UNIX° TEXT PROCESSING

Figures and Special Effects

This chapter discusses a variety of formatter requests that you can use to draw figures and achieve special effects like overstriking and vertically stacked text. It also dissects some of the most complex macros we’ve seen so far, so it should advance your knowledge of how to write macros as well as your knowledge of its explicit subject matter.

▪   Formatter Escape Sequences   ▪

Preprocessors like tbl and pic draw boxes, lines, and simple figures using an underlying library of formatter escape sequences that you can also use directly. The eqn preprocessor also uses many of these escape sequences, as well as others that are more appropriate for creating special effects with text characters.

The escape sequences are listed in Table 15-1. As you can see, there are quite a few! Fortunately, many of these need not be learned by the average user. The various preprocessors often allow a user to achieve the same effect more easily. Although tbl or eqn might seem difficult to learn, they are far simpler than the formatter commands they replace. For example, an eqn construct like 10% sup 5% is easier to learn and type than an equivalent troff construct like:

10\s-3\v'-3p'5\v'3p'\s0

When it comes to drawing lines and figures, things get even more complex.

For this reason, many of the escape sequences we are about to discuss are not often used by the average ...