Advice with undo config

Advice with undo config

[Nick Helm]

Hi there,

I keep bumping into the default undo limits and I'm trying to configure
my Emacs for greater undo capacity. If I add something like this to my
init:

  (setq undo-limit        (* 16 1024 1024))
  (setq undo-strong-limit (* 24 1024 1024))
  (setq undo-outer-limit (* 240 1024 1024))

will there be any side-effects I should be aware of? Are these numbers
reasonable? I've tested this setup with some of the files that normally
give me problems and I can undo until the cows come home without any
obvious issues.

Many thanks!
Nick

Re: Advice with undo config

[Emanuel Berg]

Nick Helm wrote:

> (setq undo-limit        (* 16 1024 1024)) [...]
>
> will there be any side-effects I should be
> aware of? Are these numbers reasonable?

There should not be any side-effects save for
the increased storage, which is what you want,
but is it reasonable to have >16 MB of undo
data? A better question is probably "is it
reasonable to do, and then undo, that much"?

-- 
underground experts united
http://user.it.uu.se/~embe8573

Re: Advice with undo config

[Nick Helm]

On Wed, 21 Mar 2018 at 12:04:27 +0100, Emanuel Berg wrote:

> Nick Helm wrote:
>
>> (setq undo-limit        (* 16 1024 1024)) [...]
>>
>> will there be any side-effects I should be
>> aware of? Are these numbers reasonable?
>
> There should not be any side-effects save for
> the increased storage, which is what you want,

Thanks. 

> but is it reasonable to have >16 MB of undo
> data? A better question is probably "is it
> reasonable to do, and then undo, that much"?

In an ideal world, wouldn't undo be unlimited?

Some commands can bump into the default undo limits pretty
quickly – org-table-delete-column is a good example. In those
situations, the count of "do" is 2 and you've already hit the
limit. Isn't it reasonable to expect a bit more than that?

Re: Advice with undo config

[Emanuel Berg]

Nick Helm wrote:

>> but is it reasonable to have >16 MB of undo
>> data? A better question is probably "is it
>> reasonable to do, and then undo, that much"?
>
> In an ideal world, wouldn't undo
> be unlimited?

I don't know, but you can have virtually
unlimited undo in practice because what is
stored is just text, and on today's HDs which
can save tons of multimedia, what in past days
would amount to huge archives, there is
certainly room for all the undos anyone would
ever care for.

> Some commands can bump into the default undo
> limits pretty quickly –
> org-table-delete-column is a good example.
> In those situations, the count of "do" is 2
> and you've already hit the limit. Isn't it
> reasonable to expect a bit more than that?

Well, if one has to pile up those kind of
quantities of text data perhaps another column
is called for instead? :)

-- 
underground experts united
http://user.it.uu.se/~embe8573

Re: Advice with undo config

[Stefan Monnier]

> I keep bumping into the default undo limits

Sounds like you're hitting a bug, then.  I suggest you M-x report-emacs-bug.

> Some commands can bump into the default undo limits pretty
> quickly – org-table-delete-column is a good example.  In those
> situations, the count of "do" is 2 and you've already hit the
> limit.  Isn't it reasonable to expect a bit more than that?

Yes it is, and you shouldn't need to manually change your config
for that.


        Stefan

Re: Advice with undo config

[Nick Helm]

On Thu, 22 Mar 2018 at 09:44:50 -0400, Stefan Monnier wrote:

>> I keep bumping into the default undo limits
>
> Sounds like you're hitting a bug, then. I suggest you 
> M-x report-emacs-bug.
>
>> Some commands can bump into the default undo limits pretty
>> quickly – org-table-delete-column is a good example.  In those
>> situations, the count of "do" is 2 and you've already hit the
>> limit.  Isn't it reasonable to expect a bit more than that?
>
> Yes it is, and you shouldn't need to manually change your config for
> that.

I never thought about it like that, but you're right. I'll come up with
a good example and open a bug.

Thanks.