[lltx] microtype and OpenType "opbd" feature

[Pablo Rodríguez]

Hi,

I’m not a LuaLaTeXt user myself (I use ConTeXt), but a friend asked me
how to enable the OpenType feature "opbd" (which is actually
"lfbd"+"rtbd") in LuaLaTeX.

ConTeXt has enabled recently optical bounds for the new font loader:

  \definefontfeature[default][default][protrusion=yes,opbd=yes]
  \setupbodyfont[ebgaramond, 150pt]
  \setupalign[hanging]
  \showframe
  \starttext
       \input tufte
  \stoptex

It requires protrusion to be enabled too.

I asked Will Robertson to implement the "opbd" feature in fontspec
(https://github.com/wspr/fontspec/issues/282), but since protrusion is
involved, it may require also implementation in microtype.

Would it be possible to implement optical bounds in LuaLaTeX?

Many thanks for your help,

Pablo
-- 
http://www.ousia.tk