Function glib::source::idle_add

pub fn idle_add<F>(func: F) -> SourceId where
    F: FnMut() -> Continue + 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.