the last parameter of XChangeProperty is the number of elements.. and when the element format is 32.. the element is "long" so we have 5 long elements here.

Yes this seems confusing as on mac+linux Long is either 32 or 64bits depending on the architecture, but this is how the X11 protocol is defined. Thus 5 is the correct value for the nelts here.  Not 5 or 10 depending on the architecture.

More info on the confusion https://bugs.freedesktop.org/show_bug.cgi?id=16802

visualtest/config.h

@@ -0,0 +1,23 @@
+/* config.h.  Generated from config.h.in by configure.  */
+/* config.h.in.  Generated from configure.in by autoheader.  */
+
+/* Define to the address where bug reports for this package should be sent. */
+#define PACKAGE_BUGREPORT "apoorvupreti@gmail.com"
+
+/* Define to the full name of this package. */
+#define PACKAGE_NAME "sdlvisualtest"
+
+/* Define to the full name and version of this package. */
+#define PACKAGE_STRING "sdlvisualtest 0.01"
+
+/* Define to the one symbol short name of this package. */
+#define PACKAGE_TARNAME "sdlvisualtest"
+
+/* Define to the home page for this package. */
+#define PACKAGE_URL ""
+
+/* Define to the version of this package. */
+#define PACKAGE_VERSION "0.01"
+
+/* Define to empty if `const' does not conform to ANSI C. */
+/* #undef const */