memset(&st->fill[(st->height-st->inclear-1)*st->width], 0, sizeof(int)*st->width);
st->inclear++;
XDrawLine(st->dpy, st->window, st->erase_gc, 0, st->inclear, st->width-1, st->inclear);
memset(&st->fill[(st->height-st->inclear-1)*st->width], 0, sizeof(int)*st->width);
st->inclear++;
XDrawLine(st->dpy, st->window, st->erase_gc, 0, st->inclear, st->width-1, st->inclear);