2013-11-10 19:36, Markus Ernst wrote:
Having a look at the proposal, and reading the thread especially with
regard to complexity and verbosity, I got the impression that @src-n
shares a main objection with @srcset and <picture>, that it mixes up
content and design to some extent.
That would be my main concern, too. But I would rather say that it
really mixes up content and presentation, moving to HTML something that
belongs to the scope of styling and can currently be handled in CSS.
Thus I suggest a modified approach which moves the distinction of
viewing situations, or breakpoints, to the head of the document,
creating some variable-like references to be used instead of numbers.
Some kind of src-var instead of src-N. Therefore, a new element for the
head would be necessary; I call it <situations>, it could also be
<breakpoints> or whatever is considered more appropriate:
Adding new elements is questionable, especially if they have content
(which would be rendered as-is by current user agents).
<head>
<situations>
small: (max-width: 400px);
small2x: (max-width: 400px) 2x;
medium: (max-width: 1000px);
medium2x: (max-width: 1000px) 2x; and
large2x: (min-width: 1000.01px) 2x;
</situations>
</head>
<body>
<img src-small="pic-small.jpg"
src-small2x="pic-medium.jpg"
src-medium="pic-medium.jpg"
src-medium2x="pic-large.jpg"
src-large2x="pic-x-large.jpg"
src="pic-large.jpg"
alt="Obama talking to a soldier in hospital scrubs.">
This, too, would mix content and presentation. Admittedly, the line
between them isn't always crystal clear, even if most of HTML5 pretends
that it is. But here the approach should let an author specify an img
element in markup and separately specify, in a style sheet language,
that in some cases the src attribute value is to be overridden.
If people think that current CSS media queries are inadequate for the
purpose (and I'm not convinced that they are), then the first question
should be whether CSS can be suitably enhanced. Failing that, it would
seem natural to define a new, restricted style language. Something like
this:
<style type="text/is">
@media(max-width: 400px) { #pic { src: url(pic-small.jpg); } }
...
</style>
...
<img id=pic src="pic-large.jpg" alt=""
title="Obama talking to a soldier in hospital scrubs.">
If the problem with current CSS approach is that browsers would still
download the resource pointed to by the src attribute, then the
processing of IS (image styling) style sheets could be defined so that
they are evaluated when encountered and they are applied according to
the browsing situation, so that they will take effect when the <img>
elements are processed. This would be no more adhockery than src-*
attributes would be. Actually, less.
Yucca
