blob: 374feb03f572003ad0c8bf9d6963de4aecfdf6df (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
|
;;; 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 data structure.
;;
;;; Code:
(define-module (2d game)
#:use-module (srfi srfi-9)
#:use-module ((sdl sdl) #:prefix SDL:)
#:use-module (figl gl)
#:use-module (2d agenda)
#:use-module (2d event)
#:use-module (2d signal)
#:use-module (2d window)
#:export (ticks-per-second
tick-interval
game-agenda
paused-agenda
draw-hook
run-game-loop
quit-game
pause-game
resume-game
game-running?
game-paused?))
;;;
;;; Game Loop
;;;
;; Possible states are:
;; * stopped
;; * running
;; * paused
(define game-loop-status (make-parameter 'stopped))
(define ticks-per-second 60)
(define tick-interval (make-parameter 0))
(define draw-hook (make-hook 2))
(define accumulator (make-parameter 0))
(define game-agenda (make-agenda))
;; This agenda is only ticked when the game loop is in the paused
;; state. Useful for things like the REPL that should be run even
;; though the game is paused.
(define paused-agenda (make-agenda))
(define (run-game-loop)
"Start the game loop."
(parameterize ((game-loop-status 'running)
(tick-interval (floor (/ 1000 ticks-per-second)))
(accumulator 0))
(game-loop (SDL:get-ticks))))
(define (draw dt alpha)
"Render a frame."
(let ((width (signal-ref window-width))
(height (signal-ref window-height)))
(gl-viewport 0 0 width height))
(gl-clear (clear-buffer-mask color-buffer depth-buffer))
(run-hook draw-hook dt alpha)
(SDL:gl-swap-buffers))
(define (update)
"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."
(while (>= (accumulator) (tick-interval))
(process-events)
(tick-agenda! game-agenda)
(accumulator (- (accumulator) (tick-interval)))))
(define (alpha)
(/ (accumulator) (tick-interval)))
(define (update-and-render dt)
(update)
(draw dt (alpha)))
(define (tick dt)
"Advance the game by one frame."
(if (game-paused?)
(begin
(tick-agenda! paused-agenda)
(SDL:delay (tick-interval))
accumulator)
(catch #t
(lambda ()
(update-and-render dt))
(lambda (key . args)
(pause-game)
accumulator)
(lambda (key . args)
(display-backtrace (make-stack #t)
(current-output-port))))))
(define (game-loop last-time)
"Update game state, and render. LAST-TIME is the time in
milliseconds of the last iteration of the loop."
(when (game-running?)
(let* ((current-time (SDL:get-ticks))
(dt (- current-time last-time)))
(accumulator (+ (accumulator) dt))
(tick dt)
(game-loop current-time))))
;;;
;;; State management
;;;
(define (game-running?)
(or (eq? (game-loop-status) 'running)
(eq? (game-loop-status) 'paused)))
(define (game-paused?)
(eq? (game-loop-status) 'paused))
(define (pause-game)
"Pauses the game loop. Useful when developing."
(game-loop-status 'paused))
(define (resume-game)
"Resumes the game loop."
(when (game-paused?)
(game-loop-status 'running)))
(define (quit-game)
"Finish the current frame and terminate the game loop."
(game-loop-status 'stopped))
|
