(This won't prevent people from viewing your source, but no one
will want to steal it.)
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Thread

Removing a Control from the taborder Gene Wirchenko <genew@ocis.net> - 2012-03-08 13:56 -0800
  Re: Removing a Control from the taborder "Evertjan." <exjxw.hannivoort@interxnl.net> - 2012-03-09 00:07 +0000
    Re: Removing a Control from the taborder Gene Wirchenko <genew@ocis.net> - 2012-03-08 19:37 -0800
      Re: Removing a Control from the taborder Norman Peelman <npeelmandog@cfl.rr.com> - 2012-03-09 18:56 -0500
        Re: Removing a Control from the taborder Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-03-10 01:42 +0100
          Re: Removing a Control from the taborder Norman Peelman <npeelmandog@cfl.rr.com> - 2012-03-09 22:59 -0500
            Re: Removing a Control from the taborder "Jukka K. Korpela" <jkorpela@cs.tut.fi> - 2012-03-10 08:40 +0200
              Re: Removing a Control from the taborder Norman Peelman <npeelmandog@cfl.rr.com> - 2012-03-10 06:18 -0500
                Re: Removing a Control from the taborder Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-03-10 13:33 +0100
            Re: Removing a Control from the taborder Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-03-10 12:33 +0100
          Re: Removing a Control from the taborder Norman Peelman <npeelmandog@cfl.rr.com> - 2012-03-09 23:22 -0500
      Re: Removing a Control from the taborder Dr J R Stockton <reply1210@merlyn.demon.co.uk> - 2012-03-10 20:51 +0000
        Re: Removing a Control from the taborder Gene Wirchenko <genew@ocis.net> - 2012-03-10 23:55 -0800
          Re: Removing a Control from the taborder Dr J R Stockton <reply1211@merlyn.demon.co.uk.invalid> - 2012-03-12 19:46 +0000
          Re: Removing a Control from the taborder David Mark <dmark.cinsoft@gmail.com> - 2012-03-12 18:24 -0700

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