RE: [icu-design] API proposal: two variants to the Unicode BiDi algorithm

[Schilling, B. <ber...@sa...>]

Mati,=20
=20
I have to apologize - I had not read and checked carefully enough. We
had actually focussed on testing the BIDI algorithm in RTL environments.

=20
1) In both LTR and RTL orientation of the Notepad window the string
123AB (where A and B are Hebrew characters) appeared visually as BA123,
whereas it should be 123BA in LTR orientation. This is exactly what you
describe. =20
=20
2) A string of Arabic digits with space characters in between like '12
34 56' actually behaves like a string of ASCII characters if the
orientation of the Notepad window is LTR. This is again what you
described. And yes, a LRE mark creates a LTR environment in RTL windows,
so that also this observation gives a consistent picture.=20

I tested on Windows XP, Professional, Version 2002, Service Pack 1. The
system settings were English, with Hebrew and Arabic locales installed.=20
=20
The reason why I thought that a Windows compatibility mode of the BIDI
algorithm should specify the Windows version and API is the experience
from the past. For example, the property of the hyphen-minus character
changed on Windows 2000 between service pack 2 and 3 from 'other
neutral' to 'European separator'. But maybe it is stable enough now.=20
=20
Best regards,=20
Bernhard=20
=20
  _____ =20

From: icu...@li...
[mailto:icu...@li...] On Behalf Of Matitiahu
Allouche
Sent: Thursday, June 23, 2005 10:06 AM
To: icu...@li...
Cc: Sievers, Phillip
Subject: RE: [icu-design] API proposal: two variants to the Unicode BiDi
algorithm



Bernhard,=20

Thank you for your comments.  I would like some clarifications.=20

1) When you write "in Notepad on Windows XP we could not reproduce the
display behavior of '123AB' that you describe", what version of Windows
XP did you test? Professional or Home? Localized or US with
Hebrew/Arabic locale?  Is the Notepad window oriented LTR or RTL? (what
I describe is for Notepad in LTR orientation).=20

2) When you write " the behavior of Arabic-Inidic digits, seems to be
correct in Notepad", is the Notepad window oriented LTR or RTL?  The
difference from the Unicode algorithm is visible only when the embedding
level is LTR.  That would explain why adding LRE makes a difference.

Shalom (Regards),  Mati
          Bidi Architect
          Globalization Center Of Competency - Bidirectional Scripts
          IBM Israel
          Phone: +972 2 5888802    Fax: +972 2 5870333    Mobile: +972
52 2554160




"Schilling, Bernhard" <ber...@sa...>=20
Sent by: icu...@li...=20

21/06/2005 14:41=20
Please respond to
icu-design


To
<icu...@li...>=20
cc
"Sievers, Phillip" <phi...@sa...>=20
Subject
RE: [icu-design] API proposal: two variants to the Unicode BiDi
algorithm=09

	=09




Mati,=20
 =20
we also have the problem of displaying BIDI text uniformly on
heterogeneous platforms, and in older ICU releases we even had modified
the ICU algorithm locally in order to get a Windows compatible BIDI
algorithm. This modification was for the characters '+', '-', and '/'
which were handled differently by Microsoft and Unicode before Unicode
4.0.1.=20
 =20
However, this difference disappeared with Unicode 4.0.1 because the
character properties of these three characters were changed in the
Unicode standard.=20
 =20
The problem is that there are also differences beween different
Microsoft products. For example, in Notepad on Windows XP we could not
reproduce the display behavior of '123AB' that you describe in the
proposed API.=20
 =20
Also the second case, the behavior of Arabic-Inidic digits, seems to be
correct in Notepad. At least, if you really use the Unicode values of
the Arabic-Indic digits and not the display option under Control Panel
-> Regional and Language Options. In the latter case ASCII digits are
replaced with Arabic-Indic digits after the BIDI algorithm is applied.=20

A difference between Notepad and the Unicode BIDI algorithm that we can
see is the behaviour of Arabic-Indic digits after an LRE mark. However,
this is an exotic case.=20

Our impression is that a Windows compatibility mode of the BIDI
algorithm, if really needed, should specify which Windows versions and
which Windows applications or APIs are covered.=20
 =20
Best regards,=20
Bernhard Schilling=20
SAP Netweaver, I18n development=20