table with \textwidth is wider than \tcblisting minipage

Question

When using a tabular with textwidth (manually calculated) it turns out to be wider than the minipage created by \tcblisting:

\documentclass{article}

\newlength\mylenA
\newlength\invoicedescwidth

\usepackage{tcolorbox}
\tcbuselibrary{listings}

\usepackage{tabularx}
\begin{document}

    \begin{tcblisting}{title=tabular with manual column widths}
\settowidth\mylenA{%   
    \textsf{\textbf{Pos.Total sum}}}
\setlength\invoicedescwidth{%
    \dimexpr\textwidth-\mylenA\relax}       
\begin{tabular}
    {
    r
    p{\invoicedescwidth}
    r
    }%
    \textbf{Pos.} & \textbf{Other text} & \textbf{Total sum} \\
    \hline\\
\end{tabular}
    \end{tcblisting}


    \begin{tcblisting}{title=tabularx with textwidth}
\begin{tabularx}{\textwidth}
    {
    r
    X
    r
    }%
    \textbf{Pos.} & \textbf{Other text} & \textbf{Total sum} \\
    \hline\\
\end{tabularx}
    \end{tcblisting}
    
\end{document}

Tabularx work. Should both not be the same? I do not want to use tabularx since the multiple calls during the LaTeX build break calculations that are done in tabularx...

Answer 1

You're forgetting to subtract the \tabcolsep spaces and there are six of them. Also, since you're typesetting the table in serif type, using \textsf will choose the wrong width.

I'd use \linewidth in both instances, but it seems that \textwidth is correctly updated in the tcolorbox, so if you're typesetting in single column there's no real problem.

\documentclass{article}

\newlength\mylenA
\newlength\invoicedescwidth

\usepackage{tcolorbox}
\tcbuselibrary{listings}

\usepackage{tabularx}
\begin{document}

\begin{tcblisting}{title=tabular with manual column widths}
  \settowidth\mylenA{\textbf{Pos.Total sum}}
  \setlength\invoicedescwidth{%
    \dimexpr\linewidth-\mylenA-6\tabcolsep\relax
  }
  \begin{tabular}{
    r
    p{\invoicedescwidth}
    r
  }
  \textbf{Pos.} & \textbf{Other text} & \textbf{Total sum} \\
  \hline
  \end{tabular}
\end{tcblisting}


\begin{tcblisting}{title=tabularx with textwidth}
  \begin{tabularx}{\textwidth}{
    r
    X
    r
  }
  \textbf{Pos.} & \textbf{Other text} & \textbf{Total sum} \\
  \hline
  \end{tabularx}
\end{tcblisting}
    
\end{document}