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- To: Unicode List <unicode at unicode dot org>
- Subject: Re: Windows Glyph Handling
- From: Adam Twardoch <list dot adam at twardoch dot com>
- Date: Fri, 26 Aug 2005 12:22:08 +0200
- User-agent: Mozilla Thunderbird 1.0.6 (Macintosh/20050716)
Christopher Fynn wrote:
You can of course build fonts with both AAT and OpenType layout tables.
The two font file formats are not incompatible. And there are open source layout engines (such as that in ICU) with at least some support for AAT tables. So, for a script unsupported by Uniscribe, you can build a font with AAT tables and state machine for the script and have immediate support for your script in applications which support AAT fonts. Later, once the OT features for that script have been specified by MS OpenType tables can be added.
Only that, in a famous shoot-in-the-foot maneuver, when Apple released Mac OS X 10.4 (Tiger), they added some elementary OpenType Layout support -- but in a way that a mere presence of even simple OTL features completely disables all AAT features that exist in the font. If you build one Arabic font with shaping rules expressed in both OTL and AAT, none will work in Tiger because the OTL support in Tiger does not include Arabic shaping while the AAT features are disabled due to the presence of the OTL features in the font.
SIL recently released their free Arabic font Scheherezade: http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&item_id=ArabicFonts
They could have made one hybrid version but since it wouldn't have worked at all, they had to make separate OTL and AAT versions. (I'm not sure if they would have made a hybrid font otherwise, since it nonetheless adds complexity to the font, but at least it would have been feasible.)
A.
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