[Tex/LaTex] Undefined font shape

fontsxepersian

I have a xepersian document, e.g.

\documentclass[10pt,a4paper]{report}
\usepackage{xepersian} 
\settextfont{Nazli}% http://http.debian.net/debian/pool/main/f/fonts-farsiweb/fonts-farsiweb_0.4.dfsg.orig.tar.xz
\begin{document}
این یک متن فارسی  است.
\textit{ادامه}
 متن فارسی...
\end{document}

Upon compiling I get these warnings:

LaTeX Font Warning: Font shape `EU1/Nazli(0)/m/it' undefined
(Font)              using `EU1/Nazli(0)/m/n' instead on input line ***.

and the text inside \textit{} is not italic.
What is causing the problem? and how can I fix this?

I have used Nazli in LibreOffice and it has an italic shape; or isn't that the same?

Best Answer

Word processors like LibreOffice usually fake missing italic shape by geometrically slanting the glyphs. You can obtain the same result with XeLaTeX using the FakeSlant option to fontspec.

\documentclass[10pt,a4paper]{report}
\usepackage{xepersian} 
\settextfont[
  Script=Arabic,
  ItalicFont=Nazli,
  ItalicFeatures={FakeSlant=-0.5},
]{Nazli}
\begin{document}
این یک متن فارسی  است.
\textit{ادامه}
 متن فارسی...
\end{document}

Probably 0.5 is exaggerated, but I used it for making the slanting more visible. The value should be negative in order to slant to the left.

enter image description here