libsigc++ 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.

See the [libsigc++ web site](https://libsigcplusplus.github.io/libsigcplusplus/)

Distribution of library and components is under the LGPL as listed in the

file COPYING. Examples and tests are Public Domain.

Compatible compilers must support C++17, such as the decltype(auto) specifier

(from C++14) and std::invoke().