Hmm, I’m very inexperienced with all this font and encoding work, can someone explain the “combining” of a letter with a diacritic?
In a word like café there is an accented letter. It is called e acute. Many languages use accented letters. For historical reasons, some accented letters have a regular Unicode codepoint of their own. The é character has a codepoint of its own. It is a precomposed accented character. However, some characters, such as m macron, do not have a codepoint of their own. There is now a policy of not adding any more precomposed accented characters.
However, accented characters such as m macron and indeed e acute can be expressed as the base letter followed by a combining accent.
When one types an ordinary letter, such as, say, p, all of the “ink” is after where the cursor is and then the cursor moves forward. With a combining diacritic all of the “ink” is before where the cursor is and the cursor does not move. So, the diacritic, often known as “the accent”, appears to be on top of the letter just before the cursor. So, one may “construct” an m macron as one proceeds, even though there is not an m macron encoded as a single character in regular Unicode.
However, the font will have one “combining macron” and that needs to be used for both m macron and M macron as well as other macron characters such as n macron and N macron. This can result in ugly typography, as the font designer may have felt the need to have the combining macron glyph high and not too far back, so that N macron would look reasonable. In which case, M macron would have the accent too far to the right to look good, though one could work out the intended meaning alright. The n macron would have the accent look too high, though one could work out the intended meaning alright. The m macron would have the accent look too far to the right and too high, though one could work out the intended meaning alright.
There are broadly two ways around this in order to get good looking typography.
One is to use an Opentype font with an expensive software package such as InDesign. The other is to add precomposed glyphs for M macron, m macron, N macron and n macron to the font, in the Unicode Private Use Area: this has the advantage of making keying the characters easier too, yet does mean that the encoding in a saved file is not regular Unicode.
How would I type, for example, an “M” and and “m” with carons on top?
I noticed that you mentioned carons. I used macrons in my example. The reason for that is that I have not made any glyphs in the Unicode Private Use Area using carons, but I have made some glyphs in the Unicode Private Use Area using macrons.
http://www.users.globalnet.co.uk/~ngo/QUESTTXT.TTF
http://www.users.globalnet.co.uk/~ngo/CHRONTXT.TTF
If one saves the fonts to hard disc local storage on can then open them in FontCreator and look for the characters using macrons.
They are also linked from the following page.
I hope that this helps.
William Overington
17 November 2007