4.1 Characters and Glyphs
It may seem obvious that a font must contain symbols for each letter or character of the writing system in focus. However, each of those characters may be visually represented by one or more glyphs - the individual graphic shapes defined in the font. At this point it’s really important to have a clear understanding of the differences and interrelationships between characters, keystrokes, codepoints and glyphs. Chapter 2 of the online book Implementing Writing Systems is an excellent and thorough way to deepen that understanding.
When choosing which characters to support we recommend that you consider the full range of uses for the font, both linguistic and typographic. In addition to the basic letters, numerals, and punctuation, you may need to consider:
- letters and diacritics used for loan words, foreign terms, or names
- punctuation used in publishing applications, such as formal quote marks, text markers, footnote symbols, and special-width spaces
You may also need to consider alternate glyphs for special purposes, and create smart font rules for them:
- different numeral forms (old-style and tabular in Latin, for example)
- contextual alternates and ligatures
Non-Latin fonts should also contain a basic set of Latin glyphs. For technical reasons, the font is less likely to cause problems in certain OSes and environments if a basic Latin set is present. Our recommendation is that you support the following list: Basic Set of characters needed in a Non-Roman font.
If you don’t want to draw all of these Latin glyphs yourself, and are making a font that will be released freely under the SIL Open Font License, you can get the glyphs from some other OFL font as long as you acknowledge the source and follow the conditions of the OFL.