Polygons

• ((draw-polygon viewport) posn-list posn color)
  draw-polygon takes a viewport descriptor. It returns a function that draws a polygon border in the viewport using posn-list for the polygon vertices and posn as an offeset for the polygon. The optional color argument defaults to black.
• ((clear-polygon viewport) posn-list posn)
  clear-polygon takes a viewport descriptor. It returns a function that erases a polygon border in the viewport using posn-list for the polygon vertices and posn as an offeset for the polygon.
• ((flip-polygon viewport) posn-list posn)
  flip-polygon takes a viewport descriptor. It returns a function that flips a polygon border in the viewport using posn-list for the polygon vertices and posn as an offeset for the polygon.
• ((draw-solid-polygon viewport) posn-list posn color)
  draw-solid-polygon takes a viewport descriptor. It returns a function that paints a solid polygon in the viewport using posn-list for the polygon vertices and posn as an offeset for the polygon. The optional color argument defaults to black.
• ((clear-solid-polygon viewport) posn-list posn)
  clear-solid-polygon takes a viewport descriptor. It returns a function that erases a solid polygon in the viewport using posn-list for the polygon vertices and posn as an offeset for the polygon.
• ((flip-solid-polygon viewport) posn-list posn)
  flip-solid-polygon takes a viewport descriptor. It returns a function that flips a solid polygon in the viewport using posn-list for the polygon vertices and posn as an offeset for the polygon.