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Re: Re: v6: still no multiple undo?

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  • Subject: [mg77433] Re: [mg77407] Re: v6: still no multiple undo?
  • From: "Barthelet, Luc" <lucb at>
  • Date: Fri, 8 Jun 2007 05:38:57 -0400 (EDT)

While I strongly support that multiple undo is a feature we need to see
soon, it will take some real work to get there.

The editor, and the kernels are linked in an efficient exchange of messages
and information about what needs to be displayed where and when.

While implementing multiple undo-redo in a stand alone editor usually
requires only to implement a tokenized undo-redo, in the v6 font end, it
will require a more complex model. It is a bit like if you were trying to
implement multiple undo on a wiki site like wikipedia where they are
multiple contributors.

We probably do not want the kernel to "undo", just the front end. So one
solution would be to make the kernel and the user to appear as a single
contributor, and to undo both effects on the front end. So one undo might
remove an output created by the kernel.

Even that is challenging, because Dynamics now create a lot of updates and
you will not want to roll those back.

Anyway, the front end team is obviously smart enough to find a solution for
all those things, but it is not going to be easy.

A cheap thing that I would like to see, is a text buffer of all my input and
all the code I deleted saved as a log on disk. It might be ugly, but it
would be VERY USEFUL.



On 6/7/07 3:34 AM, "David Bailey" <dave at> wrote:

> David wrote:
>> Will Robertson wrote:
>>> Hello,
>>> I am baffled that technical software is released in 2007 with only a
>>> single undo level. Am I missing something here? Is it because I'm
>>> using a student license? How hard can an undo stack really be in the
>>> notebook interface?
>>> I've been irritated a few times in v5.2 from clumsy keypresses losing
>>> me work that I would expect to be two "undo"s away. Alas not. Still.
>>> Will Robertson
>> Good point! I've wondered the same thing for a long time. This is the
>> only app I run that doesn't happen multiple levels of undo. I think it's
>> time WRI spent some time on this issue.
> How much time could it possibly take! Once you have a 1-level undo
> working, all you need to do is spill the relevant data into a structure
> - possibly on disk - and retrieve it as needed!
> David Bailey

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