[XeTeX] OT features

David J. Perry hospes.primus at verizon.net
Tue Feb 15 04:38:36 CET 2011


I had the exact same problem last weekend.  I constructed an OT feature to 
replace a long s with a regular s if followed by a comma, period, space, 
etc.  The longs-space combination did not work.  I am not a low-level TeX 
programming kind of guy, but I had learned a bit somewhere about TeX's 
"glue" and I wondered if the OT parser did not see the space character. 
Thanks to Khaled for confirming this.

David


----- Original Message ----- 
From: "Khaled Hosny" <khaledhosny at eglug.org>
To: "Unicode-based TeX for Mac OS X and other platforms" <xetex at tug.org>
Sent: Monday, February 14, 2011 6:35 PM
Subject: Re: [XeTeX] OT features


> On Mon, Feb 14, 2011 at 10:24:14PM +0100, Georg A. Duffner wrote:
>> For my font project (see www.georgduffner.at/ebgaramond) i have been
>> playing around with some opentype features. It seems, that
>> contextual features involving the character "space" don’t work as
>> expected.
>
> AFAIK, XeTeX processes each word in isolation, so space never part of
> context (also in TeX space is not a character/glyph but a kind of a
> property named glue, so it does not get handled by OT layout).
>
> Generally speaking, using space in context is fragile and not guaranteed
> to work everywhere.
>
>> I wanted to implement a feature for latin texts that
>> replaces "u" at the beginning of a word by a letter that looks like
>> "v". The rule looks like this:
>
> 'init' feature should be more suitable here, but almost all OT engine
> supports it for few selected scripts (Arabic mainly). With 'init' it is
> the responsibility of the engine to detect word beginning.
>
> Regards,
> Khaled
>
> -- 
> Khaled Hosny
> Egyptian
>
>
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