GtkApplication *application;
GtkWindow *window;
GtkWidget *dialog;
GError *error = NULL;

application = GTK_APPLICATION (user_data);
window = gtk_application_get_active_window (application);

gtk_show_uri (window ? gtk_window_get_screen (GTK_WINDOW (window)) : gdk_screen_get_default (),
              "help:boilerplate-for-c-gtk3",
              gtk_get_current_event_time (),
              &error);

if (error)
{
    dialog = gtk_message_dialog_new (window ? GTK_WINDOW (window) : NULL,
                                     GTK_DIALOG_MODAL,
                                     GTK_MESSAGE_ERROR,
                                     GTK_BUTTONS_OK,
                                     _("There was an error displaying help: \n%s"),
                                     error->message);
    g_signal_connect (G_OBJECT (dialog), "response",
                      G_CALLBACK (gtk_widget_destroy),
                      NULL);

    gtk_window_set_resizable (GTK_WINDOW (dialog), FALSE);
    gtk_widget_show (dialog);
    g_error_free (error);
}