font(5) DG/UX 4.30 font(5)
NAME
font - description files for device-independent troff
SYNOPSIS
troff -Tptty ...
DESCRIPTION
For each high-quality output device supported by troff(1)
and available on this system, there is a directory
containing files describing the device and its fonts. This
directory is named /usr/lib/font/devptty where ptty is the
name of the device. Currently the only ptty supported is
i10 for the IMAGEN laser printer.
For a particular device, ptty, the ASCII file DESC in the
directory /usr/lib/font/devptty describes its
characteristics. Each line starts with a word identifying
the characteristic and followed by appropriate specifiers.
Blank lines and lines beginning with a # are ignored.
The legal lines for DESC are:
res num resolution of device in basic
increments per inch
hor num smallest unit of horizontal motion
vert num smallest unit of vertical motion
unitwidth num pointsize in which widths are
specified
sizescale num scaling for fractional pointsizes
paperwidth num width of paper in basic increments
paperlength num length of paper in basic increments
biggestfont num maximum size for a font
spare2 num available for use
sizes num num ... list of pointsizes available on
typesetter
fonts num name ... number of initial fonts followed by
the names of the fonts. For
example:
fonts 4 R I B S
charset this always comes last in the file
and is on a line by itself.
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font(5) DG/UX 4.30 font(5)
Following it is the list of special
character names for this device.
Names are separated by a space or a
newline. The list can be as long
as necessary. Names not in this
list are not allowed in the font
description files.
Res is the basic resolution of the device in increments per
inch. Hor and vert describe the relationships between
motions in the horizontal and vertical directions. If the
device is capable of moving in single basic increments in
both directions, both hor and vert would have values of 1.
If the vertical motions only take place in multiples of two
basic units while the horizontal motions take place in the
basic increments, then hor would be 1, while vert would be
2. Unitwidth is the pointsize in which all width tables in
the font description files are given. Troff automatically
scales the widths from the unitwidth size to the pointsize
it is working with. Sizescale is not currently used and is
1. Paperwidth is the width of the paper in basic
increments. The Imagen laser printer's width is 1851
increments. Paperlength is the length of a sheet of paper
in the basic increments. The Imagen laser printer's length
is 3703 increments.
For each font supported by the phototypesetter, there is
also an ASCII file with the same name as the font (e.g., R,
I, CW). The format for a font description file is:
name name name of the font, such as R or CW
internalname name internal name of font
special sets flag indicating that the font
is special
ligatures name ... 0
Sets flag indicating font has
ligatures. The list of ligatures
follows and is terminated by a
zero. Accepted ligatures are:
ff fi fl ffi ffl.
spare1 available for use
spacewidth num width of space if something other
than 1/3 of the width of the \(em
character is desired as a space.
charset The charset must come at the end.
Each line following the word
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font(5) DG/UX 4.30 font(5)
charset describes one character in
the font. Each line has one of two
formats:
name width kerning code
name "
where name is either a single ASCII character or a
special character name from the list found in DESC.
The width is in basic increments. The kerning
information is 1 if the character descends below the
line, 2 if it rises above the letter 'a', and 3 if it
both rises and descends. The kerning information for
special characters is not used and so may be 0. The
code is the number sent to the typesetter to produce
the character. The second format is used to indicate
that the character has more than one name. The double
quote indicates that this name has the same values as
the preceding line. The kerning and code fields are
not used if the width field is a double quote
character.
Troff and its postprocessors read this information from
binary files produced from the ASCII files by a program
distributed with troff called makedev. For those with
a need to know, a description of the format of these
files follows:
The file DESC.out starts with the dev structure,
defined by dev.h:
/*
dev.h: characteristics of a typesetter
* /
struct dev {
short filesize; /* number of bytes in file, */
/* excluding dev part */
short res; /* basic resolution in goobies/inch */
short hor; /* goobies horizontally */
short vert;
short unitwidth; /* size at which widths are given*/
short nfonts; /* number fonts physically available */
short nsizes; /* number of pointsizes */
short sizescale; /* scaling for fractional pointsizes */
short paperwidth; /* max line length in units */
short paperlength; /* max paper length in units */
short nchtab; /* number of funny names in chtab */
short lchname; /* length of chname table */
short spare1; /* in case of expansion */
short spare2;
};
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font(5) DG/UX 4.30 font(5)
Filesize is just the size of everything in DESC.out
excluding the dev structure. Nfonts is the number of
different font positions available. Nsizes is the
number of different pointsizes supported by this
typesetter. Nchtab is the number of special character
names. Lchname is the total number of characters,
including nulls, needed to list all the special
character names. At the end of the structure are two
spares for later expansions.
Immediately following the dev structure are a number of
tables. First is the sizes table, which contains
nsizes + 1 shorts(a null at the end), describing the
pointsizes of text available on this device. The
second table is the funny_char_index_table. It
contains indices into the the table which follows it,
the funny_char_strings. The indices point to the
beginning of each special character name which is
stored in the funny_char_strings table. The
funny_char_strings table is lchname characters long,
while the funny_char_index_table is nchtab shorts long.
Following the dev structure will occur nfonts
{font}.out files, which are used to initialize the font
positions. These {font}.out files, which also exist as
separate files, begin with a font structure and then
are followed by four character arrays:
struct font { /* characteristics of a font */
char nwfont; /* number of width entries */
char specfont; /* 1 == special font */
char ligfont; /* 1 == ligatures exist on this font */
char spare1; /* unused for now */
char namefont[10]; /* name of this font, e.g., R */
char intname[10]; /* internal name of font, in ASCII */
};
The font structure tells how many defined characters
there are in the font, whether the font is a "special"
font and if it contains ligatures. It also has the
ASCII name of the font, which should match the name of
the file it appears in, and the internal name of the
font on the typesetting device (intname). The internal
name is independent of the font position and name that
troff knows about. For example, you might say mount R
in position 4, but when asking the typesetter to
actually produce a character from the R font, the
postprocessor which instructs the typesetter would use
intname.
The first three character arrays are specific for the
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font(5) DG/UX 4.30 font(5)
font and run in parallel. The first array, widths,
contains the width of each character relative to
unitwidth. Unitwidth is defined in DESC. The second
array, kerning, contains kerning information. If a
character rises above the letter 'a', 02 is set. If it
descends below the line, 01 is set. The third array,
codes, contains the code that is sent to the typesetter
to produce the character.
The fourth array is defined by the device description
in DESC. It is the font_index_table. This table
contains indices into the width, kerning, and code
tables for each character. The order that characters
appear in these three tables is arbitrary and changes
from one font to the next. In order for troff to be
able to translate from ASCII and the special character
names to these arbitrary tables, the font_index_table
is created with an order which is constant for each
device. The number of entries in this table is 96 plus
the number of special character names for this device.
The value 96 is 128 - 32, the number of printable
characters in the ASCII alphabet. To determine whether
a normal ASCII character exists, troff takes the ASCII
value of the character, subtracts 32, and looks in the
font_index_table. If it finds a 0, the character is
not defined in this font. If it finds anything else,
that is the index into widths, kerning, and codes that
describe that character.
To look up a special character name, for example \(pl,
the mathematical plus sign, and determine whether it
appears in a particular font or not, the following
procedure is followed. A counter is set to 0 and an
index to a special character name is picked out of the
counterth position in the funny_char_index_table. A
string comparision is performed between
funny_char_strings [ funny_char_index_table [ counter ]
] and the special character name, in our example pl,
and if it matches, then troff refers to this character
as ( 96 + counter). When it wants to determine whether
a specific font supports this character, it looks in
font_index_table[(96+counter)], (see below), to see
whether there is a 0, meaning the character does not
appear in this font, or number, which is the index into
the widths, kerning, and codes tables.
Notice that since a value of 0 in the font_index_table
indicates that a character does not exist, the 0th
element of the width, kerning, and codes arrays are not
used. For this reason the 0th element of the width
array can be used for a special purpose, defining the
width of a space for a font. Normally a space is
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font(5) DG/UX 4.30 font(5)
defined by troff to be 1/3 of the width of the \(em
character, but if the 0th element of the width array is
non-zero, then that value is used for the width of a
space.
FILES
/usr/lib/font/dev{X}/DESC.out
description file for device X
/usr/lib/font/dev{X}/{font}.out
font description files for device X
SEE ALSO
troff(1), troff(5).
Using the Documenter's Tool Kit on the DG/UX System.
Documenter's Tool Kit Technical Summary for the DG/UX
System.
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