Re: RTL PUA?

Michael Everson 於 2011年8月19日 上午11:15 寫道：

> On 19 Aug 2011, at 18:01, Shriramana Sharma wrote:
>
>>> Even though it isn't encoded? That is, my understanding is that we *can't* change the PUA to ON now, but that there is a suggestion that some *new* hunk of PUA be created that is R, in order to balance the existing L. Is that right?
>>
>> Right, Michael is suggesting that, but since the properties of the PUA characters aren't binding as said above, this is also unnecessary.
>
> Saying that does not make it possible for people to use PUA characters with RTL directionality, since all the OSes treat them as LTR.
>

Mac OS has a mechanism to override that default assumption, the 'prop' table. And hopefully people support RLO and LRO properly, which provides a general-purpose mechanism.

>> Would mean yet another chunk of space where we aren't allowed to encode anything. (Yes yes I know all that about "plenty of space", but that space gets filled up pretty quickly. I predict/expect the SMP will be filled soon.)
>
> Put a RTL PUA zone in Plane 14, which is mostly empty, and expected to remain so, and you're done.
>

No, you're not, because the OSs/rendering engines would have to rev, and to be honest, there won't be a lot of enthusiasm for doing something something like this so long as it isn't actually *required* in order to be Unicode conformant. (It's hard enough to get people to do the required stuff.) RTL, PUA support, and optional features are usually pretty low on most people's priority lists.

I'm very sympathetic with the frustration people feel over the current situation, but, again, before you could convince the UTC to do this, you'd have to present pretty solid evidence that the current solution doesn't work and that this would.

=====
John H. Jenkins
jenkins_at_apple.com
Received on Fri Aug 19 2011 - 12:51:59 CDT