How are encodings and charset tables organized in CFF font file?

KySpace

The CFF specification Chapter 11 to Chapter 13 gives a rough description of what encodings and charset data are organized in a file. CFF Specification. Here are some questions.

1. Considering the possible existence of multi-font file, and that charstrings are accessed in a per-font manner, the corresponding index should also be meaningful only for each font. However, is there only at most one encoding and one charset table for the file? If so, how are the glyph indices correspond to the ones for the charstrings? If not, do they appear multiple times in the TopDict from where they are accessed?

2. It seems that charsets give names to each glyph. How about encoding? What is that Card8 data stored in each array element? Given its 256 limit, wouldn't the encoding be very restrained? And why in the supplement format the data come via SID? What is the designed method to access glyphs through encodings (In a hybrid string/code way)? And why again are these data strings when it comes to predefined encodings.

This question is also posted here https://stackoverflow.com/questions/63406122

Thanks!

Chris Lozos

You can create your own custom character set file in a text editor and put them in whatever order makes sense you.  Just follow the format of any existing font.

John Hudson

Are you asking about a CFF font per se, or an OpenType font with a CFF table? The latter involves some specific restrictions and formats: https://docs.microsoft.com/en-us/typography/opentype/spec/cff

KySpace

John Hudson said:

Are you asking about a CFF font per se, or an OpenType font with a CFF table? The latter involves some specific restrictions and formats: https://docs.microsoft.com/en-us/typography/opentype/spec/cff

I now only have question for CFF per se. Specifically how does encoding work? What is the input if I want to access code from encoding? I understand question 1 now.