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 doesn't know about current
indentation, point sizes, margins, registers, and so on.
Consequently, no troff input can be placed between the .GS and
.GE macros. 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 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.
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 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 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 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) 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
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 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.
