From 13a438c91ecb24d0966f1464e30e8eb1b9634370 Mon Sep 17 00:00:00 2001
From: Camilla Berglund <elmindreda@elmindreda.org>
Date: Thu, 9 Feb 2012 01:53:26 +0100
Subject: [PATCH] Replaced NSDate time source with mach_absolute_time.

---
 readme.html          |  1 +
 src/cocoa_init.m     |  2 ++
 src/cocoa_platform.h |  6 +++++-
 src/cocoa_time.m     | 38 ++++++++++++++++++++++++++++++++++----
 4 files changed, 42 insertions(+), 5 deletions(-)

diff --git a/readme.html b/readme.html
index eb18fced..19e4285d 100644
--- a/readme.html
+++ b/readme.html
@@ -310,6 +310,7 @@ version of GLFW.</p>
   <li>Bugfix: The FSAA test did not check for the availability of <code>GL_ARB_multisample</code></li>
   <li>[Cocoa] Added support for OpenGL 3.2 core profile in 10.7 Lion and above</li>
   <li>[Cocoa] Added support for joysticks</li>
+  <li>[Cocoa] Replaced <code>NSDate</code> time source with <code>mach_absolute_time</code></li>
   <li>[Cocoa] Bugfix: The loop condition for saving video modes used the wrong index variable</li>
   <li>[Cocoa] Bugfix: The OpenGL framework was not retrieved, making glfwGetProcAddress crash</li>
   <li>[X11] Added support for the <code>GLX_EXT_swap_control</code> extension as an alternative to <code>GLX_SGI_swap_control</code></li>
diff --git a/src/cocoa_init.m b/src/cocoa_init.m
index bf4f7c2e..2c747515 100644
--- a/src/cocoa_init.m
+++ b/src/cocoa_init.m
@@ -230,6 +230,8 @@ int _glfwPlatformInit(void)
     _glfwPlatformGetGammaRamp(&_glfwLibrary.originalRamp);
     _glfwLibrary.currentRamp = _glfwLibrary.originalRamp;
 
+    _glfwInitTimer();
+
     _glfwInitJoysticks();
 
     return GL_TRUE;
diff --git a/src/cocoa_platform.h b/src/cocoa_platform.h
index d5daf775..93492dbb 100644
--- a/src/cocoa_platform.h
+++ b/src/cocoa_platform.h
@@ -85,7 +85,8 @@ typedef struct _GLFWwindowNS
 typedef struct _GLFWlibraryNS
 {
     struct {
-        double t0;
+        double base;
+        double resolution;
     } timer;
 
     // dlopen handle for dynamically loading OpenGL extension entry points
@@ -101,6 +102,9 @@ typedef struct _GLFWlibraryNS
 // Prototypes for platform specific internal functions
 //========================================================================
 
+// Time
+void _glfwInitTimer(void);
+
 // Joystick input
 void _glfwInitJoysticks(void);
 void _glfwTerminateJoysticks(void);
diff --git a/src/cocoa_time.m b/src/cocoa_time.m
index d7e7d2b8..4facbffb 100644
--- a/src/cocoa_time.m
+++ b/src/cocoa_time.m
@@ -29,6 +29,36 @@
 
 #include "internal.h"
 
+#include <mach/mach_time.h>
+
+
+//========================================================================
+// Return raw time
+//========================================================================
+
+static uint64_t getRawTime(void)
+{
+    return mach_absolute_time();
+}
+
+
+//////////////////////////////////////////////////////////////////////////
+//////                       GLFW internal API                      //////
+//////////////////////////////////////////////////////////////////////////
+
+//========================================================================
+// Initialise timer
+//========================================================================
+
+void _glfwInitTimer(void)
+{
+    mach_timebase_info_data_t info;
+    mach_timebase_info(&info);
+
+    _glfwLibrary.NS.timer.resolution = (double) info.numer / (info.denom * 1.0e9);
+    _glfwLibrary.NS.timer.base = getRawTime();
+}
+
 
 //////////////////////////////////////////////////////////////////////////
 //////                       GLFW platform API                      //////
@@ -40,8 +70,8 @@
 
 double _glfwPlatformGetTime(void)
 {
-    return [NSDate timeIntervalSinceReferenceDate] -
-           _glfwLibrary.NS.timer.t0;
+    return (double) (getRawTime() - _glfwLibrary.NS.timer.base) *
+        _glfwLibrary.NS.timer.resolution;
 }
 
 //========================================================================
@@ -50,7 +80,7 @@ double _glfwPlatformGetTime(void)
 
 void _glfwPlatformSetTime(double time)
 {
-    _glfwLibrary.NS.timer.t0 =
-        [NSDate timeIntervalSinceReferenceDate] - time;
+    _glfwLibrary.NS.timer.base = getRawTime() -
+        (uint64_t) (time / _glfwLibrary.NS.timer.resolution);
 }