From c70443c83a5a337d082fc58e0067a5f14cfae805 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson@vistahigherlearning.com>
Date: Tue, 15 Dec 2020 20:02:31 -0500
Subject: Use a more precise timer.

---
 guix.scm             | 12 +++++-------
 starling/kernel.scm  |  2 +-
 starling/node-2d.scm |  6 ++++--
 starling/system.scm  |  5 ++++-
 4 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/guix.scm b/guix.scm
index f6380cd..a52a052 100644
--- a/guix.scm
+++ b/guix.scm
@@ -90,7 +90,7 @@
                (invoke "autoreconf" "-vfi")))))))))
 
 (define guile-sdl2
-  (let ((commit "ed821d76b70a1454285d415dfae7db9394c535f2"))
+  (let ((commit "5b965d180a1f536affd51ffc2b51d5e90fbc362d"))
     (package
       (name "guile-sdl2")
       (version (string-append "0.5.0-1." (string-take commit 7)))
@@ -101,7 +101,7 @@
                       (commit commit)))
                 (sha256
                  (base32
-                  "1kh3hzf2lmpf773hbxzb0g7c0ghqydp9s969sigg58l8wbr85iyf"))))
+                  "13x93kmpb9qp2zhp3ff3878xp2cj3z6gclmxqahyqj7fkxy1ffg5"))))
       (build-system gnu-build-system)
       (arguments
        '(#:make-flags '("GUILE_AUTO_COMPILE=0")
@@ -118,9 +118,7 @@
       (inputs
        `(("guile" ,target-guile)
          ("sdl2" ,sdl2)
-         ("sdl2-image" ,sdl2-image)
-         ("sdl2-mixer" ,sdl2-mixer)
-         ("sdl2-ttf" ,sdl2-ttf)))
+         ("sdl2-image" ,sdl2-image)))
       (synopsis "Guile bindings for SDL2")
       (description "Guile-sdl2 provides pure Guile Scheme bindings to the
 SDL2 C shared library via the foreign function interface.")
@@ -128,7 +126,7 @@ SDL2 C shared library via the foreign function interface.")
       (license license:lgpl3+))))
 
 (define chickadee
-  (let ((commit "5610b6a4a23855680d0d105b85f35a79d4015124"))
+  (let ((commit "8726cc42e3e7e5e6f34f7328898e35ed207bfb08"))
     (package
      (name "chickadee")
      (version (string-append "0.5.0-1." (string-take commit 7)))
@@ -139,7 +137,7 @@ SDL2 C shared library via the foreign function interface.")
                     (commit commit)))
               (sha256
                (base32
-                "0kki4lr5qbirikfa3axdn330iczzxczf67vmizl6xj7pkgk0kxgv"))))
+                "11l79c4365xlnkk53ma52pjzhphvq8xa9bd6qfxr1whklhi66isj"))))
      (build-system gnu-build-system)
      (arguments
       '(#:make-flags '("GUILE_AUTO_COMPILE=0")
diff --git a/starling/kernel.scm b/starling/kernel.scm
index e302df1..52d7adb 100644
--- a/starling/kernel.scm
+++ b/starling/kernel.scm
@@ -331,7 +331,7 @@
   (abort-game))
 
 (define-method (fps kernel)
-  (/ 1000.0 (avg-frame-time kernel)))
+  (/ 1.0 (avg-frame-time kernel)))
 
 (define-method (boot-kernel (kernel <kernel>) thunk)
   (sdl-init)
diff --git a/starling/node-2d.scm b/starling/node-2d.scm
index 6d83da2..f7a40df 100644
--- a/starling/node-2d.scm
+++ b/starling/node-2d.scm
@@ -39,6 +39,7 @@
   #:use-module (chickadee scripting)
   #:use-module (ice-9 match)
   #:use-module (oop goops)
+  #:use-module (rnrs base)
   #:use-module (starling asset)
   #:use-module (starling node)
   #:use-module (starling scene)
@@ -499,8 +500,9 @@
          (frame-duration (frame-duration anim))
          (frames (frames anim))
          (anim-duration (* frame-duration (vector-length frames)))
-         (time (modulo (- (elapsed-time) (start-time sprite)) anim-duration))
-         (frame (vector-ref frames (floor (/ time frame-duration)))))
+         (time (mod (- (elapsed-time) (start-time sprite)) anim-duration))
+         (frame (vector-ref frames (inexact->exact
+                                    (floor (/ time frame-duration))))))
     (set! (index sprite) frame)
     (next-method)))
 
diff --git a/starling/system.scm b/starling/system.scm
index 293d92d..a33647d 100644
--- a/starling/system.scm
+++ b/starling/system.scm
@@ -28,8 +28,11 @@
             current-window
             current-window-size))
 
+(define %time-freq (exact->inexact (sdl-performance-frequency)))
+
 (define (elapsed-time)
-  (sdl-ticks))
+  "Return the current value of the system timer in seconds."
+  (/ (sdl-performance-counter) %time-freq))
 
 (define current-window (make-parameter #f))
 
-- 
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