Queries the type of the parameter that must be given when activating
action.
When activating the action using g_action_activate(), the GVariant
given to that function must be of the type returned by this function.
In the case that this function returns NULL, you must not give any
GVariant, but NULL instead.
Since 2.28
Queries the type of the parameter that must be given when activating action. When activating the action using g_action_activate(), the GVariant given to that function must be of the type returned by this function. In the case that this function returns NULL, you must not give any GVariant, but NULL instead. Since 2.28