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

On Oct 26, 2011, at 9:46 , Brian Blakely wrote:

> 10pt text is unreadable on a monitor at TV-distance viewing, and is excessively large on a hand-held device with a high-res screen capable of displaying crisp text at smaller sizes.
> 
> 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).  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.

But it's the reverse. Your hypothesis seems to be that when a new device comes along, for which some kind of adaptation is beneficial, everyone will magically revise their web sites to handle it.  Actually, the converse is what happens; the manufacturer of that device wants to make sure the existing world-wide web 'works satisfactorily' on that device, and does the adaptation.

I don't believe that most sites will try to adapt, and I even doubt that those that try will always 'get it right'.

And there is a major hole in 'absolute lengths' in knowing on what surface (physical or virtual) they are measured.  When printing, it's usually on the surface of the paper.  For projection spectacles, it's probably a virtual surface at some convenient focus distance, and so on.


> We can make all kinds of accurate assumptions in this way.  A 3"-wide screen is probably a touchscreen phone and should have big, finger-friendly UI elements (we can enhance this prediction by detecting touch events).
> 
> You make a case by mentioning a far-future technology like wall screens that are feasibly 10 or more feet wide, but the same case could be made for non-rectangular or holographic displays to undermine anything in CSS.  The supposition that subtended units are more useful for the lion's share of actual web design simply isn't true.  I wouldn't debate their utility, but I think the goal for units like "cm" should be to abolish old ambiguities, not introduce a new one.
> 
> -Brian
> 

David Singer
Multimedia and Software Standards, Apple Inc.