OT and combining diacritics (was Re: Representative glyphs for combining kannada signs)

From: Andrew Cunningham (lang.support@gmail.com)
Date: Wed Mar 22 2006 - 22:24:26 CST

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    Actually, there are a small number of OT fonts that support combining
    diacritic combinations very well, assuming your application is using
    an appropriate version of Uniscribe. We work with OT fonts everyday
    with African languages requiring use of combining diacritics and
    diacritic stacking.


    On 23/03/06, Philippe Verdy <verdy_p@wanadoo.fr> wrote:

    > That's what is happening anyway with lots of diacritics applied to latin letters (for example dot below african consonnants which is often incorrectly centered below the previous letter in most current fonts, including OpenType ones, only because there's no positioning rule for such pair in the OT tables) ; users would still prefer having correct typography, but it's more important to be able to render such diacritic with a reasonable "best-effort" solution, rather than just displaying a box for a missing glyph for the diacritic.
    > It would of course be better if the font had smarter positioning rules by anotating the glyphs for base letters with enough information to position any diacritic with it (including diacritics currently not implemented in that font but only found in another unspecified one). For this to work, fonts should avoid mapping inimplemented characters to the internal box that denotes a missing glyph, or it should map them only to the conventional glyph ID that denotes a missing glyph (so that the renderer knows that this font mapping is replacable using other fallback fonts when available).

    Andrew Cunningham
    Language IT support
    Dinka Language Institute

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