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Re: [css3-2d-transforms][css3-images] <position> grammar is duplicated or points to the wrong spec

From: L. David Baron <dbaron@dbaron.org>
Date: Thu, 2 Feb 2012 18:38:04 +0100
To: Aryeh Gregor <ayg@aryeh.name>
Cc: "Tab Atkins Jr." <jackalmage@gmail.com>, Brad Kemper <brad.kemper@gmail.com>, Brian Manthos <brianman@microsoft.com>, Sylvain Galineau <sylvaing@microsoft.com>, www-style list <www-style@w3.org>, fantasai <fantasai@inkedblade.net>
Message-ID: <20120202173804.GA5344@pickering.dbaron.org>
On Thursday 2012-02-02 12:19 -0500, Aryeh Gregor wrote:
> On Thu, Feb 2, 2012 at 5:23 AM, Tab Atkins Jr. <jackalmage@gmail.com> wrote:
> > I don't understand how this would accomplish what you want.  Assume
> > that the font-size was originally 15px, so this resolves to .2em. Then
> > the element changes to font-size:30px.  This then resolves to .1em,
> > *not* to 6px like I think you want.  If you were counting on this to
> > work with inheritance, ems are never inherited - they get computed
> > into px (this is why line-height can be specified with a <number> as
> > well).
> 
> ems are inherited in transforms:
> 
> data:text/html,<!doctype html>
> <div style="font-size:0;transform:translate(5em)">
> <div style="height:100px;width:100px;background:red;
> font-size:20px;transform:inherit">Translated</div></div>
> 
> The div is translated in IE10 Developer Preview, Firefox 13.0a1, and
> Opera Next 12.00 alpha, although not in Chrome 18 dev.  (Make sure to
> prefix 'transform' appropriately.)  Whether this makes any sense is
> perhaps debatable, but it's what most browsers do, and also what the
> spec said until quite recently -- Computed value: As specified
> (https://www.w3.org/Bugs/Public/show_bug.cgi?id=15797).

This is true in Firefox only since we implemented 3-D transforms,
which required changing transforms to have a computed value that is
actually stored as a list, in order to handle the interaction of
percentage translations with other transforms.

I think I missed that it would change this behavior, and we probably
could change it easily to compute lengths up front.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Thursday, 2 February 2012 17:38:36 GMT

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