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Re: Success criteria 1.4.4

From: Gregg Vanderheiden <gv@trace.wisc.edu>
Date: Sun, 30 Oct 2011 10:19:27 -0500
To: Ramón Corominas <listas@ramoncorominas.com>
Cc: "w3c-wai-ig@w3.org" <w3c-wai-ig@w3.org>
Message-id: <296B794B-BAF4-455C-A0C6-BEADA663874B@trace.wisc.edu>
The intent of the WCAG WG (as reflected in the WCAG documents) was that 200% was the same as 200% in browsers or in font size in points --- meaning 200% of height - not area. 

Thank you for pointing out the "firefox" reference that did not include a version number.   We will add one  - since FF clearly does have zoom now.   (and the reference never should have been put in there without a version number).   We will have to check for others. 


Gregg Vanderheiden Ph.D.
Director Trace R&D Center
Professor Industrial & Systems Engineering
and Biomedical Engineering
University of Wisconsin-Madison

Co-Director, Raising the Floor - International
and the Global Public Inclusive Infrastructure Project
http://Raisingthefloor.org   ---   http://GPII.net

On Oct 30, 2011, at 8:38 AM, Ramón Corominas wrote:

> Hi all!
> While re-reading this thread, I noticed this sentence from Felix:
> "One need only raise the size of a 16px font to about 22.4px to get a doubling of size. A doubling of a CSS "size" produces an nominal _size_ increase of 400%."
> This seems to consider "size" as the *area* of the block of text, which would imply that an "increase of 200%" means "original font-height * sqrt(2)"; but according to the Understanding SC 1.4.4 document:
> "Content satisfies the Success Criterion if it can be scaled up to 200%, that is, up to twice the width and height."
> I've always interpreted that 200% means "original font-size * 2", but some customers use the "area" argument to reduce the impact of this requirement on their CSS, because "size" is not explicitly defined in the WCAG's main document.
> On the other hand, the Understanding document also says:
> "The author cannot rely on the user agent to satisfy this Success Criterion for HTML content if users do not have access to a user agent with zoom support. For example, if they work in an environment that requires them to use IE 6 or Firefox."
> This may suggest that, for a *global* scenario (where we cannot guarantee what UA is used), using absolute units for text size can be considered a failure of SC 1.4.4. But then it would be very easy for the WAI WG to include a Common Failure in the Techniques document saying that absolute units are not valid.
> I've alwayd interpreted that the absence of such faikure in WCAG 2.0 means that absolute units are not strictly prohibited, unless they cause overlapping/hidden content (F69, for example).
> My concern is that, if I consider the Understanding as an "informative only" document, then the 200% is still subject to interpretation; but if I consider the 200% definition in the Understanding as *the* -mandatory- definition, then the absolute units shoukd also be considered as a direct failure.
> What do you think?
> Regards,
> Ramón.
> Felix wrote:
>> One need only raise the size of a 16px font to about 22.4px to get a doubling of size. A doubling of a CSS "size" produces an nominal _size_ increase of 400%.
Received on Sunday, 30 October 2011 15:20:18 UTC

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