bug#22429: Force character to be recognized as LTR inside RTL paragraph

[Filipe Moreira <famoreira@gmail.com>]

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On Fri, Jan 22, 2016 at 2:01 PM, Eli Zaretskii <eliz@gnu.org> wrote:

> > From: Filipe Moreira <famoreira@gmail.com>
> > Date: Fri, 22 Jan 2016 11:54:45 +0000
> > Cc: 22429@debbugs.gnu.org
> >
> >     Emacs being Emacs, you can programmatically change the bidirectional
> >     class of every character, but that change has global effect: it will
> >     affect the directionality of that character everywhere in the Emacs
> >     session. So this is not recommended.
> >
> > Also this is not recommended, I would be willing to have the bidi class
> > property of some characters set to left-to-right, like the example of
> the slash
> > character.
>
> Can you tell why?  There are ways to produce the display you expect
> without changing the character properties; I described 3 such ways.
> If you change the properties, the text will only display correctly on
> your system, any other user who displays your text, either in Emacs or
> in other editor that supports bidirectional display, will see the text
> in the same jumbled order you wanted to avoid.  So I see very little
> sense in such changes.
>
> > Can you point somewhere regarding this? I saw the
> > get-char-code-property function but could not find anyway to
> > actually change the setting.
>
> You want put-char-code-property.  Again, I very much recommend not to
> do that.
>
> >     \begin{hebrew}
> >     \pstart
> >
> >     בְּרֵאשִׁ֖ית‪\footnoteA{This is a Hebrew related footnote}‬ בָּרָ֣א
> אֱלֹהִ֑ים אֵ֥ת הַשָּׁמַ֖יִם וְאֵ֥ת
> >     הָאָֽרֶץ׃
> >
> >     \pend
> >     \end{hebrew}
> >
> >
> > In this example the direction of the surrounding Hebrew text has been
> changed.
> > The word בְּרֵאשִׁ֖ית should come before (i.e. on the right) of the word
> בָּרָ֣א. So
> > while the footnote command is correctly shown as LTR the Hebrew text has
> been
> > changed. I don't think is is the expected. See the updated image
> > (
> http://emacs.stackexchange.com/questions/19696/handling-left-to-right-inside-right-to-left-paragraphs-using-emacs-and-auctex
> )
> > that shows TextEdit correct handling of this.
>
> What version of Emacs do you have?  The above renders correctly for
> me, both in Emacs 24.5 and in the development version.  The word
> בְּרֵאשִׁ֖ית is shown to the right of the footnote, and all the rest is
> shown to the left of it.  Maybe you have an older Emacs which somehow
> has a bug?
>

I have just tested wrapping the footnote command within LTM (on both ends)
in a clean Emacs 24.5.1 (started with -Q) and it worked! This wasn't
working on my normal environment so I will need to investigate why that is.


>
> > Is there any change of having a way to set the unicode bidirectionally
> of a
> > character within each separate mode? Could this be considered a feature?
>
> I think it would be a misfeature, for the reasons explained above.
> It's the same as using a private font to display some character in a
> different shape -- you are the only one who will enjoy that shape.
>
> However, nothing prevents a mode from using put-char-code-property in
> some ingenious ways to do what you want.
>

I appreciate your help. This is all new to me and I've already learned a
lot from you and others regarding this. Thank you for making Emacs so
great.

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