Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> It should be possible to use post-command-hook, I didn't use it because
>> it makes harder the communication between the minibuffer and the preview
>> buffer.
>
> The patch below seems to work for my extremely limited testing.

Here the serie of patches with your patch included.
Let me know if the commit is incorrect (patch 0004).
I will test this extensively next week, too tired now to do something
useful.

Thanks.

-- 
Thierry