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Re: px-based fonts

From: Felix Miata <mrmazda@earthlink.net>
Date: Tue, 18 Jan 2011 20:26:11 -0500
Message-ID: <4D363DB3.9070207@earthlink.net>
To: w3c-wai-ig@w3.org
On 2011/01/18 19:55 (GMT-0500) Jennison Mark Asuncion composed:

> In the two checkpoints below, WCAG 2.0 refers to pt-based fonts (14pt and
> 18pt).  Is there a set of equivalent px-based fonts that can be used
> instead?
>    *        1.4.3 Contrast (Minimum): The visual presentation of text and
>    images of text has a contrast ratio of at least 4.5:1, except for the
>    following: (Level AA)
>    *        1.4.6 Contrast (Enhanced): The visual presentation of text and
>    images of text has a contrast ratio of at least 7:1, except for the
>    following: (Level AAA)

I have to believe these refer to real 14pt and 18pt sizes, not logical pt 
sizes on display screens. Device pixels are units of size that varies 
considerably according to display device pixel density[1]. CSS (logical) 
pixels (which in latest spec proposals bear a 4:3 ratio to logical pt) though 
defined as though they could be a known physical size, as practical matter 
also vary in actual size widely. Either pixel size would constitute a poor 
way to inform authors of a threshold size compared to using a real physical 
dimension such as pt.

That use of px sizing for text is given very short shrift in WCAG is one of 
if not its greatest shortcomings. Sizing text in px completely disregards 
user preferences and requirements, and is thus rude and rarely advisable.

[1] http://fm.no-ip.com/Auth/Font/fonts-pt2px.html
-- 
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Felix Miata  ***  http://fm.no-ip.com/
Received on Wednesday, 19 January 2011 01:26:34 GMT

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