% To be loaded *after* microtype
%
% Patching \pickup@font to emulate LuaTeX's font expansion interface using \adjustspacing...
\RequirePackage{microtype}% Just to ensure it isn't loaded in the wrong position. Normally this shouldn't be necessary
\def\luametalatex@@setexpansion#-#1#2#3#-\relax{%
  \adjustspacingstretch #1
  \adjustspacingshrink #2
  \adjustspacingstep #3
}%
\newluafunction\luametalatex@@expandglyphsinfont
\protected\luadef\pdffontexpand\luametalatex@@expandglyphsinfont
\def\luametalatex@@everyjobandnow#1{\toksapp\everyjob{#1}#1}%
%
\begingroup
\catcode`\!=\catcode`\%
\catcode`\%=12
\expanded{!
  \endgroup
  \def\noexpand\pickup@font{!
    \unexpanded\expandafter{\pickup@font
      \expandafter\expandafter\expandafter\luametalatex@@setexpansion\csname pickup@font@@hook@luametalatex@microtype@\the\fontid\font@name\endcsname{0}{0}{0}\relax
    }!
  }!
  \noexpand\luametalatex@@everyjobandnow{\noexpand\directlua{!
    lua.get_functions_table()[\the\luametalatex@@expandglyphsinfont] = function()
      token.put_next(token.create'fontid')
      local font = token.scan_int()
      local stretch = token.scan_int()
      local shrink = token.scan_int()
      local step = token.scan_int()
      token.set_macro('pickup@font@@hook@luametalatex@microtype@' .. font, string.format("{}{%i}{%i}{%i}", stretch, shrink, step), "global")
    end
  }}
}%