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Re: [css3-mediaqueries] (min-resolution: 0dpi) is false in several browsers.

From: Simon Sapin <simon.sapin@kozea.fr>
Date: Sun, 21 Oct 2012 14:25:38 +0200
Message-ID: <5083E9C2.7060002@kozea.fr>
To: Kenneth Rohde Christiansen <kenneth.r.christiansen@intel.com>
CC: "www-style@w3.org list" <www-style@w3.org>
Le 21/10/2012 14:06, Kenneth Rohde Christiansen a écrit :
> Then that is very different from the device-pixel-ratio it is supposed
> to replace, as device-pixel-ratio: 1 on iOS etc corresponds to a DPI
> of 160, and 2 to a DPI of the double.

Where is this 160 number coming from? By "a DPI of 160", do you mean 
device pixels per physical inch on a particular device?

The CSS dpi unit is not the same, it is in device pixels per CSS inch. A 
CSS inch is always 96 CSS pixels.


About device-pixel-ratio, what is it’s exact definition? I couldn’t find 
it. Apparently it ways supposed to be documented in [1] but according to 
archive.org is never was.

The best hint I found is in a Mozilla bug[2]:

> It looks like Webkit's 'ratio' is the number of device pixels per CSS pixel.


There is also a CSSWG blog post[3] suggesting that eg.
(-webkit-device-pixel-ratio: 2) is exactly the same as
(resolution: 192dpi)


[1] http://webkit.org/specs/MediaQueriesExtensions.html
[2] https://bugzilla.mozilla.org/show_bug.cgi?id=474356#c6
[3] 
http://www.w3.org/blog/CSS/2012/06/14/unprefix-webkit-device-pixel-ratio/


-- 
Simon Sapin
Received on Sunday, 21 October 2012 12:26:12 GMT

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