Re: [Groff] horizontal trap

[Peter Schaffter]

On Sat, Dec 26, 2015, Dave wrote:
> Here's what I'm trying to do.  I have a lengthy input file to be
> processed in no-fill mode.  For 99% of this file, that will work
> just fine: that is, the input lines will fit within the the page.
> A few lines, however, are too long for the page, and in no-fill
> mode groff happily sends them past the margin and even past the
> edge of the paper.
> 
> I don't want groff to handle these lines; the exact way each such
> line should be handled depends on a number of factors and really
> requires manual intervention.  But I do want groff to alert me to
> such cases, so that I know where to find them without having to
> flip through a couple hundred pages of output.

Since you're in no-fill mode, it's a perfect job for the little-used
input line trap request.  This should do what you want.

.de foo
. it 1 bar
. di baz
..
.
.de bar
. di
. if \\n[dl]>\\n[.l] \
.   tm Line \\n[.c] exceeds width.
. baz
. foo
..
.
.de bat
.di
..
.
.em bat
.
.ll 4i
.nf
.foo
First line of text.
Second line of text.
etc.

Any line exceeding 4i will be reported.  The .em (bat) prevents
groff from complaining about the final diversion being incomplete.

-- 
Peter Schaffter
http://www.schaffter.ca