[ REQ 6105]: Bug in PS snapshot

[erikjan at dutcg01.tudelft.nl]

Hi,

The program PS snapshot (included with geomview 1.5) produces PostScript
files which can not be included into other PostScript files. The cause
of this `bug' is the PostScript procedure `drawpoly' which is defined in
the output files of PS snapshot. This procedure uses the size of the
operand stack to determine the number of points on the current polygon.
This works fine if the stack is empty before the first polygon is drawn.
However, this is usually not the case if the output file of PS snapshot is
included into another PostScript file.

An easy way to fix this bug, is to replace the current definition of the 
procedure `drawpoly':

  /drawpoly { setgray newpath moveto count 4 ge {
     count 2 idiv { lineto } repeat closepath
          gsave fill grestore edgecolor stroke  }
    { count 2 eq {lineto} {0 0 rlineto} ifelse stroke }
   ifelse
  } def  


by the following definitions:


  count /offset exch def                      % Save the current stack size
  /numpoints { count offset sub 2 idiv } def  % Number of points on the stack

  /drawpoly { setgray newpath moveto numpoints 2 ge {
     numpoints { lineto } repeat closepath
          gsave fill grestore edgecolor stroke  }
    { numpoints 1 eq {lineto} {0 0 rlineto} ifelse stroke }
   ifelse
  } def    


Of course, a more elegant solution would be to pass the number of points
to be drawn to the procedure `drawpoly' (using the stack).

Sincerely yours,

Erik Jan Lingen.



 F.J. Lingen                       | 
 Department of Civil Engineering   | phone  : +31-15-2782164
 Delft University of Technology    | fax    : +31-15-2611465
 P.O. Box 5048                     | e-mail : EJ.Lingen at CT.TUDelft.NL
 2600 GA DELFT                     |
 The Netherlands                   |