Dear Phil,
Having said all that, I must say that I actually use the code that I wrote quite rarely. I now tend to use UTF8 everywhere and treat it as a sequence of bytes. Because of the properties of UTF8 I find it's rare to need to identify individual code points. For example, if I'm scanning for a matching " or ) I can just look for the next matching byte, without worrying about where the character boundaries are.
Using UTF-8 can work well if you are only targeting American and Western Europe for non-literary use. If you need to support the rest of the world you really need to move to UTF-32 due to the large number of characters and the grapheme and glyph handling [e.g. in Urdu you can type 3 characters and they are displayed as a single combined glyph, and the cursor should never be placed between them]. Even in UTF-8 things can get a bit tricky. For example, where do you break the line if you needed in the middle of: joe)jack -> joe) <br> jack joe(jack -> joe <br> (jack joe+jack -> guess which is the standard ! For programmers we don't mind too much, but when you are writing text editors this can be really important. Now think how many characters there are with special rules on whether they can be split before, after, or never split, and you start to touch on the reason for the Unicode standard and why you need character properties. Yours, Graham