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

From: mpsuzuki
Subject: Re: [ft-devel] Re: Preliminary support to CMap files on CID-keyed fonts.
Date: Sun, 10 Sep 2006 03:00:26 +0900

On Sat, 09 Sep 2006 15:16:46 +0200 (CEST)
Werner LEMBERG <address@hidden> wrote:
>> 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?

Sorry, we've discussed how to implement what Hidetoshi wanted to do.

>> 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.

I meant TTF cmap, a few names (family name, style name), and
several flags (italic, bold).

>> (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.

I agree. But I'm not sure what kind of applications they want to
use with their CID-keyed PS font, so it's difficult to discuss
what kind of support in FT2 is required. I'm not sure if attaching
fully-specified CMap to CID-keyed font (a minimum implementation of
"composefont" operator) is what they want. If you receive some
concrete request for CMap + CID font support, please let me know.

I suppose, Hidetoshi wanted to implement full-featured "composefont"
operation into FT2, but it was too big task.

>> (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 :-(

Please check his TODO list:

>> 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'.

Excuse me, you are thinking of the application which can determine
the proper CMap? In such cases, I have no objection. I suppose,
Hidetoshi's proposal was for others. As Hidetoshi's TODO item #2,
he thought such support was required for the softwares which cannot
determine proper CMap name.

In summary, please check Hidetoshi's TODO list, and give me comment
which item should be solved and which item can be suspended as
future issue.


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