NAMEgroff_font - format of groff device and font description files
The groff font format is roughly a superset of the ditroff font format.
Unlike the ditroff font format, there is no associated binary format.
The font files for device name are stored in a directory devname.
There are two types of file: a device description file called DESC and
for each font F a font file called F. These are text files; there is
no associated binary format.
DESC file format
The DESC file can contain the following types of line:
res n There are n machine units per inch.
hor n The horizontal resolution is n machine units.
vert n The vertical resolution is n machine units.
The scale factor for pointsizes. By default this has a value of
1. One scaled point is equal to one point/n. The arguments to
the unitwidth and sizes commands are given in scaled points.
Quantities in the font files are given in machine units for
fonts whose point size is n scaled points.
This means that the postprocessor can handle the t and u output
sizes s1 s2...sn 0
This means that the device has fonts at s1, s2,...sn scaled
points. The list of sizes must be terminated by a 0. Each si
can also be a range of sizes m-n. The list can extend over more
than one line.
styles S1 S2...Sm
The first m font positions will be associated with styles
fonts n F1 F2 F3...Fn
Fonts F1...Fn will be mounted in the font positions m+1,...,m+n
where m is the number of styles. This command may extend over
more than one line. A font name of 0 will cause no font to be
mounted on the corresponding font position.
The default font family is fam.
This line and everything following in the file are ignored. It
is allowed for the sake of backwards compatibility.
The res, unitwidth, fonts and sizes lines are compulsory. Other com‐
mands are ignored by troff but may be used by postprocessors to store
arbitrary information about the device in the DESC file.
Font file format
A font file has two sections. The first section is a sequence of lines
each containing a sequence of blank delimited words; the first word in
the line is a key, and subsequent words give a value for that key.
name F The name of the font is F.
The normal width of a space is n.
The characters of the font have a slant of n degrees. (Positive
ligatures lig1 lig2...lign 
Characters lig1, lig2,...,lign are ligatures; possible ligatures
are ff, fi, fl and ffl. For backwards compatibiliy, the list of
ligatures may be terminated with a 0. The list of ligatures may
not extend over more than one line.
The font is special; this means that when a character is
requested that is not present in the current font, it will be
searched for in any special fonts that are mounted.
Other commands are ignored by troff but may be used by postprocessors
to store arbitrary information about the font in the font file.
The first section can contain comments which start with the # character
and extend to the end of a line.
The second section contains one or two subsections. It must contain a
charset subsection and it may also contain a kernpairs subsection.
These subsections can appear in any order. Each subsection starts with
a word on a line by itself.
The word charset starts the charset subsection. The charset line is
followed by a sequence of lines. Each line gives information for one
character. A line comprises a number of fields separated by blanks or
tabs. The format is
name metrics type code comment
name identifies the character: if name is a single character c then it
corresponds to the groff input character c; if it is of the form \c
where c is a single character, then it corresponds to the groff input
character \c; otherwise it corresponds to the groff input character
\[name] (if it is exactly two characters xx it can be entered as \(xx.)
Groff supports eight bit characters; however some utilities has diffi‐
culties with eight bit characters. For this reason, there is a conven‐
tion that the name charn is equivalent to the single character whose
code is n . For example, char163 would be equivalent to the character
with code 163 which is the pounds sterling sign in ISO Latin-1. The
name --- is special and indicates that the character is unnamed; such
characters can only be used by means of the \N escape sequence in
The type field gives the character type:
1 means the character has an descender, for example, p;
2 means the character has an ascender, for example, b;
3 means the character has both an ascender and a descender, for
The code field gives the code which the postprocessor uses to print the
character. The character can also be input to groff using this code by
means of the \N escape sequence. The code can be any integer. If it
starts with a 0 it will be interpreted as octal; if it starts with 0x
or 0X it will be intepreted as hexdecimal.
Anything on the line after the code field will be ignored.
The metrics field has the form:
There must not be any spaces between these subfields. Missing sub‐
fields are assumed to be 0. The subfields are all decimal integers.
Since there is no associated binary format, these values are not
required to fit into a variable of type char as they are in ditroff.
The width subfields gives the width of the character. The height sub‐
field gives the height of the character (upwards is positive); if a
character does not extend above the baseline, it should be given a zero
height, rather than a negative height. The depth subfield gives the
depth of the character, that is, the distance below the lowest point
below the baseline to which the character extends (downwards is posi‐
tive); if a character does not extend below above the baseline, it
should be given a zero depth, rather than a negative depth. The
italic_correction subfield gives the amount of space that should be
added after the character when it is immediately to be followed by a
character from a roman font. The left_italic_correction subfield gives
the amount of space that should be added before the character when it
is immediately to be preceded by a character from a roman font. The
subscript_correction gives the amount of space that should be added
after a character before adding a subscript. This should be less than
the italic correction.
A line in the charset section can also have the format
This indicates that name is just another name for the character men‐
tioned in the preceding line.
The word kernpairs starts the kernpairs section. This contains a
sequence of lines of the form:
c1 c2 n
This means that when character c1 appears next to character c2 the
space between them should be increased by n. Most entries in kernpairs
section will have a negative value for n.
@FONTDIR@/devname/DESC Device description file for device name.
@FONTDIR@/devname/F Font file for font F of device name.
Groff Version @VERSION@ @MDATE@ GROFF_FONT(@MAN5EXT@)