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

From: Koji Ishii <kojiishi@gluesoft.co.jp>
Date: Fri, 12 Aug 2011 06:03:14 -0400
To: John Daggett <jdaggett@mozilla.com>
CC: "www-style@w3.org" <www-style@w3.org>
Message-ID: <A592E245B36A8949BDB0A302B375FB4E0AC4DAA3DD@MAILR001.mail.lan>
> 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"?

Sorry for not being able to write clearly, allow me to try again. What I'm trying to say is that to allow applying 'vert' feature to horizontal runs that are then rotated. Existence of 'vert' for a code point means that font designer want to use the glyph if it appears within East Asian vertical text flow.


> > 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?

Yes.

> 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."

I meant exactly as in the spec. That column is to debug the spec, so it follows definitions in the spec. I'm seeing some issues with this table, so I might propose to fix the spec soon, but haven't got clear idea what and how to fix yet.

You could understand that, the column represents the calculated result of the current spec, unless my script doesn't have bugs.


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

This is probably we have different opinions. I think, at least for some code points, glyph orientation should change depending on font information, because neither Unicode code points nor neighbor characters can determine the correct glyph orientation.


Regards,
Koji
Received on Friday, 12 August 2011 10:03:15 GMT

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