;; -*- lisp -*-

(in-package :ucw-standard)

;;;; ** Task

(defcomponent task-component ()
  ()
  (:documentation "A controller for a single task or operation to
  be performed by the user.

  A task component's START action is called as soon as the
component is instantiated. Task components do not have their own
RENDER method, in fact they have no graphical representation but
serve only to order a sequence of other components."))

(defgeneric/cc start (task)
  (:documentation "action which gets called automatically when
task-component is active. Use defmethod/cc to define your specialized
\"start\" methods"))

(defmethod render ((task task-component))
  (with-call/cc
    (start task))
  (let ((active-component (place (component.place task))))
    ;; active-component is the object currently in the place of the
    ;; task component. after calling and answering active-component
    ;; should not be TASK itself.
    (when (eq task active-component)
      (error "No active component after calling task's start method"))
    (render active-component)))

;; Copyright (c) 2003-2005 Edward Marco Baringer
;; All rights reserved. 
;; 
;; Redistribution and use in source and binary forms, with or without
;; modification, are permitted provided that the following conditions are
;; met:
;; 
;;  - Redistributions of source code must retain the above copyright
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;; 
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;; 
;;  - Neither the name of Edward Marco Baringer, nor BESE, nor the names
;;    of its contributors may be used to endorse or promote products
;;    derived from this software without specific prior written permission.
;; 
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