How to access non-Unicode glyphs from OTFs with Lua(La)TeX?

Question

I opened Shobhika font in FontForge and it has certain glyphs which I am guessing aren't encoded in Unicode (if I understand this business correctly). E.g., have a look at the following slot.

What I guessed from this is that the slot I have selected is a non-Unicode position because I see U+????. Is there any way to load this shape by calling either 65664/0x10080/BhaRa.dv? Disclaimer: I don't know what all of them mean, I am just guessing they are different types of identifier for this shape. Which of these identifiers are understood by TeX (especially LuaTeX)? I found this solution, but it didn't work for the glyph I want.

Answer 1

You can use slot_of_name from luaotfload:

\documentclass{article}
\usepackage{fontspec}
\setmainfont{Shobhika}
\begin{document}
The BhaRa.dv character is:
\directlua{tex.sprint("\\char" .. luaotfload.aux.slot_of_name(font.current(), [[BhaRa.dv]]))}
\end{document}

---

You can also enter the code directly with \char[code] if you know the slot number. I am not entirely sure how the codes correspond to the values that FontForge shows. You can however print the font table with numbers that \char understands with the following code, adapted from https://tex.stackexchange.com/a/666152/ (which is itself adapted from https://tex.stackexchange.com/a/98789/). The code is basically a for-loop around slot_of_name for each character.

\documentclass[a5paper]{article}
\usepackage{luacode}
\usepackage[margin=0.5cm]{geometry}
\usepackage{fontspec}
\usepackage{multicol}
\setlength{\columnsep}{0.3cm} \setlength{\columnseprule}{1pt}
\setmainfont{Shobhika Regular}
\newfontface\OD{Shobhika-Regular.otf}
\begin{document}
\begin{multicols}{4}\noindent
\begin{luacode*}
local f = fontloader.open('/usr/share/texlive/texmf-dist/fonts/opentype/public/shobhika/Shobhika-Regular.otf')
local glyphs = {}
for i = 0, f.glyphmax - 1 do
   local g = f.glyphs[i]
   if g then
       table.insert(glyphs, {name = g.name, unicode = g.unicode})
   end
end
table.sort(glyphs, function (a,b) return (a.unicode < b.unicode) end)
for i = 1, #glyphs do
   if (glyphs[i].unicode > 0) then
      tex.sprint(glyphs[i].unicode .. ": ")
      tex.sprint("{\OD\char" .. glyphs[i].unicode .. "}");
   else
      local charcode = luaotfload.aux.slot_of_name(font.current(), glyphs[i].name)
      tex.sprint("{\tiny " .. tostring(charcode) .. ":}")
      if (charcode ~= false) then
         tex.sprint("{\OD\char" .. charcode .. "}")
      end
   end
   tex.sprint("\ {\small(" .. string.gsub(glyphs[i].name, "", "\") .. ")}\\")
end
fontloader.close(f)
\end{luacode*}
\end{multicols}
\end{document}

Small part of the output:

Now for example ShaVa.dv can be printed with \char984278 etc.