%N pgpoly %F $MIR/src/pgpoly.f
%D Draw a polygon, using fill-area attributes
%B
      SUBROUTINE PGPOLY (N, XPTS, YPTS)
      INTEGER N
      REAL XPTS(*), YPTS(*)

 Fill-area primitive routine: shade the interior of a closed
 polygon in the current window.  The action of this routine depends
 on the setting of the Fill-Area Style attribute (see PGSFS).
 The polygon is clipped at the edge of the
 window. The pen position is changed to (XPTS(1),YPTS(1)) in world
 coordinates (if N > 1).  If the polygon is not convex, a point is
 assumed to lie inside the polygon if a straight line drawn to
 infinity intersects and odd number of the polygon's edges.

 Arguments:
  N      (input)  : number of points defining the polygon; the
                    line consists of N straight-line segments,
                    joining points 1 to 2, 2 to 3,... N-1 to N, N to 1.
                    N should be greater than 2 (if it is 2 or less,
                    nothing will be drawn).
  XPTS   (input)  : world x-coordinates of the vertices.
  YPTS   (input)  : world y-coordinates of the vertices.
                    Note: the dimension of arrays XPTS and YPTS must be
                    greater than or equal to N.
