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SUBROUTINE PGNA2 (XARRAY,INCX, YARRAY,INCY, NVERTX)
C$ (Polygon Absolute 2-D)
C$ Draw a 2-D polygon. A move is automatically made to the
C$ first vertex, and then implicit closure is provided by
C$ connecting the last vertex to the first, and the current
C$ point is left at the first vertex. If a polygon "plain"
C$ interior style filling and a visible pattern or color has
C$ been selected by a prior call to SETPIS and SETPFI/SETPCI,
C$ the polygon is filled with that pattern or color. The
C$ polygon vertices are assumed to be arranged so that the
C$ interior lies to the left of each line segment between
C$ vertices i and i+1. Drawing and filling is suppressed if
C$ the polygon lies entirely outside the current viewport.
C$ The arguments are:
C$
C$ XARRAY(*)........Array of X coordinates.
C$ INCX.............Displacement between successive X
C$ coordinates in XARRAY(*) (normally 1).
C$ YARRAY(*)........Array of Y coordinates.
C$ INCY.............Displacement between successive Y
C$ coordinates in YARRAY(*) (normally 1).
C$ NVERTX...........Number of polygon vertices (.GE. 3).
C$
C$ If an increment INCX or INCY is negative, the starting
C$ vertex is taken as (1-N)*INC + 1 instead of 1, so that the
C$ array is stepped through in reverse order. Because of the
C$ ordering convention on the vertices, reversing the order of
C$ traversal of the vertex list interchanges the interior and
C$ the exterior of the polygon. No error is raised if there
C$ are fewer than 3 vertices, but filling will be suppressed.
C$ (14-SEP-87)