From 257b4c2498640dc31c3d807e04c1637cf5ba4967 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson@member.fsf.org>
Date: Thu, 24 Apr 2014 21:22:06 -0400
Subject: Run game loop with a prompt.

* 2d/game.scm (game-loop-status, game-running?, game-paused?)
  (pause-game, resume-game, paused-agenda): Delete.
  (run-game-loop): Call game loop with prompt.
  (quit-game): Abort to game loop prompt.
---
 2d/game.scm | 63 ++++++++++++++++---------------------------------------------
 1 file changed, 16 insertions(+), 47 deletions(-)

(limited to '2d/game.scm')

diff --git a/2d/game.scm b/2d/game.scm
index 770d3b1..7f24193 100644
--- a/2d/game.scm
+++ b/2d/game.scm
@@ -32,38 +32,29 @@
   #: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?))
+            quit-game))
 
 ;;;
 ;;; 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 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))))
-    (game-loop (SDL:get-ticks) 0)))
+  (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."
@@ -90,34 +81,12 @@ is the unused accumulator time."
 (define (game-loop previous-time lag)
   "Update game state, and render.  PREVIOUS-TIME is the time in
 milliseconds of the last iteration of the game loop."
-  (when (game-running?)
-    (let* ((current-time (SDL:get-ticks))
-           (dt (- current-time previous-time)))
-      (process-events)
-      (let ((lag (update (+ lag dt))))
-        (draw dt (alpha lag))
-        (game-loop current-time lag)))))
-
-;;;
-;;; 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)))
+  (let* ((current-time (SDL:get-ticks))
+         (dt (- current-time previous-time)))
+    (process-events)
+    (let ((lag (update (+ lag dt))))
+      (draw dt (alpha lag))
+      (game-loop current-time lag))))
 
 (define (quit-game)
-  "Finish the current frame and terminate the game loop."
-  (game-loop-status 'stopped))
+  (abort-to-prompt 'game-loop-prompt #f))
-- 
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