fill_polygon_relative/[3,4] fill_polygon_relative(+Drawable, +Points, +Shape)
fill_polygon_relative(+Drawable, +Gc, +Points, +Shape)
Draw a filled polygon. Points is a list of point(X,Y) terms,
each specifying the location of one vertex of the polygon relative
to the previous point.
Shape is either complex, meaning the polygon
may contain intersecting edges, nonconvex, meaning no edges
intersect, or convex, meaning that no edges intersect, and further,
the polygon is wholly convex.