hid: handle full ptr queues in post_load

    HIDState *s = opaque;

    hid_set_next_idle(s);

    if (s->n == QUEUE_LENGTH && (s->kind == HID_TABLET ||

                                 s->kind == HID_MOUSE)) {

        /*

         * Handle ptr device migration from old qemu with full queue.

         *

         * Throw away everything but the last event, so we propagate

         * at least the current button state to the guest.  Also keep

         * current position for the tablet, signal "no motion" for the

         * mouse.

         */

        HIDPointerEvent evt;

        evt = s->ptr.queue[(s->head+s->n) & QUEUE_MASK];

        if (s->kind == HID_MOUSE) {

            evt.xdx = 0;

            evt.ydy = 0;

        }

        s->ptr.queue[0] = evt;

        s->head = 0;

        s->n = 1;

    }

    return 0;

}