Re: Ligatures in Turkish and Azeri, was: Accented ij ligatures

From: Kenneth Whistler (
Date: Thu Jul 10 2003 - 14:37:07 EDT

  • Next message: Philippe Verdy: "Re: Ligatures in Turkish and Azeri, was: Accented ij ligatures"

    Peter Kirk asked:

    > > In Turkish and Azeri the sequences f - i and f - dotless i both occur,
    > > and are fairly frequent. So it is inappropriate in these languages to
    > > use fi ligatures in which the dot on the i is lost or invisible, at
    > > least where the second character is a dotted i. Has any thought been
    > > given to this issue? Is it possible to block such ligation on a
    > > language-dependent basis?

    and Philippe Verdy responded with another question:

    > Isn't there a "Grapheme Disjoiner" format control character to force the
    > absence of a ligature like <fi>, i.e. <f, GDJ, i>?

    The answer to Philippe's rejoinder question is no, there is not
    a "Grapheme Disjoiner" format control character.

    What Philippe has in mind, however, is covered in the standard
    by the interaction of the joiner and non-joiner characters
    with ligature control:

    "U+200C ZERO WIDTH NON-JOINER is intended to break both cursive
    connections and ligatures in rendering.

    "ZWNJ requests that glyphs in the lowest available category
    (for the given font) be used."

          -- Unicode 4.0, Section 15.2, Layout Controls

    The categories referred to, from lowest to highest, are:

    1. unconnected
    2. cursively connected
    3. ligated

    At Peter pointed out, however, it is neither expected or reasonable
    to have to go back through and drop in ZWNJ's at every relevant
    location in existing Turkish or Azeri text, simply to prevent
    fi ligation. Such use of ZWNJ is intended to be exceptional,
    to deal with special cases.

    The general solutions depend either on use of fonts (or more
    generally, renderers) which block such ligation across the
    board. It is my understanding that modern font technologies
    allow the choice of ligation to essentially be a style selection
    for the font. How well various applications take advantage
    of that and make the choice available easily to end users may
    be an open issue still, but the fundamental pieces to do this
    correctly are available.


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