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Re: Seamless transclusion of complex replaced elements

From: Bert Bos <bert@w3.org>
Date: Wed, 20 Feb 2008 15:37:46 +0100
To: www-style@w3.org
Message-Id: <200802201537.46814.bert@w3.org>

On Wednesday 20 February 2008 13:09, Philip Taylor (Webmaster) wrote:
> Brad Kemper wrote:
> > Interesting. So this is really about auto-sizing iframes? For a
> > moment there, I thought it might mean cacheable snippets of html
> > text that could be inserted into the flow of a document. Something
> > like this:
> >
> > <div style="content: url(htmlSnippet.asp); height:auto;" />
>
> This I would not like : content slipping in through
> the back door of CSS.  Bert's proposal seemed far
> cleaner to me.

The current proposal for the 'content' property[1] in level 3 indeed 
allows the DIV in the example above to be turned into a "replaced 
element" and thus my feature request for a new height calculation 
applies to that example, too.

I didn't target IFRAME elements in particular. They are an old-fashioned 
way of transcluding content and haven't been part of HTML since HTML4. 
But if replaced elements in general can have a flexible height, then so 
should IFRAMEs.

Of course, inserting content via the style sheet is a feature that is 
easily abused. The rule of thumb is still that the document should be 
fully understandable without its style sheet. But it's not CSS's task 
to make dangerous things impossible; its task is to make useful things 
possible (and try to make the statistically most useful things easy).



[Slightly unrelated:]

Now that I'm in a philosophical mood: how about transcluding inline 
content?

The height feature I requested still assumed that a replaced element is 
a rectangle. The fact that replaced elements are rectangles is one of 
the reasons that math has to become an integral part of HTML, unlike 
PNG or SVG, which are handled fine as links: formulas, unlike images, 
are not single rectangles, but can be broken over several lines.

I think math is in general easier to handle if it is mixed in with the 
surrounding text, rather than linked. Formulas are often parts of a 
sentence ("if x > 0, then f(x) is even"). But assume that we want to 
transclude them anyway:

    If <em src="m1.mml">x &gt; 0</em>, then
      <em src="m2.mml">f(x)</em> is even.

How do I say in CSS that the replaced element is not a simple box, but a 
series of inline boxes with baselines and line break opportunities?


[1] http://www.w3.org/TR/2003/WD-css3-content-20030514/#content
    (There is much in that draft that is unlikely to end up in level 3,
    but the 'content' property and its url() value have so far survived
    all discussions in the working group, so I predict that it will
    stay.)



Bert
-- 
  Bert Bos                                ( W 3 C ) http://www.w3.org/
  http://www.w3.org/people/bos                               W3C/ERCIM
  bert@w3.org                             2004 Rt des Lucioles / BP 93
  +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France
Received on Wednesday, 20 February 2008 14:37:57 GMT

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