Ligatures fj etc (from Re: Ligatures (qj) )

From: William Overington (
Date: Wed Mar 12 2003 - 08:20:27 EST

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    John Hudson wrote as follows.


    If you don't intend to use the PUA codepoint in text, there really is no
    point in having it at all.

    end quote

    Well, one useful scenario is as follows. Suppose please that one wishes to
    process incoming regular Unicode text, using a eutocode typography file to
    influence the process, details of the format on the web page, and then use
    the output Unicode format text stream as codes to look up glyphs in an
    ordinary TrueType font, so as to produce a display which includes using some
    ligature glyphs. Having a code such as U+E70B for fj and codes for other
    characters as part of a consistent set which is published has the advantage
    that if various software authors use the eutocode typography file format,
    and various people spend time encoding specific eutocode typography files,
    (such as for 18th Century English printing with long s ligatures, German
    Fraktur printing and the ligatures of languages of the Indian subcontinent),
    and various people produce ordinary TrueType fonts with ligature glyphs
    encoded using consistent lists of published Private Use Area code points for
    ligatures, then the existence of the list of Private Use Area code points
    may well help in interoperability, so that, for example, having looked at
    the result using a font produced by one artist one may have a look at the
    result using a font produced by another artist without needing to change
    the contents of the particular eutocode typography file being used for the
    processing and having then to reprocess the original text using that second
    eutocode typography file.

    Another use is that preparing some text using WordPad and other programs,
    not for interchange but just for, say, producing a local print of a poster,
    having a consistent, widely used set of Private Use Area code points for
    ligatures would mean that a poster designer could try out a number of fonts
    from various artists without needing to reset the text each time using
    whatever code points each font designer used for each particular ligature

    I would mention that my thinking on using Private Use Area codes for
    ligatures has gradually moved towards the use of the eutocode typography
    file rather than interchanging files using Private Use Area code points for
    ligatures, yet I do feel that, for local use such Private Use Area
    allocations for ligatures as the golden ligatures collection provides are
    potentially useful as they do provide for interoperability of fonts which
    contain ligatures which fonts are produced by a variety of artists. Use of
    the golden ligatures collection is entirely optional, yet it can be used to
    try to achieve some level of interoperability of fonts. Indeed, font
    designers who produce fonts using advanced font technologies, where the
    conversion tables are internal to the font rather than external as with the
    eutocode typography file, where the glyphs for ligatures are not accessed
    directly may, if they choose, make use of the code point allocations of the
    golden ligatures collection so as to allow the glyphs also to be accessed
    from other platforms with a hope of some level of interoperability.
    Certainly, using the code points of the golden ligatures collection is not
    using regular Unicode code point allocations, yet as a self-help facility
    amongst end users so that use of fonts containing ligatures is easier, the
    golden ligatures collection is perhaps of some practical use.

    I accept that the use of Private Use Area encodings does not guarantee
    compatibility, yet one can take care to try to make the use of Private Use
    Area codes for ligatures and other characters as graceful as possible.

    For example, although there is absolutely no requirement at all for me to do
    so, and no one has asked me to do so, I decided to make sure that no golden
    ligatures code point allocations made in the future will clash with the code
    points used for Phaistos Disc Script in the ConScript Registry.

    I am happy to point out, in addition, that I do quite like the idea of a
    link with traditional letterpress printing where each ligature character was
    cast as one piece of metal for the whole ligature and one could actually
    pick them up and place them in a composing stick, so the golden ligatures
    collection is about art and nostalgia as well as about technology and
    practicality of achieving a stylish display using computing equipment.

    I have added a new code recently, which is U+E700 STAFF which is a vertical
    line from the very top of the glyph and going as far below the 0 line as one
    chooses for a particular font. With Quest text I encoded this character
    early with a line going vertically from -768 font units to 2048 font units.
    This forces the overall display height of the font before I added either of
    lowercase y and g, which in fact go down to -512 font units in Quest text,
    so the U+E700 character within the font helps in the display process even
    though the character is not usually displayed, though it can be displayed
    for test purposes if desired.

    William Overington

    12 March 2003

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