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Logical property *values* (Re: [css3-text-layout] New editor's draft - margin-before/after/start/end etc.)

From: L. David Baron <dbaron@dbaron.org>
Date: Mon, 31 May 2010 20:28:19 -0700
To: MURAKAMI Shinyu <murakami@antenna.co.jp>
Cc: www-style@w3.org
Message-ID: <20100601032819.GA5099@pickering.dbaron.org>
On Wednesday 2010-04-28 19:57 +0900, MURAKAMI Shinyu wrote:
> CSS Text Layout Module Level 3
> Editor's Draft 25 April 2010
> http://dev.w3.org/csswg/css3-text-layout/

> - Logical property values: before, after, start, end

The section on logical property values says that the logical values
are added to four properties:  'float', 'clear',
'background-position', and 'text-align'.

I think the draft should really discuss these properties in two
separate groups.

In the first group, 'float', 'clear', and 'text-align', the only
values that make sense are those equivalent to 'start' and 'end'.
So the draft should propose adding 'start' and 'end' values, but
should also say what the 'left' and 'right' values do when block
progression is horizontal.  (Though there have been various
proposals for additional values of float that might get in the way
here.)

The 'background-position' property is rather different from the
others, since it supports all directions, and its syntax has a
significant number of other constraints.  (The 'transform-origin'
property in 2-D transforms (but not 3-D) also has the same syntax.)
A draft proposing to modify 'background-position' should define the
interpretation of the values, and which values are allowed.  (For
example, it should say that 'top start' is a syntax error, even
though it makes sense in lr-tb or rl-tb writing modes.  Likewise, it
should say what '50% start' means.)  But I think, really, more needs
to be done; see
http://lists.w3.org/Archives/Public/www-style/2008Dec/0147.html
It's possible Elika had a proposal related to some of this that goes
beyond what's in css3-background.

-David

-- 
L. David Baron                                 http://dbaron.org/
Mozilla Corporation                       http://www.mozilla.com/
Received on Tuesday, 1 June 2010 03:28:50 GMT

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