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Re: [css3-writing-modes] A report from a meeting w/Japanese publishing group

From: John Daggett <jdaggett@mozilla.com>
Date: Sun, 15 Jan 2012 20:13:36 -0800 (PST)
To: koba@antenna.co.jp
Cc: www-style@w3.org, MURATA Makoto <eb2m-mrt@asahi-net.or.jp>
Message-ID: <27c97cd3-04a4-47bf-9670-cf16ecaa7d86@zimbra1.shared.sjc1.mozilla.com>
Tokushige Kobayashi wrote:

> > 4. Currently, glyph selection is a function of the underlying font
> > engine (eg 'vert' gsub table in OpenType), not CSS (or Unicode)
> 
> Yes. The problem is some fonts do not supply such information as
> 'vert', but in the future there will appear more intelligent/good
> fonts.
> 
> > Is item 4 the problem under discussion in the blog post?
> 
> Partially, yes.
> 
> But my overall intention is different.
> 
> Unicode TR#4 tries to classify every characters into U, S, SB, T. I
> supose it is impossible to classify some characters to one class.
> For example, latin alphabet is U for 2.3.2.b.1-i fig. 24, but S for
> 2.3.2 b.1-ii fig.25.  

I think you've misunderstood the intent of UTR50, specifically the
East Asian Orientation property. It is *not* defining what "proper"
orientation is in all situtations, it is merely trying to define a
*default* orientation.  For use within CSS, the default orientation
will affect default rendering and hopefully will be close to what the
most common behavior is for Japanese text.  Authors will need to
override this by explicitly specifying sideways/upright in cases where
the default isn't what they want (i.e. wrapping these textruns in
spans styled with text-orientation: upright/sideways).  Having a
consistent default, rather than leaving it up to implementations to
define their own heuristics, is the goal of UTR50.

User agents, including the Webkit, IE, and the AH Formatter currently
make a decision at the codepoint level about this, in some cases using
"very heuristic methods" as you note.  The goal here is to have a
clear and well-defined default value for the orientation, one that
doesn't vary across implementations or fonts.

> But the issue is how to select a proper glyph shape and glyph
> metrics for each character in vertical writing mode.  CSS WG rejects
> modern font-technology, and trying to make a original mapping table.
> This may cause a serious issue in Japanese typesetting, may become a
> show stopper of EPUB in Japan.

You'll need to be more clear what you mean by "CSS WG rejects modern
font-technology".  I think you might have misunderstood how the
'upright-right' property value of the 'text-orientation' is intended
to work.  With this property value, characters by default have an
intrinsic orientation but authors can override this if the default is
not suitable for a given context.

For spans of Latin text, authors also have the choice of using
fullwidth Latin codepoints rather than the basic Latin codepoints,
since each will default to upright and sideways respectively.  This is
a legacy way of doing things but I'm sure there's content out there
that controls orientation this way.

The problems of defining default orientation clearly is another
example of why defining standards requires hard work in specifying small
details.  Without careful thought, implementations define what they
think best which results in different implementations defining
behavior that is not interoperable.  This is the source of the
distress that Koji is hearing from Kadokawa.

Regards,

John Daggett
Received on Monday, 16 January 2012 04:14:24 GMT

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