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I have come upon a problem with export of multi-line table headers in
long (multi-page) tables. I can't imagine that this hasn't come up
before, but I wasn't able to google up any other reports, so ...
As a simple example (using \pagebreak to reduce the number of rows
required to illustrate the problem), exporting the org table
#+attr_latex: :environment longtable
| First | Second |
| Column | Column |
|--------------+--------|
| a | 1 |
| b | 2 |
| \pagebreak c | 3 |
| d | 4 |
to LaTeX yields
\begin{longtable}{lr}
First & Second\\
Column & Column\\
\hline
\endfirsthead
\multicolumn{2}{l}{Continued from previous page} \\
Column & Column \\
\hline
\endhead
\hline\multicolumn{2}{r}{Continued on next page} \\
\endfoot
\endlastfoot
\hline
a & 1\\
b & 2\\
\pagebreak c & 3\\
d & 4\\
\end{longtable}
\end{document}
Notice that only the "firsthead" has the multi-line table header; on the
2nd page the columns will both have the one-line header "Column" when
I/we want the full column headers on every page.
This is using org version 9.5.3 and GNU Emacs 29.0.50 (snapshot).
I think that the problem occurs in the handling of the header in
org-latex-table-row. The 2nd row ends the header, so in the excerpted
code below it is output as =contents=, i.e., it gets inserted for the
4th %s. Of course this means that the previous lines of the header are
missing.
;; Special case for long tables. Define header and footers.
((and longtablep (org-export-table-row-ends-header-p table-row info))
(let ((columns (cdr (org-export-table-dimensions
(org-export-get-parent-table table-row) info))))
(format "%s
\\endfirsthead
\\multicolumn{%d}{l}{%s} \\\\
%s
%s \\\\\n
%s
\\endhead
%s\\multicolumn{%d}{r}{%s} \\\\
\\endfoot
\\endlastfoot"
(if booktabsp "\\midrule" "\\hline")
columns
(org-latex--translate "Continued from previous page" info)
(cond
((not (org-export-table-row-starts-header-p table-row info))
"")
(booktabsp "\\toprule\n")
(t "\\hline\n"))
contents
(if booktabsp "\\midrule" "\\hline")
(if booktabsp "\\midrule" "\\hline")
columns
(org-latex--translate "Continued on next page" info))))
;; When BOOKTABS are activated enforce bottom rule even when
;; no hline was specifically marked.
((and booktabsp (not (org-export-get-next-element table-row info)))
"\\bottomrule"))))))
