class KDragEvent(
    val action: KDragAction,
    val motionEvent: KMouseEvent
) : KEvent {
    val pos get() = motionEvent.pos
    override fun toString(): String = "KDragEvent(action=$action, pos=$pos)"

    enum class KDragAction {
        Start, Dragging, Finish
    }
}

on(KMouseDrag) { evt ->
    println("Mouse drag(${evt.action}):: ${evt.pos}")
}