Rectangles

• ((draw-rectangle viewport) posn width height color)
  draw-rectangle takes a viewport descriptor. It returns a function that draws a rectangle border in the viewport with the top-left of the rectangle at the position posn and with sides width across and height tall. The optional color argument defaults to black.
• ((clear-rectangle viewport) posn width height color)
  clear-rectangle takes a viewport descriptor. It returns a function that clears a rectangle border in the viewport with the top-left of the rectangle at the position posn and with sides width across and height tall. The optional color argument defaults to black.
• ((flip-rectangle viewport) posn width height color)
  flip-rectangle takes a viewport descriptor. It returns a function that flips a rectangle border in the viewport with the top-left of the rectangle at the position posn and with sides width across and height tall. The optional color argument defaults to black.
• ((draw-solid-rectangle viewport) posn width height color)
  draw-solid-rectangle takes a viewport descriptor. It returns a function that paints a solid rectangle in the viewport with the top-left of the rectangle at the position posn and with sides width across and height tall. The optional color argument defaults to black.
• ((clear-solid-rectangle viewport) posn width height color)
  clear-solid-rectangle takes a viewport descriptor. It returns a function that erases a solid rectangle in the viewport with the top-left of the rectangle at the position posn and with sides width across and height tall. The optional color argument defaults to black.
• ((flip-solid-rectangle viewport) posn width height color)
  flip-solid-rectangle takes a viewport descriptor. It returns a function that flips a solid rectangle in the viewport with the top-left of the rectangle at the position posn and with sides width across and height tall. The optional color argument defaults to black.