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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)
#:use-module (2d coroutine)
#:use-module (2d repl server)
#: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
current-fps))
(define target-fps 60)
(define *fps* 0)
(define tick-interval (floor (/ 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)))))
;;;
;;; Frames Per Second
;;;
(define accumulate-fps!
(let* ((frame-time 0)
(alpha 1/5)
(inverse-alpha (- 1 alpha)))
(lambda (dt)
"Computes a weighted average FPS."
(set! frame-time (+ (* alpha dt) (* inverse-alpha frame-time)))
(unless (zero? frame-time)
(set! *fps* (/ 1000 frame-time))))))
(define (current-fps)
"Returns the current FPS value."
*fps*)
(codefine (show-fps)
"Display the current FPS every second."
(wait 60)
(pk 'FPS (floor *fps*))
(show-fps))
;;;
;;; 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 (update accumulator)
"Call the update callback. The update callback will be called as
many times as tick-interval can divide accumulator. The return value
is the unused accumulator time."
(if (>= accumulator tick-interval)
(begin
(run-hook on-update-hook)
(update-agenda)
(update (- accumulator tick-interval)))
accumulator))
(define (time-left current-time next-time)
(max (floor (- next-time current-time)) 0))
;;;
;;; Game Loop
;;;
(define (game-loop last-time next-time accumulator)
"Runs input, render, and update hooks."
(handle-events)
(let* ((time (SDL:get-ticks))
(dt (- time last-time))
(accumulator (+ accumulator dt))
(remainder (update accumulator)))
(render)
(accumulate-fps! dt)
;; Sleep for a bit if there's time in between frames
(SDL:delay (time-left (SDL:get-ticks) next-time))
(game-loop time
(+ next-time tick-interval)
remainder)))
(define (run-game-loop)
"Spawns a REPL server and starts the main game loop."
(spawn-server)
(agenda-schedule show-fps)
(let ((time (SDL:get-ticks)))
(game-loop time (+ time tick-interval) 0)))
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