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/autogen.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+#
+# Regenerate configuration files
+cp acinclude.m4 aclocal.m4
+found=false
+for autoconf in autoconf autoconf259 autoconf-2.59
+do if which $autoconf >/dev/null 2>&1; then $autoconf && found=true; break; fi
+done
+if test x$found = xfalse; then
+    echo "Couldn't find autoconf, aborting"
+    exit 1
+fi