Internal Program Version: libsigc++2  2.12.1

This library implements a full callback system for use in widget
libraries, abstract interfaces, and general programming. It is the most
complete library of its kind with the ability to connect an abstract
callback to a class method, function, or function object. It contains
adaptor classes for connection of dissimilar callbacks and has an ease
of use unmatched by other C++ callback libraries.

http://libsigc.sourceforge.net