init_screen

static VALUE
curses_init_screen(void)
{
    rb_secure(4);
    if (rb_stdscr) return rb_stdscr;
    initscr();
    if (stdscr == 0) {
        rb_raise(rb_eRuntimeError, "can't initialize curses");
    }
    clear();
    rb_stdscr = prep_window(cWindow, stdscr);
    return rb_stdscr;
}