Graphics, Figures & Tables ⇒ How to improve diagbox spacing and automate diagonal placement?

[user49915]

Feeding the input

Code: Select all

\documentclass{article}
\pagestyle{empty}
\usepackage{diagbox}
\DeclareRobustCommand*{\concreteState}[1]{\ifmmode\mathsf{#1}\else\textsf{#1}\fi}
\begin{document}%
\newcommand{\RestOfContents}{  & \concreteState{green} & \concreteState{red}\\
	\hline
	\concreteState{green} & (\concreteState{g},\concreteState{g})  & (\concreteState{g},\concreteState{r})\\
	\concreteState{yellow} & (\concreteState{ng},\concreteState{g}) & (\concreteState{ng},\concreteState{r})\\
	\concreteState{red}  & (\concreteState{ng},\concreteState{g}) & (\concreteState{ng},\concreteState{r})\\
	\concreteState{yellowgreen} & (\concreteState{ng},\concreteState{g}) & (\concreteState{ng},\concreteState{r})
}%
\noindent%
Fallback:%%% This is ugly an not necessarily understandable.
\[
\begin{array}{l|cc}
  a\ \backslash\ b%%% That's what we do without diagbox.
  \RestOfContents
\end{array}%
\]
Good usage of horizontal space, but the diagonal is not actually a diagonal, and vertical space is wasted:
\begin{center}%
\begin{tabular}{l|cc}
	\diagbox{\(a\)}{\(b\)}%%% That's what I'd like to type in and leave the rest to the macros!
  \RestOfContents
\end{tabular}%
\end{center}
The diagonal is actually a diagonal, but both horizontal and vertical space is wasted:
\begin{center}%
\begin{tabular}{l|cc}
	\diagbox{\quad\(a\)\quad}{\quad\(b\)\quad}
  \RestOfContents
\end{tabular}%
\end{center}
\end{document}

to pdflatex results in

mwe.png (193.09 KiB) Viewed 2817 times

Is there any way to turn the purported diagonal to an actual diagonal and NOT waste horizontal and vertical space? Ideas are welcome.