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;;; guile-2d
;;; Copyright (C) 2013 David Thompson <dthompson2@worcester.edu>
;;;
;;; Guile-2d is free software: you can redistribute it and/or modify it
;;; under the terms of the GNU Lesser General Public License as
;;; published by the Free Software Foundation, either version 3 of the
;;; License, or (at your option) any later version.
;;;
;;; Guile-2d is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;; Lesser General Public License for more details.
;;;
;;; You should have received a copy of the GNU Lesser General Public
;;; License along with this program. If not, see
;;; <http://www.gnu.org/licenses/>.
;;; Commentary:
;;
;; Stages represent the game state at the present time.
;;
;;; Code:
(define-module (2d stage)
#:use-module (srfi srfi-9)
#:use-module (2d agenda)
#:use-module (2d scene)
#:export (make-stage
stage?
stage-agenda
stage-observer
stage-env
stage-scene
enter-stage
exit-stage
draw-stage
update-stage
stage-trigger
make-stage-variable
define-stage-variable
stage-on
stage-off
current-stage
push-scene
pop-scene
replace-scene))
(define-record-type <stage>
(%make-stage agenda scene state)
stage?
(agenda stage-agenda)
(scene stage-scene)
(state stage-state))
(define (make-stage scene)
"Create a new stage object for SCENE."
(%make-stage (make-agenda) scene (init-scene scene)))
;;;
;;; Scene callbacks
;;;
(define (enter-stage stage)
"Call the scene enter callback for STAGE."
(with-agenda (stage-agenda stage)
(enter-scene (stage-scene stage)
(stage-state stage))))
(define (exit-stage stage)
"Call the scene exit callback for STAGE."
(with-agenda (stage-agenda stage)
(exit-scene (stage-scene stage)
(stage-state stage))))
(define (update-stage stage)
"Call the scene update callback for STAGE."
(with-agenda (stage-agenda stage)
(update-agenda)
(update-scene (stage-scene stage)
(stage-state stage))))
(define (draw-stage stage)
"Call the scene draw callback for STAGE."
(with-agenda (stage-agenda stage)
(draw-scene (stage-scene stage)
(stage-state stage))))
(define (stage-trigger stage event . args)
(with-agenda (stage-agenda stage)
(apply scene-trigger (stage-scene stage) event args)))
;;;
;;; Stage management
;;;
(define stack '())
(define (current-stage)
"Return the top of the stage stack or #f if the stack is empty."
(if (null? stack) #f (car stack)))
(define (push-scene scene)
"Make STAGE active and push it to the top of the stack."
(let ((prev-stage (current-stage))
(stage (make-stage scene)))
(when prev-stage
(exit-stage prev-stage))
(set! stack (cons stage stack))
(enter-stage stage)))
(define (pop-scene)
"Replace the current stage with the next one on the stack, if
present."
(let ((prev-stage (current-stage)))
(when prev-stage
(exit-stage prev-stage))
(set! stack (cdr stack))
(when (current-stage)
(enter-stage (car stack)))))
(define (replace-scene scene)
"Replace the current stage with STAGE."
(let ((prev-stage (current-stage))
(stage (make-stage scene)))
(when prev-stage
(exit-stage prev-stage))
(set! stack (cons stage (cdr stack)))
(enter-stage stage)))
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