Re: RTL PUA?

On Sat, Aug 20, 2011 at 7:08 AM, Shriramana Sharma <samjnaa_at_gmail.com>
wrote:
> On 08/20/2011 01:57 PM, Martin Hosken wrote:
>>
>> D49 states that all properties of PUA characters are overridable by a
>> higher protocol. But in 'normal' implementations, there are no higher
>> level protocols to override the properties and so they use the
>> defaults in the Unicode Database. So while in *theory* it's possible
>> to override these values, nobody does. (This happens to also be the
>> case with other tailoring algorithms in Unicode). Adding the
>> configuration that tailoring requires is usually prohibitive and so
>> it just doesn't get done.
>
> Good point -- Michael should note this.
>
>>> Somebody remarked that Apple Mac OS's rendering engine already
>>> supports an extended OT table which would signal that the glyphs in
>>> a PUA font are RTL. If other rendering don't support it, again it
>>> is not the fault of the standard.
>>
>> Is there a specificatino for that OT table? Are you implementing this
>> in anything?
>
> Read a previous post by John Jenkins. He's the one who said they have a
> "prop" table in Apple's implemention of OT (or is it their own AAT) that
> enables one to do this.
>

Is this correct? that Apple solves the problem of RTL PUA user requirements?

See John Jenkins latest mail that says:
[Begin Quote]
To be honest, I don't know if using the 'prop' table to override
directionality for glyphs still works. A quick-and-dirty test on Lion
suggests that it doesn't, so I may have spoken too quickly. This is not a
part of the functionality of AAT which gets much exercise, so it's entirely
possible that it was lost at some point without anyone noticing. In any
event, my apologies for raising any false hopes.
[End Quote]

Hope a new proposal or a UTN from UC will make things clear, and RTL
community benefits.

N. Ganesan

Jonathan Kew 於 2011年8月21日 上午10:48 寫道：

> On 21 Aug 2011, at 17:21, Behdad Esfahbod wrote:
>
>> On 08/21/11 16:44, Shriramana Sharma wrote:
>>>
>>> BTW can John Jenkins show us a few entries from the "prop" table of some
font
>>> supporting the custom Apple PUA characters, especially the RTL and GC=No
ones?
>>
>> Like this?
>>
>> https://developer.apple.com/fonts/ttrefman/RM06/Chap6prop.html
>
> However, note that this documentation is very old, and does not make it
clear whether there is any support for overriding directionality in current
Mac OS X software.
>

Yes, it's very old, largely because we haven't done anything with the
structure of the 'prop' table for a long, long time. Still, anything
referring to "QuickDraw GX" is obviously overdue for an update.

To be honest, I don't know if using the 'prop' table to override
directionality for glyphs still works. A quick-and-dirty test on Lion
suggests that it doesn't, so I may have spoken too quickly. This is not a
part of the functionality of AAT which gets much exercise, so it's entirely
possible that it was lost at some point without anyone noticing. In any
event, my apologies for raising any false hopes.

=====
井作恆
John H. Jenkins
jenkins_at_apple.com

>>> If the application doesn't do this and allows Graphite to break the
>>> text into runs, then Graphite can treat PUA characters as having BC
>>> other than L? </myunderstanding>
>>
>> Yes that understanding is correct.
>
> Great! Could you then place some sample characters from your
> Scheherezade font in the PUA and render them RTL and show to us then
> Michael would be convinced.
>
> --
> Shriramana Sharma
>
>
Received on Mon Aug 22 2011 - 17:07:09 CDT