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Re: WCAG and role="presentation"

for

From: Steve Faulkner
Date: Aug 24, 2017 1:16AM

>
> Basically without role=presentation or TH you have Schrödinger's layout
> table - it will be voiced as layout or data depending on a combination of
> screen reader, browser, window size and default font size.


Which is why role=presentation is a MUST conformance requirement in HTML5
as it is the only standardised method of suppressing incorrect table
semantics.

It is never a good idea to rely on screen reader heuristics.

--

Regards

SteveF
Current Standards Work @W3C
<http://www.paciellogroup.com/blog/2015/03/current-standards-work-at-w3c/>;

On 24 August 2017 at 08:09, Mark Rogers < <EMAIL REMOVED> > wrote:

> Without role=presentation or TH screen readers use heuristics to decide if
> a table is layout or data. The heuristics vary greatly between screen
> readers, so a table can be voiced as layout in one screen reader, but data
> in another.
>
> Data used by heuristics includes: number of rows, style of cell borders
> and row background, presence of form controls, embedded objects and nested
> tables. NVDA uses different heuristics if it's running with IE (where it
> uses NVDA's own heuristics) and Firefox (where it uses Firefox's
> layout-guess heuristic).
>
> JAWS 16 and earlier (and possibly recent versions) decide that a table
> with more than 2 cells and more than 2 rows with 4 cells between 200 and
> 16,000 square pixels is a data table. This is affected by factors unrelated
> to the table data such as browser window size and default browser font
> size. It also produces different results on IE (where it includes cell
> padding in size calculation) and Firefox (excludes cell padding from size
> calculation). If you have a table with width0% you can flip it between
> layout and data just by resizing the window.
>
> Basically without role=presentation or TH you have Schrödinger's layout
> table - it will be voiced as layout or data depending on a combination of
> screen reader, browser, window size and default font size.
>
> Best Regards
> Mark
>
> --
> Mark Rogers - <EMAIL REMOVED>
> PowerMapper Software Ltd - www.powermapper.com
> Registered in Scotland No 362274 Quartermile 2 Edinburgh EH3 9GL
>
>
>
> On 23/08/2017, 15:25, "WebAIM-Forum on behalf of Jonathan Avila" <
> <EMAIL REMOVED> on behalf of
> <EMAIL REMOVED> > wrote:
>
> > Let's also keep in mind that using role="presentation" is easy.
>
> While I think we'd all agree that it is best to use role presentation
> -- the question is whether it is a violation of WCAG. If table markup is
> not used with TH, scope or other header association markup then the table
> is not identifying header cells and it can be programmatically determined
> that the table is a layout table. Since WCAG 2 was written without relying
> on ARIA and was written before the ARIA spec was finalized -- the
> supporting document seem to indicate that it's not a failure of WCAG as
> long as not using role presentation is accessibility supported. However we
> don't have specific guidance on this and others are likely to disagree.
>
> Ideally these are the types of things that need to be clearly defined
> in supporting documents so we can achieve consistency with testing tools
> and with conformance evaluations. Questions such as this can be raised
> with the Accessibility Guidelines Working Group on Github (
> https://github.com/w3c/wcag/issues). If you feel strongly about
> something it might be helpful to put together a suggested failure technique
> -- although getting failure techniques accepted has been proven difficult.
>
> Jonathan
>
> Jonathan Avila
> Chief Accessibility Officer
> Level Access, inc. (formerly SSB BART Group, inc.)
> (703) 637-8957
> <EMAIL REMOVED>
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