ctrl-z clears cell output in notebook when pressed enough times

[ivanov]

again, this may be another CodeMirror issue, but I'm not seeing it in CM demos.

Ctrl-Z works fine to undo changes made in a cell, unless you press it one too many times, which currently ends you up with a completely empty cell. I don't think this is a feature, I think it only makes sense to undo until the last save point.

I'm seeing it act the same in Chrome and Firefox under Ubuntu 10.04

[ivanov]

I should, of course, mention, that Ctrl-Y is our friend here, but I'm usually too panicked that the contents of my entire cell are gone to remember that.

[fperez]

Well, I'm not sure I'd consider this a bug: it's undoing all of your history from the first thing you typed... And I do want to be able to go past the last save point, in case I saved a mistake! I sometimes hit C-s out of reflex, only to realize that I want to undo something; I don't want to be penalized by my editor for having saved...

So IMO this is 'not a bug'. Close it?

[ivanov]

i agree that my suggestion about only being able to undo until the last save point isn't the best, so that's probably not the way to go.

I just feel that it's counterintuitive that when I open a notebook (say one of the example ones that we ship) and press ctrl-z in a cell that had things in there written for me, the entire contents of that cell are gone. A typical editor only does undo to the beginning of the session, not to the beginning of time. In other words, I only want to undo back the things I did, and so for the cells whose content I did not populate originally, undo should only go back to original content (but it currently goes to an empty cell).

[takluyver]

I'd agree with Paul that if you load a notebook with content, you don't expect Ctrl-Z to delete what's already there. I often play around with a script in an editor, then do a poor man's revert by holding down Ctrl-Z until it's back to what I first opened.

[fperez]

ah, I didn't realize this was happening on a freshly opened notebook! I thought it only did undo if you had written the cell from zero yourself, case in which 'go back all the way to the start' would indeed be 'go back to an empty cell'.

I certainly agree that C-z deleting existing content is a bug.

[ivanov]

the fix @ak3n does not work quite right for new cells. For those, it only allows you to undo up to the first set of changes in that cell.