Add elapsed-time procedure.

2 files changed, 11 insertions, 0 deletions

diff --git a/chickadee.scm b/chickadee.scm
index 10085ae..e2d8624 100644
--- a/chickadee.scm
+++ b/chickadee.scm
@@ -63,6 +63,7 @@
             set-window-size!
             set-window-position!
             set-window-fullscreen!
+            elapsed-time
             controller-button-pressed?
             controller-button-released?
             controller-axis
@@ -76,6 +77,11 @@
             run-game)
   #:re-export (abort-game))
 
+(define (elapsed-time)
+  "Return the number of milliseconds that have passed since the game
+loop was started."
+  (sdl-ticks))
+
 (define (key-pressed? key)
   "Return #t if KEY is currently being pressed."
   (sdl2:key-pressed? key))
diff --git a/doc/api.texi b/doc/api.texi
index cf82b6f..a8bac69 100644
--- a/doc/api.texi
+++ b/doc/api.texi
@@ -353,6 +353,11 @@ behavior is to simply re-throw the error.
 
 @end deffn
 
+@deffn {Procedure} elapsed-time
+Return the number of milliseconds that have passed since the game loop
+was started.
+@end deffn
+
 @node Input Devices
 @subsection Input Devices