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Re: [css3-text-layout] New editor's draft - margin-before/after/start/end etc.

From: Håkon Wium Lie <howcome@opera.com>
Date: Tue, 1 Jun 2010 09:59:01 +0200
Message-ID: <19460.48581.51213.923444@gargle.gargle.HOWL>
To: "L. David Baron" <dbaron@dbaron.org>
Cc: MURAKAMI Shinyu <murakami@antenna.co.jp>, Boris Zbarsky <bzbarsky@MIT.EDU>, David Hyatt <hyatt@apple.com>, www-style list <www-style@w3.org>
Also sprach L. David Baron:

 > So, really, it's 90 new properties (the 18 new above, but for
 > margin, padding, border-style, border-width, and border-color), or
 > perhaps 130, if you also count new shorthands separately.


 > I'd also note that there are two different proposals for how the
 > cascading of logical + physical properties should work.  My original
 > proposal was:
 >   http://lists.w3.org/Archives/Public/www-style/2002Sep/0049.html

Note the term "property glut" :)

 > which is quite similar to what is implemented in Mozilla (for -start
 > and -end properties):
 >   https://bugzilla.mozilla.org/show_bug.cgi?id=74880
 > Elika had a different proposal here:
 >   http://lists.w3.org/Archives/Public/www-style/2006Jun/0084.html

The current draft [1] seems to sketch a simpler model where:

  - the properties are not real properies but aliases for existing
    properties (although they are referred to as "logical properties";
    this should probably be changed to "direction-dependent aliases"
    (DDAs) or something, I'll use that term here)

  - DDAs are mapped to their respective properties as soon as the
    computed value of 'writing-mode' is known; thereafter DDAs --
    their values and existence -- can be forgotton

  - there is no DOM access to DDAs (I hope, the draft doesn't say)

This undertanding is supported by [2]:

 > For UAs supporting only horizontal writing, *-before, *-after,
 > logical-width and logical-height are simply aliases of *-top, *-bottom,
 > width and height respectively. No costs needed.

>From this, however, it is unclear if the properties turn into "real
properties" when/if vertical writing is supported.

A clarification on this would be helpful in assessing the
cost/benefits of DDAs vs other proposals.

[1] http://dev.w3.org/csswg/css3-text-layout/
[2] http://lists.w3.org/Archives/Public/www-style/2010May/0563.html


              Håkon Wium Lie                          CTO °þe®ª
howcome@opera.com                  http://people.opera.com/howcome
Received on Tuesday, 1 June 2010 07:59:56 UTC

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