<div dir="ltr"><pre>\ifXeTeX comes from iftex package:<br><br>\usepackage{iftex}<br><br>\ifXeTeX<br> <xetex material><br>\else<br>\ifPDFTeX<br><pdftex material><br>\else<br>\ifLuaTeX<br><luatex material><br>
\else<br><material for not using luatex or xetex or pdftex><br>\fi\fi\fi<br><br></pre></div>