HP 4 FAMILY - Manual (Page 82)

The structure of the Vertical Rotation Segment is:
Byte 15 (MSB) 8 7 (LSB) 0 Byte
0 VR (22098) 1
2
4 Data Segment Size (4) * 3
5
6 Format (0) 7
8 Descender value 9
* This segment is for Font Format 16. The Data Segment Size field for Font Format 16
fonts is 4 bytes; the segment for Font Format 15 fonts is identical except the Data
Segment Size field is 2 bytes instead.
Format (UINT16)—Set this value to 0.
Descender Value (SINT16)—Set this value to equal the
“sTypoDescender” value from the “OS/2” table of the
TrueType font.
2-46 Printer-Specific Differences