Table: Vertical and Horizontal Centering with linebreak in \multicolumn

Question

I'm trying to typeset a table with a fixed width were the cells contents are centered both vertically and horizontally, even if one cell contains a forced line-break.

I've managed to get that done, but now I want to add text with two lines that spans two columns using the \multicolumn command and have it still centered horizontally.

This is where I'm struggeling:

\documentclass{article}

\usepackage{array, tabularx}
\usepackage[textwidth=6in]{geometry}

\renewcommand{\tabcolsep}{0pt}
\setlength{\extrarowheight}{10pt}

\begin{document}
    %
    \centering%
        %
        \begin{tabularx}{\textwidth}{%
                >{\centering\arraybackslash}m{0.5\textwidth}|
                >{\centering\arraybackslash}m{0.25\textwidth}
                >{\centering\arraybackslash}m{0.25\textwidth}
            }%
            test & test & test\break test\\
            test & \multicolumn{2}{X}{test\break test}
        \end{tabularx}
        %
    %
\end{document}

As you can see, the first column of the second row is not centered vertically and the second column is not centered horizontally, which is because I used the X parameter for \multicolumn, but I don't know what else I should use instead.

How can this problem be solved?

Answer 1

To ensure a consistent cell padding, I deleted the \extrarowheight specification and added the cellspace package, in addition to a redefinition of the X column type and the use of >{\hsize=xx\hsize} to obtain X column widths in the ratio 2:1.

Unrelated: needless to load array if you load tabularx.

\documentclass{article}
\usepackage[textwidth=6in]{geometry}
\usepackage{cellspace, tabularx}
\setlength{\cellspacetoplimit}{8pt}
\setlength{\cellspacebottomlimit}{8pt}
\addparagraphcolumntypes{X}

\renewcommand{\tabularxcolumn}[1]{>{\centering\arraybackslash}m{#1}}
\renewcommand{\tabcolsep}{0pt}

\begin{document}

    \centering%

        \begin{tabularx}{\textwidth}{%
               | >{\hsize=1.5\hsize}S{X}|
                >{\hsize=0.75\hsize}S{X}
               | >{\hsize=0.75\hsize}S{X}|
            }%
        \hline
            test & test & test\break test \\
        \hline
            test & \multicolumn{2}{>{\hsize=1.5\hsize}S{X}|}{test\break test} \\
        \hline
        \end{tabularx}

\end{document}

Answer 2

Try the following:

\documentclass{article}
\usepackage[textwidth=6in]{geometry}
\usepackage{array, tabularx}
\renewcommand{\tabcolsep}{0pt}
%%--------------------------------------------------------------%
%%  patch of Ulrike Fisher (on my request)                      %
%%   (http://tex.stackexchange.com/questions/319768/            %
%%--------------------------------------------------------------%
\makeatletter
\renewcommand\mcell@classz{\@classx
\@tempcnta \count@
\prepnext@tok
\@addtopreamble{%\mcell@mstyle
\ifcase\@chnum
\hfil
\mcell@agape{\d@llarbegin\insert@column\d@llarend}\hfil \or
\hskip1sp
\mcell@agape{\d@llarbegin\insert@column\d@llarend}\hfil \or
\hfil\hskip1sp
\mcell@agape{\d@llarbegin \insert@column\d@llarend}\or
\mcell@agape{$\vcenter
\@startpbox{\@nextchar}\insert@column\@endpbox$}\or
\mcell@agape{\vtop
\@startpbox{\@nextchar}\insert@column\@endpbox}\or
\mcell@agape{\vbox
\@startpbox{\@nextchar}\insert@column\@endpbox}%
\fi
\global\let\mcell@left\relax\global\let\mcell@right\relax
}\prepnext@tok}
\makeatother

\begin{document}
    \begin{table}
    \renewcommand\tabularxcolumn[1]{m{#1}}
    \setcellgapes{10pt}
    \makegapedcells
    \centering
\begin{tabularx}{\textwidth}{|%
                >{\centering\arraybackslash}X|
                >{\centering\arraybackslash\hsize=0.5\hsize}X|
                >{\centering\arraybackslash\hsize=0.5\hsize}X|
            }%
    \hline
test & test & test\break test\\
    \hline
test & \multicolumn{2}{>{\centering\arraybackslash}X|}{test\break test}\\
    \hline
\end{tabularx}
    \end{table}
\end{document}

I add vertical and horizontal rules that you can easy see, that cells' contents are centered as you like to have.

Edit: Now is added more vertical space with use of makecell package AND PATCH of it incompatibility with m column types.