Function glib::source::unix_signal_add_once

pub fn unix_signal_add_once<F>(signum: i32, func: F) -> SourceId where
    F: FnOnce() + Send + 'static, 

Adds a closure to be called by the default main loop whenever a UNIX signal is raised.

func will be called repeatedly every time signum is raised until it returns Continue(false).

The default main loop almost always is the main loop of the main thread. Thus, the closure is called on the main thread.

In comparison to unix_signal_add(), this only requires func to be FnOnce, and will automatically return Continue(false).