Re: paragraph justification issue on @url with "texi2dvi --pdf" in texinfo.tex 2019-09-20.22

[Vincent Lefevre]

On 2019-09-24 14:30:50 +0100, Gavin Smith wrote:
> It was done this way because of the difficulty of breaking lines in a
> good place with long URL's.
> 
> https://lists.gnu.org/archive/html/bug-texinfo/2019-03/msg00007.html

Yes, but even in this case, this is not sarisfactory (see below).
Thus the user should do the page layout in such a case.

> I agree a short space at the end of the line doesn't look good. I've
> worked out the following change which means that the extra space at
> the end of the line won't always be added:
> 
> diff --git a/doc/texinfo.tex b/doc/texinfo.tex
> index af857cbbb..40fa95c49 100644
> --- a/doc/texinfo.tex
> +++ b/doc/texinfo.tex
> @@ -3099,11 +3099,14 @@ end
>  \def\wordbefore{before}
>  \def\wordnone{none}
> 
> -% Allow a ragged right output to aid breaking long URL's.  Putting stretch in
> -% between characters of the URL doesn't look good.
> +% Allow a ragged right output to aid breaking long URL's.  There can
> +% be a break at the \allowbreak with no extra glue (if the existing stretch 
> in
> +% the line is sufficent), a break at the \penalty100 with extra glue added
> +% at the end of the line, or no break at all here.
>  \def\urefallowbreak{%
> -  \hskip 0pt plus 4 em\relax
>    \allowbreak
> +  \hskip 0pt plus 4 em\relax
> +  \penalty100
>    \hskip 0pt plus -4 em\relax
>  }

This fixes some cases, but not others. I've attached a url-break.texi
file with 4 cases. And I've tested 4 different texinfo.tex solutions
(the old one, the new one, the new one with this patch, and another
one with just a \allowbreak). As a summary:

* url-break-2018.pdf obtained with texinfo.tex 2018-02-12.17 (from automake)

Issue: stretch in between characters of the URL.

* url-break-2019a.pdf obtained with texinfo.tex 2019-09-24.13 (from texinfo)
  with the unpatched \urefallowbreak macro:

\def\urefallowbreak{%
  \hskip 0pt plus 4 em\relax
  \allowbreak
  \hskip 0pt plus -4 em\relax
}

Issues:
  - stretch not avoided in the 1st case (though output is ragged right);
  - ragged right output even in the 3rd and 4th cases.

* url-break-2019b.pdf obtained with texinfo.tex 2019-09-24.13, where the
  \urefallowbreak macro has been patched:

\def\urefallowbreak{%
  \allowbreak
  \hskip 0pt plus 4 em\relax
  \penalty100
  \hskip 0pt plus -4 em\relax
}

Issues:
  - stretch not avoided in the 1st case (though output is ragged right);
  - ragged right output even in the 3rd case;
i.e. only the 4th case has been fixed.

* url-break-2019c.pdf obtained with texinfo.tex 2019-09-24.13, where the
  \urefallowbreak macro has been simplified to:

\def\urefallowbreak{%
  \allowbreak
}

Issue: more stretch in the 1st case, but this case has not been
satisfactory with any of the tested solutions anyway.

Currently I find that just a \allowbreak is the best compromise:
the cases that can be output nicely are OK; the problematic case
is a bit worse than with the new solution (patched or not), but
to fix it in a satisfactory way, it is up to the user.

-- 
Vincent Lefèvre <address@hidden> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)

url-break.texi
Description: TeXInfo document

url-break-2018.pdf
Description: Adobe PDF document

url-break-2019a.pdf
Description: Adobe PDF document

url-break-2019b.pdf
Description: Adobe PDF document

url-break-2019c.pdf
Description: Adobe PDF document