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Re: User Agents Do Not Implement Absolute Length Units, Places Responsive Design in Jeopardy

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Wed, 05 Oct 2011 17:41:51 -0400
Message-ID: <4E8CCF1F.2070907@mit.edu>
To: Brian Blakely <anewpage.media@gmail.com>
CC: www-style@w3.org
On 10/5/11 5:28 PM, Brian Blakely wrote:
> When the screen is 50ft+ wide (jumbotron), text that would normally
> comprise 8% of the screen height (living room TV or 15" laptop) would
> now comprise 40% of the screen height to maintain legibility throughout
> the expected setting (stadium).

That's just because the angular size is highly variable in a stadium, 
not because the jumbotron is big....  that is, it's a property of the 
viewing locations, not of the screen itself.

> How would this situation be better-handled by angular size?

The jumbotron case is pretty tough precisely because the angular size is 
variable for different viewers.  There's no good way to express that in 
CSS right now.  But using "big screen" as a proxy for "the viewers are 
scattered over a very large area" may not be a good assumption either.

> For that matter, how would a UA and the hardware it runs on gather angular size
> data to be transponded to the author?

Right now, a particular hardware setup makes assumptions about angular 
size information (e.g phones assume they're held at reading distance; 
computers assume they're held typing distance, etc).

In fact, they have to, given the definition of "px" in CSS.

-Boris
Received on Wednesday, 5 October 2011 21:42:21 GMT

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