CFF — Compact Font Format table
This table contains a Compact Font Format font representation (also known as a PostScript Type 1, or CIDFont) and is structured according to Adobe Technical Note #5176: “The Compact Font Format Specification,” and Adobe Technical Note #5177: “Type 2 Charstring Format.”
OpenType fonts with TrueType outlines use a glyph index to specify and access glyphs within a font; e.g., to index within the 'loca' table and thereby access glyph data in the 'glyf' table. This concept is retained in OpenType CFF fonts, except that glyph data is accessed through the CharStrings INDEX of the CFF table.
The Name INDEX in the CFF data must contain only one entry; that is, there must be only one font in the CFF FontSet. It is not a requirement that this name be the same as name ID 6 entries in the 'name' table. Note that, in an OpenType font collection file, a single 'CFF ' table can be shared across multiple fonts; names used by applications must be those provided in the 'name' table, not the Name INDEX entry. The CFF Top DICT must specify a CharstringType value of 2. The numGlyphs field in the 'maxp' table must be the same as the number of entries in the CFF’s CharStrings INDEX. The OpenType font glyph index is the same as the CFF glyph index for all glyphs in the font.