3.19) The programmer defined objects.

type gr_user =
  { us_window : gr_window
  ; mutable us_param : melted_type vect
  ; mutable us_draw : gr_user -> unit
  ; mutable us_callback : gr_user -> event -> bool
  }
;;
The last Camlwin graphics object is not built on the same model as the others. The drawing function is not distinct and fixed but linked to the defined object and defined by the programmer, in the same way as the management function. These objects have the type gr_user. This type is composed of: Basically, the first two elements of the vector us_param are of type int_type and define the coordinates of upper left corner.