% based on example posted on the list

\starttext

\defineoverlay[my overlay][\positionoverlay{my graphic}]

\startpositionoverlay{my graphic}
    \setMPpositiongraphic{three}{mypos:circle}{mypos:radius=1cm,mypos:circlecolor=red}
    \setMPpositiongraphic{three}{mypos:circle}{mypos:radius=.5cm,mypos:circlecolor=green}
\stoppositionoverlay

\startMPinclusions
    if unknown context_apos : input mp-apos.mpiv ; fi ;
    if unknown context_abck : input mp-abck.mpiv ; fi ;
\stopMPinclusions

\startMPpositiongraphic{mypos:circle}
    drawarrow
        fullcircle
            scaled \MPvar{mypos:radius}
            shifted \MPxy{\MPvar{self}}
            shifted (\MPw{\MPvar{self}}/2,ExHeight/2)
            withpen pencircle
                scaled 2pt
                withcolor \MPvar{mypos:circlecolor} ;
    anchor_box(\MPanchor{\MPvar{self}}) ;
\stopMPpositiongraphic

\framed
  [background=my overlay]
  {let's see what happens \hpos{three}{{\em here}} or there}

\stoptext
