非模式窗口如何相互跳转

astar

a = gtk_window_new (GTK_WINDOW_DIALOG);  gtk_window_set_modal (GTK_WINDOW (a), FALSE);

b = gtk_window_new (GTK_WINDOW_DIALOG);  gtk_window_set_modal (GTK_WINDOW (b), FALSE);

当前active为a窗口，如何在a中实现b窗口active， b中实现a窗口active

Thanks