path: root/man/groff_font.man

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.TH GROFF_FONT @MAN5EXT@ "@MDATE@" "Groff Version @VERSION@"
.
.
.SH NAME
groff_font \- format of groff device and font description files
.
.
.SH DESCRIPTION
The groff font format is roughly a superset of the ditroff
font format.
.
The font files for device
.I name
are stored in a directory
.BI dev name\c
\&.
.
There are two types of file: a
device description file called
.B DESC
and for each font\~\c
.I F
a font file called\~\c
.IR F .
.
These are text files;
unlike the ditroff font format,
there is no associated binary format.
.
.
.SS DESC file format
.
The DESC file can contain the following types of line as shown below.
.
Later entries in the file override previous values.
.
.LP
Empty lines are ignored.
.
.TP
.B charset
This line and everything following in the file are ignored.
.
It is allowed for the sake of backwards compatibility.
.
.TP
.BI "family " fam
The default font family is
.IR fam .
.
.TP
.BI "fonts " "n F1 F2 F3 \|.\|.\|.\| Fn"
Fonts
.IR F1 ", \|.\|.\|., " Fn
are mounted in the font positions
.IR m "\|+\|1, \|.\|.\|., " m \|+\| n
where
.I m
is the number of styles.
.
This command may extend over more than one line.
.
A font name of\~\c
.B 0
causes no font to be mounted on the corresponding font position.
.
.TP
.BI "hor " n
The horizontal resolution is
.IR n \~\c
machine units.
.
.TP
.BI "image_generator "  string
Needed for
.B \%grohtml
only.
.
It specifies the program to generate PNG images from
PostScript input.
.
Under GNU/Linux this is usually
.I gs
but under other systems (notably cygwin) it might be set to another name.
.
.TP
.BI "paperlength " n
The physical vertical dimension of the output medium in machine units.
.
This isn't used by
.B troff
itself but by output devices.
.
Deprecated.
.
Use
.B papersize
instead.
.
.TP
.BI "papersize " string
Select a paper size.
.
Valid values for
.I string
are the ISO paper types A0\[en]A7, B0\[en]B7, C0\[en]C7, D0\[en]D7,
DL, and the US paper
types letter, legal, tabloid, ledger, statement, executive, com10, and
monarch.
.
Case is not significant for
.IR string
if it holds predefined paper types.
.
Alternatively,
.I string
can be a file name (e.g.\& `/etc/papersize'); if the file can be opened,
.B groff
reads the first line and tests for the above paper sizes.
.
Finally,
.I string
can be a custom paper size in the format
.IB length , width
(no spaces before and after the comma).
.
Both
.I length
and
.I width
must have a unit appended; valid values are `i' for inches, `c' for
centimeters, `p' for points, and `P' for picas.
.
Example:
.BR 12c,235p .
.
An argument which starts with a digit is always treated as a custom paper
format.
.
.B papersize
sets both the vertical and horizontal dimension of the output medium.
.
.IP
More than one argument can be specified;
.B groff
scans from left to right and uses the first valid paper specification.
.
.TP
.BI "paperwidth " n
The physical horizontal dimension of the output medium in machine units.
.
Deprecated.
.
Use
.B papersize
instead.
.
This isn't used by
.BR troff
itself but by output devices.
.
.TP
.B pass_filenames
Make troff tell the driver the source file name being processed.
.
This is achieved by another tcommand:
.BR F \~\c
.IR filename .
.
.TP
.BI "postpro " program
Use
.I program
as the postprocessor.
.
.TP
.BI "prepro " program
Call
.I program
as a preprocessor.
.
.TP
.BI "print "  program
Use
.I program
as the spooler program for printing.
.
If omitted, the
.B \-l
and
.B \-L
options of
.B groff
are ignored.
.
.TP
.BI "res " n
There are
.I n
machine units per inch.
.
.TP
.BI "sizes " "s1 s2 \|.\|.\|.\| sn " 0
This means that the device has fonts at
.IR s1 ,
.IR s2 ", \|.\|.\|., " sn
scaled points.
.
The list of sizes must be terminated by a
.BR 0 .
.
Each
.I si
can also be a range of sizes
.IR m \- n .
.
The list can extend over more than one line.
.
.TP
.BI "sizescale " n
The scale factor for point sizes.
.
By default this has a value of 1.
.
One
.I
scaled point
is equal to
one
.RI point\|/\| n .
.
The arguments to the
.B unitwidth
and
.B sizes
commands are given in scaled points.
.
.TP
.BI "styles " "S1 S2 \|.\|.\|.\| Sm"
The first
.I m
font positions are associated with styles
.IR S1 ", \|.\|.\|., " Sm .
.
.TP
.B tcommand
This means that the postprocessor can handle the
.B t
and\~\c
.B u
output commands.
.
.TP
.B unicode
Indicate that the output device supports the complete Unicode
repertoire.
.
Useful only for devices which produce
.I character entities
instead of glyphs.
.
.IP
If
.B unicode
is present, no
.B charset
section is required in the font description files since the Unicode
handling built into
.B groff
is used.
.
However, if there are entries in a
.B charset
section, they either override the default mappings for those
particular characters or add new mappings (normally for composite
characters).
.
.IP
This is used for
.BR \-Tutf8 ,
.BR \-Thtml ,
and
.BR \-Txhtml .
.
.TP
.BI "unitwidth " n
Quantities in the font files are given in machine units
for fonts whose point size is
.IR n \~\c
scaled points.
.
.TP
.B unscaled_charwidths
Make the font handling module always return unscaled glyph widths.
.
Needed for the
.B \%grohtml
device.
.
.TP
.B use_charnames_in_special
This command indicates that troff should encode named glyphs inside
special commands.
.
.TP
.BI "vert " n
The vertical resolution is
.IR n \~\c
machine units.
.
.LP
The
.BR res ,
.BR unitwidth ,
.BR fonts ,
and
.B sizes
lines are compulsory.
.
Not all commands in the DESC file are used by
.B troff
itself; some of the keywords (or even additional ones) are used by
postprocessors to store arbitrary information about the device.
.
.LP
Here a list of obsolete keywords which are recognized by
.B groff
but completely ignored:
.BR spare1 ,
.BR spare2 ,
.BR biggestfont .
.
.
.SS Font file format
.
A font file has two sections;
empty lines are ignored in both of them.
.
.LP
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.
.
.TP
.BI "ligatures " "lig1 lig2 \|.\|.\|.\| lign \fR[" 0 \fR]
Glyphs
.IR lig1 ,
.IR lig2 ", \|.\|.\|., " lign
are ligatures; possible ligatures are
.BR ff ,
.BR fi ,
.BR fl ,
.BR ffi ,
and
.BR ffl .
.
For backwards compatibility, the list of ligatures may be terminated
with a\~\c
.BR 0 .
.
The list of ligatures may not extend over more than one line.
.
.TP
.BI "name " F
The name of the font is\~\c
.IR F .
.
.TP
.BI "slant " n
The glyphs of the font have a slant of
.IR n \~\c
degrees.
.
(Positive means forward.)
.
.TP
.BI "spacewidth "  n
The normal width of a space is\~\c
.IR n .
.
.TP
.B special
The font is
.IR 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.
.
.LP
Other commands are ignored by
.B troff
but may be used by postprocessors to store arbitrary information
about the font in the font file.
.
.LP
The first section can contain comments which start with the
.B #
character and extend to the end of a line.
.
.LP
The second section contains one or two subsections.
.
It must contain a
.I charset
subsection
and it may also contain a
.I kernpairs
subsection.
.
These subsections can appear in any order.
.
Each subsection starts with a word on a line by itself.
.
.LP
The word
.B charset
starts the charset subsection.
.
The
.B 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
.
.IP
.I name metrics type code
.RI [ entity_name ]
.RB [ \-\-
.IR comment ]
.
.LP
.I name
identifies the glyph:
if
.I name
is a single glyph
.I c
then it corresponds to the groff input character
.IR c ;
if it is of the form
.BI \[rs] c
where c is a single character, then it
corresponds to the special character
.BI \[rs][ c ]\fR;
otherwise it corresponds to the groff input character
.BI \[rs][ name ]\fR.
.
If it is exactly two characters
.I xx
it can be entered as
.BI \[rs]( xx\fR.
.
Note that single-letter special characters can't be accessed as
.BI \[rs] c\fR;
the only exception is `\[rs]\-' which is identical to `\[rs][\-]'.
.
The name
.B \-\-\-
is special and indicates that the glyph is unnamed;
such glyphs can only be used by means of the
.B \[rs]N
escape sequence in
.BR troff .
.
.LP
The
.I type
field gives the glyph type:
.
.TP
1
means the glyph has a descender, for example, `p';
.
.TP
2
means the glyph has an ascender, for example, `b';
.
.TP
3
means the glyph has both an ascender and a descender, for example,
`('.
.
.LP
The
.I 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
.B \[rs]N
escape sequence.
.
The code can be any integer.
.
If it starts with a\~\c
.B 0
it is interpreted as octal;
if it starts with
.B 0x
or
.B 0X
it is interpreted as hexadecimal.
.
Note, however, that the
.B \[rs]N
escape sequence only accepts a decimal integer.
.
.LP
The
.I 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
.B grops
to build sub-encoding arrays for PS fonts containing more than 256 glyphs.
.
(It has also been used for
.BR \%grohtml 's
entity names but for efficiency reasons this data is now compiled directly
into
.BR \%grohtml .)
.
.LP
Anything on the line after the encoding field or `\-\-' are ignored.
.
.LP
The
.I metrics
field has the form (in one line; it is broken here for the sake of
readability):
.
.IP
.I width\c
.RI [\fB, height\c
.RI [\fB, depth\c
.RI [\fB, italic-correction
.br
.RI [\fB, left-italic-correction\c
.RI [\fB, subscript-correction ]]]]]
.
.LP
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
.B char
as they are in ditroff.
.
The
.I width
subfields gives the width of the glyph.
.
The
.I 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
.I 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
.I 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
.I 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
.I 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.
.
.LP
A line in the charset section can also have the format
.
.IP
.I
name \fB"
.
.LP
This indicates that
.I name
is just another name for the glyph mentioned in the
preceding line.
.
.LP
The word
.B kernpairs
starts the kernpairs section.
.
This contains a sequence of lines of the form:
.
.IP
.I c1 c2 n
.
.LP
This means that when glyph
.I c1
appears next to glyph
.I c2
the space between them should be increased by\~\c
.IR n .
.
Most entries in kernpairs section have a negative value for\~\c
.IR n .
.
.
.SH FILES
.
.Tp \w'@FONTDIR@/devname/DESC'u+3n
.BI @FONTDIR@/dev name /DESC
Device description file for device
.IR name .
.
.TP
.BI @FONTDIR@/dev name / F
Font file for font\~\c
.I F
of device
.IR name .
.
.
.SH "SEE ALSO"
.
.BR groff_out (@MAN5EXT@),
.BR @g@troff (@MAN1EXT@).
.
.cp \n[groff_font_C]
.
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