How do I get italic correction in LuaLaTex with unicode-math and \left \right?

Question

The story about italic correction in LuaLaTeX when using unicode-math seems to be an old one. However, the issue does not appear to be fixed. Here is what it looks like with unicode-math

and without

Note the yellow box right to the second f, which indicates kerning. It looks even worse when using the Libertinus font, then the f and the > really overlap:

I guess this is because Libertinus defines the right border of the f to be different.

Here is the code used to generate the last screenshots:

%! TEX program = lualatex
\documentclass{article}

\usepackage{lua-visual-debug}

\usepackage{unicode-math}
\setmathfont{Libertinus Math}

% enable italic correction
\everymath\expandafter{\the \everymath \luatexcatcodetable\CatcodeTableLaTeX}
\everydisplay\expandafter{\th[enter image description here][4]e \everydisplay \luatexcatcodetable\CatcodeTableLaTeX}

\newcommand{\luatexcatcodetable}{}
\newcommand{\CatcodeTableLaTeX}{}

\newcommand*{\norm}[1]{{\ensuremath{\left\|{#1}\right\|}}}
\newcommand*{\inner}[1]{{\ensuremath{\left\langle{#1}\right\rangle}}}

\begin{document}
   \[
       \inner{f, f}       \hspace{2em}
       \norm{f}_2^2       \hspace{2em}
       \inner{g, g}       \hspace{2em}
       \norm{g}_2^2       \hspace{2em}
   \]
\end{document}

Also, dropping the \left and \right makes it looks as it should:

Unfortunately the once recommended workaround

\everymath\expandafter{\the\everymath\luatexcatcodetable\CatcodeTableLaTeX}
\everydisplay\expandafter{\the\everydisplay\luatexcatcodetable\CatcodeTableLaTeX}

gives me the following error:

! Undefined control sequence.
<inserted text> \@displaytrue \luatexcatcodetable 
                              \CatcodeTableLaTeX

It looks like both commands \luatexcatcodetable and CatcodeTableLaTeX do not exist anymore. Adding

\newcommand{\luatexcatcodetable}{}
\newcommand{\CatcodeTableLaTeX}{}

makes my code compile (note that I did not have to use \renewcommand!), but obviously this has then no effect on italic correction. Any idea how to get italic correction now?

Answer 1

From this answer I got the solution to add \mathitalicsmode=1 to the preamble. If I understand correctly, this enables italic correction in math mode. To obtain the desired result, one also has to remove the surrounding brackets { ... }, otherwise italic correction is not applied (except if there is a single character {f}, then it seems to work. Why?) So the following code example works fine:

%! TEX program = lualatex
\documentclass{article}

\usepackage{lua-visual-debug}

\usepackage{unicode-math}
\setmathfont{Libertinus Math}

\mathitalicsmode=1

\begin{document}
   \[
       \left\langle f,f \right\rangle
   \]
\end{document}