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Re: Warn about long lines

From: G. Branden Robinson
Subject: Re: Warn about long lines
Date: Sat, 27 Aug 2022 13:02:10 -0500

Hi Alex,

At 2022-08-27T19:42:43+0200, Alejandro Colomar wrote:
> Lines with highlighting have more characters than visible.  Of course,
> in my 80 limit, I only want to count visible ones, so I need to get
> rid of the highlighting.  I started with using [[:print:]] in grep(1),
> but it also counted part of the multibyte sequences of the
> highlighting (i.e., it didn't count the character that introduced the
> escape sequence, but counted the rest; more or less, what you'd see if
> you run less without -R; e.g., '[1m').  So I used this, as a big
> cannon; probably shooting more than necessary; I wanted to make sure
> no traces remained.

At some point you're going to hit the problem of printable UTF-8
sequences that occupy more than one byte but only one character cell.

> Although in this case it's for running groff(1)'s warnings, for which
> I'll need to run groff(1).

No, you're not running it for groff(1)'s warnings, you're running it for
the formatter's warnings.  The formatter is troff(1) and groff(1) always
runs it.

> Do I get the same warnings by passing -ww and -rCHECKSTYLE=3 to
> troff(1) and to groff(1)?  or does groff(1) have extra warnings (maybe
> since it also has access to the tbl(1) input)?

Slow down there.  groff itself has only one warning.

  warning("-TXps option is obsolete: use -X -Tps instead");

It also has a few error diagnostics because it attempts to locate the
'DESC' file for the output device and from there determine what
preprocessor (if any) and posprocessor it needs to run.

None of this has to do with the content of your document.

> > The data between troff(1) and grotty(1), or any other post-processor,
> > is in groff_out(5) format and what marks to put where has already been
> > decided, fixing the line length.
> > 
> > The man macros realise the man command might be on a terminal of varying
> > width or producing ‘cat’ man pages for storage.  To allow the man
> > command to specify the line-length required, the man macro allows the LL
> > number register to override what length it would normally use for the
> > ‘.ll’ command.  When the man command runs troff, it uses the -r option
> > to set the number register.
> > 
> > > It doesn't seem like a man(7)-specific thing
> > 
> > It is.

Only sort of.  Registers for setting line length, page offset, page
length, and vertical spacing trickled into the various macro packages in
an inconsistent way over the years.

One of the post-1.23 projects I have in mind is to complete the set for
all macro packages and teach nroff about them so I can do something
highly satisfying: give nroff an option to auto-size output to the
terminal dimensions.

> > > I mean, when searching for an option that controls the line
> > > length, I expect it to be a generic option that will be applicable
> > > to groff as a whole

This was not thought to be necessary in the 1970s, because the media
dimensions were rigidly fixed for Teletype devices and even on the
C/A/T, you had to physically cut the giant roll of "paper" into leaves

> > No, the page dimensions, etc., are set within the troff source and
> > it's up to that source to allow for external specification if
> > required.  If a document is written without specifying them then the
> > defaults apply and the user can override these by using one of the
> > paper-size macro sets, e.g. ‘-ma4’ for A4 paper from groff's
> > a4.tmac.
> > 
> >      troff -ma4

I think we just found the one remaining a4.tmac user left on the planet.

From NEWS:

o The "a4.tmac" file has been dropped from the distribution.  Its
  successor, "papersize.tmac", has been present and documented for
  nearly 20 years.  See subsection "Paper size" of groff(1).

> Ahh, it makes sense: normally documents are designed to be rendered in
> a specific device and characteristics.  It's only manual pages that
> are more generic in that regard, in that they are mostly read in
> terminals (not their original conception, but that's what it is right
> now).

We could have more flexibility than we do.  I began realizing this when
I started working on the document.

> > groff(1) is a confusing front-end program for the normal troff-based
> > pipeline so some more interesting options would be in troff(1), for
> > example.  But in this case, it's not a command-line option.  :-)

-rLL=XXn is very much a groff(1) command line option (that gets passed
to troff(1)) and I have used it for years in my own little shell

$ type gman
gman is a function
gman () 
    local width=$(stty size | cut -d' ' -f2);
    width=$(( width - 1 ));
    local cmd=$(./build/grog -Tutf8 -b -ww -P-i -rU1 -rLL=${LL:-$width}n "$1");
    ./build/test-$cmd | less -R


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