[whatwg] Simplified <picture> element draft

Tue Jan 7 12:06:51 PST 2014

On 1/7/14 2:24 PM, Ian Hickson wrote:
> It's probably just a matter of saying, in the rendering section, that nested browsing contexts that
> aren't _being_rendered_ (or that are <frame>s outside <frameset>s) get a
> 0x0 viewport.

That doesn't seem unreasonable.

> (Viewports that are being rendered seem to have an
> unambiguous dimension

Actually, nothing defines this either.  It should be the content box of 
the <iframe>, assuming iframes can't get fragmented.  If they can be 
fragmented, I have no idea.

> Right now, Chrome and Firefox seem to report 0 as the body.offsetWidth for
> a hidden iframe. (Couldn't get a result for Safari; don't have IE here.)
>
>     http://software.hixie.ch/utilities/js/live-dom-viewer/saved/2725
>     For Chrome (since it puts data: in the wrong origin)
>
>     http://software.hixie.ch/utilities/js/live-dom-viewer/saved/2726
>     For Firefox (since for some reason the message in 2725 isn't sent?)
>
> Can you elaborate on the widly different things? What should I be testing?

How about this testcase:

<!DOCTYPE html>
<style>
   div { color: purple; }
</style>
<link rel="stylesheet" href="data:text/css,%23one { color: yellow; }"
       media="(min-width: 300px)">
<link rel="stylesheet" href="data:text/css,%23two { color: yellow; }"
       media="(max-width: 300px)">
<div id="one"></div>
<div id="two"></div>
<script>
   window.onload = function() {
     alert(getComputedStyle(document.getElementById("one"), "").color +
           " | " +
           getComputedStyle(document.getElementById("two"), "").color);
   }
</script>

and variants on it.  From my testing, in a display:none iframe:

1)  Presto-based Opera treats the viewport width as 300px for purposes 
of the media queries and reports a document.body.offsetWidth of 0.

2)  Blink and WebKit both seems to treat the viewport width as 0 when 
measured using either method.

3)  Gecko doesn't allow creation of computed style objects in an iframe 
that's not being rendered and reports a document.body.offsetWidth of 0.

4)  IE11 seems to do what Blink/WebKit do.

-Boris