Adding diagbox feature to nicematrix

[Basmah1961]

tabularray has a command \diagbox which allows for convenient placement of diagonal boxes. It might be good to add this command instead of using \CodeAfter and tikzpicture

\documentclass[11pt, a4paper]{article}

\usepackage{fancyhdr}
\pagestyle{empty}

\usepackage{tikz}

\usepackage{nicematrix}

\usepackage{tabularray}
\UseTblrLibrary{diagbox}

\begin{document}

\begin{NiceTabular}[hvlines, cell-space-limits=0pt]{l l l}

    & Beta
    & Gamma
    \\

    Epsilon
    & Zeta
    & Eta
    \\

    Iota
    & Kappa
    & Lambda
    \\

    \CodeAfter
    \begin{tikzpicture}[remember picture,overlay,outer sep=0pt,inner sep=0pt]

        \draw[] (1-|1)--(2-|2);

        \node[anchor=north east] at ([shift={(-1pt,-1pt)}] 1-|2) {Pp};

        \node[anchor=south west] at ([shift={(+1pt,+1pt)}] 2-|1) {Aa};

    \end{tikzpicture}

\end{NiceTabular}

\bigskip

\begin{tblr}{colspec={Q[l,h] Q[l,t] Q[l,h]},
        rowsep=0pt, 
        hlines,vlines
}

    \diagbox{Aa}{Pp}
    & Beta
    & Gamma
    \\

    Epsilon
    & Zeta
    & Eta
    \\

    Iota
    & Kappa
    & Lambda
    \\

\end{tblr}

\end{document}

[fpantigny]

nicematrix yet has such feature with its built-in command \diagbox.

\documentclass[11pt, a4paper]{article}
\pagestyle{empty}
\usepackage{nicematrix}

\begin{document}

\begin{NiceTabular}[hvlines]{l l l}
\diagbox{Aa}{Pp}
& Beta
& Gamma
\\

Epsilon
& Zeta
& Eta
\\

Iota
& Kappa
& Lambda
\\
\end{NiceTabular}

\end{document}

[Basmah1961]

nicematrix yet has such feature with its built-in command \diagbox.

\documentclass[11pt, a4paper]{article}
\pagestyle{empty}
\usepackage{nicematrix}

\begin{document}

\begin{NiceTabular}[hvlines]{l l l}
\diagbox{Aa}{Pp}
& Beta
& Gamma
\\

Epsilon
& Zeta
& Eta
\\

Iota
& Kappa
& Lambda
\\
\end{NiceTabular}

\end{document}

I did not know it is available. However, I think it is possible to improve it by

1. Adding customizable vertical white space above and below
2. The arguments of diagbox (Aa and Pb) must have \tabcolsep margin from vertical rules

[fpantigny]

You are right. It's a good suggestion. However, I can't change easily such features without silently breaking existing documents. The command \diagbox has been introduced in the version 4.1 of 2020/05/27 (four years ago) and it's not so difficult for the final user to add a \hspace*{...} and a \strut (for the vertical space).

[Basmah1961]

Then why not make \diagbox behave as normally does, but add an optional key to change its behavior? This way, existing documents will not be affected while users get to test new functionalities which emulate tabularray