gstreamer-rs/tutorials/src/tutorials-common.rs

/// macOS has a specific requirement that there must be a run loop running on the main thread in
/// order to open windows and use OpenGL, and that the global NSApplication instance must be
/// initialized.

/// On macOS this launches the callback function on a thread.
/// On other platforms it's just executed immediately.
#[cfg(not(target_os = "macos"))]
pub fn run<T, F: FnOnce() -> T + Send + 'static>(main: F) -> T
where
    T: Send + 'static,
{
    main()
}

#[cfg(target_os = "macos")]
pub fn run<T, F: FnOnce() -> T + Send + 'static>(main: F) -> T
where
    T: Send + 'static,
{
    use cocoa::appkit::NSApplication;
    use objc::{msg_send, sel, sel_impl};

    use std::thread;

    unsafe {
        let app = cocoa::appkit::NSApp();
        let t = thread::spawn(|| {
            let res = main();

            let app = cocoa::appkit::NSApp();
            let _: () = msg_send![app, terminate: cocoa::base::nil];

            res
        });

        app.run();

        t.join().unwrap()
    }
}