Make the eventloop use a monotonic clock, where available.

This avoids bugs where the system time suddenly changes.

configure

@@ -4430,6 +4430,46 @@ if test "x$ac_cv_lib_dl_dlopen" = xyes; then :
   LIBS="$LIBS -ldl"
 fi
 
+   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for clock_gettime in -lrt" >&5
+$as_echo_n "checking for clock_gettime in -lrt... " >&6; }
+if ${ac_cv_lib_rt_clock_gettime+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lrt  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char clock_gettime ();
+int
+main ()
+{
+return clock_gettime ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_rt_clock_gettime=yes
+else
+  ac_cv_lib_rt_clock_gettime=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_rt_clock_gettime" >&5
+$as_echo "$ac_cv_lib_rt_clock_gettime" >&6; }
+if test "x$ac_cv_lib_rt_clock_gettime" = xyes; then :
+  LIBS="$LIBS -lrt"
+fi
+
    ;;
 esac
 

configure.ac

@@ -107,6 +107,7 @@ case "$target" in
    CPPFLAGS="$CFLAGS $PTHREAD_CFLAGS"
    LIBS="$PTHREAD_LIBS $LIBS"
    AC_CHECK_LIB(dl, dlopen, [LIBS="$LIBS -ldl"])
+   AC_CHECK_LIB(rt, clock_gettime, [LIBS="$LIBS -lrt"])
    ;;
 esac
 AC_SUBST([LIBMOWGLI_OS])

src/libmowgli/eventloop/eventloop.h

@@ -162,7 +162,38 @@ static inline time_t mowgli_eventloop_get_time(mowgli_eventloop_t *eventloop)
 
 static inline void mowgli_eventloop_synchronize(mowgli_eventloop_t *eventloop)
 {
-	mowgli_eventloop_set_time(eventloop, time(NULL));
+	long long time_;
+#if defined(CLOCK_MONOTONIC)
+	struct timespec tp;
+
+	clock_gettime(CLOCK_MONOTONIC, &tp);
+	time_ = tp.tv_sec;
+#elif defined(CLOCK_HIGHRES)
+	struct timespec tp;
+
+	clock_gettime(CLOCK_HIGHRES, &tp);
+	time_ = tp.tv_sec;
+#elif defined(_WIN32)
+	static ULONGLONG (CALLBACK *GetTickCount64) (void) = NULL;
+	if (winver.dwMajorVersion >= 6)
+	{
+		HINSTANCE hKernel32;
+		*(FARPROC*)&GetTickCount64 = GetProcAddress(hKernel32, "GetTickCount64");
+                if (GetTickCount64 == NULL)
+			time_ = time(NULL);
+		else
+			time_ = (int)(GetTickCount64() * 1e-3);
+	}
+#elif defined(__APPLE__)
+	static mach_timebase_info_data_t timebase;
+	if (timebase.denom == 0)
+		mach_timebase_info(&timebase);
+
+	time_ = (int)(mach_absolute_time() * timebase.numer / timebase.denom * 1e-9);
+#else
+	time_ = time(NULL);
+#endif
+	mowgli_eventloop_set_time(eventloop, (time_t)time_);
 }
 
 static inline bool mowgli_eventloop_ignore_errno(int error)