NAME¶
groff_font - format of groff device and font description files
DESCRIPTION¶
The groff font format is roughly a superset of the ditroff font 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; unlike the ditroff font format, there is no associated binary format.
The DESC file can contain the following types of line as shown below. Later
entries in the file override previous values.
Empty lines are ignored.
- charset
- This line and everything following in the file are ignored.
It is allowed for the sake of backwards compatibility.
- family fam
- The default font family is fam.
- fonts n F1 F2 F3 ... Fn
- Fonts F1, ..., Fn are 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 causes no font to be mounted on the
corresponding font position.
- hor n
- The horizontal resolution is n machine
units.
- image_generator string
- Needed for grohtml only. It specifies the program to
generate PNG images from PostScript input. Under GNU/Linux this is usually
gs but under other systems (notably cygwin) it might be set to
another name.
- paperlength n
- The physical vertical dimension of the output medium in
machine units. This isn't used by troff itself but by output
devices. Deprecated. Use papersize instead.
- papersize string
- Select a paper size. Valid values for string are the
ISO paper types A0-A7, B0-B7, C0-C7, D0-D7, DL, and the US paper types
letter, legal, tabloid, ledger, statement, executive, com10, and monarch.
Case is not significant for string if it holds predefined paper
types. Alternatively, string can be a file name (e.g.
`/etc/papersize'); if the file can be opened, groff reads the first
line and tests for the above paper sizes. Finally, string can be a
custom paper size in the format length,width (no
spaces before and after the comma). Both length and width
must have a unit appended; valid values are `i' for inches, `c' for
centimeters, `p' for points, and `P' for picas. Example: 12c,235p.
An argument which starts with a digit is always treated as a custom paper
format. papersize sets both the vertical and horizontal dimension
of the output medium.
- More than one argument can be specified; groff scans
from left to right and uses the first valid paper specification.
- paperwidth n
- The physical horizontal dimension of the output medium in
machine units. Deprecated. Use papersize instead. This isn't used
by troff itself but by output devices.
- pass_filenames
- Make troff tell the driver the source file name being
processed. This is achieved by another tcommand:
F filename.
- postpro program
- Use program as the postprocessor.
- prepro program
- Call program as a preprocessor.
- print program
- Use program as the spooler program for printing. If
omitted, the -l and -L options of groff are
ignored.
- res n
- There are n machine units per inch.
- 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.
- sizescale n
- The scale factor for point sizes. 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.
- styles S1 S2 ... Sm
- The first m font positions are associated with
styles S1, ..., Sm.
- tcommand
- This means that the postprocessor can handle the t
and u output commands.
- unicode
- Indicate that the output device supports the complete
Unicode repertoire. Useful only for devices which produce character
entities instead of glyphs.
- If unicode is present, no charset section is
required in the font description files since the Unicode handling built
into groff is used. However, if there are entries in a
charset section, they either override the default mappings for
those particular characters or add new mappings (normally for composite
characters).
- This is used for -Tutf8, -Thtml, and
-Txhtml.
- unitwidth n
- Quantities in the font files are given in machine units for
fonts whose point size is n scaled points.
- unscaled_charwidths
- Make the font handling module always return unscaled glyph
widths. Needed for the grohtml device.
- use_charnames_in_special
- This command indicates that troff should encode named
glyphs inside special commands.
- vert n
- The vertical resolution is n machine
units.
The
res,
unitwidth,
fonts, and
sizes lines are
compulsory. Not all commands in the DESC file are used by
troff itself;
some of the keywords (or even additional ones) are used by postprocessors to
store arbitrary information about the device.
Here a list of obsolete keywords which are recognized by
groff but
completely ignored:
spare1,
spare2,
biggestfont.
A font file has two sections; empty lines are ignored in both of them.
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.
- ligatures lig1 lig2 ... lign [0]
- Glyphs 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.
- name F
- The name of the font is F.
- slant n
- The glyphs of the font have a slant of
n degrees. (Positive means forward.)
- spacewidth n
- The normal width of a space is n.
- special
- The font is special; this means that when a glyph is
requested that is not present in the current font, it is 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 glyph.
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 glyph: if
name is a single glyph
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
special character
\[c]; otherwise it corresponds to the
groff input character
\[name]. If it is exactly two
characters
xx it can be entered as
\(xx. Note that
single-letter special characters can't be accessed as
\c; the
only exception is `\-' which is identical to `\[-]'. The name
--- is
special and indicates that the glyph is unnamed; such glyphs can only be used
by means of the
\N escape sequence in
troff.
The
type field gives the glyph type:
- 1
- means the glyph has a descender, for example, `p';
- 2
- means the glyph has an ascender, for example, `b';
- 3
- means the glyph has both an ascender and a descender, for
example, `('.
The
code field gives the code which the postprocessor uses to print the
glyph. The glyph 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 is interpreted as octal; if it starts with
0x or
0X it is intepreted as hexadecimal. Note, however, that the
\N
escape sequence only accepts a decimal integer.
The
entity_name field gives an ASCII string identifying the glyph which
the postprocessor uses to print that glyph. This field is optional and is
currently used by
grops to build sub-encoding arrays for PS fonts
containing more than 256 glyphs. (It has also been used for
grohtml's
entity names but for efficiency reasons this data is now compiled directly
into
grohtml.)
Anything on the line after the encoding field or `--' are ignored.
The
metrics field has the form (in one line; it is broken here for the
sake of readability):
- width[,height[,depth[,italic-correction
[
,left-italic-correction[,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 glyph. The
height subfield gives the
height of the glyph (upwards is positive); if a glyph 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 glyph, that is, the distance
below the lowest point below the baseline to which the glyph extends
(downwards is positive); if a glyph 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 glyph when it is immediately to be followed by a glyph from a
roman font. The
left-italic-correction subfield gives the amount of
space that should be added before the glyph when it is immediately to be
preceded by a glyph from a roman font. The
subscript-correction gives
the amount of space that should be added after a glyph 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 glyph 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 glyph
c1 appears next to glyph
c2 the space
between them should be increased by
n. Most entries in kernpairs
section have a negative value for
n.
FILES¶
- /usr/share/groff/1.21/font/devname/DESC
- Device description file for device name.
- /usr/share/groff/1.21/font/devname/F
- Font file for font F of device
name.
SEE ALSO¶
groff_out(5),
troff(1).