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-rw-r--r--sly/game.scm11
1 files changed, 11 insertions, 0 deletions
diff --git a/sly/game.scm b/sly/game.scm
index 615f934..38d230e 100644
--- a/sly/game.scm
+++ b/sly/game.scm
@@ -40,6 +40,7 @@
draw-hook
after-game-loop-error-hook
game-started?
+ on-start
run-game-loop
stop-game-loop))
@@ -56,6 +57,16 @@
(define-signal game-started?
(hook->signal game-start-hook #f (lambda () #t)))
+(define-syntax on-start
+ (syntax-rules ()
+ "Create a signal that evaluates EXP once the game loop has started.
+If INIT is specified, the signal uses the result of this expression as
+its initial value, otherwise #f is the initial value."
+ ((_ exp)
+ (signal-if game-started? exp #f))
+ ((_ exp init)
+ (signal-if game-started? exp init))))
+
;;;
;;; Game Loop