John Hudson wrote as follows. quote
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 http://www.users.globalnet.co.uk/~ngo/ast03300.htm 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 glyph. 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
