From 8726cc42e3e7e5e6f34f7328898e35ed207bfb08 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Tue, 15 Dec 2020 17:59:09 -0500
Subject: Switch to high resolution timer.

---
 chickadee.scm             | 9 +++++----
 chickadee/game-loop.scm   | 2 +-
 doc/api.texi              | 3 +--
 examples/particles.scm    | 2 +-
 examples/path.scm         | 6 +++---
 examples/sprite-batch.scm | 2 +-
 examples/tiled.scm        | 2 +-
 7 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/chickadee.scm b/chickadee.scm
index e00b2b1..611674a 100644
--- a/chickadee.scm
+++ b/chickadee.scm
@@ -77,10 +77,11 @@
             run-game)
   #:re-export (abort-game))
 
+(define %time-freq (exact->inexact (sdl-performance-frequency)))
+
 (define (elapsed-time)
-  "Return the number of milliseconds that have passed since the game
-loop was started."
-  (sdl-ticks))
+  "Return the current value of the system timer in seconds."
+  (/ (sdl-performance-counter) %time-freq))
 
 (define (key-pressed? key)
   "Return #t if KEY is currently being pressed."
@@ -390,7 +391,7 @@ border is disabled, otherwise it is enabled.")
           (run-game* #:update update-sdl
                      #:render render-sdl-opengl
                      #:error error
-                     #:time sdl-ticks
+                     #:time elapsed-time
                      #:update-hz update-hz)))
       (lambda ()
         (quit-audio)
diff --git a/chickadee/game-loop.scm b/chickadee/game-loop.scm
index 09f8a7b..6a14fab 100644
--- a/chickadee/game-loop.scm
+++ b/chickadee/game-loop.scm
@@ -58,7 +58,7 @@
 
 (define* (run-game* #:key update render time error
                     (update-hz 60))
-  (let ((timestep (round (/ 1000 update-hz))))
+  (let ((timestep (/ 1.0 update-hz)))
     (call-with-prompt game-loop-prompt-tag
       (lambda ()
         ;; Catch SIGINT and kill the loop.
diff --git a/doc/api.texi b/doc/api.texi
index e9aa72f..a74d6f2 100644
--- a/doc/api.texi
+++ b/doc/api.texi
@@ -354,8 +354,7 @@ 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.
+Return the current value of the system timer in seconds.
 @end deffn
 
 @node Input Devices
diff --git a/examples/particles.scm b/examples/particles.scm
index 97cdb1d..abefd94 100644
--- a/examples/particles.scm
+++ b/examples/particles.scm
@@ -49,7 +49,7 @@
     (sleep 60)
     (set! stats-text (format #f "particles: ~d   fps: ~1,2f"
                              (particles-size particles)
-                             (/ 1000.0 avg-frame-time))))))
+                             (/ 1.0 avg-frame-time))))))
 
 (define stats-text-pos (vec2 4.0 (- window-height 16.0)))
 (define sprite-position (vec2 (center-x 128.0) (center-y 128.0)))
diff --git a/examples/path.scm b/examples/path.scm
index 0223864..7bad91b 100644
--- a/examples/path.scm
+++ b/examples/path.scm
@@ -10,9 +10,9 @@
 
 (define (stats-message)
   (format #f "fps: ~1,2f"
-          (/ 1000.0 avg-frame-time)))
+          (/ 1.0 avg-frame-time)))
 (define start-time 0.0)
-(define avg-frame-time 16)
+(define avg-frame-time 0.0)
 (define stats-text (stats-message))
 (define stats-text-pos (vec2 4.0 464.0))
 (define last-update start-time)
@@ -67,7 +67,7 @@
           (+ (* (- current-time start-time) 0.1)
              (* avg-frame-time 0.9)))
     (set! start-time current-time)
-    (when (>= (- current-time last-update) 1000)
+    (when (>= (- current-time last-update) 1.0)
       (set! stats-text (stats-message))
       (set! last-update current-time))))
 
diff --git a/examples/sprite-batch.scm b/examples/sprite-batch.scm
index 4b8d433..3aad219 100644
--- a/examples/sprite-batch.scm
+++ b/examples/sprite-batch.scm
@@ -31,7 +31,7 @@
 (define (stats-message)
   (format #f "sprites: ~d   fps: ~1,2f"
           num-sprites
-          (/ 1000.0 avg-frame-time)))
+          (/ 1.0 avg-frame-time)))
 
 (define stats-text (stats-message))
 
diff --git a/examples/tiled.scm b/examples/tiled.scm
index 0f7c4fa..c528f74 100644
--- a/examples/tiled.scm
+++ b/examples/tiled.scm
@@ -16,7 +16,7 @@
 (define text "0, 0")
 (define (stats-message)
   (format #f "fps: ~1,2f"
-          (/ 1000.0 avg-frame-time)))
+          (/ 1.0 avg-frame-time)))
 (define start-time 0.0)
 (define avg-frame-time 16)
 (define stats-text (stats-message))
-- 
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