structure ClickPoints =
struct
  fun generate (start, finish, numPoints) =
    let
      val difference = finish - start
      val increment = Real32.fromInt difference / Real32.fromInt numPoints
      val start = Real32.fromInt start
    in
      Vector.tabulate (numPoints + 1, fn idx =>
        (Real32.fromInt idx * increment) + start)
    end

  fun getDrawDot (xpos, ypos, windowWidth, windowHeight) =
    let
      (* calculate normalised device coordinates *)
      val halfWidth = Real32.fromInt (windowWidth div 2)
      val halfHeight = Real32.fromInt (windowHeight div 2)
      val hpos = xpos - halfWidth
      val vpos = ~(ypos - halfHeight)

      (* coordinates to form small box around clicked area *)
      val left = (hpos - 5.0) / halfWidth
      val right = (hpos + 5.0) / halfWidth
      val bottom = (vpos - 5.0) / halfHeight
      val top = (vpos + 5.0) / halfHeight
    in
      Ndc.ltrbToVertex (left, top, right, bottom)
    end

  fun getDrawDotRgb (xpos, ypos, r, g, b, windowWidth, windowHeight) =
    let
      (* calculate normalised device coordinates *)
      val halfWidth = Real32.fromInt (windowWidth div 2)
      val halfHeight = Real32.fromInt (windowHeight div 2)
      val hpos = xpos - halfWidth
      val vpos = ~(ypos - halfHeight)

      (* coordinates to form small box around clicked area *)
      val left = (hpos - 5.0) / halfWidth
      val right = (hpos + 5.0) / halfWidth
      val bottom = (vpos - 5.0) / halfHeight
      val top = (vpos + 5.0) / halfHeight
    in
      Ndc.ltrbToVertexRgb (left, top, right, bottom, r, g, b)
    end
end