To CID, Or Not To CID

When developing OpenType/CFF fonts, in particular CJK ones or those with a large number of glyphs, one question that I am often asked by developers is whether it should be name-keyed or CID-keyed. The answer to this question is not simple, though it truly is a binary condition.

My philosophy is that most CJK fonts are best implemented as CID-keyed, mainly because the multiple scripts—Latin, symbols, ideographs, Japanese kana, and Korean hangul syllables—benefit from the multiple FDArray elements that are made possible by CID-keyed fonts. And, if the CID-keyed font is based on one of our public ROSes, such as Adobe-Japan1-x, existing resources, such as CMap resources and GSUB feature definitions, can be easily leveraged.

And, as I demonstrated at the AFDKO Workshop that was held on June 25th of this year in Tokyo, several AFDKO tools can be used to build CID-keyed fonts from one or more name-keyed source fonts, and that the FDArray structure can be easily controlled.

Still, nothing prevents a developer from making name-keyed fonts. In fact, for some purposes, name-keyed fonts are perfectly fine, even CJK ones. A good example of this are kana fonts, meaning Japanese fonts that include only the glyphs for kana (hiragana and katakana) and any necessary punctuation and symbols.

As usual, whether name-or CID-keyed fonts are best for a given developer depends on many more factors than I can encapsulate in a CJK Type Blog article such as this. Of course, I am always willing to provide advice about such issues.