[Fontconfig] TTF/OTF packaging thoughts?

[mpsuzuki at hiroshima-u.ac.jp]

Hi,

I'm sorry to ask an off-topic question in this list.

On Wed, 23 Jul 2008 13:49:58 -0400
Behdad Esfahbod <behdad at behdad.org> wrote:

>On Wed, 2008-07-23 at 19:28 +0200, Nicolas Mailhot wrote:
>> Le mercredi 23 juillet 2008 $(D+"(B 11:51 -0400, Behdad Esfahbod a $(D+1(Bcrit :
>> > On Wed, 2008-07-23 at 10:53 +0200, Nicolas Mailhot wrote:
>> 
>> > > 2. I don't know what algorithm fontconfig uses to choose between
>> > > several formats of the same fonts, or even if its choices are stable.
>> 
>> > It uses the version number to prefer one over the other.  If both have
>> > the same version, it may not be deterministic, not sure.
>> 
>> That's unfortunately the case we're likely to have.
>
>Right.  Too bad the OpenType spec does not allow having both CFF and
>TrueType outlines in one container.

According to the descriptions of existing implementations
in OpenType spec, TTC-packed CFF OpenType seems to be dealt
as too-new file format. So, a TTC including TrueType and
CFF OpenType is, furthermore, too-new and exotic.

One of the advantage to pack multiple TrueType into TTC is:
sharing same loca/glyf/EBLC/EBDT but different cmap/post is
easy to make a compact font file when most glyphs are shared
but a small group of glyphs are different (e.g. fixed-width
CJK font and proportional CJK font).

This advantage is not so significant in CFF OpenType. Using
same CFF table for such purpose is difficult, because CFF
table has its own font family names, and assigns the unique
glyph names to all glyphs. It would be expected that the
glyph names in CFF table are compatible with Adobe Glyph Names,
so using separated CFF tables for each faces would be easier.
In such case, the reduction of the font file size would not
be so significant. I guess, the advantage of TTC-packed CFF
OpenType is just the reduction of the number of font files.
It's something like "cff_fonts.tar".

What is the advantage to pack TrueType and CFF OpenType?
I guess, the shareable contents are limited as TTC-packed
CFF OpenType, so, such request comes from the people looking
for an easy archiver of font files.

If I'm missing some points, please let me know.

Regards,
mpsuzuki