summaryrefslogtreecommitdiff
path: root/2d/game.scm
blob: b59ddee873fc2bbd81221842331823de9d2ba219 (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
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
;;; 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-2)
  #:use-module (srfi srfi-9)
  #:use-module ((sdl sdl) #:prefix SDL:)
  #:use-module (figl gl)
  #:use-module (2d agenda)
  #:use-module (2d coroutine)
  #:use-module (2d game)
  #:use-module (2d mvars)
  #:use-module (2d repl server)
  #:use-module (2d repl repl)
  #:use-module (2d signals)
  #:use-module (2d vector2)
  #:use-module (2d window)
  #:export (<game>
            make-game
            game?
            game-title
            game-resolution
            game-fullscreen?
            current-fps
            run-game
            quit-game
            pause-game
            resume-game
            game-running?
            game-paused?))

;;;
;;; Games
;;;

(define-record-type <game>
  (%make-game title resolution fullscreen? draw)
  game?
  (title game-title)
  (resolution game-resolution)
  (fullscreen? game-fullscreen?)
  (draw game-draw))

(define (default-draw)
  #f)

(define* (make-game #:optional #:key
                    (title "A Guile-2D Game")
                    (resolution (vector2 640 480))
                    (fullscreen? #f)
                    (draw default-draw))
  "Return a new game. All game properties have some reasonable default
value."
  (%make-game title resolution fullscreen? draw))

(define (draw-game game)
  ((game-draw game)))

(define (run-game game)
  "Open a window and start the game loop for GAME."
  (open-window (game-title game)
               (game-resolution game)
               (game-fullscreen? game))
  (set! running? #t)
  (resume-game)
  (spawn-server)
  (game-loop game (SDL:get-ticks) 0)
  (close-window))

;;;
;;; Game Loop
;;;

(define running? #f)
(define paused? #f)

(define (update-and-render game dt accumulator)
  (let ((remainder (update accumulator)))
    (run-repl)
    (draw game dt)
    remainder))

(define (tick game dt accumulator)
  "Advance the game by one frame."
  (if paused?
      (begin
        (run-repl)
        (SDL:delay tick-interval)
        accumulator)
      (catch #t
        (lambda ()
          (update-and-render game dt accumulator))
        (lambda (key . args)
          (pause-game)
          accumulator)
        (lambda (key . args)
          (display-backtrace (make-stack #t)
                             (current-output-port))))))

(define (game-loop game last-time accumulator)
  "Update game state, and render. LAST-TIME is the time in
milliseconds of the last iteration of the loop. ACCUMULATOR is the
time in milliseconds that has passed since the last game update."
  (when running?
    (let* ((current-time (SDL:get-ticks))
           (dt (- current-time last-time))
           (accumulator (+ accumulator dt)))
      (game-loop game current-time (tick game dt accumulator)))))

(define (game-running?)
  running?)

(define (game-paused?)
  paused?)

(define (pause-game)
  "Pauses the game loop. Useful when developing."
  (set! paused? #t))

(define (resume-game)
  "Resumes the game loop."
  (set! paused? #f))

(define (quit-game)
  "Finish the current frame and terminate the game loop."
  (set! running? #f))

;;;
;;; Constants
;;;

(define target-fps 60)
(define tick-interval (floor (/ 1000 target-fps)))

;;;
;;; Event Handling
;;;

;; By default, pressing the escape key will pop the current scene, and
;; closing the window will quit the game.
;; (default-events `((key-down . ,(lambda (state key mod unicode)
;;                                  (when (eq? key 'escape)
;;                                    (pop-scene))))
;;                   (quit . ,(lambda (state)
;;                              (quit-game)))))

(define handle-events
  (let ((e (SDL:make-event)))
    (lambda ()
      "Handle all events in the SDL event queue."
      (while (SDL:poll-event e)
        (handle-event e)))))

(define-public window-size (signal-identity (vector2 0 0)))
(define-public key-down (signal-identity))
(define-public key-up (signal-identity))
(define-public mouse-position (signal-identity (vector2 0 0)))
(define-public mouse-down (signal-identity))
(define-public mouse-up (signal-identity))

(define-public (key-is-down key)
  (make-signal (lambda (value prev from)
                 (cond ((and (eq? from key-down)
                             (eq? value key))
                        #t)
                       ((and (eq? from key-up)
                             (eq? value key))
                        #f)
                       (else
                        prev)))
               #:connectors (list key-down key-up)))

(define (handle-event e)
  "Call the relevant callbacks for the event E."
  (case (SDL:event:type e)
    ((active)
     #f)
    ((video-resize)
     (signal-set! window-size (vector2 (SDL:event:resize:w e)
                                       (SDL:event:resize:h e))))
    ((quit)
     (quit-game))
    ((key-down)
     (signal-set! key-down (SDL:event:key:keysym:sym e)))
    ((key-up)
     (signal-set! key-up (SDL:event:key:keysym:sym e)))
    ((mouse-motion)
     (signal-set! mouse-position
                  (vector2 (SDL:event:motion:x e)
                           (SDL:event:motion:y e))))
    ((mouse-button-down)
     (signal-set! mouse-down
                  (list (SDL:event:button:button e)
                        (SDL:event:button:x e)
                        (SDL:event:button:y e))))
    ((mouse-button-up)
     (signal-set! mouse-up
                  (list (SDL:event:button:button e)
                        (SDL:event:button:x e)
                        (SDL:event:button:y e))))))

;;;
;;; Frames Per Second
;;;

(define game-fps 0)

(define accumulate-fps!
  (let* ((elapsed-time 0)
         (fps 0))
    (lambda (dt)
      "Increment the frames-per-second counter. Resets to 0 every
second."
      (let ((new-time (+ elapsed-time dt))
            (new-fps (1+ fps)))
        (if (>= new-time 1000)
            (begin
              (set! game-fps new-fps)
              (set! fps 0)
              (set! elapsed-time 0))
            (begin
              (set! fps new-fps)
              (set! elapsed-time new-time)))))))

(define (current-fps)
  "Return the current FPS value."
  game-fps)

;;;
;;; Update and Draw
;;;

(define (draw game dt)
  "Render a frame."
  (set-gl-matrix-mode (matrix-mode modelview))
  (gl-load-identity)
  (gl-clear (clear-buffer-mask color-buffer depth-buffer))
  (draw-game game)
  (SDL:gl-swap-buffers)
  (accumulate-fps! dt))

(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
        (handle-events)
        (update-agenda)
        ;; (update-stage stage)
        (update (- accumulator tick-interval)))
      accumulator))

;;;
;;; REPL
;;;

(define (run-repl-thunk thunk input output error stack)
  "Run THUNK with the given REPL STACK. I/O is redirected to the given
INPUT, OUTPUT, and ERROR ports."
  (put-mvar
   repl-output-mvar
   (with-input-from-port input
     (lambda ()
       (with-output-to-port output
         (lambda ()
           (with-error-to-port error
             (lambda ()
               (with-fluids ((*repl-stack* stack))
                 (thunk))))))))))

(define (run-repl)
  "Execute a thunk from the REPL is there is one."
  (unless (mvar-empty? repl-input-mvar)
    (and-let* ((vals (try-take-mvar repl-input-mvar)))
              (apply run-repl-thunk vals))))