libwnck is Window Navigator Construction Kit, i.e. a library to use
for writing pagers and taskslists and stuff.  

libwnck isn't supported in the devel platform, which means OS vendors won't
guarantee the API/ABI long-term, but authors of open source apps
should feel free to use libwnck as users can always recompile against
a new version.  (And the API/ABI has historically changed very little,
I'm not changing it gratuitously or without soname increments.)

There are API docs in the source code, and API documentation can be
generated by configuring --enable-gtk-doc. Also tasklist.c and pager.c make
good sample code.