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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:
;;
;; Animations represent a sequence of textures and/or texture regions.
;;
;;; Code:
(define-module (2d animation)
#:use-module (srfi srfi-9)
#:use-module (2d texture))
;;;
;;; Animations
;;;
;; The <animation> type represents a vector of textures or texture
;; regions that are to be played in sequence and possibly looped.
(define-record-type <animation>
(make-animation frames duration loop)
animation?
(frames animation-frames)
(duration animation-duration)
(loop animation-loop?))
(define (animation-frame animation index)
"Returns the frame for the given index."
(vector-ref (animation-frames animation) index))
(define (animation-length animation)
"Returns the number of frames in the animation"
(vector-length (animation-frames animation)))
(export make-animation
animation?
animation-frames
animation-duration
animation-loop?
animation-frame
animation-length)
;; The <animation-state> type encapsulates the state for playing an
;; animation.
(define-record-type <animation-state>
(%make-animation-state animation frame-index frame-time playing)
animation-state?
(animation animation-state-animation)
(frame-index animation-state-frame-index)
(frame-time animation-state-frame-time)
(playing animation-state-playing?))
(define (make-animation-state animation)
"Creates a new animation state object."
(%make-animation-state animation 0 0 #t))
(define (tick-animation-state state)
"Increments the frame time for the animation state and determines
which frame to show. Returns a new animation state object when the
animation is playing. Otherwise the state passed in is returned."
(let ((frame-time (1+ (animation-state-frame-time state)))
(frame-index (animation-state-frame-index state))
(playing (animation-state-playing? state))
(animation (animation-state-animation state)))
;; Return the same state object if the animation is not playing.
(cond ((not playing)
state)
;; Return a new state object with a reset frame-index and
;; frame-time if we've reached the end of the animation.
;; Stops playing the animation if the animation does not
;; loop.
((and playing (= frame-time (animation-duration animation)))
(let* ((frame-index (modulo (1+ frame-index)
(animation-length animation)))
(frame-time 0)
(playing (or (not (= frame-index 0))
(animation-loop? animation))))
(%make-animation-state animation frame-index frame-time playing)))
;; Return a new state object with an incremented frame index.
(else
(%make-animation-state animation frame-index frame-time playing)))))
(define (animation-state-frame state)
"Returns the texture or texture region for the state's animation at
the current frame index."
(animation-frame (animation-state-animation state)
(animation-state-frame-index state)))
(export make-animation-state
animation-state?
animation-state-animation
animation-state-frame-index
animation-state-frame-time
animation-state-playing?
animation-state-frame
tick-animation-state)
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