Stand-alone Graphic

[Arun Mangalam <arun_mangalam@mac.com>]

Hello,

While I was reading the Metafun manual, I found I could create a 
MetaPost-based stand-alone pdf graphic [with the appropriate bounding 
box] using

   \startMPpage
   ...
   \stopMPpage

My question is: is it possible and, if so, how do I create a stand-alone 
pdf graphic for other graphics within ConTeXt? For example, I would like 
to create a stand-alone graphic for the following code [instead of a PDF 
page]:
     \startbuffer[sample]
         \framed
             [align=middle,width=4cm,background=screen,frame=off]
             {A \METAPOST\ clip is not the same as a video clip, although 
we can use
              \METAPOST\ to produce a video clip.}
     \stopbuffer
     \startMPclip{text clip}
         clip currentpicture to fullcircle shifted (.5,.5)
             xscaled \width yscaled \height ;
     \stopMPclip
     \startuseMPgraphic{clip outline}
         draw fullcircle
             xscaled \overlaywidth yscaled \overlayheight
             withpen pencircle scaled 4mm
             withcolor .625red ;
     \stopuseMPgraphic
     \starttext
     \defineoverlay[clip outline][\useMPgraphic{clip outline}]
     \placefigure
         [here][fig:clipped text 2]
         {A clipped buffer (text).}
         {\framed
             [background=clip outline,offset=overlay,frame=off]
             {\clip
                 [nx=1,ny=1,mp=text clip]
                 {\externalfigure[sample][type=buffer,width=4cm]}}}
     \stoptext

As you can see, the above is also from the MetaFun manual. :) ConTeXt 
becomes better and better the more I find out about it.

Thank you for any help.

- Arun

PS. The reason for my question is, that I want to see if I can create an 
MacOSX graphical program like xfig that uses ConTeXt. It would be both 
educational for me in terms of understanding the Cocoa framework as well 
as improve my understanding of ConTeXt.