bug#44329: 28.0.50; Crash in bidi_mirror_char on view-hello-file when no bidi-display-reordering (harfbuzz)

[Stefan Kangas]

Eli Zaretskii <eliz@gnu.org> writes:

>> Is there something like make-obsolete-variable for this case that would
>> give a warning in init.el on this variable?
>
> The doc string already does warn.  The variable is not obsolete, it is
> useful for debugging the display code.

It sure would be helpful if the byte-compiler could warn about it
though.  Not sure if we have the facilities for that.

> You assume people who do this read the manual...

Some kind of warning does seem to be warranted, though.  The text now
seems to almost encourage users to set it:

       The buffer-local variable ‘bidi-display-reordering’ controls whether
    text in the buffer is reordered for display.  If its value is non-‘nil’,
    Emacs reorders characters that have right-to-left directionality when
    they are displayed.  The default value is ‘t’.

Should we just remove it from the manual, if it's only useful for
debugging?  Or add a warning similar to the one in the docstring?