Subject: Re: bug#5977: 24.0.50; Lao HELLO is incorrectly displayed

From: Eli Zaretskii <[email-masked]>
Date: Tue, 20 Apr 2010 12:06:33 +0300

> From: Peter Dyballa <[email-masked]>
> Date: Mon, 19 Apr 2010 22:50:11 +0200
> Cc: 
> 
> The Lao greetings are incorrectly rendered:

Does the problem go away if you type

    M-: (setq bidi-display-reordering nil) RET

?

> When I go forward or backward with the cursor keys in the greetings  
> (also in the header) the direction of cursor movement is reversed at  
> two or three spots.

I don't see cursor movement reversal on MS-Windows.  Can you tell what
characters are those where it happens, e.g., by counting the number of
C-f keystrokes from the beginning of the line?

Anyway, the problem is known: Lao (as well as quite a few other
scripts and display features in Emacs) use character compositions,
and the bidi display does not yet handle composed characters
correctly.  I need Handa-san's help in figuring out how to make
compositions work with bidi display, because I lack the necessary
knowledge of how support for character compositions is designed and
implemented, and the code is not documented enough, at least not for
me, to figure that out on my own.