[HarfBuzz] Template or sample code for writing a shaper for harfbuzz-ng?

[Ed]

Hi, Behdad and everyone!

How are new shaping engines going to be handled in harfbuzz-ng?  As
plug-in modules, or as hard-coded files?

Is there sample or template code somewhere that shows how one would
write a new shaper for harfbuzz-ng?

Also are there any guidelines on general "do"s and "don't"s when
writing shaping extensions for harfbuzz-ng in order to maximize
efficiency and avoid pitfalls?

I hope that the API and code are sufficiently mature now that you can
answer these questions or direct me to the appropriate resource(s).

Thanks!

-- Ed Trager