OK, after digesting what Eli, Jonathan, and Richard had to say (thank
you all for your feedback), I think you're in agreement that normally
RTL scripts such as Hebrew should be rendered vertically Top To Bottom
(first input character output at the top, and growing downwards, just as
with English). I erred in stating "last input, first read", as pointed
out (self-administered dope slap goes here). It sounds like my TTBHebrew
example in HarfBuzz.pdf (did anyone look at it?) is correct output, and
embedded normally LTR (e.g., English) text should not be reversed from
the order used by the normally bidirectional/RTL text (continue to write
TTB).
Regarding Phags-pa, Mongolian, and Ogham; I will ignore them for the
time being, unless someone volunteers to try them out with PDF::Builder
software (next release, 3.019, or GitHub after today). I'll just hope
that HarfBuzz handles vowel (spacing) marks correctly (on the same
"line" as the consonant?), and if anyone reports that it's incorrect,
I'll see what I can do. I'm also assuming that Arabic and related
languages will have more or less the same rules as Hebrew (again, if
documented as incorrect, I'll see what I can do). Column direction
remains to be seen, and might be dependent on the specific language.
PDF::Builder does not yet support multi-column vertical text, but I'll
probably default to right-to-left and give an option for left-to-right.
BTT is supported, if any language needs to use that.
Again, thanks! Phil
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