Re: Windows Glyph Handling

From: Adam Twardoch (
Date: Fri Aug 26 2005 - 05:22:08 CDT

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    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:

    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


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