(Note carefully the blankspace immediately after the word "@mono[outln]".)
(2) In the file POSTSCR.HDR, immediately before the line reading "@mono[initgraphics]", insert the lines:
@begin(mono)
/outln {gsave true charpath 12.5 setlinewidth
stroke grestore} bind def
@end(mono)
Thereafter, to print a symbol or a word in outline, simply embed that symbol or word as the argument of the @trc() macro.
@bar(1 point)
Technical notes:
The @trc() macro passes its argument only partially processed over to a PostScript macro, the @mono(outln) macro. In particular, if there are any typeface control instructions, size changes, spacing instructions (e.g. "@mono[@@hsp(0.1 em)]"), etc. embedded in the original argument, they will not be processed (indeed they may even end up being printed in outline!). So if you want to do more than simply print a string of characters in the current font at the current size, you will have to make the changes outside of the @trc() macro. Suppose you want to trace the diamond (char 165@-(octal)├) in the Dingbats font. You would have to place the font name outside of the @trc() macro, e.g. you'd type "@mono[^OFONTdingbats^N@@trace<@@char(165o)>^OENDF^N]". (Note that the @mono[@@char(@_)] macro works correctly inside the @trc() macro.)
The same restriction applies to full justification. To justify a line left and right, Sprint relies on features in the PostScript interpreter. If you use a string of words as the argument to @trc(), the blankspaces between them will not be expanded in a fully justified paragraph. Again, the trick is to have Sprint do the work outside of the @trc() macro. E.g. Suppose you wanted "walled city" to print in outline within a fully justified paragraph:@nohinge
@begin(Text)
Correct: @^@mono[@@trace(walled) @@trace(city)]
Incorrect: @\@mono[@@trace(walled city)]
@end(Text)
Specifically, the blankspace would have to occur between two invocations of the macro, not as a part of a two-word argument. (You probably would be wise, too, to turn off wordspacing, i.e. use "@mono{@@style[Wordspacing 1000]}". Of course, if you have full-justification turned off, i.e. are printing left-justified [as in this very paragraph], you can use strings of words as arguments to the @trc() macro: the blankspaces will print alright, they just won't be expanded. But you don't want expansion in a left-justified paragraph.)
Having the means to create an outline of any font allows one to supplement the Symbols typeface. Mathematicians and logicians have long lamented the lack of a hollow box in the Symbol set. It is easy now to create a hollow box. One need only trace the solid box in the Dingbats typeface. To scale it to the correct size, I use these instructions:
To print the hollow box, I then type "@mono[||]". If you like your hollow boxes larger, change the factor, "0.6", in the definition of "reduce" to, e.g., "0.7".
The @trc() macro works in different point sizes. Just be sure to change the point size outside of the macro, e.g. "@mono[^OSIZE 14 POINTS^N@@trace(@_)^OENDS^N]".
The thickness of the tracing line on outline typefaces is controlled by the numerical parameter preceding "setlinewidth" in the PostScript definition of "@mono[/outln]". To make the tracing line thicker increase "@mono[12.5 setlinewidth]" to, e.g., "@mono[15 setlinewidth]".
