Re: ct, fj and blackletter ligatures

From: William Overington (
Date: Tue Nov 05 2002 - 04:18:55 EST

  • Next message: Thomas Lotze: "Re: ct, fj and blackletter ligatures"

    Thomas Lotze wrote as follows.

    >William Overington wrote:
    >> I don't know for certain but I suspect that it is that font designers
    >> do this so that people can use an application such as Microsoft Paint
    >> to produce an illustration using the font. In the absence of regular
    >> Unicode code points for the ligatures, a font designer has either to
    >> use the Private Use Area and be Unicode compatible or make a
    >> non-Unicode compatible font, if the font designer wishes people to be
    >> able to have direct access to the ligature characters.
    >Judging from what I' learned by now, this is not true: If a font
    >designer wants to make a Unicode-compatible font, he has to use a font
    >file format that supports Unicode, and those formats provide means to
    >access unencoded glyphs by transforming certain strings of Unicode
    >characters into them.

    Well, I suppose it depends upon what one means by a file format that
    supports Unicode. The TrueType format does not support the ZWJ method and
    thus does not "provide means to access unencoded glyphs by transforming
    certain strings of Unicode characters into them". I am unsure as to
    whether, in formal terms, TrueType is "a file format that supports Unicode"
    as it does not allow the ZWJ sequences to be recognized. Please note that
    my sentence did have "if the font designer wishes people to be able to have
    direct access to the ligature characters". However, certainly, a font
    designer using an advanced font format may well not wish people to be able
    to have direct access to the ligature characters. The paragraph was
    replying to your question as to why someone who wants to set and print out a
    page of Fraktur at present is in practice likely to have to use a font with
    the ligatures encoded with code points less than 255. Please know that I am
    not seeking to be pedantic over the meaning of the phrase "a file format
    that supports Unicode", it is just that I get the impression that you might
    possibly have not quite understood that some font formats widely used for
    Unicode encoded characters, such as the TrueType format, do not support the
    ZWJ glyph substitution process or, in fact, any glyph substitution process,
    such as noticing the two letter ct sequence and substituting a ct ligature
    glyph within the font.

    >And if I understand it correctly, Unicode
    >compliance can only be achieved with all of compliant documents, fonts,
    >and renderers. So there appears to be no need for direct accessibility
    >of ligatures, alternates etc.

    I said compatible, I did not say compliant and did not mean compliant. I
    was meaning compatible, in the sense that, if one wishes to produce a font
    using the TrueType format and that font is to include glyphs for ligatures
    such as ct and ppe, how does one do it so that the method used does not
    conflct with Unicode. Using Private Use Area code points avoids conflicting
    with the regular Unicode code points used for other characters.

    >> There are some articles about using WordPad and Paint to produce
    >> graphic effects with large characters and gold textures and so on in
    >> our family webspace, together with the gold texture file and some
    >> other texture files too.
    >And what's the relevance to Unicode of that?

    Well, in direct terms probably nothing. However, as this is a widely
    distributed mailing list it might be that some readers, having read about
    the matter of using ligature characters in Paint and the way that one needs
    a font with code points less than 255 in order to access the ligature
    characters from Paint, might like to have a go at producing such graphics,
    so, having available some articles on the matter, I mentioned them.

    If one considers the Gutenberg sample font, the ct ligature is available as
    well, at Alt 0201 using Paint. One could use Wordpad to get the character
    as well. Yet, suppose that one has an advanced format font with a ct glyph
    within it yet where the font does not provide a direct code point access
    glyph, but only allows a ct ligature to be displayed using a combination of
    computer hardware and software which supports the advanced font format. How
    is one going to get that ct ligature to display if one does not have access
    to that hardware and software combination? Now certainly the attempt has
    been made to trivialise the matter by reference to very very old computer
    systems, yet here the problems arise with PCs manufactured in 1999.

    May I add that this posting is trying to be helpful to answer questions
    which you have posed, I am not seeking to reopen the discussion of whether
    the Unicode Technical Committee should encode any more precomposed
    ligatures. I raised that issue before the August 2002 meeting of the
    Unicode Technical Committee, the committee discussed the matter at the
    meeting, formed a consensus view and that consensus view was minuted and the
    minutes have been published. It is simply a matter that the Unicode
    Technical Committee is not going to encode any more ligatures, I have my
    golden ligatures collection on the web and if people choose to ignore the
    golden ligatures collection, then that is up to them and if people choose to
    use the golden ligatures collection then that too is up to them. My feeling
    is, that used with care, the golden ligatures collection does assist some
    facilities, such as producing stylish graphics using ligatures on older
    computers, to be available, hopefully giving pleasure to the people making
    the graphics. I have also had great enjoyment in preparing the golden
    ligatures collection in that I have learned a lot about ligatures which were
    used by printers in days gone by. Hopefully, even those people who
    criticise the golden ligatures collection strongly recognise that I take
    great care in the documents to point out that there are alternative ways to
    encode ligatures: I find no problem in doing that as my intention is to
    offer opportunities not to mislead anyone by holding back information which
    is needed so as to make an objective decision.

    William Overington

    5 November 2002

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