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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)
+ #:export (set-render-callback
+ set-update-callback
+ set-key-up-callback
+ set-key-down-callback
+ run-game-loop))
+
+(define target-fps 60)
+
+;;;
+;;; Callbacks
+;;;
+
+(define render-callback (lambda () #t))
+(define update-callback (lambda () #t))
+(define key-up-callback (lambda (key) #t))
+(define key-down-callback (lambda (key) #t))
+
+(define (set-render-callback callback)
+ "Sets the render callback procedure."
+ (set! render-callback callback))
+
+(define (set-update-callback callback)
+ "Sets the update callback procedure."
+ (set! update-callback callback))
+
+(define (set-key-up-callback callback)
+ "Sets the key up callback procedure."
+ (set! key-up-callback callback))
+
+(define (set-key-down-callback callback)
+ "Sets the key down callback procedure."
+ (set! key-down-callback callback))
+
+;;;
+;;; 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)
+ ((SDL_KEYDOWN)
+ (key-down-callback (SDL:event:key:keysym:sym e)))
+ ((SDL_KEYUP)
+ (key-up-callback (SDL:event:key:keysym:sym 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))
+ (render-callback)
+ (SDL:gl-swap-buffers))
+
+(define accumulate-fps
+ (let ((last-time (SDL:get-ticks))
+ (fps 0))
+ (lambda ()
+ "Calculates frames per second."
+ (let ((time (SDL:get-ticks)))
+ (set! fps (1+ fps))
+ (when (>= time (+ last-time 1000))
+ (pk 'FPS fps)
+ (set! last-time time)
+ (set! fps 0))))))
+
+(define update-and-render
+ (let ((last-update (SDL:get-ticks))
+ (update-interval (/ 1000 target-fps)))
+ (lambda ()
+ "Calls update and draw callback when enough time has passed since
+the last tick."
+ (let ((time (SDL:get-ticks)))
+ (when (>= time (+ last-update update-interval))
+ (set! last-update time)
+ (update-callback)
+ (accumulate-fps)
+ (render))))))
+
+;;;
+;;; Game Loop
+;;;
+
+(define (run-game-loop)
+ "Runs event handling, update, and render loop."
+ (while #t
+ (handle-events)
+ (update-and-render)))