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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:
;;
;; Game loop.
;;
;;; Code:
(define-module (2d game-loop)
#:use-module ((sdl sdl) #:prefix SDL:)
#:use-module (figl gl)
#:use-module (2d agenda)
#:export (on-active-hook
on-resize-hook
on-quit-hook
on-render-hook
on-update-hook
on-key-up-hook
on-key-down-hook
on-mouse-motion-hook
on-mouse-button-down-hook
on-mouse-button-up-hook
run-game-loop))
(define target-fps 60)
(define frame-interval (/ 1000 target-fps))
;;;
;;; Hooks
;;;
(define on-active-hook (make-hook))
(define on-resize-hook (make-hook 2))
(define on-quit-hook (make-hook))
(define on-render-hook (make-hook))
(define on-update-hook (make-hook))
(define on-key-up-hook (make-hook 3))
(define on-key-down-hook (make-hook 3))
(define on-mouse-motion-hook (make-hook 5))
(define on-mouse-button-down-hook (make-hook 3))
(define on-mouse-button-up-hook (make-hook 3))
;;;
;;; Event Handling
;;;
(define handle-events
(let ((e (SDL:make-event)))
(lambda ()
"Handles all events in the SDL event queue."
(while (SDL:poll-event e)
(handle-event e)))))
(define (handle-event e)
"Calls the relevant callback for the event."
(case (SDL:event:type e)
((active)
(run-hook on-active-hook))
((video-resize)
(run-hook on-resize-hook (SDL:event:resize:w e)
(SDL:event:resize:h e)))
((quit)
(run-hook on-quit-hook))
((key-down)
(run-hook on-key-down-hook
(SDL:event:key:keysym:sym e)
(SDL:event:key:keysym:mod e)
(SDL:event:key:keysym:unicode e)))
((key-up)
(run-hook on-key-up-hook
(SDL:event:key:keysym:sym e)
(SDL:event:key:keysym:mod e)
(SDL:event:key:keysym:unicode e)))
((mouse-motion)
(run-hook on-mouse-motion-hook
(SDL:event:motion:state e)
(SDL:event:motion:x e)
(SDL:event:motion:y e)
(SDL:event:motion:xrel e)
(SDL:event:motion:yrel e)))
((mouse-button-down)
(run-hook on-mouse-button-down-hook
(SDL:event:button:button e)
(SDL:event:button:x e)
(SDL:event:button:y e)))
((mouse-button-up)
(run-hook on-mouse-button-up-hook
(SDL:event:button:button e)
(SDL:event:button:x e)
(SDL:event:button:y e)))))
;;;
;;; Update and Render
;;;
(define (render)
"Renders a frame."
(set-gl-matrix-mode (matrix-mode modelview))
(gl-load-identity)
(gl-clear (clear-buffer-mask color-buffer depth-buffer))
(run-hook on-render-hook)
(SDL:gl-swap-buffers))
(define (increment-fps fps fps-time)
"Increment frames-per-second counter. Resets to 0 when the
difference between time and fps-time is greater than or equal to one
second."
(if (>= fps-time 1000)
(begin
(pk 'FPS fps)
0)
(1+ fps)))
(define (update accumulator)
"Call the update callback. The update callback will be called as
many times as frame-interval can divide accumulator. The return value
is the unused accumulator time."
(if (>= accumulator frame-interval)
(begin
(run-hook on-update-hook)
(update-agenda)
(update (- accumulator frame-interval)))
accumulator))
;;;
;;; Game Loop
;;;
(define (run-game-loop)
"Runs event handling, update, and render loop."
(define (game-loop time last-time fps-time accumulator fps)
(handle-events)
(let* ((dt (- time last-time))
(accumulator (+ accumulator dt))
(current-fps-time (+ fps-time dt))
(current-time (SDL:get-ticks)))
;; Update and render when the accumulator reaches the threshold.
(if (>= accumulator frame-interval)
(let ((remainder (update accumulator)))
(render)
(game-loop current-time
time
(modulo current-fps-time 1000)
remainder
(increment-fps fps current-fps-time)))
(game-loop current-time
time
current-fps-time
accumulator
fps))))
(let ((time (SDL:get-ticks)))
(game-loop time time 0 0 0)))
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