%D \module
%D   [       file=pack-pos,
%D        version=2010.11.17 % real old code, updated a bit
%D          title=\CONTEXT\ Packaging Macros,
%D       subtitle=Positioning,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright=PRAGMA-ADE]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

\writestatus{loading}{ConTeXt Packaging Macros / Positioning}

\unprotect

% An old but still usefull mechanism (updated in mkiv):
%
% \ruledvbox{\startpositioning
%     \position(1,1){test}
%     \position[xstep=relative](1,1){test}
%     \position[ystep=relative](3,-1){test}
%     \position(10,10){test}
% \stoppositioning}

\newdimen\positioningxposition  \newdimen\positioningyposition
\newdimen\positioningxdimension \newdimen\positioningydimension
\newdimen\positioningxoffset    \newdimen\positioningyoffset

\newbox\positioningbox

\unexpanded\def\startpositioning
  {\dosingleempty\dostartpositioning}

\def\dostartpositioning[#1]%
  {\bgroup
   \getparameters[\??ps][#1]%
   \positioningxposition \zeropoint  \positioningyposition \zeropoint
   \positioningxdimension\zeropoint  \positioningydimension\zeropoint
   \positioningxoffset   \zeropoint  \positioningyoffset   \zeropoint
   \hfuzz                \paperwidth \vfuzz                \paperheight
   \setbox\positioningbox\hbox\bgroup
   \ignorespaces}

\unexpanded\def\stoppositioning
  {\removeunwantedspaces
   \doifnot\@@psoffset\v!yes
     {\global\positioningxoffset\zeropoint
      \global\positioningyoffset\zeropoint}%
   \global\advance\positioningxdimension \positioningxoffset
   \global\advance\positioningydimension \positioningyoffset
   \egroup
   \vbox to \positioningydimension
     {\vskip\positioningyoffset
      \hbox to \positioningxdimension
        {\hskip\positioningxoffset
         \box\positioningbox
         \hfill}
      \vfill}%
   \egroup}

% \def\resetpositioning
%   {\getparameters[\??ps]
%      [\c!state=\v!start,
%       \c!unit=\s!cm,
%       \c!factor=\plusone,
%       \c!scale=\plusone,
%       \c!xfactor=\@@psfactor,
%       \c!yfactor=\@@psfactor,
%       \c!xscale=\@@psscale,
%       \c!yscale=\@@psscale,
%       \c!xstep=\v!absolute,
%       \c!ystep=\v!absolute,
%       \c!xoffset=\zeropoint,
%       \c!yoffset=\zeropoint]}

\def\resetpositioning
  {\let\@@psstate   \v!start
   \let\@@psunit    \s!cm
   \let\@@psfactor  \plusone
   \let\@@psscale   \plusone
   \def\@@psxfactor{\@@psfactor}%
   \def\@@psyfactor{\@@psfactor}%
   \def\@@psxscale {\@@psscale}%
   \def\@@psyscale {\@@psscale}%
   \let\@@psxstep   \v!absolute
   \let\@@psystep   \v!absolute
   \let\@@psxoffset \zeropoint
   \let\@@psyoffset \zeropoint}

\resetpositioning

\unexpanded\def\setuppositioning
  {\resetpositioning
   \dodoubleargument\getparameters[\??ps]}

\def\calculateposition#1#2#3#4#5#6#7#8#9%
  {\setdimensionwithunit\scratchdimen{#1}\@@psunit
   \scratchdimen#8\scratchdimen
   \scratchdimen#9\scratchdimen
   \advance\scratchdimen #4\relax
   % == \scratchdimen\dimexpr#8\dimexpr#9\scratchdimen\relax+#4\relax
   \doif{#2}\v!relative
     {\advance\scratchdimen#3%
      \let#4\zeropoint}%
   #3\scratchdimen
   \doifnot\@@psstate\v!overlay
     {\scratchdimen\dimexpr#5+#3\relax
      \ifdim           #3<-#7\relax \global#7-#3\relax    \fi
      \ifdim\scratchdimen> #6\relax \global#6\scratchdimen\fi}}

\def\position
  {\dosingleempty\doposition}

\def\doposition[#1]#2(#3,#4)%
  {\removeunwantedspaces
   \dowithnextbox{\dodoposition{#1}{#2}{#3}{#4}}\hbox}

\def\dodoposition#1#2#3#4%
  {\bgroup
   \dontcomplain
   \getparameters[\??ps][#1]%
   \calculateposition{#3}\@@psxstep\positioningxposition\@@psxoffset\nextboxwd  \positioningxdimension\positioningxoffset\@@psxscale\@@psxfactor
   \calculateposition{#4}\@@psystep\positioningyposition\@@psyoffset\nextboxhtdp\positioningydimension\positioningyoffset\@@psyscale\@@psyfactor
   \vbox to \zeropoint
     {\vskip\positioningyposition
      \hbox to \zeropoint
        {\hskip\positioningxposition
         \flushnextbox
         \hss}
      \vss}%
   \normalexpanded
     {\egroup
      \positioningxposition\the\positioningxposition
      \positioningyposition\the\positioningyposition
      \def\noexpand\@@psxoffset{\the\dimexpr\@@psxoffset}%
      \def\noexpand\@@psyoffset{\the\dimexpr\@@psyoffset}}%
   \ignorespaces}

\setuppositioning
  [\c!unit=\s!cm,
   \c!factor=\plusone,
   \c!scale=\plusone,
   \c!xstep=\v!absolute,
   \c!ystep=\v!absolute,
   \c!offset=\v!yes,
   \c!xoffset=\zeropoint,
   \c!yoffset=\zeropoint]

\protect \endinput