Libsigc++ - A Signal Framework for C++

Provides following features:
  * compile time typesafe callbacks (faster than run time checks)
  * typesafty violations line number reports correctly with 
    template names (no tracing template failures into headers)
  * no compiler extensions or meta compilers required
  * proper handling of dynamic objects and signals
    (deleted objects will not cause seg faults)

  * extendable API at any level
    Slot, Connection, Object, and Signal
  * extensions do not require alteration of basic components
    to allow use of extensions
  * User definable marshallers

  * provides headers for up to 7 arguments and 2 callback data
  * M4 Macros for building templates with various numbers 
    of arguments and callback data
  * Easily build support for templates with number of arguments
    and callback data not defined in library headers