Re: Luatex (actually Aleph) and Bidi_Mirrored chars in RTL mode

[Khaled Hosny <khaledhosny@eglug.org>]

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On Mon, Jun 09, 2008 at 11:08:09PM +0200, Hans Hagen wrote:
> Khaled Hosny wrote:
> > Luatex does not mirror characters that has a Bidi_Mirrored property when
> > the text direction is set to RTL (TRT in Aleph), according to 
> > http://unicode.org/reports/tr9/#Mirroring, the different types of
> > parenthesis that has Bidi_Mirrored property should be mirreored in RTL
> > mode, but this isn't what I get. Is this a bug, feature, or am I missing
> > some thing?
> 
> experimental in the beta
> 
> \setcharactermirroring[1]

It does work perfectly with unidirectional texts (RTL or LTR), but when
mixing bi-directional text, like Arabic text between brackets inside
English line, the closing bracket takes the direction of the embedded
text not the main line.
See the attached example.

Regards,
 Khaled

> 
> no high level interface yet, i need to think of how to do such things as 
> efficient as possible and prevent interference with font features and 
> such (currently it's an attribute handler that pops in quite early)
> 
> 
> -- 
> 
> -----------------------------------------------------------------
>                                            Hans Hagen | PRAGMA ADE
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-- 
 Khaled Hosny
 Arabic localizer and member of Arabeyes.org team

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% engine=luatex 

% OpenType features needed for Arabic
\definefontfeature
  [arab]
  [mode=node,language=dflt,script=arab,
   init=yes,medi=yes,fina=yes,isol=yes,
   liga=yes,dlig=yes,rlig=yes,clig=yes,
   mark=yes,mkmk=yes,kern=yes,curs=yes]

\font\Arab = arabtype*arab

\setcharactermirroring[1]

\hoffset=0pt

% For inner paragraph control within an LR paragraph

\definestartstop
  [arabictext]
  [commands=%
    {\textdir TRT%
    \Arab}]

\def\ArabicText#1{\startarabictext#1\stoparabictext}

% For separate Arabic-script paragraphs

\def\ArabicDirPar{\textdir TRT\pardir TRT}

\definestartstop
  [arab]
  [commands=%
    {\Arab%
     \ArabicDirPar}]

\showframe[text]

\starttext
\startarab
سلام (قوس) وقوس <قوس> و [قوس]

وهذا قوس حول نص غير عربي \textdir TLT (hello) \textdir TRT ثم عربي 

\stoparab

\blank

Here is some mixed {\em Arabic-} (\ArabicText{عربي}) and
Latin-script. As you can see, Aleph does a very good job mixing
{\em LR} (\ArabicText{يسار-يمين}) and {\em RL}
(\ArabicText{يمين-يسار}) texts. \ArabicText{و
هنا جملة منقطعة في وسط قرينة
لاتينية}. Aleph even does a great job breaking Arabic
phrases across lines.

(bracket) and <bracket> and [bracket]

\stoptext

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___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to the Wiki!

maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
webpage  : http://www.pragma-ade.nl / http://tex.aanhet.net
archive  : https://foundry.supelec.fr/projects/contextrev/
wiki     : http://contextgarden.net
___________________________________________________________________________________