%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 \& \CONTEXT\ Development Team}]
%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:
%
% \ruledvbox{\startpositioning
%     \position(1,1){test}
%     \position[xstep=relative](1,1){test}
%     \position[ystep=relative](3,-1){test}
%     \position(10,10){test}
% \stoppositioning}
%
% watch out: rather global

\installcorenamespace {positioning}

\installcommandhandler \??positioning {positioning} \??positioning

\setuppositioning
  [\c!state=\v!start,
   \c!unit=\s!cm,
   \c!factor=\plusone,
   \c!scale =\plusone,
   \c!xfactor=\positioningparameter\c!factor,
   \c!yfactor=\positioningparameter\c!factor,
   \c!xscale=\positioningparameter\c!scale,
   \c!yscale=\positioningparameter\c!scale,
   \c!xstep=\v!absolute,
   \c!ystep=\v!absolute,
   \c!xoffset=\zeropoint,
   \c!yoffset=\zeropoint]

\newdimen\d_pack_positioning_x_position
\newdimen\d_pack_positioning_y_position
\newdimen\d_pack_positioning_x_dimension
\newdimen\d_pack_positioning_y_dimension
\newdimen\d_pack_positioning_x_offset
\newdimen\d_pack_positioning_y_offset

\newbox\b_pack_positioning

\unexpanded\def\startpositioning
  {\bgroup
   \dodoubleempty\pack_positioning_start}

\def\pack_positioning_start[#1][#2]%
  {\ifsecondargument
     \edef\currentpositioning{#1}%
     \setupcurrentpositioning[#2]%
   \else\iffirstargument
     \doifelseassignment{#1}
       {\let\currentpositioning\empty
        \setupcurrentpositioning[#1]}%
       {\edef\currentpositioning{#1}}%
   \else
     \let\currentpositioning\empty
   \fi\fi
   \d_pack_positioning_x_position \zeropoint
   \d_pack_positioning_y_position \zeropoint
   \d_pack_positioning_x_dimension\zeropoint
   \d_pack_positioning_y_dimension\zeropoint
   \d_pack_positioning_x_offset   \zeropoint
   \d_pack_positioning_y_offset   \zeropoint
   \hfuzz\paperwidth
   \vfuzz\paperheight
   \setbox\b_pack_positioning\hbox\bgroup
   \ignorespaces}

\unexpanded\def\stoppositioning
  {\removeunwantedspaces
   \doifnot{\positioningparameter\c!offset}\v!yes
     {\global\d_pack_positioning_x_offset\zeropoint
      \global\d_pack_positioning_y_offset\zeropoint}%
   \global\advance\d_pack_positioning_x_dimension\d_pack_positioning_x_offset
   \global\advance\d_pack_positioning_y_dimension\d_pack_positioning_y_offset
   \egroup
   \vbox to \d_pack_positioning_y_dimension
     {\vskip\d_pack_positioning_y_offset
      \hbox to \d_pack_positioning_x_dimension
        {\hskip\d_pack_positioning_x_offset
         \box\b_pack_positioning
         \hfill}
      \vfill}%
   \egroup}

\unexpanded\def\pack_positioning_calculate#1#2#3#4#5#6#7#8#9%
  {\setdimensionwithunit\scratchdimen{#1}{\positioningparameter\c!unit}%
   \scratchdimen\positioningparameter#8\scratchdimen
   \scratchdimen\positioningparameter#9\scratchdimen
   \advance\scratchdimen\positioningparameter#4\relax
   % == \scratchdimen\dimexpr#8\dimexpr#9\scratchdimen\relax+#4\relax
   \doif{\positioningparameter#2}\v!relative
     {\advance\scratchdimen#3%
      \letpositioningparameter#4\zeropoint}%
   #3\scratchdimen
   \doifnot{\positioningparameter\c!state}\v!overlay
     {\scratchdimen\dimexpr#5\nextbox+#3\relax
      \ifdim           #3<-#7\relax \global#7-#3\relax    \fi
      \ifdim\scratchdimen> #6\relax \global#6\scratchdimen\fi}}

\unexpanded\def\position
  {\bgroup
   \dosingleempty\pack_positioning_position}

\def\pack_positioning_position[#1]#2(#3,#4)%
  {\iffirstargument
     \setupcurrentpositioning[#1]%
   \fi
   \removeunwantedspaces
   \dowithnextbox{\pack_positioning_position_indeed{#3}{#4}}\hbox}

\def\pack_positioning_position_indeed#1#2%
  {\dontcomplain
   \pack_positioning_calculate
     {#1}%
     \c!xstep
     \d_pack_positioning_x_position
     \c!xoffset
     \wd
     \d_pack_positioning_x_dimension
     \d_pack_positioning_x_offset
     \c!xscale
     \c!xfactor
   \pack_positioning_calculate
     {#2}%
     \c!ystep
     \d_pack_positioning_y_position
     \c!yoffset
     \htdp
     \d_pack_positioning_y_dimension
     \d_pack_positioning_y_offset
     \c!yscale
     \c!yfactor
   \vbox to \zeropoint
     {\offinterlineskip % else we get an empty line
      \vskip\d_pack_positioning_y_position
      \hbox to \zeropoint
        {\hskip\d_pack_positioning_x_position
         \box\nextbox
         \hss}
      \vss}%
   \normalexpanded
     {\egroup
      \d_pack_positioning_x_position\the\d_pack_positioning_x_position
      \d_pack_positioning_y_position\the\d_pack_positioning_y_position
      \setexpandedpositioningparameter\c!xoffset{\the\dimexpr\positioningparameter\c!xoffset}%
      \setexpandedpositioningparameter\c!yoffset{\the\dimexpr\positioningparameter\c!yoffset}}%
   \ignorespaces}

\protect \endinput