Slanted text problem for the main (cmr) font in XeLaTeX with fontspec

Question

I'm newbie in XeLaTeX and have to adopt already typeset (in LaTeX) textbook with the Computer Modern Roman mainfont. So I want to have slanted text, while the compiler with default introduction (taken somewhere)

\usepackage[T2A]{fontenc}
\usepackage[russian]{babel}
\usepackage{fontspec} 
\defaultfontfeatures{Ligatures={TeX},Renderer=Basic}
\setmainfont{CMU Serif Roman}
\setsansfont{CMU Sans Serif}  
\setmonofont{CMU Typewriter Text}

(and latex-preserved commands \textsl{} and \slshapr for the usage) writes that slanted text is replaced by the simple italic.

I tried in two ways: (I) load the font cmunsl.otf as overall-windows-installed and tried to use it as independent new font:

\font\wslant="CMU Serif Extra RomanSlanted" at 12pt

(II) In the fontspec documentation (p.11) I found that the slanted font can be added as an option to the \setmainfont; I tried (a)

\setmainfont[SlantedFont = CMU Serif Extra RomanSlanted]{CMU Serif Roman}

and (b)

\setmainfont[SlantedFont = cmunsl.otf]{CMU Serif Roman}
(this OTF-file cmunsl.otf is presented in the folder
C:\texlive\2016\texmf-dist\fonts\opentype\public\cm-unicode\)

In all cases the error is 'your font is not found'. The same if I declare Path explicitly: \setmainfont[Path=...,SlantedFont =...]

Could anybody help with proper font declaration and proper usage in the text? In the questions with tag 'slanted' I did not found the solution for the main font family.

Thanks

Answer 1

Use fullname obtained by

fc-list : file fullname

\setmainfont[SlantedFont=CMU Serif Roman Slanted]{CMU Serif Roman}

must be ok.

\setmainfont[SlantedFont=[cmunsl.otf]]{CMU Serif Roman}

may also be ok.

Answer 2

If you can call the fonts by system name, the simplest is

\documentclass[a4paper]{article}

\usepackage{fontspec}
\usepackage[russian]{babel}

\setmainfont{CMU Serif Roman}[
  SlantedFont=CMU Serif Roman Slanted,
]

\begin{document}

Normal, \textit{italic}, \textsl{slanted}.

\end{document}

Otherwise you need to specify all font file names:

\documentclass[a4paper]{article}

\usepackage{fontspec}
\usepackage[russian]{babel}

\setmainfont{cmun}[
  Extension      = .otf,
  UprightFont    = *rm,
  BoldFont       = *bx,
  ItalicFont     = *ti,
  BoldItalicFont = *bi,
  SlantedFont    = *sl,
]

\begin{document}

Normal, \textit{italic}, \textsl{slanted}.

\end{document}

Note that \usepackage[T2A]{fontenc} is not to be used with XeLaTeX. Also

\defaultfontfeatures{Ligatures={TeX},Renderer=Basic}

is not needed, because the Ligatures=TeX option is set by default and Renderer=Basic does nothing with XeLaTeX.