Re: Why people still want to encode precomposed letters

From: verdy_p (
Date: Tue Nov 25 2008 - 15:19:12 CST

  • Next message: John Hudson: "Re: Why people still want to encode precomposed letters"

    "John Hudson" wrote:
    > 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'.

    I do agree generally, for the case of base-to-base positioning that kerning is the prefered term.
    base-to-mark positioning is prefered, but for the generic mark-to-mark positioning, not enough anchors may create

    For example I spoke about the "special" mark-to-mark positioning for Vietnamese, where accents are not placed on
    their normal anchor (above centered) if they are above a circumflex: "kerning" still does occur, despite of the
    generic mark-to-mark anchor, it affects the position of the acute or grace accent (above a circumflex), but it does
    not move to the right or left the possible subsequent mark-to-mark anchor after the acute/grave accent (which
    remains above-centered, but may be at a lower position than the one normally set by the acute/grave accent alone).

    In that case, the term "kerning" is still the one to choose for the position adjustment: this is a more complex
    case: you still need generic mark-to-mark positioning, but you also need kerning for some combinations of accents,
    to move them slightly away from their normal anchor position, but also to "slide down" the next generic anchor
    (something that kerning also performs for base-to-base positioning !).


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