soul + highlight removes some characters from text

Question

Here is an MWE:

\documentclass[a4paper,11pt]{article}
\usepackage{polyglossia}
\usepackage[normalem]{ulem}
\defaultfontfeatures{Ligatures=TeX}
\setmainlanguage{magyar}
\usepackage{color}
\usepackage{soul}

\begin{document}

árvíztűrő tükörfórógép

ÁRVÍZTŰRŐ TÜKÖRFÚRÓGÉP

\hl{árvíztűrő tükörfórógép}

\hl{ÁRVÍZTŰRŐ TÜKÖRFÚRÓGÉP}

\end{document}

Here are some interesting message from the log:

Missing character: There is no ű in font ectt1000!
Missing character: There is no ő in font ectt1000!
Missing character: There is no ű in font ectt1000!
Missing character: There is no Ű in font ectt1000!
Missing character: There is no Ő in font ectt1000!
Missing character: There is no Ű in font ectt1000!

I'm not sure why it is complaining about font ectt1000. It can be seen clearly that the highlighted text and the normal text use the very same font. I do not see any error messages in the log. (Nor warnings - but this kind of misrendering should definitely throw an error!)

Here is the output:

Answer 1

As you are using xelatex/lualatex you need an open type typewriter font which contains all the glyphs. Also one must also reset the default width of the hyphen to this font. In your example you can use Latin Modern Mono, but if you have other scripts you perhaps will need another one.

\documentclass[a4paper,11pt]{article}
\usepackage{fontspec}
\usepackage{color}
\usepackage{soul}
\makeatletter
\font\SOUL@tt="LMMono10-Regular"
\setbox\z@\hbox{\SOUL@tt-}
\SOUL@ttwidth\wd\z@ %reset default width of -
\makeatother
\begin{document}

árvíztűrő tükörfórógép

ÁRVÍZTŰRŐ TÜKÖRFÚRÓGÉP

\hl{árvíztűrő tükörfórógép}

\hl{ÁRVÍZTŰRŐ TÜKÖRFÚRÓGÉP}

\end{document}