# geometry's bindingoffset seems to be ignored

The geometry's documentation tells:

• page 9: "bindingoffset removes a specified space from the lefthand-side of the page for oneside or the inner-side for twoside.",
• page 10 (caption of Figure 6): "The option bindingoffset adds the specified length to the inner margin. ".

This seems to be contradictory and, from line 748 of the code:

\advance\oddsidemargin\Gm@bindingoffset


I guess bindingoffset adds the specified length to the inner (left) margin.

Anyway, bindingoffset seems to be ignored as shown by the following MWE: if bindingoffset > 0, the effective length of the left margin (shown by the page grid) is the left length (that is oddsidemargin + 1 inch, here 31mm) and not the left + bindingoffset length (here 41mm).

\documentclass{article}
\usepackage{lipsum}
\usepackage{calc}
\usepackage[step=5mm]{pagegrid}
\usepackage{printlen}
\usepackage{geometry}
%
\uselengthunit{mm}
%
\geometry{%
paperwidth=15cm
,showframe
,verbose
,bindingoffset=1cm
}
%
\newlength{\leftplusoneinch}
\newlength{\leftplusoneinchplusbindingoffset}
%
\begin{document}
\makeatletter
\setlength{\leftplusoneinch}{\oddsidemargin+1in}
\setlength{\leftplusoneinchplusbindingoffset}{\leftplusoneinch+\Gm@bindingoffset}
\begin{tabular}{ll}
bindingoffset                 & $=\printlength{\Gm@bindingoffset}$                 \\
left (oddsidemargin + 1 inch) & $=\printlength{\leftplusoneinch}$                  \\
left + bindingoffset          & $=\printlength{\leftplusoneinchplusbindingoffset}$
\end{tabular}
\makeatother
\end{document}


Hence my question: why geometry's bindingoffset seems to be ignored?

• Use an extreme value of 10cm to better see differences. – Johannes_B Dec 14 '15 at 14:45
• have you tried using \documentclass[twoside]{article}? does that help? – cmhughes Dec 14 '15 at 14:53
• @Johannes_B Well, I better see differences but don't better understand :) – Denis Bitouzé Dec 14 '15 at 15:01
• @cmhughes Yes: in fact I got this MWE from my real document which actually uses the two-sided book class. And it's with this class I first encountered the problem. So it doesn't help. – Denis Bitouzé Dec 14 '15 at 15:04