fakebold error in fontspec or lualatex

Question

I have been trying to fake small caps which are not available in Myriad Pro. So I used the Scale and FakeBold options. Scaling is allright, but as you all know the glyphs slim out. To work against that I tried to "fatten" them somewhat.

The code below does not "fatten" the scaled characters when using lualatex (latest TeX-Live). Using xelatex (also latest TeX-Live) works fine.

I think its a bug.

\documentclass[11pt,a4paper]{article}
\usepackage{fontspec}
\setmainfont{TeX Gyre Heros}
\begin{document}
ABC {\fontspec[FakeBold=5,Scale=0.72]{TeX Gyre Heros} ABC} ABC
\end{document}

For demonstration the code above uses another fontwich actually supports small caps.

Answer 1

LuaTeX does not support emboldening, so FakeBold will not work. fontspec should issue a warning here.

It might be possible to implement emboldening in lua, say in luaotfload package, but I didn't investigate closely.

Here is a work around using pdf literals (which is essentially what XeTeX does behind the scenes).

\def\embolden#1#2{%
    \pdfliteral direct {2 Tr #1 w}%
     #2%
    \pdfliteral direct {0 Tr 0 w}%
}
ABC \embolden{0.5}{ABC} ABC
\bye

This even works with pdftex.

(Note, when you use Scale=0.72, the FakeBold will be 5*0.72, so you might want to use 0.36 instead of 0.5)