2011-11-21 11:34, Simon Pieters wrote:
On Mon, 21 Nov 2011 09:47:52 +0100, Jukka K. Korpela
<[email protected]> wrote:
Or am I missing something?
http://www.whatwg.org/specs/web-apps/current-work/multipage/rendering.html#dimRendering
This is rather confusing, but I'll try to understand what it says there.
It seems to say that for <img ... width="25%"> (though this is
disallowed in HTML5), the width attribute value "maps to" the "dimension
property" width, and this in turn is defined to mean that the value is
parsed by a routine that accepts the percent sign. Then the browser "is
expected to" use the parsed value 25% "for a presentational hint" for
the property.
This sounds like a complicated way of saying a simple thing, but I
suppose there are reasons to say things that way. But then comes the
concept of "presentational hint":
"Some rules are intended for the author-level zero-specificity
presentational hints part of the CSS cascade; these are explicitly
called out as presentational hints."
I had to read this a few times to get a grasp of it.
The definition of "presentational hint" is somewhat implicit but seems
to refer to "Precedence of non-CSS presentational hints" in the CSS 2.1
spec at http://www.w3.org/TR/CSS2/cascade.html#preshint
It might be useful to formulate the rules more explicitly, saying, for
example, that width and height attributes are mapped to presentational
hints in the sense defined in CSS 2.1 if the value matches certain rules
(and presumably ignored otherwise). But this might not be the intent, as
in the current wording, there's the "is expected to" formulation, which
is not at all the same as "is required to" or "shall".
--
Yucca, http://www.cs.tut.fi/~jkorpela/
