Re: Rendering of sequences containing double diacritic (was Re: Bantu click letters)

From: James Kass (
Date: Fri Jun 11 2004 - 10:49:36 CDT

  • Next message: John Hudson: "Re: Rendering of sequences containing double diacritic (was Re: Bantu click letters)"

    Bob Hallissy wrote,

    > >Even with OpenType experimental support here, my display looks like
    > >the GIF you sent. I'll try fixing this,
    > Um, good luck. I am not sure it is possible to correctly position
    > double-diacritics with OpenType logic. Specifically, the vertical position
    > of the double-diacritic must be adjusted so that it is above the *taller*
    > of the preceding and following combining sequence. AFAIK, such logic isn't
    > feasible in OpenType.
    > >
    > >Following the "inside-out" rule, the first sequence should render
    > >correctly, the second sequence should not.
    > Not sure what you are saying here or what you mean by the inside-out rule.
    > The two sequences are canonically equivalent and should look identical.

    The "inside-out" rule is explained and illustrated on page 125 (TUS 4.0).

    An "a" followed by combining umlaut followed by combining macron
    is not the same as "a" plus combining macron plus combining umlaut.

    So, I'd expect that entering a combiner before the spanning character would
    render the combiner below the spanning character, while reversing this order
    would render the combiner above the spanning character. Is this not the

    As you suggest for the double-wide combiners, this turns out not to
    be an easy fix. So far, I'm unsuccessful in getting a good display. I'll
    have to double-check everything in GDEF and GPOS to make sure I'm
    doing it right, but, it may simply not be possible yet.

    Best regards,

    James Kass


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