352 lines
8.0 KiB
Groff
352 lines
8.0 KiB
Groff
.\" $Id: groff_font.5,v 1.2 1993/08/02 17:44:21 mycroft Exp $ -*- nroff -*-
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.de TQ
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.br
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.ns
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.TP \\$1
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..
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.\" Like TP, but if specified indent is more than half
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.\" the current line-length - indent, use the default indent.
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.de Tp
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.ie \\n(.$=0:((0\\$1)*2u>(\\n(.lu-\\n(.iu)) .TP
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.el .TP "\\$1"
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..
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.TH GROFF_FONT 5 "24 September 1992" "Groff Version 1.08"
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.SH NAME
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groff_font \- format of groff device and font description files
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.SH DESCRIPTION
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The groff font format is roughly a superset of the ditroff
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font format.
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Unlike the ditroff font format, there is no associated binary
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format.
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The font files for device
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.I name
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are stored in a directory
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.BI dev name.
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There are two types of file: a
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device description file called
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.B DESC
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and for each font
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.I F
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a font file called
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.IR F .
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These are text files;
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there is no associated binary format.
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.SS DESC file format
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The DESC file can contain the following types of line:
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.TP
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.BI res\ n
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There are
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.I n
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machine units per inch.
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.TP
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.BI hor\ n
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The horizontal resolution is
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.I n
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machine units.
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.TP
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.BI vert\ n
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The vertical resolution is
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.I n
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machine units.
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.TP
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.BI sizescale\ n
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The scale factor for pointsizes.
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By default this has a value of 1.
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One
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.I
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scaled point
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is equal to
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one
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.RI point/ n .
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The arguments to the
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.B unitwidth
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and
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.B sizes
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commands are given in scaled points.
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.TP
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.BI unitwidth\ n
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Quantities in the font files are given in machine units
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for fonts whose point size is
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.I n
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scaled points.
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.TP
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.B tcommand
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This means that the postprocessor can handle the
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.B t
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and
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.B u
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output commands.
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.TP
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.BI sizes\ s1\ s2\|.\|.\|.\|sn\ 0
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This means that the device has fonts at
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.IR s1 ,
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.IR s2 ,\|.\|.\|.\| sn
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scaled points.
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The list of sizes must be terminated by a
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.BR 0 .
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Each
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.BI s i
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can also be a range of sizes
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.IR m \- n .
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The list can extend over more than one line.
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.TP
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.BI styles\ S1\ S2\|.\|.\|.\|Sm
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The first
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.I m
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font positions will be associated with styles
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.IR S1\|.\|.\|.\|Sm .
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.TP
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.BI fonts\ n\ F1\ F2\ F3\|.\|.\|.\|Fn
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Fonts
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.I F1\|.\|.\|.\|Fn
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will be mounted in the font positions
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.IR m +1,\|.\|.\|., m + n
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where
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.I m
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is the number of styles.
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This command may extend over more than one line.
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A font name of
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.B 0
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will cause no font to be mounted on the corresponding font position.
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.TP
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.BI family\ fam
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The default font family is
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.IR fam .
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.TP
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.B charset
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This line and everything following in the file are ignored.
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It is allowed for the sake of backwards compatibility.
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.LP
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The res, unitwidth, fonts and sizes lines are compulsory.
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Other commands are ignored by
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.B troff
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but may be used by postprocessors to store arbitrary information
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about the device in the DESC file.
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.SS Font file format
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A font file has two sections. The first section is a sequence
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of lines each containing a sequence of blank delimited
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words; the first word in the line is a key, and subsequent
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words give a value for that key.
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.TP
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.BI name\ F
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The name of the font is
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.IR F .
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.TP
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.BI spacewidth\ n
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The normal width of a space is
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.IR n .
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.TP
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.BI slant\ n
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The characters of the font have a slant of
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.I n
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degrees. (Positive means forward.)
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.TP
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.BI ligatures\ lig1\ lig2\|.\|.\|.\|lign\ \fR[ 0 \fR]
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Characters
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.IR lig1 ,
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.IR lig2 ,\|.\|.\|., lign
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are ligatures; possible ligatures are
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.BR ff ,
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.BR fi ,
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.BR fl
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and
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.BR ffl .
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For backwards compatibiliy, the list of ligatures may be terminated
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with a
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.BR 0.
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The list of ligatures may not extend over more than one line.
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.TP
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.B special
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The font is
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.IR special ;
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this means that when a character is requested that is not present in
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the current font, it will be searched for in any special fonts that
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are mounted.
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.LP
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Other commands are ignored by
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.B troff
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but may be used by postprocessors to store arbitrary information
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about the font in the font file.
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.LP
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The first section can contain comments which start with the
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.B #
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character and extend to the end of a line.
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.LP
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The second section contains one or two subsections.
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It must contain a
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.I charset
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subsection
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and it may also contain a
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.I kernpairs
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subsection.
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These subsections can appear in any order.
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Each subsection starts with a word on a line by itself.
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.LP
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The word
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.B charset
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starts the charset subsection.
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The
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.B charset
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line is followed by a sequence of lines.
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Each line gives information for one character.
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A line comprises a number of fields separated
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by blanks or tabs. The format is
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.IP
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.I
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name metrics type code comment
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.LP
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.I name
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identifies the character:
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if
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.I name
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is a single character
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.I c
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then it corresponds to the groff input character
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.IR c ;
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if it is of the form
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.BI \e c
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where c is a single character, then it
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corresponds to the groff input character
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.BI \e c\fR;
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otherwise it corresponds to the groff input character
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.BI \e[ name ]
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(if it is exactly two characters
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.I xx
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it can be entered as
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.BI \e( xx\fR.)
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Groff supports eight bit characters; however some utilities
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has difficulties with eight bit characters.
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For this reason, there is a convention that the name
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.BI char n
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is equivalent to the single character whose code is
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.I n .
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For example,
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.B char163
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would be equivalent to the character with code 163
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which is the pounds sterling sign in ISO Latin-1.
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The name
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.B \-\-\-
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is special and indicates that the character is unnamed;
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such characters can only be used by means of the
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.B \eN
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escape sequence in
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.BR troff .
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.LP
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The
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.I type
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field gives the character type:
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.TP
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1
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means the character has an descender, for example, p;
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.TP
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2
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means the character has an ascender, for example, b;
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.TP
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3
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means the character has both an ascender and a descender, for example,
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(.
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.LP
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The
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.I code
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field gives the code which the postprocessor uses to print the character.
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The character can also be input to groff using this code by means of the
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.B \eN
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escape sequence.
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The code can be any integer.
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If it starts with a
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.B 0
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it will be interpreted as octal;
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if it starts with
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.B 0x
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or
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.B 0X
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it will be intepreted as hexdecimal.
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.LP
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Anything on the line after the code field will be ignored.
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.LP
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The
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.I metrics
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field has the form:
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.IP
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.IR width [\fB, height [\fB, depth [\fB, italic_correction [\fB, \
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left_italic_correction [\fB, subscript_correction ]]]]]
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.LP
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There must not be any spaces between these subfields.
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Missing subfields are assumed to be 0.
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The subfields are all decimal integers.
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Since there is no associated binary format, these
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values are not required to fit into a variable of type
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.B char
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as they are in ditroff.
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The
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.I width
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subfields gives the width of the character.
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The
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.I height
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subfield gives the height of the character (upwards is positive);
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if a character does not extend above the baseline, it should be
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given a zero height, rather than a negative height.
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The
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.I depth
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subfield gives the depth of the character, that is, the distance
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below the lowest point below the baseline to which the
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character extends (downwards is positive);
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if a character does not extend below above the baseline, it should be
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given a zero depth, rather than a negative depth.
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The
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.I italic_correction
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subfield gives the amount of space that should be added after the
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character when it is immediately to be followed by a character
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from a roman font.
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The
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.I left_italic_correction
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subfield gives the amount of space that should be added before the
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character when it is immediately to be preceded by a character
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from a roman font.
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The
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.I subscript_correction
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gives the amount of space that should be added after a character
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before adding a subscript.
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This should be less than the italic correction.
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.LP
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A line in the charset section can also have the format
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.IP
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.I
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name \fB"
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.LP
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This indicates that
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.I name
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is just another name for the character mentioned in the
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preceding line.
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.LP
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The word
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.B kernpairs
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starts the kernpairs section.
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This contains a sequence of lines of the form:
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.IP
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.I
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c1 c2 n
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.LP
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This means that when character
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.I c1
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appears next to character
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.I c2
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the space between them should be increased by
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.IR n .
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Most entries in kernpairs section will have a negative value for
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.IR n .
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.SH FILES
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.Tp \w'/usr/share/groff_font/devname/DESC'u+3n
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.BI /usr/share/groff_font/dev name /DESC
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Device description file for device
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.IR name .
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.TP
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.BI /usr/share/groff_font/dev name / F
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Font file for font
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.I F
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of device
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.IR name .
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.SH "SEE ALSO"
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.BR groff_out (5),
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.BR troff (1).
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