Provided by: groff_1.23.0-5_amd64 
Name
grn - embed Gremlin images in groff documents
Synopsis
grn [-C] [-T dev] [-M dir] [-F dir] [file ...]
grn -?
grn --help
grn -v
grn --version
Description
grn is a preprocessor for including gremlin pictures in troff(1) 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 macros request a gremlin file; the picture in that file is converted and
placed in the troff input stream. .GS may be called with a C, L, or R argument to center, left-, or
right-justify the whole gremlin picture (the default is to 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.
Currently only the me macro package has support for .GS, .GE, and .GF.
grn produces drawing escape sequences that use groff's color scheme extension (\D'F ...'), and thus may
not work with other troffs.
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 lowercase and abbreviated down to one character.
Commands that affect a picture's environment (those listed before “default”, see below) are only in
effect for the current picture: the environment is reinitialized to the defaults at the start of the next
picture. 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, respectively).
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, respectively) 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
proportional 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
Force the picture to be N inches wide. This overrides any scaling factors present in the same
picture. “width 0” is ignored.
height N
Force the 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 multiple file commands are given, the last one controls. If name
doesn't exist, an error message is reported and processing continues from the .GE line.
Usage with groff
Since grn is a preprocessor, it has no access to elements of formatter state, such as indentation, line
length, type size, or register values. Consequently, no troff input can be placed between the .GS and
.GE macros. However, gremlin text elements are subsequently processed by troff, so anything valid in a
single line of troff input is valid in a line of gremlin text (barring the dot control character “.” at
the beginning of a line). Thus, it is possible to have equations within a gremlin figure by including in
the gremlin file eqn expressions enclosed by previously defined delimiters (e.g., “$$”).
When using grn along with other preprocessors, it is best to run tbl(1) before grn, pic(1), and/or ideal
to avoid overworking tbl. eqn(1) should always be run last. groff(1) will automatically run
preprocessors in the correct order.
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 the me macros will ensure proper placement.
grn uses troff's 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 macro (this is for those who want to rewrite
these macros).
Gremlin file format
There exist two distinct gremlin file formats: the original format for AED graphic terminals, and the Sun
or X11 version. An extension used by the Sun/X11 version allowing reference points with negative
coordinates is not compatible with the AED version. As long as a gremlin file does not contain negative
coordinates, either format will be read correctly by either version of gremlin or grn. The other
difference in Sun/X11 format is the use of names for picture objects (e.g., POLYGON, CURVE) instead of
numbers. Files representing the same picture are shown below.
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
• The first line of each gremlin file contains either the string “gremlinfile” (AED) 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 orientation, either 0 or 1, is ignored by the Sun/X11 version. 0 means that
gremlin will display things in horizontal format (a drawing area wider than it is tall, with a menu
across the top). 1 means that gremlin will display things in vertical format (a drawing area taller
than it is wide, with a menu on the 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 specifications. After the last element
specification is a line containing the string “-1”.
• Lines longer than 127 characters are truncated to that length.
Element specifications
• The first line of each element contains a single decimal number giving the type of the element (AED) or
its name (Sun/X11).
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
• After the object type comes a variable number of lines, each specifying a point used to display the
element. Each line contains an x-coordinate and a y-coordinate in floating-point format, separated by
spaces. The list of points is terminated by a line containing the string “-1.0 -1.0” (AED) or a single
asterisk, “*” (Sun/X11).
• 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 polygon with an invisible border. For text,
the brush selects a font as follows.
1 roman (R font in troff)
2 italics (I font in troff)
3 bold (B font in troff)
4 special (S font in troff)
If you're using grn to run your pictures through groff, the font is really just a starting font. The
text string can contain formatting 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 information is
used only for text elements, and contains the text string. There can be spaces inside the text. For
arcs, curves, and vectors, the character count is zero (0), followed by exactly one space before the
newline.
Coordinates
gremlin was designed for AED terminals, and its coordinates reflect the AED coordinate 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 from 0 to 367. Although you needn't absolutely stick to this
range, you'll get better 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 the printf(3) format “%f1.2”; it's probably a good idea to use the same format if you want to
modify the grn code.
Sun/X11 coordinates
There is no 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.
Options
-? and --help display a usage message, while -v and --version show version information; all exit
afterward.
-C Recognize .GS and .GE (and .GF) even when followed by a character other than space or newline.
-F dir Search dir for subdirectories devname (name is the name of the output driver) for the DESC file
before the default font directories /usr/share/groff/site-font, /usr/share/groff/1.23.0/font, and
/usr/lib/font.
-M dir Prepend dir to the search path for gremlin files. The default search path is the current
directory, the home directory, /usr/share/groff/site-tmac, and /usr/share/groff/1.23.0/tmac, in
that order.
-T dev Prepare device output using output driver dev. The default is ps. See groff(1) for a list of
valid devices.
Files
/usr/share/groff/1.23.0/font/devname/DESC
describes the output 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)