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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, 8 Jun 2010 09:16:02 +0200
Message-ID: <19469.60978.621066.366011@gargle.gargle.HOWL>
To: MURAKAMI Shinyu <murakami@antenna.co.jp>
Cc: Hakon Wium Lie <howcome@opera.com>, "Tab Atkins Jr." <jackalmage@gmail.com>, John Daggett <jdaggett@mozilla.com>, Boris Zbarsky <bzbarsky@mit.edu>, www-style list <www-style@w3.org>
Also sprach MURAKAMI Shinyu:

 > > Let's try to get an overview of the various proposals.

 > > 1) direction-dependent aliases: introduce aliases for properties with
 > > 2) duplicate sets of properties: two parallel sets of properties
 > > 3) pseudo-classes: introduce pseudo-classes to select elements based on @dir
 > > 4) media queries: like 3), except that media queries are used instead
 > > 5) alternate style sheets: put the rules for the various writing modes

 > The 3), 4) or 5) cannot solve all cases: 
 > - cannot use in inline style attributes, e.g. style="margin-left: 2em"

That's correct, you wouldn't be able to mirror a value set in the
style attribute. Unless we add selectors to the style attribute.

 > - cannot write basic default stylesheet.
 >   for example, in CSS2.1 Appendix D. Default style sheet for HTML 4:
 > 
 >     h1              { font-size: 2em; margin: .67em 0 }
 >     h2              { font-size: 1.5em; margin: .75em 0 }
 >     h3              { font-size: 1.17em; margin: .83em 0 }
 >     h4, p, blockquote, ul, fieldset, form, ol, dl, dir,
 >     menu            { margin: 1.12em 0 }
 >     blockquote      { margin-left: 40px; margin-right: 40px }
 >     ol, ul, dir,
 >     menu, dd        { margin-left: 40px }

You can use 3) and 4) to write a default style sheet. E.g.:

  h1:lrt, h1:rtl { font-size: 2em; margin: .67em 0 }
  h1:ttb { font-size: 2em; margin: 0 .67em }

For 5), you would need several files.

 > This only works when writing-mode is lr-tb. If MQ can be used as:
 >     @media (dir: ltr) {
 >       ...
 >     }
 >     @media (dir: rtl) {
 >       ...
 >     }
 >     @media (dir: ttb) {
 >       ...
 >     }
 > 
 > it doesn't work when both horizontal and vertical writing modes are
 > used in same page.

Not if we use these defintions:

  dir:lrt   horizontal writing is supported and @dir has been set to 'lrt'
  dir:rtl   horizontal writing is supported and @dir has been set to 'rtl'
  dir:ttb   vertial writing is supported and the initial value of
            'writing-mode' is 'tb-rl'

Then you could do:

  @media (dir: ttb) {
     ...
     table { 
       writing-mode: lr-tb;
       ...
     }
  }

That is, you can have horizontal content even if the intial value of
'writing-mode' is 'tb-rl'.

 > MS IE supports many writing modes (total 8 writing modes, see:
 > http://blogs.msdn.com/b/ie/archive/2009/05/29/the-css-corner-writing-mode.aspx )
 > and seems to have good default style sheet, works in all
 > writing modes,
 > 
 > I suspect that IE has logical properties internally and
 > its default style sheet is written with that.
 > 
 > It shows that the capability of CSS is very limited without 
 > logical properties.

That doesn't follow. If fact, proposal 3), 4) and 5) have greater
expressive power than 1) or 2) as they don't simply mirror values on a
limited set of properties, but can set arbitrary values on all
properties.

 > I don't believe the logical properties will be widely implemented
 > in short-term (possibly only implemented as epub book readers for
 > Japanese and Chinese contents), but I believe the CSS standards
 > must be defined for the future.

Indeed. 

 > Håkon said in Tokyo last month, I was very impressed:
 >   How long will the web last? -- 500 years!

Right -- anyone want to bet against? :)

 > It means the invention of the web, inlcuding HTML and CSS,
 > can compare with the Gutenberg's invention 500 years ago.
 > 
 > I think the cost for implementations will not be big problem
 > in such future.

Memory and battery will still be constraints in our lifetime. I
believe that the emerging e-book manufacturers in Asia agree with me.

More importantly, perhaps, is the greater expressive power that 3), 4)
and 5) has. Which is why you want one of them, I presume:

 > I want 1) or 2), plus 3), 4) or 5), as I wrote:
 > http://lists.w3.org/Archives/Public/www-style/2010Jun/0162.html

Personally, I think adding two mechanisms is too much.

Cheers,

-h&kon
              Håkon Wium Lie                          CTO °þe®ª
howcome@opera.com                  http://people.opera.com/howcome
Received on Tuesday, 8 June 2010 07:17:01 GMT

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