%D \module
%D   [       file=core-fig,
%D        version=2006.08.26, % overhaul/split of 1997.03.31 core-fig
%D          title=\CONTEXT\ Core Macros,
%D       subtitle=Transformations,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA / Hans Hagen \& Ton Otten}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

%D It may be that some functionality got lost. If it concerns
%D defined features, let me know and it will be sorted out.

\writestatus{loading}{ConTeXt Core Macros / Transformations}

\unprotect

%D Scaling:

\unexpanded\def\scale{\dodoubleempty\doscalenextbox[\??xy]}

% probably too many dimens / the width calculations can go
% since we may assume scaling is available (was not true
% long ago which is why we also calculate the width)

\newdimen\scaleboxwidth
\newdimen\scaleboxheight
\newdimen\scaleboxdepth

\newdimen\scaleboxsizex
\newdimen\scaleboxsizey
\newdimen\scaleboxoffsetx
\newdimen\scaleboxoffsety

\newdimen\scaleboxhsize
\newdimen\scaleboxvsize

% global

\newdimen\scaleboxdimx \let\figwid \scaleboxdimx
\newdimen\scaleboxdimy \let\fighei \scaleboxdimy
\newcount\scaleboxscax \let\figxsca\scaleboxscax
\newcount\scaleboxscay \let\figysca\scaleboxscay

\newdimen\scaleboxoutervsize % we cannot manipulate any global vsize !

\let\finalscaleboxxscale \!!plusone
\let\finalscaleboxyscale \!!plusone
\let\finalscaleboxwidth  \!!zeropoint
\let\finalscaleboxheight \!!zeropoint
\let\finalscaleboxxfactor\!!hundred
\let\finalscaleboxyfactor\!!hundred

\newconditional\scaleboxdone

\def\doscalenextbox[#1][#2]%
  {\bgroup
   \getparameters
     [#1]
     [\c!scale=,\c!xscale=,\c!yscale=,\c!width=,\c!height=,\c!lines=,
      \c!factor=,\c!hfactor=,\c!wfactor=,\c!grid=,\c!sx=1,\c!sy=1,
      \c!equalwidth=,\c!equalheight=,
      \c!maxwidth=\scaleparameter\c!width,\c!maxheight=\scaleparameter\c!height,
      #2]%
   \dowithnextbox{\dodoscalenextbox{#1}\egroup}\hbox}

\def\doscalebox#1%
  {\bgroup\dowithnextbox{\dodoscalenextbox{#1}\egroup}\hbox}

\let\currentscaletag\??xy

\def\scaleparameter#1%
  {\csname\currentscaletag#1\endcsname}

\def\setscaleparameter#1#2%
  {\setvalue{\currentscaletag#1}{#2}}

\def\dodoscalenextbox#1%
  {\edef\currentscaletag{#1}%
   \doif{\scaleparameter\c!depth}\v!no{\setbox\nextbox\hbox{\raise\nextboxdp\box\nextbox}}% new
   \forgetall
   \dontshowcomposition
   \dontcomplain
   \doscaleboxcalculations
   \doscaleboxindeed
   \doscaleboxposition
   \flushnextbox}

\def\doscaleboxindeed
   {\ifconditional\scaleboxdone
      \scaleboxwidth \finalscaleboxxscale\nextboxwd
      \scaleboxheight\finalscaleboxyscale\nextboxht
      \scaleboxdepth \finalscaleboxyscale\nextboxdp
      \setbox\nextbox\hbox
        {\dostartscaling \finalscaleboxxscale \finalscaleboxyscale
         \smashedbox\nextbox
         \dostopscaling}%
      \nextboxwd\scaleboxwidth
      \nextboxht\scaleboxheight
      \nextboxdp\scaleboxdepth
    \fi}

\def\doscaleboxcalculations
  {\setfalse\scaleboxdone
   % initial final value
   \global\let\finalscaleboxxscale \!!plusone
   \global\let\finalscaleboxyscale \!!plusone
   \xdef      \finalscaleboxwidth {\the\nextboxwd}%
   \xdef      \finalscaleboxheight{\the\nextboxht}%
   \global\let\finalscaleboxxfactor\!!hundred
   \global\let\finalscaleboxyfactor\!!hundred
   \ifdim\nextboxht>\zeropoint \ifdim\nextboxwd>\zeropoint
     \edef\scaleboxstampa % slow way [can be combined]
       {\scaleparameter\c!scale \scaleparameter\c!xscale \scaleparameter\c!yscale
        \scaleparameter\c!factor\scaleparameter\c!wfactor\scaleparameter\c!hfactor
        \scaleparameter\c!lines \scaleparameter\c!width  \scaleparameter\c!height}%
     \edef\scaleboxstampb % fast way [just sx/sy]
       {\scaleparameter\c!sx
        \scaleparameter\c!sy}%
     \edef\scaleboxstampc
       {11}%
     \ifx\scaleboxstampa\empty
       \ifx\scaleboxstampb\scaleboxstampc
        % no scaling, but still check; new, gone again
% wrong: scaled proportionally as side effect
%         \doifsomething{\scaleparameter\c!maxwidth }{\letvalue{\currentscaletag\c!factor}\v!fit}%
%         \doifsomething{\scaleparameter\c!maxheight}{\letvalue{\currentscaletag\c!factor}\v!fit}%
        \insidefloattrue % trick
        \dodoscaleboxcalculations
       \else
         \dosetscalboxsxsy
         \nodoscaleboxcalculations
       \fi
     \else
       \ifx\scaleboxstampb\empty
         % no need to check further
       \else
         \dosetscalboxsxsy
       \fi
       \dodoscaleboxcalculations
     \fi
   \fi \fi}

\def\dosetscalboxsxsy
  {\ifdim\scaleparameter\c!sx\onepoint=\onepoint\else
     \setevalue{\currentscaletag\c!width }{\the\dimexpr\scaleparameter\c!sx\wd\nextbox\relax}%
   \fi
   \ifdim\scaleparameter\c!sy\onepoint=\onepoint\else
     \setevalue{\currentscaletag\c!height}{\the\dimexpr\scaleparameter\c!sy\ht\nextbox\relax}%
   \fi}

\def\doscaleboxrounding#1.#2\relax{#1}

\def\scaleboxrounding#1%
  {\@EA\@EA\@EA\doscaleboxrounding\@EA\WITHOUTPT\the\dimexpr#1\points*100+32768sp\relax.\relax}

\def\nodoscaleboxcalculations
  {\settrue\scaleboxdone
   \xdef\finalscaleboxwidth  {\the\dimexpr\scaleparameter\c!sx\wd\nextbox\relax}%
   \xdef\finalscaleboxheight {\the\dimexpr\scaleparameter\c!sy\ht\nextbox\relax}%
   \xdef\finalscaleboxxscale {\scaleparameter\c!sx}%
   \xdef\finalscaleboxyscale {\scaleparameter\c!sy}%
   \ifx\finalscaleboxxscale\empty\let\finalscaleboxxscale\!!plusone\fi
   \ifx\finalscaleboxyscale\empty\let\finalscaleboxyscale\!!plusone\fi
   \xdef\finalscaleboxxfactor{\scaleboxrounding\finalscaleboxxscale}%
   \xdef\finalscaleboxyfactor{\scaleboxrounding\finalscaleboxyscale}}

\def\dodoscaleboxcalculations
  {\settrue\scaleboxdone
   % initial values
   \scaleboxoffsetx\zeropoint
   \scaleboxoffsety\zeropoint
   \scaleboxsizex  \nextboxwd
   \scaleboxsizey  \nextboxht % alleen ht wordt geschaald!
   % final values
   \global\scaleboxdimx \zeropoint % see note * (core-fig)
   \global\scaleboxdimy \zeropoint % see note * (core-fig)
   \scaleboxscax   \plusone        % see note * (core-fig)
   \scaleboxscay   \plusone        % see note * (core-fig)
   % preparations
   \setfalse\scaleboxscalingdone
   \checkscaleboxsettings
   % calculators
   % beware, they operate in sequence, and calculate missing dimensions / messy
   %setscaleboxbynature % when? needed?
   \ifconditional\scaleboxscalingdone\else\setscaleboxbyfactor   \fi
   \ifconditional\scaleboxscalingdone\else\setscaleboxbyscale    \fi
   \ifconditional\scaleboxscalingdone\else\setscaleboxbydimension\fi
   % finalizers / to be done (no longer needed this way, clean up)
   \convertscaleboxinsertscale\scaleboxhsize\figx\scaleboxscax\scax
   \convertscaleboxinsertscale\scaleboxvsize\figy\scaleboxscay\scay
   % used in actual scaling
   \xdef\finalscaleboxwidth  {\the\scaleboxdimx}%
   \xdef\finalscaleboxheight {\the\scaleboxdimy}%
   \xdef\finalscaleboxxfactor{\the\scaleboxscax}%
   \xdef\finalscaleboxyfactor{\the\scaleboxscay}%
   \xdef\finalscaleboxxscale {\withoutpt\the\dimexpr\scax\points/\plushundred\relax}%
   \xdef\finalscaleboxyscale {\withoutpt\the\dimexpr\scay\points/\plushundred\relax}}


\setvalue{\??xy:\c!grid:\v!yes     }{\getnoflines   \fighei\setevalue{\currentscaletag\c!height}{\the\noflines\lineheight}}
\setvalue{\??xy:\c!grid:\v!height  }{\getrawnoflines\fighei\setevalue{\currentscaletag\c!height}{\the\dimexpr\noflines\lineheight+\strutdepth\relax}}
\setvalue{\??xy:\c!grid:\v!depth   }{\getrawnoflines\fighei\setevalue{\currentscaletag\c!height}{\the\dimexpr\noflines\lineheight-\strutdepth\relax}}
\setvalue{\??xy:\c!grid:\v!halfline}{\getrawnoflines\fighei\setevalue{\currentscaletag\c!height}{\the\dimexpr\noflines\lineheight+.5\lineheight\relax}}
\setvalue{\??xy:\c!grid:\v!fit     }{\getrawnoflines\fighei\setevalue{\currentscaletag\c!height}{\the\noflines\lineheight}}
\letvalue{\??xy:\c!grid:\empty     }\donothing

\def\checkscaleboxsettings
  {\doifsomething{\scaleparameter\c!maxwidth }% can be defined in itself
     {\setevalue{\currentscaletag\c!maxwidth }{\the\dimexpr\scaleparameter\c!maxwidth \relax}}%
   \doifsomething{\scaleparameter\c!maxheight}% can be defined in itself
     {\setevalue{\currentscaletag\c!maxheight}{\the\dimexpr\scaleparameter\c!maxheight\relax}}%
   \doifsomething{\scaleparameter\c!lines}
     {\setevalue{\currentscaletag\c!height}{\the\dimexpr\scaleparameter\c!lines\lineheight\relax}}%
   \getvalue{\??xy:\c!grid:\scaleparameter\c!grid}}

\def\setscaleboxbynature % where ! ! ! ! !
  {\doifsomething{\scaleparameter\c!width }{\global\scaleboxdimx\scaleparameter\c!width }%
   \doifsomething{\scaleparameter\c!height}{\global\scaleboxdimy\scaleparameter\c!height}%
   \doifsomething{\scaleparameter\c!scale }       {\scaleboxscax\scaleparameter\c!scale
                                                   \scaleboxscay\scaleparameter\c!scale }%
   \doifsomething{\scaleparameter\c!xscale}       {\scaleboxscax\scaleparameter\c!xscale}%
   \doifsomething{\scaleparameter\c!yscale}       {\scaleboxscay\scaleparameter\c!yscale}} % oeps, was x

% \defineexternalfigure[width-6][factor=auto,maxwidth=\textheight,maxheight=\textwidth]
% \defineexternalfigure[width-7][factor=auto,maxwidth=\textwidth,maxheight=\textheight]
% \placefigure{none}{\rotate[frame=on,offset=overlay]{\externalfigure[t:/sources/cow.pdf][width-6]}} \page
% \placefigure{none}{\framed[frame=on,offset=overlay]{\externalfigure[t:/sources/cow.pdf][width-7]}}

\def\setscaleboxbyfactor
  {\doifinsetelse{\scaleparameter\c!factor}{\v!max,\v!fit,\v!broad,\v!auto}
     {\doapplyscaleboxsize
      \ifdim\scaleboxsizex>\scaleboxsizey
        \docalculatescaleboxnorm  \scaleboxdimx\c!factor\c!maxwidth\hsize\scaleboxhsize
        \docalculatescaleboxscales\scaleboxdimx\scaleboxsizex\scaleboxdimy\scaleboxsizey
      \else
        \docalculatescaleboxnorm  \scaleboxdimy\c!factor\c!maxheight\scaleboxoutervsize\scaleboxvsize
        \docalculatescaleboxscales\scaleboxdimy\scaleboxsizey\scaleboxdimx\scaleboxsizex
      \fi
      \donetrue}
     {\doifinsetelse{\scaleparameter\c!hfactor}{\v!max,\v!fit,\v!broad,\v!auto}
        {\doapplyscaleboxsize
         \docalculatescaleboxnorm  \scaleboxdimy\c!hfactor\c!maxheight\scaleboxoutervsize\scaleboxvsize
         \docalculatescaleboxscales\scaleboxdimy\scaleboxsizey\scaleboxdimx\scaleboxsizex
         \donetrue}
        {\doifinsetelse{\scaleparameter\c!wfactor}{\v!max,\v!fit,\v!broad,\v!auto}
           {\doapplyscaleboxsize
            \docalculatescaleboxnorm  \scaleboxdimx\c!wfactor\c!maxwidth\hsize\scaleboxhsize
            \docalculatescaleboxscales\scaleboxdimx\scaleboxsizex\scaleboxdimy\scaleboxsizey
            \donetrue}
           {\docalculatescaleboxnorm\scaleboxdimy\c!factor \c!height \textheight\scaleboxvsize
            \docalculatescaleboxnorm\scaleboxdimy\c!hfactor\c!height \textheight\scaleboxvsize
            \docalculatescaleboxnorm\scaleboxdimx\c!wfactor\c!width  \hsize     \hsize
            \donefalse}}}%
   \ifdone
     \settrue\scaleboxscalingdone
     \ifdim\scaleboxdimx>\scaleboxhsize
       \global\scaleboxdimy\zeropoint \global\scaleboxdimx\scaleboxhsize
     \else\ifdim\scaleboxdimy>\scaleboxvsize
       \global\scaleboxdimx\zeropoint \global\scaleboxdimy\scaleboxvsize
     \fi\fi
   \fi}

\def\setscaleboxbyscale
  {\doifsomething{\scaleparameter\c!scale\scaleparameter\c!xscale\scaleparameter\c!yscale}
     {\doapplyscaleboxscale\scaleboxdimx\scaleboxsizex\scaleboxscax\c!xscale
      \doapplyscaleboxscale\scaleboxdimy\scaleboxsizey\scaleboxscay\c!yscale
      \global\scaleboxdimx\zeropoint
      \global\scaleboxdimy\zeropoint
      \doifelsenothing{\scaleparameter\c!maxwidth}
        {\doifsomething{\scaleparameter\c!maxheight}
           {\ifdim\scaleboxsizey>\scaleparameter\c!maxheight\relax
              \global\scaleboxdimy\scaleparameter\c!maxheight
            \fi}}
        {\ifdim\scaleboxsizex>\scaleparameter\c!maxwidth\relax
           \global\scaleboxdimx\scaleparameter\c!maxwidth
         \fi}}}

\def\setscaleboxbydimension
  {\ifdim\scaleboxdimx>\zeropoint
     \ifdim\scaleboxdimy>\zeropoint
       \dosetdimensionscaleboxsize
         {\docalculatescaleboxscale\scaleboxdimy\scaleboxsizey\scaleboxscay
          \docalculatescaleboxscale\scaleboxdimx\scaleboxsizex\scaleboxscax}%
         {\docalculatescaleboxscale\scaleboxdimy\scaleboxsizey\scaleboxscay
          \docalculatescaleboxscale\scaleboxdimx\scaleboxsizex\scaleboxscax}%
         {\docalculatescaleboxscale\scaleboxdimy\scaleboxsizey\scaleboxscay
          \docalculatescaleboxscale\scaleboxdimx\scaleboxsizex\scaleboxscax}%
     \else
       \dosetdimensionscaleboxsize
         {\docalculatescaleboxscales\scaleboxdimx\scaleboxsizex\scaleboxdimy\scaleboxsizey}%
         {\docalculatescaleboxscales\scaleboxdimx\scaleboxsizex\scaleboxdimy\scaleboxsizey}%
         {\docalculatescaleboxscales\scaleboxdimx\scaleboxsizex\scaleboxdimy\scaleboxsizey}%
     \fi
   \else
     \ifdim\scaleboxdimy>\zeropoint
       \dosetdimensionscaleboxsize
         {\docalculatescaleboxscales\scaleboxdimy\scaleboxsizey\scaleboxdimx\scaleboxsizex}%
         {\docalculatescaleboxscales\scaleboxdimy\scaleboxsizey\scaleboxdimx\scaleboxsizex}%
         {\docalculatescaleboxscales\scaleboxdimy\scaleboxsizey\scaleboxdimx\scaleboxsizex}%
     \else
       \dosetdimensionscaleboxsize
         {\doapplyscaleboxscale\scaleboxdimx\scaleboxsizex\scaleboxscax\c!xscale
          \doapplyscaleboxscale\scaleboxdimy\scaleboxsizey\scaleboxscay\c!yscale}%
         {\docalculatescaleboxscales\scaleboxdimx\scaleboxsizex\scaleboxdimy\scaleboxsizey}%
         {\docalculatescaleboxscales\scaleboxdimy\scaleboxsizey\scaleboxdimx\scaleboxsizex}%
     \fi
   \fi}

\def\dosetdimensionscaleboxsize#1#2#3%
  {#1\relax
   \doifsomething{\scaleparameter\c!maxwidth}
     {\ifdim\scaleboxdimx>\scaleparameter\c!maxwidth\relax
        \global\scaleboxdimx\scaleparameter\c!maxwidth
        #2\relax
      \fi}%
   \doifsomething{\scaleparameter\c!maxheight}
     {\ifdim\scaleboxdimy>\scaleparameter\c!maxheight\relax
        \global\scaleboxdimy\scaleparameter\c!maxheight
         #3\relax
      \fi}}

\def\docalculatescaleboxnorm#1#2#3#4#5% 2 3 parameters (dodo:speedup)
  {\processaction
      [\scaleparameter#2]
      [     \v!max=>\global#1\dimexpr#4\relax,
            \v!fit=>\global#1\dimexpr#5\relax,
          \v!broad=>\global#1\dimexpr#5-4\@@exbodyfont\relax,
           \v!auto=>\doifsomething{\scaleparameter#3}{\global#1\dimexpr\scaleparameter#3\relax},
        \s!default=>\doifsomething{\scaleparameter#3}{\global#1\dimexpr\scaleparameter#3\relax},
        \s!unknown=>\global#1\dimexpr\scaleparameter#2\dimexpr\@@exbodyfont/10\relax\relax]}

\def\docalculatescaleboxscales#1#2#3#4%
  {\scratchdimen\dimexpr#1/\dimexpr#2/\plusthousand\relax\relax
   \scaleboxscax\scratchdimen
   \scaleboxscay\scratchdimen
   #3\dimexpr\scaleboxscax\dimexpr#4/\plusthousand\relax\relax}

\def\docalculatescaleboxscale#1#2#3%
  {#3\dimexpr#1/\dimexpr#2/\plusthousand\relax\relax}

\def\doapplyscaleboxscale#1#2#3#4% $4 = parameter / scale can be empty
  {\ifcase0\scaleparameter#4\relax
     \ifcase0\scaleparameter\c!scale\relax
       #3=\plusthousand
     \else
       #3=\scaleparameter\c!scale
     \fi
   \else
     #3=\scaleparameter#4%
   \fi
   \relax % important ! still ?
   \global#1\ifnum#3=\plusthousand#2\else\dimexpr#3\dimexpr#2/\plusthousand\relax\relax\fi
   \relax}

\def\doapplyscaleboxsize
  {\doifelsenothing{\scaleparameter\c!maxheight}
     {\scaleboxoutervsize\textheight
      \ifinner
        \scaleboxoutervsize \vsize % \textheight =\vsize
        \scratchdimen\vsize % \scratchdimen=\textheight
      \else\ifinsidefloat
        \scaleboxoutervsize \vsize % \textheight =\vsize
        \scratchdimen\vsize % \scratchdimen=\textheight
      \else\ifinpagebody
        \scaleboxoutervsize \vsize % \textheight =\vsize
        \scratchdimen\vsize % \scratchdimen=\textheight
      \else % hm, there should be an option to force this
        \ifdim\pagegoal<\maxdimen
          \ifdim\pagetotal<\pagegoal
            \scratchdimen\pagegoal
            \advance\scratchdimen -\pagetotal
          \else
            \scratchdimen\scaleboxoutervsize % \textheight
          \fi
        \else
          \scratchdimen\scaleboxoutervsize % \textheight
        \fi
      \fi\fi\fi}
     {\scaleboxoutervsize\scaleparameter\c!maxheight}%
   \doifelsenothing{\scaleparameter\c!height}
     {\scaleboxvsize\scratchdimen}
     {\scaleboxvsize\scaleparameter\c!height}%
   \doifelsenothing{\scaleparameter\c!width}
     {\scaleboxhsize\hsize}
     {\scaleboxhsize\scaleparameter\c!width}}

\def\convertscaleboxinsertscale#1#2#3#4%
  {\scratchdimen#1\relax
   \ifnum#3=\plusthousand
     % == scale 1
   \else
     % better 1000 100 10 ranges, evt round 2sp
     \divide\scratchdimen \plusthousand
     \multiply\scratchdimen #3\relax
   \fi
   \scratchdimen-\scratchdimen  % beter hier - dan in driver
   \edef#2{\the\scratchdimen}%
   \scratchcounter#3\relax
   \ifnum\scratchcounter>\plustenthousand
     \divide\scratchcounter\!!ten \scratchdimen\the\scratchcounter\points
   \else
     \scratchdimen\the\scratchcounter\points \divide\scratchdimen\!!ten
   \fi
   \edef#4{\withoutpt\the\scratchdimen}}

% \startcombination
%     {\externalfigure[cow.pdf] [frame=on,height=3cm,equalwidth=6cm]} {}
%     {\externalfigure[mill.png][frame=on,height=3cm,equalwidth=6cm]} {}
% \stopcombination

\def\doscaleboxposition
   {\doifsomething{\scaleparameter\c!equalwidth}
      {\scratchdimen\scaleparameter\c!equalwidth\relax
       \ifdim\wd\nextbox<\scratchdimen
         \setbox\nextbox\hbox to \scratchdimen{\hss\box\nextbox\hss}%
       \fi}%
    \doifsomething{\scaleparameter\c!equalheight}
      {\scratchdimen\scaleparameter\c!equalheight\relax
       \ifdim\ht\nextbox<\scratchdimen
         \setbox\nextbox\vbox to \scratchdimen{\vss\box\nextbox\vss}%
       \fi}}

%D \macros
%D   {clip, setupclipping}
%D
%D Although related to figures, clipping can be applied to
%D arbitrary content. We can use \METAPOST\ to provide a non
%D rectangular clipping path.
%D
%D \starttyping
%D \startMPclip{fun}
%D   clip currentpicture to fullcircle
%D     shifted (.5,.5) xscaled \width yscaled \height ;
%D \stopMPclip
%D \stoptyping
%D
%D We get a rectangular piece of the figure when we say:
%D
%D \starttyping
%D \clip[x=2,y=1]{\externalfigure[photo]}
%D \stoptyping
%D
%D When we want to clip to the oval we defined a few lines ago,
%D we say:
%D
%D \starttyping
%D \clip[nx=1,ny=1,x=1,y=1,mp=fun]{\externalfigure[photo]}
%D \stoptyping
%D
%D The general characteristics of clipping can be set up with
%D
%D \showsetup{setupclipping}

\def\setupclipping
  {\dodoubleargument\getparameters[\??cp]}

\def\clip
  {\dosingleempty\doclip}

\def\doclip[#1]% nb top->bottom left->right
  {\bgroup
   \getparameters[\??cp][#1]%
   \doifelse\@@cpstate\v!start\dodoclip{\egroup\hbox}}

\def\dodoclip
  {\dowithnextbox
     {\ifdim\@@cpwidth>\zeropoint
        \!!dimena\@@cpwidth
        \!!dimenc\@@cphoffset
      \else
        \!!dimena\nextboxwd
        \divide\!!dimena \@@cpnx
        \!!dimenc\@@cpx\!!dimena
        \advance\!!dimenc -\!!dimena
        \!!dimena\@@cpsx\!!dimena
      \fi
      \relax % sure
      \ifdim\@@cpheight>\zeropoint
        \!!dimenb\@@cpheight
        \!!dimend\nextboxht
        \advance\!!dimend -\@@cpvoffset
        \advance\!!dimend -\!!dimenb
      \else
        \!!dimenb\nextboxht
        \divide\!!dimenb \@@cpny
        \!!dimend-\@@cpy\!!dimenb
        \advance\!!dimend -\@@cpsy\!!dimenb
        \advance\!!dimend \!!dimenb
        \!!dimenb\@@cpsy\!!dimenb
        \advance\!!dimend \nextboxht % dimend !
      \fi
      \setbox\nextbox\hbox                            % old
        {\advance\!!dimenc -\@@cpleftoffset           % new !
         \advance\!!dimend -\@@cpbottomoffset         % new ! % - added
         \hskip-\!!dimenc\lower\!!dimend\flushnextbox}% old
      \nextboxwd\zeropoint
      \nextboxht\zeropoint
      \nextboxdp\zeropoint
      \setbox\nextbox\hbox
        {\advance\!!dimena \@@cpleftoffset         % new !
         \advance\!!dimena \@@cprightoffset        % new !
         \advance\!!dimenb \@@cpbottomoffset       % new !
         \advance\!!dimenb \@@cptopoffset          % new !
         \dostartclipping\@@cpmp\!!dimena\!!dimenb % old
           \flushnextbox
         \dostopclipping}%
      \setbox\nextbox\hbox                       % new !
        {\!!dimena-\@@cpleftoffset               % new !
         \!!dimenb \@@cpbottomoffset             % new ! % - removed
         \hskip\!!dimena\lower\!!dimenb\flushnextbox}% new !
      \nextboxwd\!!dimena
      \nextboxht\!!dimenb
      \nextboxdp\zeropoint
      \flushnextbox
      \egroup}%
   \hbox}

\setupclipping
  [\c!state=\v!start,
   \c!n=1, % was 2
   \c!nx=\@@cpn,\c!x=1,\c!sx=1,
   \c!ny=\@@cpn,\c!y=1,\c!sy=1,
   \c!width=\!!zeropoint,
   \c!height=\!!zeropoint,
   \c!hoffset=\!!zeropoint,
   \c!voffset=\!!zeropoint,
   \c!offset=\zeropoint,
   \c!leftoffset=\@@cpoffset,  % \zeropoint,
   \c!rightoffset=\@@cpoffset, % \zeropoint,
   \c!topoffset=\@@cpoffset,   % \zeropoint,
   \c!bottomoffset=\@@cpoffset,% \zeropoint,
   \c!mp=]

%D \startbuffer
%D \startuseMPgraphic{test}
%D   path p ; p := fullcircle scaled 4cm ;
%D   draw p withpen pencircle scaled 1cm ;
%D   setbounds currentpicture to boundingbox p ;
%D \stopuseMPgraphic
%D
%D \hbox to \hsize \bgroup
%D   \hss
%D   \ruledhbox{\useMPgraphic{test}}%
%D   \hss
%D   \ruledhbox{\clip{\useMPgraphic{test}}}%
%D   \hss
%D \egroup
%D \stopbuffer
%D
%D \typebuffer \getbuffer

%D Mirroring.

\def\domirrorbox % \hbox/\vbox/\vtop
  {\bgroup
   \dowithnextbox
     {\dontshowcomposition
      \scratchdimen\nextboxwd
      % better use an hbox (if no \forgetall, leftskip etc may creep in)
     %\setbox\nextbox\vbox{\forgetall\dostartmirroring\hskip-\nextboxwd\flushnextbox\dostopmirroring}%
      \setbox\nextbox\hbox{\dostartmirroring\hskip-\nextboxwd\flushnextbox\dostopmirroring}%
      \nextboxwd\scratchdimen
      \flushnextbox
      \egroup}}

\unexpanded\def\mirror
  {\domirrorbox\hbox}

% \setbox0=\hbox{gans}
% \ruledhbox{\copy0 \schaal[sx=2,sy=2]{\copy0}}
% \mirror{\ruledhbox{\copy0 \schaal{\box0}}}

\protect \endinput