Re: Back to Hebrew, was OT:darn'd fools

From: John Hudson (
Date: Tue Jul 29 2003 - 19:28:56 EDT

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    At 04:11 PM 7/29/2003, Peter Kirk wrote:

    >Either I have not made myself clear or my understanding of the rendering
    >process is even less than I thought. Perhaps I should have said "glyph"
    >rather than "character". But the real point is that I am suggesting some
    >kind of flag which could be preserved from outputting on glyph to
    >outputting the next, on the lines of "the last glyph I output was a vowel"
    >or "... a consonant" - with "vowel" or "consonant" defined simply as one
    >of a particular list of glyphs or combinations. Is that possible, or is
    >the rendering engine unable to preserve any kind of state from glyph to glyph?

    It is possible to store information about a glyph for processing purposes.
    In OpenType this is done in the GDEF table, but the glyph types are
    currently limited to simple, ligature, mark and component. It is not
    essential to make such assignments much of the time; for example, you only
    need to classify a ligature as such if you want to position marks relative
    to different parts of the ligature (in which case you also define how many
    components the ligature has. The only GDEF classification currently
    necessary for Hebrew is 'mark'. If you wanted the GDEF table specification
    extended for, e.g. a distinction between consonants and vowels, you would
    need to approach MS and Adobe. I really don't recommend doing that at this
    stage, since this really is a problem that should be solveable at the text
    encoding level. The OpenType philosophy is very much opposed to handling
    anything that looks like a character processing issue in glyph space
    (unlike AAT and Graphite).

    John Hudson

    Tiro Typeworks
    Vancouver, BC

    The sight of James Cox from the BBC's World at One,
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    surrounded by a scrum of furiously scribbling print
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