Re: [isabelle] Number of undos

On Tue, 30 Sep 2014, Joachim Breitner wrote:

I’m not sure if this is an issue with jEdit or with Isabelle/jEdit, but I find the default number of 100 undo steps very low, and I occasionally lose work when some change turned out to be contraproductive and I want to go back.

I have never encountered this limit myself in 8 years of using jEdit as my main editor, as well as a few years of using Isabelle/jEdit as Prover IDE.

After spending 5min with the sources and properties of jEdit, I now see that there is buffer.undoCount, which can be changed in Global Options / Editing / Number of undos. The change is made persistent in $ISABELLE_HOME_USER/jedit/properties as usual.

It is normal that personal properties accumulate, and require manual maintenance on Isabelle releases. The main inconvenience here is the erratic order of the lines in the file -- something that is worth improving and submitting to one of the trackers at

I could add more Isabelle/jEdit default changes to $ISABELLE_HOME/src/Tools/jEdit/src/jEdit.props, but it needs a minimum level of significance to diverge further from the defaults.

Given the resource demands that Isabelle has anyways (16GB RAM was suggested recently, I think)

There is a misunderstanding: Isabelle/jEdit resource requirements are not very special. A small machine for small applications (4 GB RAM), a medium machine for medium applications (8 GB RAM), a slightly bigger machine for big applications (16 GB). Really big machines by today's standards have 32-128 GB RAM.

That may sound hilarious, but Proof General with XEmacs required much more resources in relation to the hardware of its time. When crafting Isabelle/jEdit over so many years, I always kept an eye on current consumer hardware parameters. One problem that I did not foresee is the general stagnation of the market: people don't upgrade their machines anymore as they used to do in the past.

I don’t believe that there is a problem raising that limit by an order of magnitude or two.

I don't know much about the jEdit undo manager, so I can't tell. This discussion is better moved to

So far I have been mostly alone on that mailing list to represent the needs of Isabelle/jEdit users.

I need to emphasize once more that Isabelle/jEdit is not a fork of jEdit, but an application on top of it. As much required changes as possible should be handed back to the main project, even though this is some extra work.


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