libsigc++ (a.k.a. libsigcplusplus) implements a typesafe callback system for standard C++.
It allows you to define signals and to connect those signals to any callback function, either
global or a member function, regardless of whether it is static or virtual.
libsigc++ is used by gtkmm to wrap the GTK signal system. It does not depend on GTK or gtkmm.
sigc++-2.0 and sigc++-3.0 are different parallel-installable ABIs. This file describes sigc++-3.0.