Re: Scary undo

["Lennart Borgman (gmail)" <lennart.borgman@gmail.com>]

David Kastrup wrote:
> "Lennart Borgman (gmail)" <lennart.borgman@gmail.com> writes:
> 
>> I would like to undo a change made by a function that I call with
>> funcall. I do not know exactly what the function does, but hopefully
>> it will only indent the current line. However the new indentation
>> might be wrong.
>>
>> The scenario is something like this
>>
>>    (funcall the-indentation-function)
>>    (when (= 0 (current-indentation))
>>       ;; undo what `the-indentation-function' did,
>>       ;; but how?
>>       )
>>
>> I am a bit scared of writing this undo part so if someone could help
>> me I would be glad. I do not think I can use `undo-boundary' here.
> 
> I'd be tempted to do something like
> 
> (condition-case nil
>    (atomic-change-group
>      (funcall the-indentation-function)
>      (when (=0 (current-indentation))
>        (signal 'barfout nil)))
>   (barfout))

Thanks David and Juanma, that was what I needed.