Different interword spacing depending on the Renderer

[xscheuer]

Hello, I use the Aref Ruqaa font to have a textual version of Euler in Latin alphabet.
Using luatex and fontspec I get a much smaller interword spacing if I use the default Renderer (Node) than if I use the Opentype or HarfBuzz Renderer.
As the Aref Ruqaa font is the only one to exhibit this behavior, I am reporting it here first, but it may be a luaotfload bug (you are probably more qualified to say).

Thank you and have a nice day.

MWE:

\documentclass{scrartcl}

\usepackage{fontspec}

\setmainfont{Aref Ruqaa}[
  % Renderer=Node,
]

\usepackage{lipsum}

\begin{document}

\section{Aref Ruqaa with \texttt{fontspec}'s default renderer (\texttt{Renderer = Node}): small interword space}

\lipsum[1]


\section{Aref Ruqaa with \texttt{Renderer = OpenType} (or \texttt{HarfBuzz}: bigger interword space)}

\setmainfont{Aref Ruqaa}[
  Renderer=OpenType,
]

\lipsum[1]


\end{document}

[khaledhosny]

The wider spacing is the expected one. Since Aref Ruqaa is primarily an Arabic font, the default spacing is tuned for Arabic text. For Latin text space glyph is substituted with a wider one more appropriate for Latin. It looks like node mode is not applying this substitution or not using the width of the alternate space glyph it when constructing word glue.