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Re: Clarification on normative glossary definition of "Large scale (text)"

From: Patrick H. Lauke <redux@splintered.co.uk>
Date: Tue, 07 Oct 2014 08:51:18 +0100
Message-ID: <54339B76.5080601@splintered.co.uk>
To: IG - WAI Interest Group List list <w3c-wai-ig@w3.org>
On 07/10/2014 03:48, CAE-Vanderhe wrote:
> The WCAG definition covers the issues quite well.  The issues raised
> in these various posts was considered in creating the SC and the
> definitions.
> The goal is to have text be larger than typical font.    The size
> that a font appears to the user is dependent on lots of things - like
> zoom of browser, pixel density of the display, scaling (some displays
> like the retina) do not render a pixel as one pixel on the display,
> viewing distance, etc — all of which are outside of the control of
> the author — so it is meaningless to have an accessibility guideline
> for web authors that requires that the user see the font in a
> particular size, or angle subtended.
> So the guidelines were written to talk about minimum RELATIVE size of
> the font.   If the font is relatively larger — and the user does not
> use a screen resolution that is too dense — it all works out.

So basically, the 18point/14point values are anchored on the assumption 
that 1em is set to the default UA text size *and* is readable.

If an author set the base font size on HTML/BODY to be something far too 
small, like 0.5em, would text which is then later defined to be 1.5em 
still count as large scale, as it is large relative to the base font 
size? So "large text" would simply mean "larger by at least a factor of 
1.5 compared to the base font"? If so, this part is confusing

"The point size should be obtained from the user agent, or calculated 
based on font metrics as the user agent does, when evaluating this 
success criterion."

as in the scenario above, the calculated pt size would end up being 9pt, 
*but* it would still be 1.5x the size of the base font.

In short, are the values of 18pt/14pt anchored to the CSS pixel size 
(regardless of whether it's actually close to the reference pixel 
dimensions or not, leaving out any issues of viewport), or are they used 
as an indication of relative size, in which case it would be more 
appropriate to basically say that ("text that is 1.5x the size of the 
base font size, or 1.2x the size and bold").

Patrick H. Lauke

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Received on Tuesday, 7 October 2014 07:51:41 UTC

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