Re: RTL PUA?

On 08/22/2011 04:34 PM, Behdad Esfahbod wrote:
> On 08/22/11 06:53, Shriramana Sharma wrote:
>> >
>> >
>> > While I don't know much about RTL scripts, if the logic order is ALEF + LAMED,
>> > but the presentation order is LAMED + ALEF*because of the RTL nature* do you
>> > write the rule as ALEF + LAMED = ALEF_LAMED_LIGATURE or LAMED + ALEF =
>> > ALEF_LAMED_LIGATURE ?
> Depends on your specific shaping engine logic. OpenType assumes native
> direction per script. So if you have Arabic text between LRO/PDF, you have to
> reverse the order then apply OpenType shaping. Other engines may decide to
> handle these differently. But the general statement is true: ligatures are
> visual artifacts and hence only form in one direction, not the other (except
> if it's, say, the "ff" ligature).

Hi Behdad. I only asked whether the OT *tables* would contain the
entries in the logical order or the visual order. Clearly it would still
be the visual order (but Philippe Verdy seemed to imagine/suggest
otherwise).

It is clear that in the *script itself* the ligature would form in the
direction of writing.

-- 
Shriramana Sharma