bug#9571: 24.0.50; user option to turn off bidi, please

[Richard Stallman <rms@gnu.org>]

    The way I understand this request is: make it so that the result of
    reordering is the text in its original logical (i.e. buffer or string)
    order.  The code that is involved in reordering, largely in bidi.c and
    xdisp.c, will still work as it normally does.

Exactly.

    Again, I don't think this is what the original proponents of the
    option wanted, because implementing what you suggest will not bypass
    any of the code in the new display.  IOW, I think it's an entirely
    different feature.

Maybe you're right.  I didn't follow the whole discussion.  I am not
sure why they particularly want to bypass code in the new display;
that seems like an internal implementation detail, and I don't see why
a user would care how the job gets done as long as the output is what
he wants.

    But simply overwriting default_type with STRONG_L isn't right, either.
    That's because as long as we run the code in bidi.c unaltered, there
    are some characters whose bidirectional properties are still needed
    for the code to work: newlines, paragraph separators, line separators,
    and a few others.

Ok, my proposed patch won't do the job.  But wouldn't a slightly more
complicated patch in the same place do the job?

The method of replacing the unicode property table seems to have
several drawbacks:

1. Creating the modified table is more work.

2. It is a big data structure, so having another one would be a waste.

3. It feels wrong to alter the information describing the characters.
This is a matter of choosing a different way to display some characters,
not a matter of redefining what they mean.

I think an easy implementation in bidi_get_type is to have an if
statement choose between the existing switch statement and a new
switch statement.  The new switch statement would return different
values that would avoid reordering and give the Emacs 23 behavior.

-- 
Dr Richard Stallman
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