Re: Installing OpenType fonts

[Eric Mader <mader jtcsv com>]

Hi Stefan,

So far as I know, nobody has done this yet.

At first glance this seems like a pretty easy problem, if you already have 
a mechanism in place to deal with ligature formation and mark positioning. 
After looking into implementing it, I found out that it's more complicated 
than it seems.

A complete implementation should be able to handle arbitrary accents, in 
arbitrary order, on arbitrary base glyphs. For example a + under-dot + 
umlaut, a + umlaut + under-dot, a-umlaut + under-dot, and a-under-dot + 
umlaut should all be handled, and all rendered the same way.

To do this, you either need a huge GSUB and / or GPOS table in the font, or 
you need to normalize the text before GSUB / GPOS processing. i.e. all of 
the above might be normalized to a-umlaut + under-dot. For this example if 
you normalize, you only need one rule in the font instead of four.

There has been a discussion on the OpenType list about this, but so far, we 
can't agree on what to do. Some of the complication comes from the fact 
that it seems like different normalizations work best for different 
scripts. In fact, for Hebrew the Unicode normalization algorithm puts the 
accents in an order which is completely unnatural for Hebrew speakers...

At some point, I'll put Latin processing into the ICU LayoutEngine and port 
that support into Pango. The soonest that's likely to happen is around the 
end of this year.

Regards,
Eric Mader
IBM GCoC - San José
5600 Cottle Rd.  M/S 50-2/B11
San Jose, CA 95193

At 01:41 PM 1/9/2003, Stefan Baums wrote:
> Dear list,
>
> regarding my question of 3 January (as yet unanswered) about how to
> install a Latin-diacritic OpenType font for use by Pango.  Am I right
> in thinking that this would require writing a specific "language" (=
> "writing system"?)  module for "Latin Script"?  Has this already been
> done by somebody?  How does one write such modules?  How does one then
> install the font?
>
> Best regards,
> Stefan
>
> --
> Stefan Baums
> Asian Languages and Literature
> University of Washington
> _______________________________________________
> gtk-i18n-list mailing list
> gtk-i18n-list gnome org
> http://mail.gnome.org/mailman/listinfo/gtk-i18n-list