Undoes the effect of a previous
g_signal_handler_block() call. A
blocked handler is skipped during signal emissions and will not be
invoked, unblocking it (for exactly the amount of times it has been
blocked before) reverts its “blocked” state, so the handler will be
recognized by the signal system and is called upon future or
currently ongoing signal emissions (since the order in which
handlers are called during signal emissions is deterministic,
whether the unblocked handler in question is called as part of a
currently ongoing emission depends on how far that emission has
handler_id has to be a valid id of a signal handler that is
connected to a signal of
instance and is currently blocked.
The instance to unblock the signal handler of.
The data is owned by the caller of the function.
Handler id of the handler to be unblocked.