[master] Imported from libpng-1.6.14.tar

contrib/gregbook/rpng2-x.c

@@ -103,9 +103,6 @@
 #define RESNAME   "rpng2"       /* our X resource application name */
 #define RESCLASS  "Rpng"       /* our X resource class name */
 
-/* This is temporary until the code is rewritten to use nanosleep(). */
-#define usleep(x) sleep(((x)+499999)/1000000)
-
 #include <stdio.h>
 #include <stdlib.h>
 #include <ctype.h>
@@ -118,6 +115,18 @@
 #include <X11/Xos.h>
 #include <X11/keysym.h>   /* defines XK_* macros */
 
+#if _POSIX_C_SOURCE >= 199309L /* have nanosleep() */
+# undef usleep
+# define usleep(usec) {        \
+   struct timespec ts;         \
+   ts.tv_nsec = (usec) * 1000; \
+   nanosleep(&ts, NULL); }
+#  endif
+
+#ifndef usleep /* have neither nanosleep() nor usleep() */
+#  define usleep(x) sleep(((x)+499999)/1000000)
+#endif
+
 #ifdef VMS
 #  include <unistd.h>
 #endif