David Arnold wrote:
Hans et al,
Let me try to be more specific. Here is a file which is very typical of the way I draw graphs for my mathematics classes. When you compile, you will see the graph of the absolute value of x-1. That is, it draws the graph of y=|x-1|, but only after clipping it to the cpath. What I would like to do is draw the graph with the drawdblarrow command so that the graph of the absolute value ends in arrowheads. So, I want to clip the graph to the bounding box, save the picture, null the picture, then somehow extract the path into the variable F in its clipped form (not the original path F that extends outside the clip path) so that I can replace the command draw pic with drawdblarrow F.
hm, this need some more brainpower than the previous solution, in mp-tool there is a repathed macro that does most of the job so let's extend that one a bit: \starttext \setupcolors[state=start] \startMPpage def restroke suffix p = p := repathed (21,p) enddef ; % keep attributes def reprocess suffix p = p := repathed (22,p) enddef ; % no attributes vardef repathed (expr mode, p) text t = begingroup ; if mode=0 : save withcolor ; remapcolors ; fi ; save _p_, _pp_, _ppp_, _f_, _b_, _t_ ; picture _p_, _pp_, _ppp_ ; color _f_ ; path _b_ ; transform _t_ ; _b_ := boundingbox p ; _p_ := nullpicture ; for i within p : _f_ := (redpart i, greenpart i, bluepart i) ; if bounded i : _pp_ := repathed(mode,i) t ; setbounds _pp_ to pathpart i ; addto _p_ also _pp_ ; elseif clipped i : _pp_ := repathed(mode,i) t ; clip _pp_ to pathpart i ; addto _p_ also _pp_ ; elseif stroked i : if mode=21 : _ppp_ := i ; % indirectness is needed addto _p_ also image(scantokens(t & " pathpart _ppp_") dashed dashpart i withpen penpart i withcolor _f_ ; ) ; elseif mode=22 : _ppp_ := i ; % indirectness is needed addto _p_ also image(scantokens(t & " pathpart _ppp_")) ; else : addto _p_ doublepath pathpart i dashed dashpart i withpen penpart i withcolor _f_ % (redpart i, greenpart i, bluepart i) if mode=2 : t fi ; fi ; elseif filled i : if mode=11 : _ppp_ := i ; % indirectness is needed addto _p_ also image(scantokens(t & " pathpart _ppp_") withcolor _f_ ; ) ; elseif mode=12 : _ppp_ := i ; % indirectness is needed addto _p_ also image(scantokens(t & " pathpart _ppp_")) ; else : addto _p_ contour pathpart i withcolor _f_ if (mode=1) and (_f_<>refillbackground) : t fi ; fi ; elseif textual i : % textpart i <> "" : if mode <> 4 : addto _p_ also i if mode=3 : t fi ; fi ; else : addto _p_ also i ; fi ; endfor ; setbounds _p_ to _b_ ; _p_ endgroup enddef ; picture pic; pic := image( draw fullcircle scaled 5cm withpen pencircle scaled 5mm ; draw fullsquare scaled 2cm withpen pencircle scaled 5mm ; fill fullcircle scaled 1cm withpen pencircle scaled 5mm ; ) ; redraw pic withpen pencircle scaled 1mm withcolor red ; % restroke pic "drawdblarrow" ; pic := repathed(21,pic) "drawdblarrow" ; pic := repathed(11,pic) "drawdblarrow" ; draw pic ; \stopMPpage \stoptext the new restroke variant takes a macro name that itself takes one argument, i.e. a path, so in order to do more complex things, you need to define those Hans ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | fax: 038 477 53 74 | www.pragma-ade.com | www.pragma-pod.nl -----------------------------------------------------------------