RE: [CSS21] Issue 149 - px vs. pt

Zooming is not orthogonal when it is the result of simulating a viewport far larger than the device's own.
The author is the one who tells the device whether the content uses true units or not (using proprietary
conventions, it seems) and that, today at least, is what will make a given media query match or not.

If we mean to better address such scenarios by mapping units this way in CSS2.1 and adding new ones
for media queries, it would be nice to understand how it relates to common practice, what exact problems it addresses and solves etc.


________________________________
From: rocallahan@gmail.com [rocallahan@gmail.com] on behalf of Robert O'Callahan [robert@ocallahan.org]
Sent: Wednesday, June 30, 2010 10:17 PM
To: Sylvain Galineau
Cc: fantasai; www-style@w3.org
Subject: Re: [CSS21] Issue 149 - px vs. pt

On Thu, Jul 1, 2010 at 5:03 PM, Sylvain Galineau <sylvaing@microsoft.com<mailto:sylvaing@microsoft.com>> wrote:
There effectively are different viewports today. On an iPhone, a web page is told it renders on a viewport much larger than it physically is. That 1”
may turn into 1/10 of an inch until I zoom it up.

Zooming is an orthogonal issue. Assertions about the meaning of units are only true when the UA is not applying zooming. The ratio of two lengths should be independent of the zoom factor, but I'm not sure what else we can say.

Given this, if my home page has a stylesheet with a media query for (min-width: 254truemm) and another for (min-width:19”), what happens ? Should
they both match ?

"You could get any combination of results, depending on the device.

Rob
--
"He was pierced for our transgressions, he was crushed for our iniquities; the punishment that brought us peace was upon him, and by his wounds we are healed. We all, like sheep, have gone astray, each of us has turned to his own way; and the LORD has laid on him the iniquity of us all." [Isaiah 53:5-6]