Re: Why people still want to encode precomposed letters

From: John Hudson (
Date: Tue Nov 25 2008 - 12:16:24 CST

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    Asmus Freytag wrote:

    > I think Hans was not too far off in his comparison: there are aspects of
    > mark placement, that - to a lay person - seem reminiscent of kerning, in
    > the way that hey depend on the details of the shape of the base
    > character and accent(s) to allow them to be tucked in more closely.

    I'm not disagreeing with that, I'm saying that from a technical
    perspective kerning and mark positioning are necessarily independent
    actions, since you generally do not want positioning of marks to
    directly affect the position of subsequent base glyphs. So for the sake
    of clarity, one should avoid talking about mark positioning as 'kerning'.

    There are, of course, circumstances such as you describe, in which the
    *affects* of kerning and of mark positioning need to interract, either
    by contextually adjusting kerning to make space for the mark or by
    contextually shifting the mark to make space for a kerned base. But the
    actual mechanisms remain separate: the contextual kerning adjustment is
    a <kern> lookup and the contextual mark positioning is a <mark> lookup.

    > I don't think his intention was to
    > usurp a term from the holy vocabulary ;-)

    Perhaps not, but having spent a lot of time over the past decade
    explaining to people why you can't use a kerning mechanism to position
    marks, I'm sensitive to the potential for confusion.

    John Hudson

    Tiro Typeworks
    Gulf Islands, BC
    You can't build a healthy democracy with people
    who believe in little green men from Venus.
                        -- Arthur C. Clark

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