bugGNU troff - Bugs: bug #60790, [tbl] does not sufficiently...


bug #60790: [tbl] does not sufficiently document valid tab() characters

Submitted by:  G. Branden Robinson <gbranden>
Submitted on:  Thu 17 Jun 2021 04:25:15 PM UTC  
Category:  Preprocessor tbl Severity:  3 - Normal
Item Group:  Documentation Status:  None
Privacy:  Public Assigned to:  None
Open/Closed:  Open Planned Release:  None

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Sun 20 Jun 2021 10:15:43 AM UTC, comment #1: 

Groff's native input encoding is Latin-1 (a.k.a. ISO 8859-1), so I would expect tbl and other preprocessors to use the same one (though yes, this should be documented clearly, if it isn't already).  Indeed, tab() accepts 8-bit Latin-1 characters (though only in Latin-1 encoding; the same characters in UTF-8 become more than one byte, thus triggering the "must be a single character" diagnostic).

Dave <barx>
Project Member
Thu 17 Jun 2021 04:25:15 PM UTC, original submission:  

Oliver Corff noted on the groff mailing list:

"For the global option "tab(x)", the man page says:

tab(x) Use the character x instead of a tab to separate items in a line
of input data.

This works as long as x is a 7-bit ascii character, it does not work
with utf-8 characters. E.g.: "tab(|)" (with the pipe symbol) works,
"tab(¦)" does not work and yields the message: "argument to `tab' option
must be a single character".

I suggest either specifying "7-bit ascii character" in the manpage
and/or make the tbl parser utf8-aware."

Support for UTF-8 input would be a major feature, and probably major work, and would require either preconv-ish rewriting of non-ASCII glyphs as special character escapes on output, or the UTF-8-ification of troff(1) itself.

Probably best to document.  See what non-printing characters (C0 controls) tbl(1) will also accept to tab().


G. Branden Robinson <gbranden>
Project Administrator


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