Re: RTL PUA?

I suggested 'R' for Plane 16, not 'ON'.

What's a LANGUAGE MARK?

--
Doug Ewell • doug_at_ewellic.org
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-----Original Message-----
From: Richard Wordingham <richard.wordingham_at_ntlworld.com>
Sender: unicode-bounce_at_unicode.org
Date: Sun, 21 Aug 2011 23:31:58 
To: <unicode_at_unicode.org>
Subject: Re: RTL PUA?
On Sun, 21 Aug 2011 11:00:26 -0600
"Doug Ewell" <doug_at_ewellic.org> wrote:
> I think as soon as we start talking about this many scenarios, we are
> no longer talking about what the *default* bidi class of the PUA (or
> some part of it) should be.  Instead, we are talking about being able
> to specify private customizations, so that one can have 'AL' runs and
> 'ON' runs and so forth.
I was exploring the consequences to see if there was a one size fits
all solution.  Someone (you?) suggested ON as a default, and I like
it.  I think it would also work fairly well for practical CJK
applications as well - the only problems are that LRM and RLM would
occasionally be needed, and the subtle differences between AL and R
would be lost.  I expect ARABIC LANGUAGE MARK would not go down well
- has it already been proposed and rejected?.
> Through most of the 1990s, most 
> existing applications and technologies didn't support Unicode at all,
> or very small parts of it, and the solution generally was to update
> them so that they would.  The same should be true here.
Agreed.  I also noted that changes would be of limited assistance for
extending existing supported scripts.
> I would
> suggest that installing a modified copy of UnicodeData.txt seems like
> a rather clumsy solution; if text files are involved, I'd suggest
> leaving UnicodeData.txt alone and creating some sort of "overrides"
> file.
While partial overrides are cleaner, that appears to be the way to fix
Pango, albeit via recompilation.  According to the comments, its BiDi
settings are derived from the file automatically.  Also, one needs a
method of updating the properties of codepoints as they become assigned
and properties change.  There are also advantages to trying out proposed
changes.
Richard.