[XeTeX] 'locl' feature with Arabic script

Jonathan Kew jfkthame at googlemail.com
Tue Jan 3 17:39:49 CET 2012


On 3 Jan 2012, at 16:25, Khaled Hosny wrote:

> I don't get the 'locl' feature to work with Arabic script, the attached
> sample should give diagonal dots not rounded ones (it does if processed
> with luatex). 'locl' feature works just fine with Latin script in other
> fonts.
> 
> Is this a XeTeX bug, feature or even a known limitation? The font might
> be buggy off course (though it works with other OpenType engines as
> well), but I want to be sure before putting much effort debugging the
> font.

Known limitation of XeTeX (or rather, of the ICU layout engine implementation it's using).... the Arabic shaper doesn't support the 'locl' feature, sorry.

(Note, btw, that 'locl' isn't mentioned in the MS spec for Arabic shaping, at http://www.microsoft.com/typography/otfntdev/arabicot/features.aspx. Nevertheless, I think it should be implemented.)

As a possible workaround, you could implement language-specific variants of a supported feature such as 'ccmp' and include the appropriate localized-form substitutions there.

JK




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