Error when using imakeidx and xwatermark

Question

I was editing a text that carries a watermark and decided to add an index. Everything was going fine until at some point an error message came out. After debugging I could identify the issue.

There is some incompatibility between packages imakeidx and xwatermark when more than one page with indexes are presented, but not always. I mean, it seems to have a certain event, which I don't know, that returns an error when there is more than one index page AND a certain number of indexes. I must say this because sometimes there are two index pages and no error appears.

The erro mensage is something like:

Something's wrong--perhaps a missing \item. {\bf P

I checked the lines of the generated .ind file and nothing seemed to be wrong. All blocks follow the same structure.

  \indexspace
{\bf P}\nopagebreak%
 \indexspace\nopagebreak%
  \item p, \hyperpage{1}

If I change the number of columns to more than one, it won't have any error since all indexes fit in only one page. That's a nice workaround, but not a general solution. Another workaround is to prevent the watermark to be printed over index pages, by changing allpages for something like pages=1-3.

The following MWE reproduces the problem.

\documentclass{article}
\usepackage{imakeidx}
\makeindex[columns=1, options=-s style_file_imakeidx_alfa_01.ist]
% columns=2 works fine, since it doesn't need more than one page
\usepackage{tikz}
\usepackage[printwatermark]{xwatermark}
\newsavebox\myboxr\savebox\myboxr{\tikz[color=red!80,opacity=0.4]\node{\huge{Watermark}};}
\newwatermark[allpages, angle=45, scale=6, xpos=-10, ypos=10]{\usebox\myboxr}
% Another workaround: Don't print wateermark over index. Example: allpages <-> pages=1-3.
\begin{document}
Text.
\clearpage
a\index{a}
\clearpage
b\index{b}
c\index{c}
d\index{d}
e\index{e}
f\index{f}
g\index{g}
h\index{h}
i\index{i}
j\index{j}
k\index{k}
l\index{l}
m\index{m}
n\index{n}
o\index{o}
After letter p, if columns = 1, error. % Something's wrong--perhaps a missing \item. {\bf P
% (Un)comment these lines to change from error/no error when columns = 1
p\index{p}
q\index{q}
r\index{r}
\printindex
\end{document}

This is the file style_file_imakeidx_alfa_01.ist to generate the formatted index list (I don't if this setup contributes to the error).

quote '+'
headings_flag 1
symhead_positive "Symbol"
numhead_positive "Number"
heading_prefix "{\\bf "
heading_suffix "}\\nopagebreak%\n \\indexspace\\nopagebreak%"
delim_r "~--~"
suffix_2p "\\,f"
suffix_3p "\\,ff"
preamble
"\\markright{Index}\n\n\\begin{theindex}\n\\thispagestyle{headings}\n"
postamble "\n\n\\end{theindex}\n"

Of course I can continue working with or watermark or printindex, but not both at the same time, or even limiting the pages with watermark.

The question is: know what is going on and how to correct it? If possible.

It seems that the issue arises during the output routine. I get no error and essentially identical output with draftwatermark instead. — egreg, Sep 24 '20 at 19:47
I wouldn't use xwatermark, it loads catoptions which is incompatible with various other packages and LaTeX code, and will probably not work at all with the next LaTeX release. — Ulrike Fischer, Sep 24 '20 at 20:41
@egreg, also no errors with draftwatermark, but with draftwatermark the watermark goes behind figures as shown here and here. I learned about xwatermark because it prints above figures. — FHZ, Sep 24 '20 at 21:23
@C.F.G, command latex --versionreturns MiKTeX-pdfTeX 4.0.1 (MiKTeX 20.7). command pdflatex \stop returns This is pdfTeX, Version 3.14159265-2.6-1.40.21 (MiKTeX 20.7) — FHZ, Sep 24 '20 at 21:27
@UlrikeFischer, as stated in CTAN draftwatermark, this package doesn't stamp, i.e., print above the document text. Is there any method to stamp that is also suitable for future LaTeX releases? — FHZ, Sep 24 '20 at 21:32
Off topic: Why pdfTeX, version (for all) is the pi number? Just for fun? — , Sep 24 '20 at 21:38
@C.F.G, Off topic: Versions of TeX are numbered by adding additional digits of pi, because Knuth doesn't want to add new features: it's supposed to be stable and only bug-fixed, so the idea is it's approaching a limit. — FHZ, Sep 24 '20 at 21:40
I normally use eso-pic to print stuff below or above text. With the next latex release I will perhaps use the new shipout/background and shipout/foreground hooks. — Ulrike Fischer, Sep 24 '20 at 21:40

score 1 · Accepted Answer · answered Sep 25 '20 at 00:06

I followed @Ulrike Fischer's advice about eso-pic and now the watermark works with imakeidx and can be printed above the text (stamped).

Although it is still not clear the reason behind xwatermark's issue, I shall say this solution is very nice.

The following MWE show the answer.

\documentclass{article}
\usepackage{lipsum}
\usepackage{imakeidx}
\makeindex[columns=1, columnseprule, options=-s style_file_imakeidx_alfa_01.ist]
% columns=2 works fine, since it doesn't need more than one page
\usepackage{tikz}
\newsavebox\myboxr\savebox\myboxr{\tikz[color=red!80,opacity=0.4]\node{\huge{Watermark}};}
\usepackage{eso-pic}
\AddToShipoutPictureFG{%
  \AtPageCenter{\put(-320,-230){\scalebox{7}{\rotatebox{45}{\usebox\myboxr}}}}%
  \AtStockLowerLeft{\put(0,0){\scalebox{7}{\rotatebox{45}{\usebox\myboxr}}}}%
}
\begin{document}
Text.
\includegraphics{example-image-a}
\clearpage
a\index{a}
\clearpage
b\index{b} c\index{c} d\index{d} e\index{e} f\index{f}
g\index{g} h\index{h} i\index{i} j\index{j} k\index{k}
l\index{l} m\index{m} n\index{n} o\index{o} p\index{p}
q\index{q} r\index{r}
\lipsum[1-2]
\printindex
\end{document}

The following figures show the results.

Error when using imakeidx and xwatermark

1 Answers1