crop marks not drawn on colored pages with geometry package

Question

I have created a document where some pages have a background color. I would like the pages to have crop marks, using the "showcrop" option of the package geometry (I do not want to use the "crop" package, for some reasons). The following MWE shows that the crop marks are missing in the colored pages.

\documentclass{book}

\usepackage{lipsum}
\usepackage{xcolor}

\usepackage{geometry}
\geometry{paper=a4paper, layoutwidth=170mm, layoutheight=240mm, layoutvoffset= 20mm, layouthoffset= 20mm, showcrop=true}

\begin{document}

\lipsum
\newpage \pagecolor{yellow}
\lipsum
\newpage \nopagecolor
\lipsum

\end{document}

Would anyone have any idea what is going on, and how to fix it ?

PS : it is not the same question as Color in bleed using pagecolor and crop : I am not using the crop package !

Answer 1

The following is a bit clumsy but the result seems to be ok. The idea is to use the definition of showcrop from the geometry source combined with a custom page coloring approach with a zero-width zero-height colored \vrule, the definition of which is copied from the crop package. When you draw the vrule before the geometry crop marks the color does not overlap the marks.

Because I couldn't find out how to undo the \AtBeginShipout definition for subsequent pages without color, the \nopagecolorcrop command just sets the color of the rule to white.

\documentclass{book}

\usepackage{lipsum}
\usepackage{xcolor}

\usepackage{geometry}
\usepackage{atbegshi}
\geometry{paper=a4paper, layoutwidth=170mm, layoutheight=240mm, layoutvoffset= 20mm, layouthoffset= 20mm}

\makeatletter
\def\mypagecolor{white}
\AtBeginShipout{\setbox\AtBeginShipoutBox=\vbox to\z@{\vskip-1in\vbox{%
        \rlap{\smash{{\color{\mypagecolor}\hskip\dimexpr -\hoffset-1in\relax\vrule width\paperwidth height\z@ depth\paperheight}}}%
        \baselineskip\z@skip\lineskip\z@skip\lineskiplimit\z@
        \vskip1in%
        \Gm@pageframes\box\AtBeginShipoutBox}}}
\newcommand{\pagecolorcrop}[1]{
    \def\mypagecolor{#1}
}
\newcommand{\nopagecolorcrop}{%
    \def\mypagecolor{white}%
}
\Gm@showcroptrue
\makeatother

\begin{document}
\lipsum
\newpage \pagecolorcrop{yellow}
\lipsum
\newpage \nopagecolorcrop
\lipsum
\end{document}