- From: Kenneth Rohde Christiansen <kenneth.christiansen@gmail.com>
- Date: Sun, 21 Oct 2012 16:36:09 +0200
- 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 UTC