@parameter will always be of the expected type. In the event that
an incorrect type was given, no signal will be emitted.
Since GLib 2.40, if no handler is connected to this signal then the
default behaviour for boolean-stated actions with a %NULL parameter
type is to toggle them via the #GSimpleAction::change-state signal.
For stateful actions where the state type is equal to the parameter
type, the default is to forward them directly to
#GSimpleAction::change-state. This should allow almost all users
of #GSimpleAction to connect only one handler or the other.
Indicates that the action was just activated.
@parameter will always be of the expected type. In the event that an incorrect type was given, no signal will be emitted.
Since GLib 2.40, if no handler is connected to this signal then the default behaviour for boolean-stated actions with a %NULL parameter type is to toggle them via the #GSimpleAction::change-state signal. For stateful actions where the state type is equal to the parameter type, the default is to forward them directly to #GSimpleAction::change-state. This should allow almost all users of #GSimpleAction to connect only one handler or the other.