invalidate-bitmap-cache

When on-paint is overridden, call this method when the state of on-paint's drawing changes.

• (send an-editor invalidate-bitmap-cache x y width height) -> void
      x = 0.0 : real number
      y = 0.0 : real number
      width = 'end : non-negative real number or 'end
      height = 'end : non-negative real number or 'end

  The x, y, width, and height arguments specify the area that needs repainting in editor coordinates. If width/height is 'end, then the total height/width of the editor is used.