[XeTeX] latin-1 encoded characters in commented out parts trigger log warnings

[Ross Moore]

Hi Jonathan, and others.

On 22 Feb 2021, at 10:39 am, Jonathan Kew <jfkthame at gmail.com<mailto:jfkthame at gmail.com>> wrote:

On 21/02/2021 22:55, Ross Moore wrote:
The file reading has failed  before any tex accessible processing has happened (see the ebcdic example in the TeXBook)
OK.

Also pdfTeX has no trouble with an xstring example.
It just seems pretty crazy that the comments need to be altered
for that package to be used with XeTeX.

Well.... as long as the Latin-1 accented characters are only in comments, it arguably doesn't "really" matter; xetex logs a warning that it can't interpret them, but if you know that part of the line is going to be ignored anyway, you can ignore the warning.

There’s actually a pretty easy fix, at least for XeLaTeX.
The package contains 2 files only:   xstring.sty  and  xstring.tex .
The .sty is just a 1-liner to load the .tex .

It could be beefed up with:

 \RequirePackage{ifxetex}     %   is this still the best package for  \ifxetex   ?
\ifxetex
  \XeTeXdefaultencoding "iso-8859-1"
\input{xstring.tex}
  \XeTeXdefaultencoding "utf8"
\else
 \input{xstring.tex}
\fi

(ignore if straight quotes have become curly ones in my email editor!)



Even nicer would be to beef it up further by:
 1. record the current default encoding – is this possible ?
     then restore from this.
 2. use a grouping while deciding what to do,
     expanding the required commands before ending the group.

\showthe\XeTeXdefaultencoding  doesn’t work,
so is there another container that tells what is the default encoding?
Or should we always assume it is UTF-8 and revert to that afterwards?

e.g. something like:

\RequirePackage{ifxetex}
\begingroup
 \def\next{\endgroup \input{xstring.tex}}%
 \ifxetex
  \XeTeXdefaultencoding "iso-8859-1"
  \def\next{\endgroup
   \input{xstring.tex}%
   \XeTeXdefaultencoding "utf8"}%
 \fi
\next




(pdfTeX doesn't care because it simply reads the bytes from the file; any interpretation of bytes as one encoding or another is handled at the TeX macro level.)

Right.
Which is why I do my PDF development work in pdfTeX before
testing whether it can be adapted also to XeTeX and/or LuaTeX.


JK



Cheers.

Ross


Dr Ross Moore
Department of Mathematics and Statistics
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T: +61 2 9850 8955  |  F: +61 2 9850 8114
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