Hi, how to declare function (GIOFunc) which is specified as following:
pub type GIOFunc =
Option<unsafe extern "C" fn(*mut GIOChannel, GIOCondition, gpointer) -> gboolean>;
And it is used here:
pub fn g_io_add_watch(
channel: *mut GIOChannel,
condition: GIOCondition,
func: GIOFunc,//here, how to define that function?
user_data: gpointer,
) -> c_uint;