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Re: BIDI, LaTeX (auctex) and the «evil» backslash
From: |
Uwe Brauer |
Subject: |
Re: BIDI, LaTeX (auctex) and the «evil» backslash |
Date: |
Sat, 21 May 2016 17:44:32 +0000 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) |
>>> "Eli" == Eli Zaretskii <address@hidden> writes:
>> From: Uwe Brauer <address@hidden>
>> Date: Sat, 21 May 2016 13:55:18 +0000
>> Cc: auctex-devel <address@hidden>
>>
>> In my understanding UTF distinguish between
> What is "UTF" in this context?
My bad I mean Unicode.
>> - LTR chars such as a,b,c
>>
>> - RLT chars such as א,ב,ג
>>
>> - «neutral» chars such as (),\ etc.
> You should read the description of UBA, the Unicode Bidirectional
> Algorithm (which Emacs implements). There you will see that there are
> actually 4 classes of characters:
> . string (LTR and RTL)
> . weak (numbers, number separators, diacriticals)
> . neutral (punctuation and whitespace)
> . formatting control characters (RLM etc.)
> So:
> (get-char-code-property ?\\ 'bidi-class) => ON
> ("ON" stands for "other neutral", see the node "Character Properties"
> in the ELisp manual.)
>> - set bidi-paragraph-direction to left (shown in the next
>> screenshot.) The display is correct, however typing Hebrew, when
>> bidi-paragraph-direction is set to left is as unpleasant as
>> writing English with bidi-paragraph-direction set to right.
>>
>> - use LRM chars before the backslash (see the last screenshot;
>> having set `glyphless-char-display-control' to `acronym'.
>> This looks well to but adding these chars is cumbersome.
>>
>> - hack auctex (CC to the auctex list): a new variable is
>> introduced, say bidi-support, which is per default nil, but if it
>> is t, then LRM chars are inserted before a backslash. I am
>> pretty sure the auctex team will not like this idea very much.
>>
>> - back emacs: in a LaTeX buffer, backslash is considered as LTR, I
>> don't know whether this can be done one the lisp level or whether
>> it can be done at all.
>>
>> Comments?
> The last one is possible, of course (this is Emacs), but that way lies
> madness: arbitrarily changing bidirectional properties of characters
> will bite you elsewhere, because the corresponding tables are global.
So that cannot be restricted just to LaTeX mayor modes?
In any case how could I change the backslash on a lisp level, ie change
(get-char-code-property ?\\ 'bidi-class)
>From ON to whatever is necessary.
I just would like to check and see what happens
> The other 3 alternatives are indeed the available solutions.
> Personally, I recommend the 1st one; I see no problem with typing
> RTL text in a left-to-right paragraph (and vice versa), and don't
> understand what unpleasant things you bump into when doing that.
> TeX files are fundamentally left-to-right, as any program text, so
> that would be my suggestion.
Well I don't like the cursor movements in such a situation and that is
why for the moment I use the LRM chars, which don't cause any
problem at least not using unicode and xelatex.
Again thanks for all your efforts for providing BIDI support.