[openbox] Switching virtual desktops from C?

[mpb]

Hi Openbox,

I want to write my own standalone C program to switch virtual
desktops, functionality equivalent  Openbox's DesktopNext and
DesktopPrevious actions.  I have used various third-party pagers with
Openbox, so I assume this must be possible.  Can anyone give me some
pointers on how to proceed?  For example, source code samples
(possibly even from inside the Openbox source code), or links to
relevant documentation.

I have extensive experience with C, minimal experience with Xlib, and
zero experience with Freedesktop.  (Perhaps Freedesktop is not even
relevant?)

Thanks!

-mpb