Function glib::source::idle_add_once

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

Adds a closure to be called by the default main loop when it’s idle.

func will be called repeatedly 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 idle_add(), this only requires func to be FnOnce, and will automatically return Continue(false).