[XeTeX] Problems with some "exotic" RTL scripts
Jonathan Kew
jonathan_kew at sil.org
Wed May 9 15:03:36 CEST 2007
On 9 May 2007, at 1:28 pm, François Charette wrote:
> I have tested N'Ko with Code2000, and it turns out that contextual
> substitutions are not performed, even though they seem to be properly
> implemented in the font.
I'd think that it is impossible to judge "properly implemented"
without a shaping engine specification.
> This occurs with XeTeX+ICU but also with the
> latest version of Pango on my Linux box. Does anyone on this list have
> any experience with the N'Ko script?
I'm not surprised by this; the ICU layout library has no shaping
engine for N'Ko, as far as I know. Presumably Pango doesn't either.
Nor do I see a specification for OpenType features for N'Ko on the
Microsoft typography site; do you know if there is any information
available? It would presumably be a fairly simple extension to the
Arabic engine, but without a font spec, any implementation is going
to be an arbitrary, hit-or-miss affair.
While I'd love to have complete support for everything :-) the
reality is that N'Ko is not at the top of my personal priorities for
now. But if someone cares to offer a patch, either for XeTeX or
(better) directly to the ICU project, I'd be happy for it to be
included in due course.
>
> The other problem concerns Old Italic (Etruscan): even though the
> script
> is declared in the fonts Code2000 and MPH B2 Damase, it is not
> processed
> as right-to-left scripts as it should (I have to type \char"202E in
> front of each word to have them displayed correctly). Any idea?
Old Italic is encoded in Unicode with left-to-right directionality;
see The Unicode Standard 5.0, p 474. Right-to-left rendering will
require directional overrides (and currently, you'll have to apply
these to each word in XeTeX; this is a shortcoming of the
implementation).
JK
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