GTK+ Maximize bugs

test.vala

// Compile with: valac --pkg gtk+-3.0 test.vala
public class Application : Gtk.Window {

    public Application(){
      // Uncomment these lines to test with a headerbar
      //var hb = new Gtk.HeaderBar();
      //hb.show_close_button = true;
      //set_titlebar(hb);

      title = "Test Window";
      set_default_size(800,1200);

      this.destroy.connect(Gtk.main_quit);
    }

}

int main(string[] args){
    Gtk.init(ref args);
    new Application().show_all();
    Gtk.main();
    return 0;
}