Re: Windows Glyph Handling

From: Christopher Fynn (
Date: Tue Aug 23 2005 - 23:44:27 CDT

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    John Hudson wrote:

    > But if you ask anyone at Microsoft and Adobe, they will tell you that
    > this is the expectation, because separation of common language shaping
    > from glyph processing is one of the key design philosophies of OpenType.
    > This has been stated so many times in so many places, beginning with the
    > OT Jamboree at Microsoft way back in 1998, that I'm surprised we're
    > having this conversation.

    When first reading about OpenType, I think it is still fairly easy for
    people to get the impression that, if there are lookups in the font,
    almost any feature will be applied to to any character by the shaping
    engine. It is not made clear enough that for non-Latin complex script
    rendering the logic for each particular script is built into the shaping
    engine - and that for any given script only a particular (defined)
    sub-set of OT features is automatically applied by the shaping engine.

    If one wants to Microsoft's shaping engine (Uniscribe) for a particular
    script then that script has to be already supported (or one has to wait
    for Microsoft to add support) - and, in the font, one has to use lookups
    only under the particular sub-set of OT features Uniscribe actually
    supports for that script.

    For unsupported scripts, applying OT shaping to PUA characters and so on
      in MS Windows there aren't many choices: 1) Try to find an application
    supporting a font and shaping system where you can put all the necessary
    logic into the font tables (GRAPHITE, AAT) and use that. 2) Find an
    application using an open source OpenType shaping engine (like Pango or
    ICU) and add your own code to enable shaping support for the script /
    characters you need. 3) Wait for Microsoft to add support for your
    script in Uniscribe.

    - Chris

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