Xcursor and X11 mouse themes under XFree86 4.3

Hello,
I am trying to figure out how the Xcursor extension of XFree86 4.3 works 
and I can only find partial information, no complete documentation. I 
would like to know if it is possible, using Xcursor and the 
~/icons/default/index.theme file, to enlarge the X cursors for all 
applications.
I tried to browse the XFree86 4.3 online documentation, but Xcursor is 
only mentioned in the Release Notes and the Xcursor library functions 
are described in the Xcursor man page. I tried to search on 
www.google.com, but I only get useless information that link me to 
www.kde-look.org which provides me with a bunch of pre-created themes 
without telling me the format of the index.theme file.
Is there some more complete documentation? If not, which source file(s) 
of the XFree86 project should I look into to figure out how to achieve 
my goals?
Thanks in advance