Create tabular/table with exact width

Question

The Problem

I want to create a table with an exact width. So I thought I'd use the tabular* environment. Then I realised, that it might be a little more difficult than I imagined in the beginning. The problem is the horizotal alignment/positioning: \tabcolsep and \arrayrulewidth change the positioning.

No additional packages loaded

Consider the following:

\documentclass[varwidth=3.5cm,margin=2mm]{standalone}

\setlength{\arrayrulewidth}{.6pt}
\setlength{\tabcolsep}{0pt}
\begin{document}
\textbf{No packages}\par\vspace{5pt}
\begin{tabular*}{14mm}{ |@{} p{7mm} @{}|@{} p{7mm} @{}| } % 1: shifts---because of the vlines
    \hline
    \hspace{2pt}foo & \hspace{2pt}bar
\end{tabular*} (1)
\par\vspace{5pt}


\verb|\tabcolsep=0pt|\par
\begin{tabular*}{14mm}{ | p{7mm} | p{7mm} | } % 2: default, alignment is correct
    \hline
    \hspace{2pt}foo & \hspace{2pt}bar
\end{tabular*} (2) default

\begin{tabular*}{14mm}{% 3: manually corrected outer vertical line
        @{\kern.5\arrayrulewidth}|@{\kern-\arrayrulewidth}%
        p{7mm} | p{7mm}%
        @{\kern-.5\arrayrulewidth}| }
    \hline
    \hspace{2pt}foo & \hspace{2pt}bar
\end{tabular*} (3) fixed1
\par\vspace{5pt}


\verb|\tabcolsep=2pt|\par
\setlength{\tabcolsep}{2pt}
\begin{tabular*}{14mm}{ | p{7mm} | p{7mm} | } % 4: default, alignment is NOT correct
    \hline
    foo & bar
\end{tabular*} (4) default

\begin{tabular*}{14mm}{% 5: manually corrected with tabcolsep active
        @{\kern.5\arrayrulewidth}|%
        p{\dimexpr 7mm-2\tabcolsep-.5\arrayrulewidth\relax}%
        |%
        p{\dimexpr 7mm-2\tabcolsep-.5\arrayrulewidth\relax}%
        |}
    \hline
    foo & bar
\end{tabular*} (5) fixed2

\begin{tabular*}{14mm}{% 6: manually corrected(2) with tabcolsep active
        p{\dimexpr 7mm-2\tabcolsep-0 \arrayrulewidth\relax}%
        p{\dimexpr 7mm-2\tabcolsep-.5\arrayrulewidth\relax}%
        |}
    \hline
    foo & bar
\end{tabular*} (6) fixed3
\end{document}

First impression: the left vline is not aligned with the table border. As one can see, I first tried to get rid of all \tabcolseps manually (1). This still has the widths of the vlines though. Curiously, the default behaviour with \tabcolsep=0pt does manage shifts caused by the vlines (2). One can fix the ugly outer vlines (not matching the edge of the table) manually (3). But this still leaves the problem of horizontal spacing in the cells. One could put a shifted parbox in there. A lot of work for many cells. So it might be better to use \tabcolsep. If I do, the default behaviour is shown in (4). Not working correctly, so one has to start fixing again. Curiously, this time one has to consider the width of the vlines in the fix (5). Obviously this is the better solution compared to (3). But this leads to potentially many manual adjustments with big tables, especially if there are not vlines between every column, as this has to be considered (6).

With package array

Trying to use one of the packages that should improve the behaviour of tables, I tried the array package:

\documentclass[varwidth=3.5cm,margin=2mm]{standalone}
\usepackage{array}
\setlength{\arrayrulewidth}{.6pt}
\setlength{\tabcolsep}{0pt}
\begin{document}
\textbf{array package}\par\vspace{5pt}
\begin{tabular*}{14mm}{ |@{} p{7mm} @{}|@{} p{7mm} @{}| } % 1: shifts---because of the vlines
    \hline
    \hspace{2pt}foo & \hspace{2pt}bar
\end{tabular*} (1)
\par\vspace{5pt}


\verb|\tabcolsep=0pt|\par
\begin{tabular*}{14mm}{ | p{7mm} | p{7mm} | } % 2: default, alignment is correct
    \hline
    \hspace{2pt}foo & \hspace{2pt}bar
\end{tabular*} (2) default

\begin{tabular*}{14mm}{% 3: manually corrected outer vertical line
        |@{\kern-\arrayrulewidth}%
        p{7mm}%
        @{\kern-.5\arrayrulewidth}|@{\kern-.5\arrayrulewidth}%
        p{7mm}%
        @{\kern-\arrayrulewidth}| }
    \hline
    \hspace{2pt}foo & \hspace{2pt}bar
\end{tabular*} (3) fixed1
\par\vspace{5pt}


\verb|\tabcolsep=2pt|\par
\setlength{\tabcolsep}{2pt}
\begin{tabular*}{14mm}{ | p{7mm} | p{7mm} | } % 4: default, alignment is NOT correct
    \hline
    foo & bar
\end{tabular*} (4) default

\begin{tabular*}{14mm}{% 5: manually corrected with tabcolsep active
        |%
        p{\dimexpr 7mm-2\tabcolsep-1.5\arrayrulewidth\relax}%
        |%
        p{\dimexpr 7mm-2\tabcolsep-1.5\arrayrulewidth\relax}%
        |}
    \hline
    foo & bar
\end{tabular*} (5) fixed2

\begin{tabular*}{14mm}{% 6: manually corrected(2) with tabcolsep active
        p{\dimexpr 7mm-2\tabcolsep-0\arrayrulewidth\relax}%
        p{\dimexpr 7mm-2\tabcolsep-1\arrayrulewidth\relax}%
        |}
    \hline
    foo & bar
\end{tabular*} (6) fixed3
\end{document}

The left alignment of the vline seems to be corrected automatically, good. Sadly, this isn't really improving the overall result: To the right, the same issues appear. (1) is the same as before with corrected left vline. (2) shows the default behaviour with \tabcolsep=0pt. Again, manual fixing is needed (3). Better is to use \tabcolsep though. The default behaviour is shown in (4). This obviously has to be fixed as well (5). Here the situation is even worse than without the arrays package. One has to consider whether the column is an outer column or not, in order to fix the parbox widths. This doesn't get better if some vlines are not used (6). tabularx result looks similar. There is always the need to adjust manually.

tabularx package

\documentclass[varwidth=3.5cm,margin=2mm]{standalone}
\usepackage{tabularx}
\setlength{\arrayrulewidth}{1pt}
\setlength{\tabcolsep}{2pt}
\begin{document}
\textbf{tabularx package}\par\vspace{5pt}

\begin{tabular*}{14mm}{% 1: target layout
        |%
        p{\dimexpr 7mm-2\tabcolsep-1.5\arrayrulewidth\relax}%
        |%
        p{\dimexpr 7mm-2\tabcolsep-1.5\arrayrulewidth\relax}%
        |}
    \hline
    foo & bar
\end{tabular*} (1) target

\begin{tabularx}{14mm}{ |X|X| }% default without manual sizing
    \hline
    foo & bar
\end{tabularx} (2) default1

\begin{tabularx}{14mm}{ |>{\hsize=7mm}X|X| }
    \hline
    foo & bar
\end{tabularx} (3) default2

\begin{tabularx}{14mm}{ |>{\hsize=\dimexpr7mm-2\tabcolsep-1.5\arrayrulewidth\relax}X|X| }
\hline
foo & bar
\end{tabularx} (4) fixed
\end{document}

This does some things better (e.g. right vline is always aligned), but one still has to do manual calculations based on vlines before or after...

Correct tables by default?

I would like to use a normal environment without the need to adjust it manually. Something like

\newlength{\mylength}
\def\mylength{-2\tabcolsep-.5\arrayrulewidth}

could work, if I can make them sensitive to the context vlines. Using array,

\newcolumntype{P}[1]{>{\raggedright\arraybackslash}p{\dimexpr#1-2\tabcolsep-\arrayrulewidth\relax}}

could work almost automated, if it could see surrounding vlines. I don't want to create a ton of column types and take care of which one to take (outer, inner column, surrounded by zero, one, two vlines).

How can I get a table of the predefined width without manual interaction?

Answer 1

Try this simple code:

\documentclass[varwidth=3.5cm,margin=2mm]{standalone}
\usepackage{tabularx}
\setlength{\arrayrulewidth}{.6pt}
\setlength{\tabcolsep}{0pt}

\begin{document}

\textbf{tabularx package}\par\vspace{5pt}
\begin{tabularx}{14mm}{ |X|X| }
    \hline
    \hspace{2pt}foo & \hspace{2pt}bar \\
\hline
\end{tabularx} (1)
\par\vspace{5pt}

\end{document}

Answer 2

It's not completely clear what the requirements are but as far as I can see you want a table with two equal columns, three vertical rules and a total width of 14mm, for that I would do the following.

\documentclass{article}
\usepackage{lmodern}

\usepackage{array}
\newlength\zz

\begin{document}

\setlength\zz{\dimexpr 14mm - 4\tabcolsep-3\arrayrulewidth}
\setlength\tabcolsep{2pt}
\fontsize{3.5pt}{4pt}\selectfont


\begin{tabular}{|p{.5\zz}|p{.5\zz}|}
foo  &bar\\
zz&zzz
\end{tabular}

\end{document}

Answer 3

You could define a phantom vrule that takes the same space as a standard rule. Or the other way round a vrule that doesn't take space:

\documentclass{article}
\usepackage{array}
\setlength\arrayrulewidth{4pt} %for better view

\newcolumntype\pvline{!{\hspace{\arrayrulewidth}}}

\newcolumntype\vline{!{\hspace{-0.5\arrayrulewidth}\vrule width \arrayrulewidth\hspace{-0.5\arrayrulewidth}}}

\begin{document}
\begin{tabular}{p{\dimexpr1cm-2\tabcolsep}|p{\dimexpr1cm-2\tabcolsep}}
\hline
blb& blb \\
blb&blbl 
\end{tabular}

\begin{tabular}{p{\dimexpr1cm-2\tabcolsep}\pvline p{\dimexpr1cm-2\tabcolsep}}
\hline
blb& blb
\end{tabular}

\bigskip

\begin{tabular}{p{\dimexpr1cm-2\tabcolsep}\vline p{\dimexpr1cm-2\tabcolsep}}
\hline
blb& blb\\
blb&blbl
\end{tabular}

\begin{tabular}{p{\dimexpr1cm-2\tabcolsep} p{\dimexpr1cm-2\tabcolsep}}
\hline
blb& blb
\end{tabular}

\end{document}