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Re: [emacs-bidi] Bidirectional editing in Emacs -- main design decisions
From: |
mhsekhavat |
Subject: |
Re: [emacs-bidi] Bidirectional editing in Emacs -- main design decisions |
Date: |
Wed, 18 May 2016 05:29:21 -0700 (MST) |
Hi,
Eli Zaretskii wrote
> If Emacs would follow UAX#9 to the letter, each line could have different
> base direction,
> which is, of course, intolerable. We could avoid this nonsense by
> using the "soft newline" or similar features, but I firmly believe
> that Emacs should DTRT with bidirectional text even in the simplest
> modes, including the Fundamental mode, where every newline is hard.
>
> Fortunately, UAX#9 acknowledges that applications could have other
> ideas about what is a "paragraph". It calls this ``higher
> protocol''. So I decided to use such a higher protocol -- namely,
> the Emacs definition of a paragraph, as determined by the
> `paragraph-start' and `paragraph-separate' regexps. Therefore, the
> first strong directional character after `paragraph-start' or
> `paragraph-separate' determines the paragraph direction, and that
> direction is kept for all the lines of the paragraph, until another
> `paragraph-separate' is found. (Of course, this means that
> inserting a single character near the beginning of a paragraph
> might affect the display of all the lines in that paragraph, so
> some of the current redisplay optimizations which deal with changes
> to a single line need to be disabled in this case.)
I agree that most of the time, having different base direction for each line
is nonsense. But there are cases where the text does not have "paragraph"s,
but consists of a number of sentences, each in a line. So an empty line does
not semantically mean paragraph separator and a right-to-left line appears
just after a left-to-right line.
How can I set variables `paragraph-start` and `paragraph-separate` so that
each line have different direction? I tried setting `paragraph-start` to "."
and `paragraph-separate` to "$" but didn't work?
Thanks for the great work on bidi.
--
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