From eede75fe5e8320bd0962ad40c6eebb486267e7e1 Mon Sep 17 00:00:00 2001
From: Camilla Berglund <elmindreda@elmindreda.org>
Date: Tue, 20 Sep 2011 00:55:20 +0200
Subject: [PATCH] Added initial support for CLOCK_MONOTONIC.

---
 readme.html        |  1 +
 src/x11_init.c     |  3 ++
 src/x11_platform.h |  5 ++--
 src/x11_time.c     | 68 ++++++++++++++++++++++++++++++----------------
 4 files changed, 51 insertions(+), 26 deletions(-)

diff --git a/readme.html b/readme.html
index b933810a..8a7303e9 100644
--- a/readme.html
+++ b/readme.html
@@ -309,6 +309,7 @@ version of GLFW.</p>
   <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>
+  <li>[X11] Added the POSIX <code>CLOCK_MONOTONIC</code> time source as the preferred method</li>
   <li>[X11] Bugfix: Calling <code>glXCreateContextAttribsARB</code> with an unavailable OpenGL version caused the application to terminate with a <code>BadMatch</code> Xlib error</li>
   <li>[Win32] Removed explicit support for versions of Windows older than Windows XP</li>
   <li>[Win32] Bugfix: Window activation and iconification did not work as expected</li>
diff --git a/src/x11_init.c b/src/x11_init.c
index 03cc617f..9af7783e 100644
--- a/src/x11_init.c
+++ b/src/x11_init.c
@@ -639,6 +639,9 @@ const char* _glfwPlatformGetVersionString(void)
 #else
         " no-extension-support"
 #endif
+#if defined(_POSIX_TIMERS) && defined(_POSIX_MONOTONIC_CLOCK)
+        " clock_gettime"
+#endif
 #if defined(_GLFW_USE_LINUX_JOYSTICKS)
         " Linux-joystick-API"
 #else
diff --git a/src/x11_platform.h b/src/x11_platform.h
index df7cdb15..b3cf642e 100644
--- a/src/x11_platform.h
+++ b/src/x11_platform.h
@@ -31,9 +31,9 @@
 #ifndef _platform_h_
 #define _platform_h_
 
-#include <sys/time.h>
 #include <unistd.h>
 #include <signal.h>
+#include <stdint.h>
 #include <X11/Xlib.h>
 #include <X11/keysym.h>
 #include <X11/Xatom.h>
@@ -220,8 +220,9 @@ typedef struct _GLFWlibraryX11
 
     // Timer data
     struct {
+        GLboolean   monotonic;
         double      resolution;
-        long long   t0;
+        uint64_t    t0;
     } timer;
 
 #if defined(_GLFW_DLOPEN_LIBGL)
diff --git a/src/x11_time.c b/src/x11_time.c
index ab7d0c40..431389c4 100644
--- a/src/x11_time.c
+++ b/src/x11_time.c
@@ -30,6 +30,33 @@
 
 #include "internal.h"
 
+#include <time.h>
+
+
+//========================================================================
+// Return raw time
+//========================================================================
+
+static uint64_t getRawTime(void)
+{
+#if defined(_POSIX_TIMERS) && defined(_POSIX_MONOTONIC_CLOCK)
+    if (_glfwLibrary.X11.timer.monotonic)
+    {
+        struct timespec ts;
+
+        clock_gettime(CLOCK_MONOTONIC, &ts);
+        return (uint64_t) ts.tv_sec * (uint64_t) 1000000000 + (uint64_t) ts.tv_nsec;
+    }
+    else
+#endif
+    {
+        struct timeval tv;
+
+        gettimeofday(&tv, NULL);
+        return (uint64_t) tv.tv_sec * (uint64_t) 1000000 + (uint64_t) tv.tv_usec;
+    }
+}
+
 
 //========================================================================
 // Initialise timer
@@ -37,15 +64,21 @@
 
 void _glfwInitTimer(void)
 {
-    struct timeval tv;
+#if defined(_POSIX_TIMERS) && defined(_POSIX_MONOTONIC_CLOCK)
+    struct timespec ts;
 
-    // "Resolution" is 1 us
-    _glfwLibrary.X11.timer.resolution = 1e-6;
+    if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0)
+    {
+        _glfwLibrary.X11.timer.monotonic = GL_TRUE;
+        _glfwLibrary.X11.timer.resolution = 1e-9;
+    }
+    else
+#endif
+    {
+        _glfwLibrary.X11.timer.resolution = 1e-6;
+    }
 
-    // Set start-time for timer
-    gettimeofday(&tv, NULL);
-    _glfwLibrary.X11.timer.t0 = (long long) tv.tv_sec * (long long) 1000000 +
-		                        (long long) tv.tv_usec;
+    _glfwLibrary.X11.timer.t0 = getRawTime();
 }
 
 
@@ -59,14 +92,8 @@ void _glfwInitTimer(void)
 
 double _glfwPlatformGetTime(void)
 {
-    long long t;
-    struct timeval tv;
-
-    gettimeofday(&tv, NULL);
-    t = (long long) tv.tv_sec * (long long) 1000000 +
-	(long long) tv.tv_usec;
-
-    return (double)(t - _glfwLibrary.X11.timer.t0) * _glfwLibrary.X11.timer.resolution;
+    return (double) (getRawTime() - _glfwLibrary.X11.timer.t0) *
+        _glfwLibrary.X11.timer.resolution;
 }
 
 
@@ -76,14 +103,7 @@ double _glfwPlatformGetTime(void)
 
 void _glfwPlatformSetTime(double t)
 {
-    long long t0;
-    struct timeval  tv;
-
-    gettimeofday(&tv, NULL);
-    t0 = (long long) tv.tv_sec * (long long) 1000000 +
-	 (long long) tv.tv_usec;
-
-    // Calulate new starting time
-    _glfwLibrary.X11.timer.t0 = t0 - (long long)(t / _glfwLibrary.X11.timer.resolution);
+    _glfwLibrary.X11.timer.t0 = getRawTime() -
+        (uint64_t) (t / _glfwLibrary.X11.timer.resolution);
 }