HP PCL/PJL reference (PCL 5 Printer Language) - Technical Reference Manual Part I

EN Font Header Format 11-41
Data segments with an unrecognized identifier are ignored.
Segment Size (UI)
For each entry in the Segmented Font Data section, the Segment
Size indicates the number of bytes in the immediately following Data
Segment. The size for the Null Segment is 0.
Formats of Data Segments
AP (Application Support Segment) The definition of this segment is
reserved.
CC (Character Complement) This field has the same form (i.e., 8
unsigned bytes) and function as does the Character Complement of
Format 11 fonts. The Character Complement field should be present
with type 10 and 11 (unbound) fonts, but has no role to play in type 0,
1 and 2 (bound) fonts.
CP, copyright This field will consist of ASCII data and is optional.
GI (Global Intellifont Data) Reserved for future use.
GT (Global TrueType Data) This data segment contains first a Table
Directory, then five or more tables used by the TrueType font scaler.
Every TrueType font needs to have this segment.
The Table Directory is patterned after the initial segment of the
TrueType font file as described in True Type Font Files. The Table
Directory has a 12-byte header and 16 bytes per entry in the Table
Directory. The Table Directory is organized in alphabetical order by
the 4-byte table names. For each entry, there is an offset relative to
the beginning of the soft font’s Global TrueType Data Segment.
The Global TrueType Data for every TrueType font entity must
contain a head, hhea, hmtx and maxp table.
Another required table is the gdir table. When the font header is
downloaded, the gdir table should have a size of 0 and an offset of 0.
The gdir table is then built in RAM to accommodate the maximum
number of glyphs to be downloaded to the given font — with 2 or 4
bytes of offset and 2 bytes of length per glyph. This maximum number
of glyphs is obtained from the numGlyphs field of the maxp table.
Entries in the gdir table are filled in by the TrueType rasterizer as
characters are downloaded.