the instance the signal is being emitted on.
the signal id
the detail
a list of parameters to be passed to the signal, followed by a location for the return value. If the return type of the signal is #G_TYPE_NONE, the return value location can be omitted.
Emits a signal.
Note that g_signal_emit_valist() resets the return value to the default if no handlers are connected, in contrast to g_signal_emitv().