From: Michael Everson <>
Date: Fri, 19 Aug 2011 15:37:59 +0100

On 19 Aug 2011, at 15:24, Shriramana Sharma wrote:

> On 08/19/2011 07:13 PM, Michael Everson wrote:
>> This is a very good question.
> It seems Michael speaks tongue-in-cheek.

Not at all. I think there should be a RTL PUA.

> I personally don't see the point in allocation RTL areas in the PUA. It is after all the *P*UA. Do you expect rendering engines to support the PUA?

I can get certain CSUR scripts to behave as expected using PUA code positions. Unless they are RTL.

> Yeah OK maybe simply base+diacritic stuff or even ligatures would be easy to do via simple substitution rules in tables, but how about glyph reordering?

No problem unless you are using Uniscribe.

> Indic scripts involving reordering and split-positioning vowel signs can't be handled by placing them in the PUA.

There are other ways of handling such clusters.

> In what way are RTL scripts different that proper rendering should be supported for them even though they are in the PUA?

They, um, go RTL.

> If you want proper rendering in terms of bidi formatting and glyph reordering etc you should make a proposal for official encoding. The PUA will not help.

It would help for exchange of private scripts that are RTL, or for software development of RTL scripts, etc.

> Ergo there is no scope for specifying directionality for PUA code-points.

Sure there is. It's just giving some otherwise-undefined code points a strong 'R' directionality for the benefit of those users who need to use that. After all, the rest of the PUA gives some otherwise-undefined code points a strong 'L' directionality.

Michael Everson *
Received on Fri Aug 19 2011 - 09:39:06 CDT

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