Coloured diacritics (Was: Transcoding Tamil in the presence of markup)

From: John Hudson (
Date: Sat Dec 06 2003 - 21:47:52 EST

  • Next message: John Hudson: "Re: Coloured diacritics (Was: Transcoding Tamil in the presence of markup)"

    At 03:53 PM 12/6/2003, Philippe Verdy wrote:

    >Still this is an interesting problem: some texts for example want to
    >exhibit some diacritics added to a base letter with a distinct color,
    >notably in linguistic texts related to grammar or orthography.
    >So for example you could want to exhibit the difference between the two
    >French words "désert" and "dessert" by coloring the accent of the first
    >word or the second s of the second; or even more accurately between
    >"bailler" (concéder un bail, des baux) and "bâiller" (ouvrir en grand)
    >where the presence or absence of the circumflex on letter 'a' is
    >necessary to reflect the difference of both meaning and pronounciation.

    The way to do this is to decompose bases and marks at the glyph level if
    they are not already decomposed at the character level, and then to apply a
    colour to the mark. In order to do this you need to know what is a mark
    glyph and what is abase glyph (this doesn't necessarily correspond to what
    is a mark character and a base character, so areguably this is not a
    Unicode question). This is one of the benefits of the OpenType GDEF table,
    which includes information about individual glyphs including whether they
    are marks, simple glyphs (potential bases), ligatures (potential bases),
    etc. Recent versions of Word already take advantage of this and allow you
    to colour diacritics independently of bases; this is mainly used for
    Arabic. Of course, this is not the only possible method to colour
    diacritics, and it relies on font developers decomposing precomposed glyph
    involving diacritics and bases (which slows down performance) and correctly
    setting GDEF values.

    John Hudson

    Tiro Typeworks
    Vancouver, BC

    Theory set out to produce texts that could not be processed successfully
    by the commonsensical assumptions that ordinary language puts into play.
    There are texts of theory that resist meaning so powerfully ... that the
    very process of failing to comprehend the text is part of what it has to offer
                 - Lentricchia & Mclaughlin, _Critical terms for literary study_

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