From: Christopher Fynn (cfynn@gmx.net)
Date: Tue May 22 2007 - 04:24:15 CDT
Philippe Verdy wrote:
> mpsuzuki@hiroshima-u.ac.jp wrote:
>> "Philippe Verdy" <verdy_p@wanadoo.fr> wrote:
>>> Is the OTC extension for Opentype able to handle such case, by creating
>>> in a single font file multiple fonts packed together, and crosslinked
>>> with an explicit fallback from one font to the other in the same pack?
>> Excuse me, OTC is the OpenType/TrueType Collection
>> described in OpenType specification v1.4? If so,
>> I remember, it doesn't mention anything about the
>> relationship among the faces included in same package
>> (if I'm wrong, please correct). In fact, Microsoft
>> had ever used TTC to pack independent faces (think
>> about Courier & Helvetica) into single file, for
>> Japanese and Korean markets. There might be requirement
>> to use OTC for 32bit glyph collection, but I don't
>> know if there's any movement for standardization.
> I spoke about OTC (or TTC) because it is backward compatible and would allow
> referring to a single font for drawing the legacy subset, while still having
> the possibilitily to refer to the other subet using the alternate font name.
> But with an extra (very small) table within each fontpacked into the
> collection, there would be the possibility to insert explicit font linking
> for ranges not covered in the current font in that collection; This small
> table could be inserted in each font part of the OTC/TTC pack.
Hi Philippe
True Type Collections are essentially for sharing glyphs between fonts (where
you have glyphs which you want to use in common in more than one font - e.g. you
might have a single set of Roman glyphs you want to use in several different CJK
fonts). Unfortunately TrueType Collections were *not* designed for 'linking'
several fonts together to form a larger virtual font - say one with over 64k
glyphs - which looks like a single font to applications.
In Windows XP there is apparently an undocumented way of linking fonts together
so that particular fonts are used for particular scripts. (Rather than the fonts
being 'hardwired' - there is apparently a registry entry which governs this that
can be altered.) The default system fonts Windows uses for different scripts
seem to be 'linked' this way - so you can type several different scripts in a
single text file in Notepad (e.g. Roman, Arabic, Devanagari and Thai) - and all
will appear, though the glyphs are coming from several discrete fonts [and
Notepad only allows you to specify one font]. Although it seems pretty crude,
you can probably effectively get a font with over 64k glyphs like this.
Of course there needs to be a standardized, documented, cross platform and much
more sophisticated way of specifying links between fonts - say one that allowed
a font developer to specify default fonts for other scripts that worked well
with a his particular font - the links would need to include information about
relative size and baseline offset as well as font name for each script (or
script/language pair). Users should also have an easy way of overriding the
'default' and creating their own sets of linked fonts if they want to.
- Chris
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