GRN(1) General Commands Manual GRN(1)
NAME
grn - groff preprocessor for gremlin files
SYNOPSIS
grn [-Cv] [-T dev] [-M dir] [-F dir] [file ...]
DESCRIPTION
grn is a preprocessor for including gremlin pictures in groff input.
grn writes to standard output, processing only input lines between two
that start with .GS and .GE. Those lines must contain grn commands
(see below). These commands request a gremlin file, and the picture in
that file is converted and placed in the troff input stream. The .GS
request may be followed by a C, L, or R to center, left, or right jus-
tify the whole gremlin picture (default justification is center). If
no file is mentioned, the standard input is read. At the end of the
picture, the position on the page is the bottom of the gremlin picture.
If the grn entry is ended with .GF instead of .GE, the position is left
at the top of the picture.
Please note that currently only the -me macro package has support for
.GS, .GE, and .GF.
OPTIONS
Whitespace is permitted between a command-line option and its argument.
-Tdev Prepare output for printer dev. The default device is ps. See
groff(1) for acceptable devices.
-Mdir Prepend dir to the default search path for gremlin files. The
default path is (in that order) the current directory, the home
directory, /usr/lib/groff/site-tmac, /usr/share/groff/site-tmac,
and /usr/share/groff/1.22.4/tmac.
-Fdir Search dir for subdirectories devname (name is the name of the
device) for the DESC file before the default font directories
/usr/share/groff/site-font, /usr/share/groff/1.22.4/font, and
/usr/lib/font.
-C Recognize .GS and .GE (and .GF) even when followed by a charac-
ter other than space or newline.
-v Print the version number.
GRN COMMANDS
Each input line between .GS and .GE may have one grn command. Commands
consist of one or two strings separated by white space, the first
string being the command and the second its operand. Commands may be
upper or lower case and abbreviated down to one character.
Commands that affect a picture's environment (those listed before de-
fault, see below) are only in effect for the current picture: The envi-
ronment is reinitialized to the defaults at the start of the next pic-
ture. The commands are as follows:
1 N
2 N
3 N
4 N Set gremlin's text size number 1 (2, 3, or 4) to N points. The
default is 12 (16, 24, and 36, respectively).
roman f
italics f
bold f
special f
Set the roman (italics, bold, or special) font to troff's font f
(either a name or number). The default is R (I, B, and S, re-
spectively).
l f
stipple f
Set the stipple font to troff's stipple font f (name or number).
The command stipple may be abbreviated down as far as ‘st’ (to
avoid confusion with special). There is no default for stipples
(unless one is set by the default command), and it is invalid to
include a gremlin picture with polygons without specifying a
stipple font.
x N
scale N
Magnify the picture (in addition to any default magnification)
by N, a floating point number larger than zero. The command
scale may be abbreviated down to ‘sc’.
narrow N
medium N
thick N
Set the thickness of gremlin's narrow (medium and thick, respec-
tively) lines to N times 0.15pt (this value can be changed at
compile time). The default is 1.0 (3.0 and 5.0, respectively),
which corresponds to 0.15pt (0.45pt and 0.75pt, respectively).
A thickness value of zero selects the smallest available line
thickness. Negative values cause the line thickness to be pro-
portional to the current point size.
pointscale <off/on>
Scale text to match the picture. Gremlin text is usually
printed in the point size specified with the commands 1, 2, 3,
or 4, regardless of any scaling factors in the picture. Setting
pointscale will cause the point sizes to scale with the picture
(within troff's limitations, of course). An operand of anything
but off will turn text scaling on.
default
Reset the picture environment defaults to the settings in the
current picture. This is meant to be used as a global parameter
setting mechanism at the beginning of the troff input file, but
can be used at any time to reset the default settings.
width N
Forces the picture to be N inches wide. This overrides any
scaling factors present in the same picture. ‘width 0’ is ig-
nored.
height N
Forces picture to be N inches high, overriding other scaling
factors. If both ‘width’ and ‘height’ are specified the tighter
constraint will determine the scale of the picture. Height and
width commands are not saved with a default command. They will,
however, affect point size scaling if that option is set.
file name
Get picture from gremlin file name located the current directory
(or in the library directory; see the -M option above). If two
file commands are given, the second one overrides the first. If
name doesn't exist, an error message is reported and processing
continues from the .GE line.
NOTES ABOUT GROFF
Since grn is a preprocessor, it doesn't know about current indents,
point sizes, margins, number registers, etc. Consequently, no troff
input can be placed between the .GS and .GE requests. However, gremlin
text is now processed by troff, so anything valid in a single line of
troff input is valid in a line of gremlin text (barring ‘.’ directives
at the beginning of a line). Thus, it is possible to have equations
within a gremlin figure by including in the gremlin file eqn expres-
sions enclosed by previously defined delimiters (e.g. $$).
When using grn along with other preprocessors, it is best to run tbl
before grn, pic, and/or ideal to avoid overworking tbl. Eqn should al-
ways be run last.
A picture is considered an entity, but that doesn't stop troff from
trying to break it up if it falls off the end of a page. Placing the
picture between ‘keeps’ in -me macros will ensure proper placement.
grn uses troff's number registers g1 through g9 and sets registers g1
and g2 to the width and height of the gremlin figure (in device units)
before entering the .GS request (this is for those who want to rewrite
these macros).
GREMLIN FILE FORMAT
There exist two distinct gremlin file formats, the original format from
the AED graphic terminal version, and the SUN or X11 version. An ex-
tension to the SUN/X11 version allowing reference points with negative
coordinates is not compatible with the AED version. As long as a grem-
lin file does not contain negative coordinates, either format will be
read correctly by either version of gremlin or grn. The other differ-
ence from SUN/X11 format is the use of names for picture objects (e.g.,
POLYGON, CURVE) instead of numbers. Files representing the same pic-
ture are shown in Table 1 in each format.
sungremlinfile gremlinfile
0 240.00 128.00 0 240.00 128.00
CENTCENT 2
240.00 128.00 240.00 128.00
185.00 120.00 185.00 120.00
240.00 120.00 240.00 120.00
296.00 120.00 296.00 120.00
* -1.00 -1.00
2 3 2 3
10 A Triangle 10 A Triangle
POLYGON 6
224.00 416.00 224.00 416.00
96.00 160.00 96.00 160.00
384.00 160.00 384.00 160.00
* -1.00 -1.00
5 1 5 1
0 0
-1 -1
Table 1. File examples
• The first line of each gremlin file contains either the string
gremlinfile (AED version) or sungremlinfile (SUN/X11)
• The second line of the file contains an orientation, and x and y
values for a positioning point, separated by spaces. The orien-
tation, either 0 or 1, is ignored by the SUN/X11 version. 0
means that gremlin will display things in horizontal format
(drawing area wider than it is tall, with menu across top). 1
means that gremlin will display things in vertical format (draw-
ing area taller than it is wide, with menu on left side). x and
y are floating point values giving a positioning point to be
used when this file is read into another file. The stuff on
this line really isn't all that important; a value of “1 0.00
0.00” is suggested.
• The rest of the file consists of zero or more element specifica-
tions. After the last element specification is a line contain-
ing the string “-1”.
• Lines longer than 127 characters are chopped to this limit.
ELEMENT SPECIFICATIONS
• The first line of each element contains a single decimal number
giving the type of the element (AED version) or its ASCII name
(SUN/X11 version). See Table 2.
gremlin File Format − Object Type Specification
AED Number SUN/X11 Name Description
0 BOTLEFT bottom-left-justified text
1 BOTRIGHT bottom-right-justified text
2 CENTCENT center-justified text
3 VECTOR vector
4 ARC arc
5 CURVE curve
6 POLYGON polygon
7 BSPLINE b-spline
8 BEZIER Bézier
10 TOPLEFT top-left-justified text
11 TOPCENT top-center-justified text
12 TOPRIGHT top-right-justified text
13 CENTLEFT left-center-justified text
14 CENTRIGHT right-center-justified text
15 BOTCENT bottom-center-justified text
Table 2.
Type Specifications in gremlin Files
• After the object type comes a variable number of lines, each
specifying a point used to display the element. Each line con-
tains an x-coordinate and a y-coordinate in floating point for-
mat, separated by spaces. The list of points is terminated by a
line containing the string “-1.0 -1.0” (AED version) or a single
asterisk, “*” (SUN/X11 version).
• After the points comes a line containing two decimal values,
giving the brush and size for the element. The brush determines
the style in which things are drawn. For vectors, arcs, and
curves there are six valid brush values:
1 − thin dotted lines
2 − thin dot-dashed lines
3 − thick solid lines
4 − thin dashed lines
5 − thin solid lines
6 − medium solid lines
For polygons, one more value, 0, is valid. It specifies a poly-
gon with an invisible border. For text, the brush selects a
font as follows:
1 − roman (R font in groff)
2 − italics (I font in groff)
3 − bold (B font in groff)
4 − special (S font in groff)
If you're using grn to run your pictures through groff, the font
is really just a starting font: The text string can contain for-
matting sequences like “\fI” or “\d” which may change the font
(as well as do many other things). For text, the size field is
a decimal value between 1 and 4. It selects the size of the
font in which the text will be drawn. For polygons, this size
field is interpreted as a stipple number to fill the polygon
with. The number is used to index into a stipple font at print
time.
• The last line of each element contains a decimal number and a
string of characters, separated by a single space. The number
is a count of the number of characters in the string. This in-
formation is only used for text elements, and contains the text
string. There can be spaces inside the text. For arcs, curves,
and vectors, this line of the element contains the string “0”.
NOTES ON COORDINATES
gremlin was designed for AEDs, and its coordinates reflect the AED co-
ordinate space. For vertical pictures, x-values range 116 to 511, and
y-values from 0 to 483. For horizontal pictures, x-values range from 0
to 511 and y-values range from 0 to 367. Although you needn't abso-
lutely stick to this range, you'll get best results if you at least
stay in this vicinity. Also, point lists are terminated by a point of
(-1, -1), so you shouldn't ever use negative coordinates. gremlin
writes out coordinates using format “%f1.2”; it's probably a good idea
to use the same format if you want to modify the grn code.
NOTES ON SUN/X11 COORDINATES
There is no longer a restriction on the range of coordinates used to
create objects in the SUN/X11 version of gremlin. However, files with
negative coordinates will cause problems if displayed on the AED.
FILES
/usr/share/groff/1.22.4/font/devname/DESC
Device description file for device name.
AUTHORS
David Slattengren and Barry Roitblat wrote the original Berkeley grn.
Daniel Senderowicz and Werner Lemberg modified it for groff.
SEE ALSO
gremlin(1), groff(1), pic(1), ideal(1)
groff 1.22.4 7 March 2023 GRN(1)
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