groff_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 [Toc] [Back]
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.
sizescale n
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.
unitwidth n
Quantities in the font files are given in machine
units for fonts whose point size is n scaled
points.
tcommand
This means that the postprocessor can handle the t
and u output commands.
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 S1...Sm.
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.
family fam
The default font family is fam.
use_charnames_in_special
This command indicates that troff should encode
named characters inside special commands.
pass_filenames
requests that troff tells the driver the source
file name being processed. This is achieved by
another tcommand: F filename.
charset
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 commands are ignored by troff but may be used by
postprocessors to store arbitrary information about the
device in the DESC file.
Here a list of obsolete keywords which are recognized by
groff but completely ignored: spare1, spare2, biggestfont.
Font file format [Toc] [Back]
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.
spacewidth n
The normal width of a space is n.
slant n
The characters of the font have a slant of n
degrees. (Positive means forward.)
ligatures lig1 lig2...lign [0]
Characters lig1, lig2,...,lign are ligatures; possible
ligatures are ff, fi, fl, ffi and ffl. For
backwards compatibility, the list of ligatures may
be terminated with a 0. The list of ligatures may
not extend over more than one line.
special
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 [entity_name] [-- 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 difficulties with eight bit characters. For
this reason, there is a convention 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 troff.
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 example, (.
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 hexadecimal.
The entity_name field gives an ascii string identifying
the glyph which the postprocessor uses to print the character.
This field is optional and has been introduced so
that the html device driver can encode its character set.
For example, the character `\[Po]' is represented as
`£' in html 4.0.
Anything on the line after the encoding field resp. after
`--' will be ignored.
The metrics field has the form:
width[,height[,depth[,italic_correc-
tion[,left_italic_correc-
tion[,subscript_correction]]]]]
There must not be any spaces between these subfields.
Missing subfields 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 subfield
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
positive); 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
name "
This indicates that name is just another name for the
character mentioned 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.
/usr/share/groff_font/devname/DESC
Device description file for device name.
/usr/share/groff_font/devname/F
Font file for font F of device name.
groff_out(5), troff(1).
Groff Version 1.16.1 April 8, 2001 GROFF_FONT(5)
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