[emacs-bidi] Input methods and mirrored characters

[Eli Zaretskii]

As long as we discuss input methods, here's another problem which
might need some attention.

As you know, some characters need to be mirrored when their resolved
direction is R.  An example is the parentheses ().

Now, suppose I want to type text which will be displayed (in visual
order) like this (UPPER case are strong R characters, as usual):

                    FE(DC)BA

At least in Hebrew, users will type this (in logical order) like this:

                    AB)CD(EF

In other words, users will type the same parenthesis as what is
expected to be displayed on the screen.

However, both mirroring and UAX#9 require that the logical-order
storage of this text is this:

                    AB(CD)EF

This seems to mean that the Emacs input method should mirror the
parentheses when they are typed: if I type `)', Emacs should instead
insert a `(' into the buffer.  And this means, in turn, that toggling
the input method modifies the character inserted into the buffer when
I press one of the keys that produce mirrored characters.  In effect,
we now have a ``Hebrew ('' and a ``Latin (''.

This has a nasty consequence that pressing a `(' in the middle of a
strong R2L text will display either `(' or `)', depending on whether
the input method was on or off.  That is not something users will
like, I think.  It is quite customary to have the input method either
on or off when proofreading an already written document, if you need
to insert a character, such as `(', which is supposed to be
independent of the state of the input method.

Comments?  Thoughts?