Demo Gtk.ApplicationWindow

//valac -o demo-appwin --pkg gtk+-3.0 demo_appwin.vala
using Gtk;

public class DemoApp: Gtk.Application
{
    private Builder builder;
    private Window main_window;

    public DemoApp() {
        Object(application_id: "com.susilolabs.demoapp", flags: ApplicationFlags.FLAGS_NONE);
    }

    protected override void activate() {
        try {
            builder = new Builder();
            builder.add_from_file("demo_appwin.glade");
            this.main_window = builder.get_object("appwin") as Window;
            this.main_window.application = this;
            this.main_window.show_all();

        }catch(Error e) {
            stderr.printf("%s\n", e.message);
        }
    }

    public static int main(string[] args) {
        DemoApp app = new DemoApp();
        return app.run(args);
    }
}