\ProvidesPackage{cxltx-style-abspos}
% thx to http://tex.stackexchange.com/a/37300/28067

\usepackage{zref-abspos}
\usepackage{tikz}
\usetikzlibrary{calc}
% \usepackage{geometry}
\usepackage{siunitx}

% ##########################################################################################################
\makeatletter

% ----------------------------------------------------------------------------------------------------------
\newdimen\ap@LastX
\newdimen\ap@LastY
\setlength{\ap@LastX}{0mm}
\setlength{\ap@LastY}{\paperheight}

% ----------------------------------------------------------------------------------------------------------
\catcode`\%=11
\newcommand{\apWriteAuxComment}[1]{\immediate\write\@auxout{% #1}}
\catcode`\%=14


% ----------------------------------------------------------------------------------------------------------
\newcommand\apToMm[1]{%
  \strip@pt\dimexpr 0.351459804\dimexpr#1\relax\relax mm%
}

% \newcommand\apToMm[1]{%
%   \num[round-mode=places,round-precision=4]{\strip@pt\dimexpr 0.351459804\dimexpr#1\relax\relax mm}%
% }

% ----------------------------------------------------------------------------------------------------------
\newcommand{\apSaveXy}[1]{%
  \zsavepos{#1}%
  \apWriteAuxComment{#1: %
    abs: ( \apToMm{\zposx{#1}sp}, %
           \apToMm{\the\paperheight-\zposy{#1}sp} ), %
    rel: ( \apToMm{\zposx{#1}sp-\ap@LastX}, %
           \apToMm{\ap@LastY-\zposy{#1}sp} )%
  }%
  \setlength{\ap@LastX}{\zposx{#1}sp}%
  \setlength{\ap@LastY}{\zposy{#1}sp}%
}

% ----------------------------------------------------------------------------------------------------------
% \newwrite\ap@writer
% \openout\ap@writer=\jobname.cxltx-abspos.txt\relax


% ##########################################################################################################
\makeatother