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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, 26 Oct 2011 13:04:03 -0400
Message-ID: <4EA83D83.6010003@mit.edu>
To: www-style@w3.org
On 10/26/11 12:47 PM, Brian Blakely wrote:
> David, this is exactly why factual physical units are really, really
> important and useful.  A screen that will be viewed at TV-distance is
> likely a large display (e.g. a TV).

Yes, but the converse is not true.  A large display per se tells you 
absolutely nothing about distance.  Maybe it's a TV to be viewed from 18 
feet, and maybe it's a wall-mounted touchscreen for a game (these are 
starting to appear in airports).  You just don't know.

> In this situation, media queries
> would make said text larger as we can safely make this assumption
> (larger screen, larger distance) in nearly all cases.

I think this assumption is unsafe and will continue to become _more_ unsafe.

And the point is, the "px" unit already handles this sort of scaling for 
you.  That's its purpose in life in CSS.  You don't have to do media 
queries to get it....

> We can make all kinds of accurate assumptions in this way.  A 3"-wide
> screen is probably a touchscreen phone

Or a portable car GPS system, which gets used at a totally different 
viewing distance than a phone does.  The device knows this; you do not.

> You make a case by mentioning a far-future technology like wall screens
> that are feasibly 10 or more feet wide

This is not far-future.  This is now.  See the game thing above; on a 
recent trip I encountered just such a game (at either Logan or National 
airport; can't recall which) which involved a touch screen about 10' by 
6' where you try to control electricity consumption in a building by 
touching vacated rooms to turn off lights, etc.

-Boris
Received on Wednesday, 26 October 2011 17:04:41 GMT

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