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Re: [css3-values][css3-transforms] relative length in functional notation

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Wed, 11 Apr 2012 08:48:46 -0700
Message-ID: <CAAWBYDCk4Cz_W9y3Ytx3Sr9a-kv7KaS8h21JzafExJ_TTbW=DQ@mail.gmail.com>
To: "Kang-Hao (Kenny) Lu" <kennyluck@csail.mit.edu>
Cc: WWW Style <www-style@w3.org>
On Wed, Apr 11, 2012 at 7:04 AM, Kang-Hao (Kenny) Lu
<kennyluck@csail.mit.edu> wrote:
> The CSS3 V&U spec doesn't explicitly say whether relative units are
> calc() are resolved in inheritance time, and this, unfortuately, has
> already led to browser inconsistency. In the following test case,
>
> data:text/html,<!DOCTYPE html>
> <div style="background-color: blue; font-size: 2em;
>            width: calc(1em); height: 1em;
>             transform: translateX(1em);">
>  <div style="background-color: red; font-size: 0.5em;
>              width: inherit; height: 1em; transform: inherit">
>  </div>
> </div> (unprefixed)
>
> , Firefox14a but not IE9 resolves relative unit *in calc()*. Firefox14a,
> Operal12alpha and IE9 but not Chromium18 *don't* resolve relative unit
> in translateX(), matching Areyh's observation[1].
>
> (Given that Firefox does this inconsistently, I am interested in how
> WebKit implements -webkit-calc(). Unfortunately, I don't have WebKit
> nightly at hand.)
>
> If we still want to keep the "as specified, but with relative lengths
> converted into absolute lengths" convention, I think CSS3 V&U should say
> that loudly, and we might want to ping IE people as soon as possible
> becuase calc() is already unprefixed since IE9.

Yup, that's definitely an oversight.  We never want "X" and "calc(X)"
to have different behavior.


> == A Somehow Irrelevant Nitpick on attr() ==
>
> The spec now says
>
>  # The computed value of the ‘attr()’ expression is the value of the
>  # attribute with that name on the element, according to the rules
>  # given below.
>
> . This seems like a misuse of the term "computed value". For exmple, if
> the value of an attribute is an "1em" fed to 'attr(foo length)', it
> can't be a computed value because it is relative.
>
> I suggest we just s/computed value/value/ here.
>
> [1] https://www.w3.org/Bugs/Public/show_bug.cgi?id=15797

That doesn't help, it just defers the issue.  We need to do the same
thing here as with the calc() issue above.  (And similarly with the
url type.)

~TJ
Received on Wednesday, 11 April 2012 15:49:38 GMT

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