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Re: [emacs-bidi] Bidirectional editing in Emacs -- main design decisions

From: James Cloos
Subject: Re: [emacs-bidi] Bidirectional editing in Emacs -- main design decisions
Date: Sat, 10 Oct 2009 13:18:37 -0400
User-agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1.50 (gnu/linux)

>>>>> "Eli" == Eli Zaretskii <address@hidden> writes:

Eli> I'm slowly working on adding support for bidirectional editing in Emacs.

Thanks for posting that.  It is a great summary of the concerns and
needs of an editor when dealing with bidi test.

To be fair, I should point out before continuing that I do not read any
rtl scripts.  My interests deal with fonts and typography and at least
seeing bidi email in its correct visual order, if only to try to learn
some of it.

Eli> 1. Text storage
Eli> 2. Support for Unicode Bidirectional Algorithm
Eli> 3. Bidi formatting codes are retained
Eli> 4. Reordering of text for display
Eli> 5. Visual-order information is volatile
Eli> 6. Reordering of strings from `display' properties
Eli> 7. Paragraph base direction
Eli> 8. User control of visual order

Of those points, all but #6 are no brainers; your choices are exactly
what an editor must do.

Point six is an interesting problem; I'm also unaware of any prior
art.  I suspect that in the long term it would be best to note the
start and end directionality of such chunks of text and set them
chunk-by-chunk in a manner similar to how glyphs are set in the
absence of such properties.  But in the short term I agree with
the choice you outlined.

James Cloos <address@hidden>         OpenPGP: 1024D/ED7DAEA6

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