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

RE: Behavior of device-pixel-ratio under zoom

From: Sylvain Galineau <sylvaing@microsoft.com>
Date: Tue, 13 Nov 2012 01:32:08 +0000
To: "robert@ocallahan.org" <robert@ocallahan.org>
CC: www-style <www-style@w3.org>
Message-ID: <3C4041FF83E1E04A986B6DC50F0178291BE68D67@TK5EX14MBXC221.redmond.corp.microsoft.com>

[Robert O'Callahan:]
>I agree with David and Rune, if that wasn't already clear.

>>On Sun, Nov 11, 2012 at 7:13 PM, Simon Fraser <smfr@me.com> wrote:
>>We (Apple) feel quite strongly that device-pixel-ratio, like window.devicePixelRatio,
>>should not change under zoom. It's answering a question about the device hardware,
>>not the current zoom state of the page.

>>I think in general authors should not be able to directly affect the layout of the page
>>under different zoom levels. Zooming should shouldn't have unsurprising side effects
>>for the user.

>For years Firefox has supported a zoom mode that does relayout the page (by changing the viewport size in CSS pixels). I believe >Safari has supported something similar.

>I'm asking whether *that* kind of zoom should affect devicePixelRatio and device-pixel-ratio.

Fwiw this is what IE has done since IE8. Our default zoom resizes the viewport and affects the 
screen.deviceXDPI property; thus a top-level width:50% computes to a different value at each zoom level. 
In Windows 8 optical zoom - what Rune refers to as a magnifying glass, or the default zooming mode on
smartphones - has no effect on deviceXDPI or used length resolution i.e. it's treated as a display 

Received on Tuesday, 13 November 2012 01:33:24 UTC

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