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

[Richard Stallman]

    > Why are you opposed to a flag to turn bidi display off?

    I explained that at length in followups.

Those messages seem to be arguing against maintaining big changes to
implement non-bidi display.  I agree with that.

But they don't seem to be an argument against simple code that would
disable the recognition of the bidi specialness of characters.

    >                 If there are [no R2L characters], there is no
    > reordering, thus no possibility it can cause confusion.

    You are wrong: _all_ characters are displayed in Emacs 24 via the
    reordering engine.  It's just that plain left-to-right text emerges
    from that reordering in its original buffer order.  But the reordering
    engine doesn't "know" that, it just implements the rules of
    reordering.

We are miscommunicating.  When I say "no reordering", I'm not talking
about what code is running -- just how the text gets displayed.
When there are no R2L characters, the text will be displayed in L2R order,
which means no reordering in the display.

    That will not resolve any confusion.  As someone who happened to read
    R2L text in Emacs 23 (e.g., in email messages), I can assure you:
    seeing R2L text in buffer order confuses even more than seeing results
    of slightly incorrect reordering.  It makes the reading process very
    slow and error prone, even if your command of the language is very
    good.

That's an argument not to do your normal editing with such a mode.  I
only suggest we provide it as a way to check the order of characters
in the buffer, when needed.

    It's not useful for users, believe me.  It could be useful to someone
    who debugs Emacs display, but there's no need for user option for
    that use case.

I am not sure what the best user interface would be.
Perhaps a command to toggle the flag for the current buffer.

    Easier maintenance.  Emacs display engine is already more complex that
    humanly perceptible.  Having two divergent engines in one means
    unnecessarily complicating maintenance and slowing down development,

I agree with you, but I am not arguing for having two engines.
Only for having a flag.

See the other message for how I suggest implementing it.

-- 
Dr Richard Stallman
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