W3C home > Mailing lists > Public > www-style@w3.org > October 2012

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

From: Kenneth Rohde Christiansen <kenneth.christiansen@gmail.com>
Date: Sun, 21 Oct 2012 16:36:09 +0200
Message-ID: <CAEC208ueiEJv83ky0vcvz6KP6pkOYXotBuBG7ELP5bvCNGO9ew@mail.gmail.com>
To: Simon Sapin <simon.sapin@kozea.fr>
Cc: "www-style@w3.org list" <www-style@w3.org>
The first iPhone (and many later phones) shipped with a DPI of 160,
which is what most mobile web apps have been optimized for.

The iPhone 4, shipped with a DPI of 320 (retina display) and a
device-pixel-ratio == 2.0, meaning that one CSS unit is defined at 160
DPI still.

A bit of background:

http://www.quirksmode.org/blog/archives/2012/06/devicepixelrati.html
http://www.quirksmode.org/blog/archives/2012/07/more_about_devi.html
http://www.rictus.com/muchado/wp-content/uploads/2011/04/multiscreen-dev-with-flex-360flex-2011.pptx.pdf
http://web.archiveorange.com/archive/v/OOYmTvfzzo75fCpH6kHs

Cheers
Kenneth

On Sun, Oct 21, 2012 at 2:25 PM, Simon Sapin <simon.sapin@kozea.fr> wrote:
> 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
>



-- 
Kenneth Rohde Christiansen
Senior Engineer, WebKit, Qt, EFL
Phone  +45 4093 0598 / E-mail kenneth at webkit.org

﹆﹆﹆
Received on Sunday, 21 October 2012 14:36:57 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 17:21:01 GMT