Re: Is there a way to know if this-command altered the buffer?

[Marcin Borkowski]

On 2021-05-12, at 06:27, Emanuel Berg via Users list for the GNU Emacs text 
editor <help-gnu-emacs@gnu.org> wrote:

> Marcin Borkowski wrote:
>
>> I want to run some function in a certain hook. This function
>> will update some info displayed using an overlay. The info
>> depends on the buffer contents and is pretty expensive to
>> compute, so I'd like to only display it if the buffer
>> really changed.
>>
>> Is there a way to know if `this-command' actually changed
>> the buffer (as opposed to e.g. point motion)?
>
> Maybe these
>
>   buffer-chars-modified-tick
>   buffer-modified-tick

Wow, I never heard about those!  Interesting!  Though I think I found
the best answer (after-change-functions), this is also very interesting
and possibly useful (though in other circumstances, I think).

Thanks!

-- 
Marcin Borkowski
http://mbork.pl