longtabu table with captionsetup{labelsep=newline} problem

Question

I would like to create the table below with the "labelsep=newline"option in \captionsetup{}. However, I get an error message. Without the "labelsep=newline" parameter the code is running fine (see example). Any help would be appreciated. Thank you.

\documentclass[float=false, crop=false]{standalone}
\usepackage{collcell}
\usepackage[latin1]{inputenc}
\usepackage{longtable,tabu}
\usepackage{xcolor}
\usepackage{hyperref}
\usepackage{caption}
\usepackage{geometry}
\geometry{a4paper, top=25mm, left=40mm, right=25mm, bottom=30mm,
    headsep=10mm, footskip=12mm}
\captionsetup[table]{justification=centering,labelsep=newline}
%\captionsetup[table]{justification=centering}
\begin{document}
{\footnotesize
\begin{longtabu} to \textwidth {
    X[15,l]
    X[4,l]
    X[6,l]
    X[8,l]
    }
    \caption{Caption 1}\\
    \caption*{Caption 2}\\
    \label{tab:table genral information es50} \\
    \hline \hline \hline \hline
    \textbf{Column 1} & 
    \textbf{Column 2} &
    \textbf{Column 3} &
    \textbf{Column 4} 

    \\  \hline \hline \hline \hline   
                            &        &         &  \\
     entry& entry     & entry & entry\\
     entry & entry           & entry & entry\\
     entry & entry                          & entry & entry\\
\end{longtabu}
}
\end{document}

Answer 1

longtable and captions

The reason for this is that for longtable to be able to split a table into pages, it cannot be in a floating environment. This is problematic for the \caption-macro, which need to be in a floating environment, like table or figure. To get around this, longtable redefines the \caption-macro, essentially making it only some text in a multicolumn

This is described in the documentation for longtable Note that you can always locate the documentation using the command-line/terminal by writing texdoc longtable, and that works for any package. The documentation is also available at http://ctan.org/pkg/longtable

Why is this probematic for us?

when you specify that the seperator for labels should be a newline, that means that a \\ will be inserted after Table #, but in tables, \\, means something more than just to insert a newline, as you already know, it will create a new row, which gives us an error since we are effectively inside a multicolumn now, because of the redefenition of \caption, as mentioned above.

Solution

Add a new label seperator, with the command

\DeclareCaptionLabelSeparator{tableNewline}{\par}

which we will use only in longtables. This will give us the intended result. The downside is that we have need to keep track of two different formats.

Output

Code

\documentclass[float=false, crop=false]{standalone}
\usepackage{collcell}
\usepackage[latin1]{inputenc}
\usepackage{longtable}
\usepackage{tabu}
\usepackage{xcolor}
\usepackage{hyperref}
\usepackage{caption}
\usepackage{geometry}
\usepackage{booktabs}% some new rules for tables
\DeclareCaptionLabelSeparator{tableNewline}{\par}
\geometry{a4paper, top=25mm, left=40mm, right=25mm, bottom=30mm,
    headsep=10mm, footskip=12mm}
\captionsetup{
  justification=centering,
  labelsep=newline,
  }
\captionsetup[longtable]{
  justification=centering,
  labelsep=tableNewline,
  }
\begin{document}

\begin{table}

  \caption{Some test caption for a regular table}
  \centering
  \begin{tabular}{ll}
    \toprule
    Foo & Baz \\
    \midrule
    baz & foobaz \\
    \bottomrule
  \end{tabular}
\end{table}
{\footnotesize

\begin{longtabu} to \textwidth {
    X[15,l]
    X[4,l]
    X[6,l]
    X[8,l]
    }
    \caption{Caption 1}
    \label{tab:table genral information es50} \\
    \toprule
    \textbf{Column 1} &
    \textbf{Column 2} &
    \textbf{Column 3} &
    \textbf{Column 4}
    \\
    \midrule
                            &        &         &  \\
     entry& entry     & entry & entry\\
     entry & entry           & entry & entry\\
     entry & entry                          & entry & entry\\
     \bottomrule
\end{longtabu}
}
\end{document}