[HarfBuzz] Recursive ligatures - Devanagari shaping

[Tom Hacohen]

Dear all,

I can't read/write in Devanagari but, I was requested to assist someone
who does in supporting it using harfbuzz. He wrote some code using the
old harfbuzz that shapes it just fine, while my code using the new
harfbuzz does not (but my code does shape everything else just fine).

Inspecting the font I noticed it has recursive ligatures, that is,
ligatures that are defined as composed by two other ligatures that are
defined as composed by the basic characters that were used.

I wonder, am I doing anything wrong? is the font bad (I doubt it)? or is
harfbuzz currently lacking recursive shaping?

Example to the issue I'm talking about is the combination of the
following Devanagari characters: ta, virama (aka halant) ra.
ta - त
virama - ्
ra - र

Which should look (if your mail client can shape properly) like: त्र

But it doesn't in my code.

Any tips?

--
Tom.