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Re: pixel densities, text sizing (was Re: Accessible college websites)

From: Patrick H. Lauke <redux@splintered.co.uk>
Date: Thu, 08 May 2014 02:45:39 +0100
Message-ID: <536AE1C3.8030600@splintered.co.uk>
To: w3c-wai-ig@w3.org
On 08/05/2014 02:06, Patrick H. Lauke wrote:

> http://i.imgur.com/q76abmy.jpg
>
> MacBook Pro with Retina display on the left, MacBook Pro with non-Retina
> on the right. At same viewing distance all the text looks exactly the
> same size...because the OS compensates for the higher pixel density. So
> your example screenshots don't actually reflect the reality in this
> particular case.
>
> In fact, this is consistent with the reference px definition: at the
> same viewing distance, the CSS reference pixel dimension needs to remain
> the same, regardless of actual physical device pixels. If I follow the
> rationale of your viewing instructions, you seem to imply that a viewer
> should adapt their viewing distance in order to keep the ratio of the
> dimension of a *physical* pixel and the viewing distance constant,
> whereas the CSS px reference definition is based on the ratio of the
> dimension of a *CSS* pixel and the viewing distance. For the same
> type/class of device, with same screen size, I should not adjust my
> viewing distance at all...it's the OS that needs to adjust its mapping
> of CSS pixels to physical pixels.

And yes, in trying to further understand the rationale of your 
alternative viewing option instructions, I see where the problem 
lies...the difference between the "new" CSS lengths definition (where a 
"CSS" inch, cm, pt etc  is anchored on the size of the reference pixel) 
and the old one (where an inch, cm, pt etc would map to a real-world, 
physical inch).

http://lists.w3.org/Archives/Public/www-style/2014Jan/0213.html

As the reality outside of KDE/KHTML seems to be that of the "new" 
definition, I'm not sure there will be a common ground here to argue one 
way or the other, as we'd be comparing apples (and windows) to oranges. 
(Sure, we *could* argue that KDE is right and all other OSs are 
wrong...though that's probably a discussion to be had back on the W3C 
Style list)

P
-- 
Patrick H. Lauke

www.splintered.co.uk | https://github.com/patrickhlauke
http://flickr.com/photos/redux/ | http://redux.deviantart.com
twitter: @patrick_h_lauke | skype: patrick_h_lauke
Received on Thursday, 8 May 2014 01:46:02 UTC

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