Re: [emacs-bidi] Emacs for Arabic

[Eli Zaretskii <eliz at is dot elta dot co dot il>]

On Tue, 2 Jul 2002, Nadim Shaikli wrote:

> 2. Regarding the "simplified" Bidi, could I suggest the following
>    rather simple addition.  Pseudo-code would get the point across
>    simpler.
> 
>      if ( first_char_is_RTL )
>        Assume entire line is Right-To-Left
>      else
>        /* default */
>        Assume entire line is Left-To-Right

I cannot say I like this approach.  In my experience, it yields 
dreadfully wrong results in many practical cases.  (MS-Windows implements 
something very similar.)

> 3. Your comment about "Handa's available time" pertains to modifying
>    the code to upload this to emacs' live CVS ?  In other words, this
>    work/effort will make it to emacs' proper repository, correct ?

The entire approach to the bidi reordering that Handa-san wrote several 
years ago was more or less rejected by Gerd Moellmann, who was very 
unhappy about the way the code caches characters/glyphs before reordering 
them.  Gerd was convinced that this will slow down the display engine to 
an unbearable degree.

That is why Handa-san's code was never added to Emacs, although it exists 
for quite some time now.

An algorithm for bidi reordering that fits better into the Emacs display 
engine was developed, but its integration into Emacs awaits for me to 
have some free time to work on that.  Unfortunately, I'm working on this 
alone, since no one has stepped forward willing to hack the Emacs display 
code.

>    So that we can expect emacs-21.3 (or emacs-21.4) once released to
>    have this as native support.

I very much doubt that.  Emacs 21.3 is a bugfix-only release which is 
already in pretest; it has no new features.  Emacs 21.4 will be delivered 
from the current CVS head codebase, but for the reasons I explained 
above, I don't think it will use the code mentioned here.

In the meantime, the code mentioned here can be used as a testbed for 
user-level features and some initial experience with bidi editing.  That 
will come in handy when bidi support is integrated into Emacs.