type
  Control = ref object of RootObj

method handleKeyDownEvent(control: Control, event: KeyboardEvent) {.base.}

method handleKeyDownEvent(control: Control, event: KeyboardEvent) =
  echo "control.handle key down"

type
  ControlImpl = ref object of Control

proc pControlKeyPressSignal(widget: pointer, event: var GdkEventKey, data:
pointer): Gboolean {.cdecl.} =
  let control = cast[ControlImpl](data)
  try:
    control.handleKeyDownEvent(evt)
  except:
    handleException()


type
  MyWidget = ref object of ControlImpl

method handleKeyDownEvent(control: MyWidget, event: KeyboardEvent) =
  echo "MyWidget.handle key down"