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

[Eli Zaretskii <eliz@gnu.org>]

> From: "Drew Adams" <drew.adams@oracle.com>
> Cc: "'Eli Zaretskii'" <eliz@gnu.org>, <stepnem@gmail.com>,
>         <9571@debbugs.gnu.org>
> Date: Fri, 23 Sep 2011 17:32:08 -0700

I said everything I could in this matter.  What is left is discussion
of what is limbo and what the church thinks about that, for which I
have neither time nor motivation.

Just a few minor remarks, before I get back to fixing the bug I was
working on before this erupted.

> I mention Richard here because he is more likely than I to listen to and
> understand correctly the explanations about the design.

We will not see what Richard thinks until we are done with basics.
Any serious discussion of these issues and the related trade-offs must
be based on good understanding of the details of the design and
implementation.  We are not there yet, sadly.  ("Sadly" because I wish
I had someone more experienced and talented than myself available to
delve into the design and talk about this during the past 2 years,
while I labored on it.)

> > Do you understand what kind and amount of highly technical stuff
> > will have to be in the manual in order to explain this in enough
> > detail for users to understand it?
> 
> What kind and amount of "highly technical stuff" did you have to go into, to
> communicate to us those few corner cases?

They are not "few".  I just mentioned a few, but that doesn't mean
that's all there is to it.

> Then so is the same variable as a NON-option bogus.  And then so is its
> treatment in two (count 'em!) Emacs manuals.  I didn't create that variable, nor
> did I describe it in the manuals.

There's a very good reason why this variable is in the manuals.  The
words used to describe it in both manuals were carefully chosen, both
to avoid any factual inaccuracies and still leave it vague enough to
allow changes in the underlying implementation.  In particular, it's
not an incident that it expressly does NOT say in any of the 2 manuals
what is the precise effect on reordering of buffer text if this
variable is set to a nil value.

I encourage you to re-read the text with that in mind.  Maybe then you
will understand why I described it, even though using it means living
closer to the edge, and why the fact that it is documented says
nothing at all about the legitimacy of using it as a user-level
toggle.