pan_oy
tc->pan_oy = tty->ooy;
if (tc->pan_oy > adjust)
tc->pan_oy -= adjust;
tc->pan_oy = 0;
tc->pan_oy += adjust;
if (tc->pan_oy > w->sy - tty->osy)
tc->pan_oy = w->sy - tty->osy;
c->pan_oy = 0;
else if (c->pan_oy + *sy > w->sy)
c->pan_oy = w->sy - *sy;
*oy = c->pan_oy;