Example: ToolItem

public class Application : Gtk.Window {
public Application () {
// Prepare Gtk.Window:
this.title = "My Gtk.ToolItem";
this.window_position = Gtk.WindowPosition.CENTER;
this.destroy.connect (Gtk.main_quit);
this.set_default_size (350, -1);


// The Toolbar:
Gtk.Toolbar bar = new Gtk.Toolbar ();
this.add (bar);

// ToolItem:
Gtk.ToolItem button = new Gtk.ToolItem ();
bar.add (button);

// ToolItem content:
Gtk.Spinner spinner = new Gtk.Spinner ();
button.add (spinner);
spinner.start ();
}

public static int main (string[] args) {
Gtk.init (ref args);

Application app = new Application ();
app.show_all ();
Gtk.main ();
return 0;
}
}

 valac --pkg gtk+-3.0 Gtk.ToolItem.vala

See: