// ExampleApp.vala public class ExampleApp : Gtk.Application { public ExampleApp () { Object (application_id: "com.example.App"); } public override void activate () { var win = new Gtk.ApplicationWindow (this); var btn = new Gtk.Button.with_label ("Hello World"); btn.clicked.connect (win.close); win.child = btn; win.present (); } public static int main (string[] args) { var app = new ExampleApp ()