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.\"	@(#)termdesc.me	6.2 (Berkeley) 5/20/86
.\"
.+c
.(l C
.sz 14
.b "Writing \s-2NROFF\s0 Terminal Descriptions"
.sp
.sz 10
Eric Allman
.i "Britton-Lee, Inc."
.)l
.sp 2
.sh 1 "INTRODUCTION"
.eh 'SMM:20-%''Writing NROFF Terminal Descriptions'
.oh 'Writing NROFF Terminal Descriptions''SMM:20-%'
.pp
As of the Version 7 Phototypesetter release of \s-2UNIX\s0,*
.(f
*\s-2UNIX\s0 is a trademark of Bell Laboratories.
.)f
\s-2NROFF\s0 has supported terminal description files.
These files describe the characteristics of available hard-copy printers.
This document describes some of the details of how to write
terminal description files.
.pp
.ul
Disclaimer.
This document describes the results of my personal experience.
The effects of changing some of the fields from the norms
may not be well defined,
even if it seems like it
.q ought
to work given the descriptions herein.
These tables are known to vary slightly
for different versions of \s-2UNIX\s0.
I have not seen \s-2UNIX\s0 3.0 at this time,
so this may be irrelevant in that context.
.sh 1 "GENERAL"
.pp
When \s-2NROFF\s0 starts up,
it looks for a
.b \-T
flag describing the terminal type.
For example,
if the command line is given as
.(b
nroff \-T300s
.)b
\s-2NROFF\s0 prepares output for a
.i DTC300S
terminal.
This terminal is described in the file
/usr/lib/term/tab300s
on most systems.
.pp
If no
.b \-T
flag is given,
the terminal type
.b 37
(ASR 37 \*- a relic assumed for historical humor only)
is assumed.
.pp
The terminal description table is a stripped
.q \&.o
file generated from a data structure,
shown in figure one.
.(z
.hl
.ta 8n 24n
#define INCH 240	/* one inch in units */
struct
{
	int bset;	/* stty bits to set */
	int breset;	/* stty bits to reset */
	int Hor;	/* horizontal resolution in units */
	int Vert;	/* vertical resolution in units */
	int Newline;	/* the distance a newline moves */
	int Char;	/* the distance one char moves */
	int Em;	/* size of an Em */
	int Halfline;	/* the distance a halfline up/down moves */
	int Adj;	/* default adjustment width */
	char *twinit;	/* string to init the terminal */
	char *twrest;	/* string to reset the terminal */
	char *twnl;	/* string to send a newline (CR-LF) */
	char *hlr;	/* half line reverse string */
	char *hlf;	/* half line forward string */
	char *flr;	/* full line reverse string */
	char *bdon;	/* string to turn boldface on */
	char *bdoff;	/* string to turn boldface off */
	char *ploton;	/* string to turn plot on */
	char *plotoff;	/* string to turn plot off */
	char *up;	/* move up in plot mode */
	char *down;	/* move down in plot mode */
	char *right;	/* move right in plot mode */
	char *left;	/* move left in plot mode */
	char *codetab[256-32];  /* the codes to send for characters */
	int zzz;	/* padding */
};
.sp
.ce
Figure 1 \*- the terminal descriptor data structure
.hl
.)z
This structure can be dealt with in two sections:
the terminal capability descriptor (everything to codetab),
and the output descriptor.
.sh 1 "TERMINAL CAPABILITIES"
.pp
The section of the data structure up to but excluding
.i codetab
describes the basic functions and setup requirements of the terminal.
Distances are measured in
.q units,
which are 1/240 of an inch in \s-2NROFF\s0.
In general, \s-2NROFF\s0 assumes that there is a
.q "plot mode"
on the terminal that allows you to move in small increments.
A terminal has a resolution when in plot mode
that is measured in units.
This limits how well the terminal can simulate
printing Greek and special characters.
.sh 2 "bset, breset"
.pp
These fields define bits in a vanilla stty(2) word
(sg_flags) to
set and clear respectively when
\s-2NROFF\s0 starts.
They are normally represented in octal,
although you could include <sgtty.h>.
[Note:
these fields are presumably different
in \s-2UNIX\s0 3.0.]
.sh 2 "Hor, Vert"
.pp
These represent the horizontal and vertical resolution respectively
of the terminal when it is in plot mode.
They are given in units.
.sh 2 "Newline"
.pp
This field describes the distance that the
.i twnl
field (below) will move the paper;
it is literally the size of a newline.
.sh 2 "Char"
.pp
This is the distance that a regular character
will move the print head to the right.
.sh 2 "Em"
.pp
The
.q em
is a typesetting unit,
approximately equal to the width of the letter
.q m .
In \s-2NROFF\s0 driver tables,
this must be the distance a space or backspace character will move
the carriage.
.sh 2 "Halfline"
.pp
This is the distance that the
.i hlr
or
.i hlf
strings move the print head
(reverse or forward respectively).
.sh 2 "Adj"
.pp
This is the resolution that \s-2NROFF\s0 will normally adjust
your lines to horizontally.
Typically this is the same as Char.
If the
.b \-e
flag is given to \s-2NROFF\s0,
output resolution will be to the full device resolution.
.sh 2 "twinit, twrest"
.pp
These strings are output when \s-2NROFF\s0 starts and finishes
respectively.
.sh 2 "twnl"
.pp
This string is output when \s-2NROFF\s0 wants to do a carriage return.
Typically it will be
.q "\er\en" .
Remember,
the terminal will normally have CRMOD turned off
when this is set.
.sh 2 "hlr, hlf"
.pp
These strings are sent to move the carriage back or forward
one half line respectively.
The actual amount that they moved is defined by
Halfline.
The carriage should be left in the same column.
.sh 2 "flr"
.pp
The string to send to move a full line backwards.
This should leave the carriage in the same column.
.sh 2 "bdon, bdoff"
.pp
These strings are sent to turn boldface mode on and off
respectively.
Normally this will set the terminal into overstrike mode.
If they are not given,
some newer versions of \s-2NROFF\s0 will output the characters
four times to force overstriking.
.sh 2 "ploton, plotoff"
.pp
These strings turn plot mode on and off respectively.
In plot mode,
the carriage moves a very small amount,
and only under specific control;
i.e., characters do not automatically cause any carriage motion.
.sh 2 "up, down, right, left"
.pp
These strings are only output in plot mode.
They should move the carriage up, down, left, and right
respectively;
they will move the carriage a distance of Hor or Vert
as appropriate.
.sh 2 "An Example"
.pp
Consider the following table describing a
DTC300S:
.(b
.ta 1.5i
/*bset*/	0,
/*breset*/	0177420,
/*Hor*/	INCH/60,
/*Vert*/	INCH/48,
/*Newline*/	INCH/6,
/*Char*/	INCH/10,
/*Em*/	INCH/10,
/*Halfline*/	INCH/12,
/*Adj*/	INCH/10,
/*twinit*/	"\e033\e006",
/*twrest*/	"\e033\e006",
/*twnl*/	"\e015\en",
/*hlr*/	"\e033H",
/*hlf*/	"\e033h",
/*flr*/	"\e032",
/*bdon*/	"",
/*bdoff*/	"",
/*ploton*/	"\e006",
/*plotoff*/	"\e033\e006",
/*up*/	"\e032",
/*down*/	"\en",
/*right*/	" ",
/*left*/	"\eb",
.)b
This describes a terminal that should have the
ALLDELAY and CRMOD bits turned off,
1/60" horizontal and 1/48" vertical resolution,
six lines per inch and ten characters per inch, including space,
halfline takes 1/12" (one half of a full line),
should send ESC-control-F to initialize and reset the terminal
(to insure that it is in a normal state),
takes <CR><LF> to give a newline,
<ESC>H to move back one half line,
<ESC>h to move forward one half line,
control-Z to move back one full line,
has no bold mode,
takes control-F to enter plot mode
and escape-control-F to exit plot mode,
and uses control-Z, linefeed, space, and backspace
to move up, down, right, and left respectively
when in plot mode.
.sh 1 "CHARACTER DESCRIPTIONS"
.pp
There is one character description
for each possible character to be output.
The easiest way to find what character corresponds to what position
is to edit an existing character table;
one is given in the appendix as an example.
Character representations are represented as a string per
character.
.pp
The first character of the string
is interpreted as a binary number
giving the number of character spaces taken up
by this character.
For regular characters
this will always be
.q "\e001" ,
but Greek and special characters can take more.
If the 0200 bit is set in this character,
it indicates that the character should be underlined
if we are in italic (underline) mode.
Thus,
alphabetic and numeric descriptions
will begin
.q "\e201" .
.pp
The remainder of the string is output to represent the character.
If the first output character
(i.e.,
the second character in the total string)
has the 0200 bit set,
the character will be output in plot mode
so that fancy characters can be built up from existing characters.
If necessary,
the
.q "\e200"
character can be used as a null character
to force \s-2NROFF\s0 to set the terminal into plot mode.
All characters without the 0200 bit are output literally;
characters with the 0200 bit are not output,
but are used to indicate local carriage movement.
The next two bits (0140 bits) represent direction:
.(b
.ta \w'0200  'u
0200	right
0240	left
0300	down
0340	up
.)b
The bottom five bits represent a distance in terminal resolution units.
This is rather confusing,
but the examples should make this much more clear.
.sh 2 "Some Examples"
.pp
The following examples are from the DTC300S table:
.(b
.ta 2i
"\e001 ",	/*space*/
"\e001=",	/*=*/
"\e201A",	/*A*/
.)b
These entries show that all of these characters
take one character width when output.
The letter A is underlined in italic mode,
but neither space nor equal sign is.
.(b
.ta 2i
"\e001o\eb+",	/*bullet*/
"\e002[]",	/*square*/
"\e202f\^i",	/*f\^i*/
.)b
The bullet character takes only one character position,
but is created by outputing the letter
.q o
and overstriking it with a plus sign.
The square character is approximated
with two brackets;
it takes two full character positions
when output.
The
.q fi
ligature
is produced using the letters
.q f
and
.q i
(surprise!);
it is underlined in italic mode.
.(b
"\e001\e241c\e202(\e241", /*alpha*/
"\e001\e200B\e242\e302|\e202\e342", /*beta*/
.)b
The letters alpha and beta both take a single character position.
The alpha is output by entering plot mode,
moving left 1 terminal unit (1/60" if you recall),
outputing the letter
.q c ,
moving right 2/60",
outputing a left parenthesis,
and finally moving left 1/60";
it is critical that the net space moved
be zero both horizontally and vertically.
The beta first has a dummy 0200 character
to enter plot mode but not output anything.
It then outputs a
.q B ,
moves left 2/60",
moves down 2/48",
outputs a vertical bar
(which is designed to partically overstrike the left edge of the
.q B ,
and finally move right 2/60" and up 2/48"
to set us back to the right place.
.sh 1 "INSTALLATION"
.pp
To install a terminal descriptor,
make it up by editing an existing terminal descriptor.
Assuming your terminal name is
.i term ,
call your new descriptor
.b tab \c
.i term \c
.b .c .
Then, execute the following commands:
.(b
cc -c tabterm.c
strip tabterm.c
cp tabterm.o /usr/lib/term/tabterm
.)b
The directory /usr/src/cmd/troff/term
typically has a shell file to do this.
.+c
.ce 2
APPENDIX
.sp
A Sample Table
.sp 3
This table describes the DTC 300S.
.(l
.re
#define INCH 240
/*
DASI300S
nroff driving tables
width and code tables
*/

struct {
	int bset;
	int breset;
	int Hor;
	int Vert;
	int Newline;
	int Char;
	int Em;
	int Halfline;
	int Adj;
	char *twinit;
	char *twrest;
	char *twnl;
	char *hlr;
	char *hlf;
	char *flr;
	char *bdon;
	char *bdoff;
	char *ploton;
	char *plotoff;
	char *up;
	char *down;
	char *right;
	char *left;
	char *codetab[256-32];
	int zzz;
	} t = {
/*bset*/	0,
/*breset*/	0177420,
/*Hor*/		INCH/60,
/*Vert*/	INCH/48,
/*Newline*/	INCH/6,
/*Char*/	INCH/10,
/*Em*/		INCH/10,
/*Halfline*/	INCH/12,
/*Adj*/		INCH/10,
/*twinit*/	"\e033\e006",
/*twrest*/	"\e033\e006",
/*twnl*/	"\e015\en",
/*hlr*/		"\e033H",
/*hlf*/		"\e033h",
/*flr*/		"\e032",
/*bdon*/	"",
/*bdoff*/	"",
/*ploton*/	"\e006",
/*plotoff*/	"\e033\e006",
/*up*/		"\e032",
/*down*/	"\en",
/*right*/	" ",
/*left*/	"\eb",
	/*codetab*/
"\e001 ",	/*space*/
"\e001!",	/*!*/
"\e001\e"",	/*"*/
"\e001#",	/*#*/
"\e001$",	/*$*/
"\e001%",	/*%*/
"\e001&",	/*&*/
"\e001'",	/*' close*/
"\e001(",	/*(*/
"\e001)",	/*)*/
"\e001*",	/***/
"\e001+",	/*+*/
"\e001,",	/*,*/
"\e001-",	/*- hyphen*/
"\e001.",	/*.*/
"\e001/",	/*/*/
"\e2010",	/*0*/
"\e2011",	/*1*/
"\e2012",	/*2*/
"\e2013",	/*3*/
"\e2014",	/*4*/
"\e2015",	/*5*/
"\e2016",	/*6*/
"\e2017",	/*7*/
"\e2018",	/*8*/
"\e2019",	/*9*/
"\e001:",	/*:*/
"\e001;",	/*;*/
"\e001<",	/*<*/
"\e001=",	/*=*/
"\e001>",	/*>*/
"\e001?",	/*?*/
"\e001@",	/*@*/
"\e201A",	/*A*/
"\e201B",	/*B*/
"\e201C",	/*C*/
"\e201D",	/*D*/
"\e201E",	/*E*/
"\e201F",	/*F*/
"\e201G",	/*G*/
"\e201H",	/*H*/
"\e201I",	/*I*/
"\e201J",	/*J*/
"\e201K",	/*K*/
"\e201L",	/*L*/
"\e201M",	/*M*/
"\e201N",	/*N*/
"\e201O",	/*O*/
"\e201P",	/*P*/
"\e201Q",	/*Q*/
"\e201R",	/*R*/
"\e201S",	/*S*/
"\e201T",	/*T*/
"\e201U",	/*U*/
"\e201V",	/*V*/
"\e201W",	/*W*/
"\e201X",	/*X*/
"\e201Y",	/*Y*/
"\e201Z",	/*Z*/
"\e001[",	/*[*/
"\e001\e\e",	/*\e*/
"\e001]",	/*]*/
"\e001^",	/*^*/
"\e001_",	/*_ dash*/
"\e001`",	/*` open*/
"\e201a",	/*a*/
"\e201b",	/*b*/
"\e201c",	/*c*/
"\e201d",	/*d*/
"\e201e",	/*e*/
"\e201f",	/*f*/
"\e201g",	/*g*/
"\e201h",	/*h*/
"\e201i",	/*i*/
"\e201j",	/*j*/
"\e201k",	/*k*/
"\e201l",	/*l*/
"\e201m",	/*m*/
"\e201n",	/*n*/
"\e201o",	/*o*/
"\e201p",	/*p*/
"\e201q",	/*q*/
"\e201r",	/*r*/
"\e201s",	/*s*/
"\e201t",	/*t*/
"\e201u",	/*u*/
"\e201v",	/*v*/
"\e201w",	/*w*/
"\e201x",	/*x*/
"\e201y",	/*y*/
"\e201z",	/*z*/
"\e001{",	/*{*/
"\e001|",	/*|*/
"\e001}",	/*}*/
"\e001~",	/*~*/
"\e000\e0",	/*narrow sp*/
"\e001-",	 /*hyphen*/
"\e001o\eb+",	 /*bullet*/
"\e002[]",	 /*square*/
"\e001-",	 /*3/4 em*/
"\e001_",	 /*rule*/
"\e000\e0",	 /*1/4*/
"\e000\e0",	 /*1/2*/
"\e000\e0",	 /*3/4*/
"\e001-",	 /*minus*/
"\e202f\^i",	 /*fi*/
"\e202f\^l",	 /*fl*/
"\e202f\^f",	 /*ff*/
"\e203f\^f\^i",	 /*ffi*/
"\e203f\^f\^l",	 /*ffl*/
"\e000\e0",	 /*degree*/
"\e000\e0",	 /*dagger*/
"\e000\e0",	 /*section*/
"\e001'",	 /*foot mark*/
"\e001'",	 /*acute accent*/
"\e001`",	 /*grave accent*/
"\e001_",	 /*underrule*/
"\e001/",	 /*slash (longer)*/
"\e000\e0",	/*half narrow space*/
"\e001 ",	/*unpaddable space*/
"\e001\e241c\e202(\e241", /*alpha*/
"\e001\e200B\e242\e302|\e202\e342", /*beta*/
"\e001\e200)\e201/\e241", /*gamma*/
"\e001\e200o\e342<\e302", /*delta*/
"\e001<\eb-", /*epsilon*/
"\e001\e200c\e201\e301,\e241\e343<\e302", /*zeta*/
"\e001\e200n\e202\e302|\e242\e342", /*eta*/
"\e001O\eb-", /*theta*/
"\e001i",	 /*iota*/
"\e001k",	 /*kappa*/
"\e001\e200\e\e\e304\e241'\e301\e241'\e345\e202", /*lambda*/
"\e001\e200u\e242,\e202", /*mu*/
"\e001\e241(\e203/\e242", /*nu*/
"\e001\e200c\e201\e301,\e241\e343c\e241\e301`\e201\e301", /*xi*/
"\e001o",	 /*omicron*/
"\e001\e341-\e303\e"\e301\e"\e343", /*pi*/
"\e001\e200o\e242\e302|\e342\e202", /*rho*/
"\e001\e200o\e301\e202~\e341\e242", /*sigma*/
"\e001\e200t\e301\e202~\e243~\e201\e341", /*tau*/
"\e001v",	 /*upsilon*/
"\e001o\eb/", /*phi*/
"\e001x",	 /*chi*/
"\e001\e200/-\e302\e202'\e244'\e202\e342", /*psi*/
"\e001\e241u\e203u\e242", /*omega*/
"\e001\e242|\e202\e343-\e303\e202`\e242", /*Gamma*/
"\e001\e242/\e303-\e204-\e343\e\e\e242", /*Delta*/
"\e001O\eb=", /*Theta*/
"\e001\e242/\e204\e\e\e242", /*Lambda*/
"\e000\e0",	 /*Xi*/
"\e001\e242[]\e204[]\e242\e343-\e303", /*Pi*/
"\e001\e200>\e302-\e345-\e303", /*Sigma*/
"\e000\e0",	 /**/
"\e001Y",	 /*Upsilon*/
"\e001o\eb[\eb]", /*Phi*/
"\e001\e200[]-\e302\e202'\e244`\e202\e342", /*Psi*/
"\e001\e200O\e302\e241-\e202-\e241\e342", /*Omega*/
"\e000\e0",	 /*square root*/
"\e000\e0",	 /*terminal sigma*/
"\e000\e0",	 /*root en*/
"\e001>\eb_",	 /*>=*/
"\e001<\eb_",	 /*<=*/
"\e001=\eb_",	 /*identically equal*/
"\e001-",	 /*equation minus*/
"\e001=\eb~",	 /*approx =*/
"\e000\e0",	 /*approximates*/
"\e001=\eb/",	 /*not equal*/
"\e002->",	 /*right arrow*/
"\e002<-",	 /*left arrow*/
"\e001|\eb^",	 /*up arrow*/
"\e000\e0",	 /*down arrow*/
"\e001=",	 /*equation equal*/
"\e001x",	 /*multiply*/
"\e001/",	 /*divide*/
"\e001+\eb_",	 /*plus-minus*/
"\e001U",	 /*cup (union)*/
"\e000\e0",	 /*cap (intersection)*/
"\e000\e0",	 /*subset of*/
"\e000\e0",	 /*superset of*/
"\e000\e0",	 /*improper subset*/
"\e000\e0",	 /* improper superset*/
"\e002oo",	 /*infinity*/
"\e001\e200o\e201\e301`\e241\e341`\e241\e341`\e201\e301", /*partial derivative*/
"\e001\e242\e\e\e343-\e204-\e303/\e242", /*gradient*/
"\e001\e200-\e202\e341,\e301\e242", /*not*/
"\e001\e200|'\e202`\e243\e306'\e241`\e202\e346",	/*integral sign*/
"\e000\e0",	 /*proportional to*/
"\e000\e0",	 /*empty set*/
"\e000\e0",	 /*member of*/
"\e001+",	 /*equation plus*/
"\e001r\ebO",	 /*registered*/
"\e001c\ebO",	 /*copyright*/
"\e001|",	 /*box rule */
"\e001c\eb/",	 /*cent sign*/
"\e000\e0",	 /*dbl dagger*/
"\e000\e0",	 /*right hand*/
"\e001*",	 /*left hand*/
"\e001*",	 /*math * */
"\e000\e0",	 /*bell system sign*/
"\e001|",	 /*or (was star)*/
"\e001O",	 /*circle*/
"\e001|",	 /*left top (of big curly)*/
"\e001|",	 /*left bottom*/
"\e001|",	 /*right top*/
"\e001|",	 /*right bot*/
"\e001|",	 /*left center of big curly bracket*/
"\e001|",	 /*right center of big curly bracket*/
"\e001|",	/*bold vertical*/
"\e001|",	/*left floor (left bot of big sq bract)*/
"\e001|",	/*right floor (rb of ")*/
"\e001|",	/*left ceiling (lt of ")*/
"\e001|"};	/*right ceiling (rt of ")*/
.)l