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Re: bidi discussion list was: Bidi Markup vs Unicode control characters

From: Steve Zilles <szilles@adobe.com>
Date: Fri, 19 Aug 2005 13:14:28 -0700
To: Stephen Deach <sdeach@adobe.com>, fantasai <fantasai.lists@inkedblade.net>, Stephen Deach <sdeach@adobe.com>
Cc: Martin Duerst <duerst@it.aoyama.ac.jp>, Ognyan Kulev <ogi@fmi.uni-sofia.bg>, Tex Texin <tex@xencraft.com>, Addison Phillips <addison.phillips@quest.com>, www-international@w3.org, Richard Ishida <ishida@w3.org>, Bert Bos <bert@w3.org>
Message-id: <6.2.1.2.2.20050819130449.02cc40c0@mailsj-v1.corp.adobe.com>
At 04:37 PM 8/18/2005, Stephen Deach wrote:

>Mongolian was originally written as RL-TB in an Aramaic-derivative script.
>
>Then the whole page was rotated 90-deg CCW (glyphs and layout are simply 
>rotated from the original form). This is essentially its current vertical 
>writing form TB-LR.
>
>-- Now comes the wierd part. Small snippets of horizontal text are now 
>written LTR with glyphs inverted 180-degrees from the original form.
>
>So yes, it is currently laid out LTR, but it is really written as if it 
>was RTL-inverted.

To be more precise, the Sogdian script from which Mongolian is derived has 
been rotated 180 degrees so that that script is now upside down. Since most 
of the historical use of the Mongolian script seems to be in its vertical 
form, the LTR form of Mongolian is only a 90 degree rotation from the 
historical usage.

The following is pure conjecture, but I suspect the LTR use of the 
Mongolian script came about when Traditional Mongolian Script was included 
in Cyrillac Mongolian texts. I certainly have examples of Mongolian texts 
that combine both Cyrillac Mongolian and traditional Mongolian in the LTR 
from. These texts also show that the Sogdian script has been rotated 180 
degrees in the LTR form as noted above.

It is the 180 degree rotation of the script that converted what is a RTL 
script to and LTR script just as one would expect from the embeddings of 
rotated Roman and Arabic scripts in vertical documents. For example, Arabic 
rotated 90 degrees counter clock-wise becomes top to bottom (and when it is 
rotated 90 degree clockwise it becomes a bottom to top script).




>At 2005.08.16-04:35(-0400), fantasai wrote:
>>Stephen Deach wrote:
>>>I would like to see your list of languages using RTL scripts.
>>>The only scripts identified as RTL in Unicode are Arabic and Hebrew. 
>>>(Then there is the strange case of Mongolian which is marked as LTR but 
>>>I think should be treated as "RTL rotated to read top-down".)
>>
>>Mongolian is LTR because when it goes horizontal for brief spans, it is
>>usually LTR. (Probably because most scripts out there are LTR.) Longer
>>texts are always laid out vertically, in which case Mongolian has the
>>same directionality behavior as CJK.
>>
>>~fantasai
>
>
>---Steve Deach
>    sdeach@adobe.com

         Steve
=====================================
Steve Zilles
115 Lansberry Court,
Los Gatos, CA 95032-4710
steve@zilles.org 
Received on Friday, 19 August 2005 20:14:57 GMT

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