This manual page describes the format output by GNU troff. The output format used by GNU troff is very similar to that used by Unix device-independent troff. Only the differences are documented here.
The argument to the s command is in scaled points (units of points/n, where n is the argument to the sizescale command in the DESC file.) The argument to the x Height command is also in scaled points.
The first three output commands are guaranteed to be:
x T device x res n h v x init
If the tcommand line is present in the DESC file, troff will use the following two commands
xxx is any sequence of characters terminated by a space or a newline; the first character should be printed at the current position, the the current horizontal position should be increased by the width of the first character, and so on for each character. The width of the character is that given in the font file, appropriately scaled for the current point size, and rounded so that it is a multiple of the horizontal resolution. Special characters cannot be printed using this command.
This is same as the t command except that after printing each character, the current horizontal position is increased by the sum of the width of that character and n.
Note that single characters can have the eighth bit set, as can the names of fonts and special characters.
The names of characters and fonts can be of arbitrary length; drivers should not assume that they will be only two characters long.
When a character is to be printed, that character will always be in the current font. Unlike device-independent troff, it is not necessary for drivers to search special fonts to find a character.
The x device control command has been extended.
x u n
If n is 1, start underlining of spaces. If n is 0, stop underlining of spaces. This is needed for the cu request in nroff mode and is ignored otherwise.
The D drawing command has been extended. These extensions will not be used by GNU pic if the -n option is given.
Set the shade of gray to be used for filling solid objects to n; n must be an integer between 0 and 1000, where 0 corresponds solid white and 1000 to solid black, and values in between correspond to intermediate shades of gray. This applies only to solid circles, solid ellipses and solid polygons. By default, a level of 1000 will be used. Whatever color a solid object has, it should completely obscure everything beneath it. A value greater than 1000 or less than 0 can also be used: this means fill with the shade of gray that is currently being used for lines and text. Normally this will be black, but some drivers may provide a way of changing this.
Draw a solid circle with a diameter of d with the leftmost point at the current position.
DE dx dyn
Draw a solid ellipse with a horizontal diameter of dx and a vertical diameter of dy with the leftmost point at the current position.
Dp dx 1 dy 1 dx 2 dy 2 ... dx n dy n n
Draw a polygon with, for i1,...,n+1, the i-th vertex at the current position + ij- 11 (dx j ,dy j ). At the moment, GNU pic only uses this command to generate triangles and rectangles.
DP dx 1 dy 1 dx 2 dy 2 ... dx n dy n n
Like Dp but draw a solid rather than outlined polygon.
Set the current line thickness to n machine units. Traditionally Unix troff drivers use a line thickness proportional to the current point size; drivers should continue to do this if no Dt command has been given, or if a Dt command has been given with a negative value of n. A zero value of n selects the smallest available line thickness.
A difficulty arises in how the current position should be changed after the execution of these commands. This is not of great importance since the code generated by GNU pic does not depend on this. Given a drawing command of the form
Dc x 1 y 1 x 2 y 2 ... x n y n
where c is not one of c, e, l, a or __, Unix troff will treat each of the x i as a horizontal quantity, and each of the y i as a vertical quantity and will assume that the width of the drawn object is in1 x i , and that the height is in1 y i . (The assumption about the height can be seen by examining the st and sb registers after using such a D command in a w escape sequence.) This rule also holds for all the original drawing commands with the exception of De. For the sake of compatibility GNU troff also follows this rule, even though it produces an ugly result in the case of the Df, Dt, and, to a lesser extent, DE commands. Thus after executing a D__ command of the form
Dc x 1 y 1 x 2 y 2 ... x n y n n
the current position should be increased by ( in1 x i , ni 1 y i ).