W3C home > Mailing lists > Public > www-style@w3.org > August 2011

Re: [css3-writing-modes] "vert" OpenType feature tag and glyph orientation

From: John Daggett <jdaggett@mozilla.com>
Date: Fri, 12 Aug 2011 00:53:41 -0700 (PDT)
To: Koji Ishii <kojiishi@gluesoft.co.jp>
Cc: www-style@w3.org
Message-ID: <333128295.169614.1313135621719.JavaMail.root@zimbra1.shared.sjc1.mozilla.com>
> We're actually relying on font data by using vertical alternate
> glyphs, right? What I don't understand is what kind of benefits
> we're trying to pursue by ignoring some of vertical alternate glyphs
> defined in the fonts.
>
> I agree that it's a good thing to develop a good rule for layout
> apps. But font developers should also be allowed to adjust glyphs
> and/or positions when they think is necessary, and my concern is
> current our efforts may prohibit that.

I'm not clear what you're saying here.  What I proposed was "always
apply the 'vert' feature to vertical runs but not to horizontal runs
that are then rotated".  So all vertical alternates are used via the
'vert' feature, punctuation, kumimoji, etc.  Are you labeling the
'vrt2' alternates as "vertical alternates"?

> > I don't quite follow the "CSSVT" classification that you list in
> > your table of Unicode codepoints [1]. You have "horizontal",
> > "sideways", "sideways (default)", "upright" and "use-font".  What
> > are the meaning/intent of these categories?  Basic numbers are
> > "sideways (default)" but simple Latin letters are "horizontal",
> > along with Greek and Cyrillic.  What's the distinction you're
> > making?  And how are you distinguishing between "sideways",
> > "horizontal" and "use-font" in the U+2100:21FF range of symbols.
> >
> > [1] http://lists.w3.org/Archives/Public/www-archive/2011Aug/att-0013/vert.htm
>
> I'm sorry for the lack of explanations and cryptic value names. I
> followed all the statements in Appendix C: Vertical Typesetting
> Synthesis[2] and Appendix B: Bi-orientational Transformations[3],
> distinction of the terminologies is to know which part of the spec
> determined the orientation to help debug my script and the spec
> itself. I should make them clearer before posting, sorry about that.
>
> I modified value names so that all code points are classified to:
> sideways, upright, or use-font. "use-font" means "either upright
> using vertical font settings if available or sideways if they are
> not" in the spec, and reason to determine so was moved to
> parenthesis. Is this clear?

So you mean "horizontal", "sideways" and "sideways (default)" are all
the same?  And what exactly do you mean by "vertical font settings"
here?  Are you referring to the vert/vrt2 features?  The current
Appendix C wording has:

  "In OpenType, vertical font settings are provided by the vhea, vmtx,
   and VORG tables, as well as the vert and vrt2 GSUB features. If any of
   these are present, the font is considered to have vertical font
   settings available."

We need to have a definition of orientation that is consistent whether
a font has vertical metrics and/or vertical alternates available.

Cheers,

John Daggett
Received on Friday, 12 August 2011 07:54:09 GMT

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