Re: bidi-display-reordering is now non-nil by default

[Eli Zaretskii <eliz@gnu.org>]

> From: Andreas Schwab <schwab@linux-m68k.org>
> Cc: Chong Yidong <cyd@stupidchicken.com>,  dak@gnu.org,  monnier@iro.umontreal.ca,  emacs-devel@gnu.org
> Date: Tue, 16 Aug 2011 09:40:45 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Translated into Emacs-speak, this means we need a variable that, when
> > bound to some special value, instructs the reordering engine to treat
> > certain characters as segment separators.
> 
> They already exist: comment-start and comment-end, for example.

These are strings, not characters.  I meant single characters.
Making that a string would make the job of implementing such a
high-level protocol much harder, because the reordering engine always
considers only one character, with a very few exceptions.

Also, a segment cannot span more than a single line (up to a newline),
so multi-line comments cannot use this solution.

What I had in mind was not comments and strings in program source, but
issues with display of foobar<1> buffer names and lines in
mail-summary buffers, which I thought was what Chong had in mind.  It
could also be a solution for displaying XML, although that use case
needs more thorough analysis, to see if this would really be a good
solution.

The key issue here is whether those same characters can appear in
context where we do want them to be reordered as "normal" punctuation.
If the answer is YES, then this idea won't hold water.