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Re: [ft-devel] Re: Preliminary support to CMap files on CID-keyed fonts.

From: Werner LEMBERG
Subject: Re: [ft-devel] Re: Preliminary support to CMap files on CID-keyed fonts.
Date: Sat, 09 Sep 2006 15:16:46 +0200 (CEST)

> A few months ago, I discussed with Masatake Yamato about this issue:
> it should be finished soon (or not)? with Masatake Yamato.

What should be finished?  The discussion or the implementation?

> I understand Hidetoshi's work was an intention to emulate TTF-like
> properties in FT_Face, by builtin charcode-cid conversion with CMap.

I currently can't remember how his code works.  The idea that I have
is to load a CID PS font into FreeType, then attach a CMap file to it.
This gives proper charcode->glyph conversion.

It's not really clear to me what you mean with `TTF-like properties'.
Please elaborate.

> (1) migration from CJK PS font to OpenType/CFF
> When Hidetoshi posted his proposal, the popular CJK PS font was
> CID-keyed PS font which has no interface for character code
> handling.  But, today, most commercial font vendors switched to sell
> OpenType/CFF as replacement of CID-keyed PS font.

Indeed, but I'm quite sure that people who have bought CID-keyed PS
fonts won't be able to switch easily.  First of all, buying new fonts
might be expensive, and secondly, most font licenses forbid
modification of fonts.

> What kind of situation that emulation by CID-keyed PS font + CMap
> works better than real OpenType/CFF?

Well, the CMap system is far more flexible, but this is probably
something not really needed by most users.

> (2) FreeType2 does not handle OpenType layout
> In Hidetoshi's post, he noted about GSUB emulation issue.

Uh, oh, I can't remember at all :-(

> Let me explain again.  When we create a TTF-style cmap from CJK PS
> font by CMap, nothing to say, it cannot store various glyph
> variations (for Adobe-Japan1, Japanese character code does not
> specify writing direction, same character code point is used for
> horizontal & vertical forms). Thus, to retain cid for glyph
> variations, GSUB emulation is required.

???  I don't understand that.  By selecting the proper CMap you
automatically get vertical glyph variants, say.  Compare, for example,
the CMap files `EUC-V' and `EUC-H'.

GSUB emulation is far beyond what I imagine.


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