Re: Defined Private Use was: SSP default ignorable characters

From: John Jenkins (
Date: Wed Apr 28 2004 - 17:55:14 EDT

  • Next message: Peter Kirk: "Re: Defined Private Use was: SSP default ignorable characters"

    On Apr 28, 2004, at 2:19 PM, John Hudson wrote:

    > The only interaction between glyphs in a font and character codes in
    > text is via mapping (which is done either internally or externally,
    > depending on the font format). Fonts do not contain any character
    > information other than which glyphs corrrespond to which characters.
    > All other information in the font is glyph-centric; e.g. ligature and
    > other substitution lookups map glyphs to glyphs, not characters to
    > glyphs. Trying to introduce character properties into such a
    > glyph-centric architecture would be, at best, an awkward fit.

    FWIW, AAT includes an optional 'prop' table which allows people to
    associate a number of Unicode properties -- most notably directionality
    -- with specific glyphs in a font. It *is* a little weird to do this,
    as John says, but it's there.

    John H. Jenkins

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