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)

---

With the advent of LuaTeX 0.95.0 the \pdf... primitives have been moved to the unified \pdfextension interface. The above code does not work anymore and has to be modified to reflect these changes.

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

Alternatively one could define \pdfliteral as devised in the LuaTeX manual:

\protected\def\pdfliteral{\pdfextension literal}