<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">Alexander Krumeich wrote:<br>
</div>
<blockquote type="cite" cite="mid:CALeLr1mfjEPcdMi2CQWrnF1U0uAZ9TXcrVqP9NgoizuJ-HKuxQ@mail.gmail.com">
<pre wrap="">[...] in the text representation a space is added after some characters. Consider
the following MWE:
\listfiles
\documentclass[a4paper]{scrartcl}
\usepackage{fontspec}
\setmainfont{roboto}
\begin{document}
This is a test.
\end{document}
</pre>
</blockquote>
<br>
I was unable to get your example to work at all, despite downloading and installing the Roboto family from Google and then running "fc-cache <etc>", but I was able to use Roboto in plain XeTeX, as in :<br>
<br>
<blockquote type="cite">\font \thisfont = "Roboto Medium"
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">
\thisfont</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">
This is a test.</p>
<p style=" margin-top:0px; margin-bottom:0px; margin-left:0px;
margin-right:0px; -qt-block-indent:0; text-indent:0px;">
\end</p>
</blockquote>
<br>
Viewing the resulting PDF in Adobe Acrobat CC, then using "File / Export to / Text (plain) yielded :<br>
<br>
<blockquote type="cite">This is a test. <br>
</blockquote>
<br>
with no anomalous spaces or lack thereof. Copy-and-paste similarly evidenced no anomalies.<br>
<br>
<i>Philip Tayor</i><br>
<br>
</body>
</html>