I'm having a problem with eulervm integral sign. I get the usual slanted instead of the expected upright integral sign. I'm using MikTeX 2.9 in combination with Lyx 2.1.3. This is the code exported by LyX. The result is the same in TeXstudio.
%% LyX 2.1.3 created this file. For more info, see http://www.lyx.org/.
%% Do not edit unless you really know what you are doing.
\documentclass[12pt]{book}
\usepackage{amsmath}
\usepackage{fontspec}
\setmainfont[Mapping=tex-text]{Footlight MT Light}
\usepackage[b4paper]{geometry}
\geometry{verbose,tmargin=3cm,bmargin=3cm,lmargin=3cm,rmargin=5cm}
\usepackage{fancyhdr}
\pagestyle{fancy}
\setlength{\parskip}{\bigskipamount}
\setlength{\parindent}{0pt}
\usepackage{color}
\usepackage{float}
\usepackage{booktabs}
\usepackage{units}
\usepackage{graphicx}
\usepackage{esint}
\usepackage[unicode=true,pdfusetitle,
bookmarks=false,
breaklinks=false,pdfborder={0 0 1},backref=false,colorlinks=true]
{hyperref}
\hypersetup{
linkcolor=RoyalBlue}
\makeatletter
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% LyX specific LaTeX commands.
%% Because html converters don't know tabularnewline
\providecommand{\tabularnewline}{\\}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% User specified LaTeX commands.
%Footlight MT LIght, Heuristica
%\usepackage[garamond]{mathdesign}
\usepackage{eulervm}
\usepackage[usenames,dvipsnames]{xcolor}
%\newfontfamily\cyrillicfont{Minion Cyr Regular}
%\newfontfamily\cyrillicfont{Times New Roman}
\newfontfamily\cyrillicfont[Ligatures = TeX]{EB Garamond}
%\renewcommand*{\partpagestyle}{empty}
\fancyhead[RE,LO]{\leftmark}
\fancyhead[LE,RO]{\thepage}
\fancyfoot[C]{}
%Options: Sonny, Lenny, Glenn, Conny, Rejne, Bjarne, Bjornstrup
%\usepackage[Conny]{fncychap}
\usepackage{titlesec}
\renewcommand{\thechapter}{\Roman{chapter}}
\titleformat{\chapter}[display]
{\bfseries\Large}
{\filright\MakeUppercase{\chaptertitlename} \Huge\thechapter}
{4ex}
{\titlerule
\vspace{2ex}%
\filleft}
[\vspace{2ex}%
\titlerule]
%\DeclareMathSizes{10}{10.5}{7}{7}
\usepackage[labelfont={color=RoyalBlue,bf}]{caption}
\makeatother
\usepackage{xunicode}
\usepackage{polyglossia}
\setdefaultlanguage{serbian}
\begin{document}
\[
P\left(x_{1},x_{2}\right)=\intop_{x_{1}}^{x_{2}}p(x)dx
\]
\end{document}
\usepackage{esint}
@
sign followed by the user name.