Rename game loop procedures and remove parameter.

* 2d/game.scm (tick-interval): No longer a parameter.
  (run-game-loop, start-game-loop): Rename.
  (quit-game, stop-game-loop): Rename.

* examples/animation.scm: Use start-game-loop and stop-game-loop.

* examples/common.scm: Use start-game-loop and stop-game-loop.

* examples/coroutine.scm: Use start-game-loop and stop-game-loop.

* examples/font.scm: Use start-game-loop and stop-game-loop.

* examples/guile-2048/guile-2048.scm: Use start-game-loop and stop-game-loop.

* examples/particles.scm: Use start-game-loop and stop-game-loop.

* examples/simple.scm: Use start-game-loop and stop-game-loop.

* examples/tilemap.scm: Use start-game-loop and stop-game-loop.

9 files changed, 31 insertions, 32 deletions

diff --git a/2d/game.scm b/2d/game.scm
index 14543e8..b25cd1d 100644
--- a/2d/game.scm
+++ b/2d/game.scm
@@ -29,33 +29,21 @@
   #:use-module (2d event)
   #:use-module (2d signal)
   #:use-module (2d window)
-  #:export (ticks-per-second
-            tick-interval
+  #:export (tick-interval
             game-agenda
             draw-hook
-            run-game-loop
-            quit-game))
+            start-game-loop
+            stop-game-loop))
 
 ;;;
 ;;; Game Loop
 ;;;
 
-(define ticks-per-second 60)
-(define tick-interval (make-parameter 0))
+;; Update 60 times per second by default.
+(define tick-interval (floor (/ 1000 60)))
 (define draw-hook (make-hook 2))
 (define game-agenda (make-agenda))
 
-(define (run-game-loop)
-  "Start the game loop."
-  (parameterize ((tick-interval (floor (/ 1000 ticks-per-second))))
-    (call-with-prompt
-     'game-loop-prompt
-     (lambda ()
-       (game-loop (SDL:get-ticks) 0))
-     (lambda (cont callback)
-       (when (procedure? callback)
-         (callback cont))))))
-
 (define (draw dt alpha)
   "Render a frame."
   (let ((width (signal-ref window-width))
@@ -69,20 +57,20 @@
   "Call the update callback. The update callback will be called as
 many times as tick-interval can divide LAG. The return value
 is the unused accumulator time."
-  (if (>= lag (tick-interval))
+  (if (>= lag tick-interval)
       (begin
         (tick-agenda! game-agenda)
-        (update (- lag (tick-interval))))
+        (update (- lag tick-interval)))
       lag))
 
 (define (alpha lag)
   "Calculate interpolation factor in the range [0, 1] for the
 leftover frame time LAG."
-  (/ lag (tick-interval)))
+  (/ lag tick-interval))
 
 (define (frame-sleep time)
   "Sleep for the remainder of the frame that started at TIME."
-  (let ((t (- (+ time (tick-interval))
+  (let ((t (- (+ time tick-interval)
               (SDL:get-ticks))))
     (usleep (max 0 (* t 1000)))))
 
@@ -97,5 +85,16 @@ milliseconds of the last iteration of the game loop."
       (frame-sleep current-time)
       (game-loop current-time lag))))
 
-(define (quit-game)
+(define (start-game-loop)
+  "Start the game loop."
+  (call-with-prompt
+   'game-loop-prompt
+   (lambda ()
+     (game-loop (SDL:get-ticks) 0))
+   (lambda (cont callback)
+     (when (procedure? callback)
+       (callback cont)))))
+
+(define (stop-game-loop)
+  "Abort the game loop."
   (abort-to-prompt 'game-loop-prompt #f))
diff --git a/examples/animation.scm b/examples/animation.scm
index d72637c..8be77ef 100644
--- a/examples/animation.scm
+++ b/examples/animation.scm
@@ -44,4 +44,4 @@ sprite out of it."
 (add-hook! draw-hook (lambda (dt alpha) (draw-sprite sprite)))
 
 (with-window (make-window #:title "Animation")
-  (run-game-loop))
+  (start-game-loop))
diff --git a/examples/common.scm b/examples/common.scm
index b26186a..0acb6c2 100644
--- a/examples/common.scm
+++ b/examples/common.scm
@@ -29,9 +29,9 @@
 
 (add-hook! key-press-hook (lambda (key unicode)
                             (when (eq? key 'escape)
-                              (quit-game))))
+                              (stop-game-loop))))
 
-(add-hook! window-close-hook quit-game)
+(add-hook! window-close-hook stop-game-loop)
 
 (schedule-interval game-agenda
                    (lambda ()
diff --git a/examples/coroutine.scm b/examples/coroutine.scm
index cb2f929..98dec16 100644
--- a/examples/coroutine.scm
+++ b/examples/coroutine.scm
@@ -47,4 +47,4 @@
 (with-window (make-window #:title "Coroutines"
                           #:resolution (vector2 window-width
                                                 window-height))
-  (run-game-loop))
+  (start-game-loop))
diff --git a/examples/font.scm b/examples/font.scm
index a48bc37..304070f 100644
--- a/examples/font.scm
+++ b/examples/font.scm
@@ -52,4 +52,4 @@
                        (draw-label (signal-ref mouse-label))))
 
 (with-window (make-window #:title "Fonts")
-  (run-game-loop))
+  (start-game-loop))
diff --git a/examples/guile-2048/guile-2048.scm b/examples/guile-2048/guile-2048.scm
index d5ded0a..637650b 100755
--- a/examples/guile-2048/guile-2048.scm
+++ b/examples/guile-2048/guile-2048.scm
@@ -475,8 +475,8 @@
 
 (start-2d-repl)
 
-(add-hook! window-close-hook quit-game)
+(add-hook! window-close-hook stop-game-loop)
 (add-hook! draw-hook (lambda (dt alpha) (render)))
 
 (with-window (make-window #:title "2048")
-  (run-game-loop))
+  (start-game-loop))
diff --git a/examples/particles.scm b/examples/particles.scm
index 648bab7..d811eb7 100644
--- a/examples/particles.scm
+++ b/examples/particles.scm
@@ -82,4 +82,4 @@
 (with-window (make-window #:title "Particles"
                           #:resolution (vector2 window-width
                                                 window-height))
-  (run-game-loop))
+  (start-game-loop))
diff --git a/examples/simple.scm b/examples/simple.scm
index 2cc85f9..a2c1fa4 100644
--- a/examples/simple.scm
+++ b/examples/simple.scm
@@ -28,4 +28,4 @@
 (add-hook! draw-hook (lambda (dt alpha) (draw-sprite sprite)))
 
 (with-window (make-window #:title "Simple Sprite Demo")
-  (run-game-loop))
+  (start-game-loop))
diff --git a/examples/tilemap.scm b/examples/tilemap.scm
index 9125abf..284c760 100644
--- a/examples/tilemap.scm
+++ b/examples/tilemap.scm
@@ -104,4 +104,4 @@
 (add-hook! draw-hook (lambda (dt alpha) (draw-map-layer layer)))
 
 (with-window (make-window #:title "Tilemap")
-  (run-game-loop))
+  (start-game-loop))