Re: Limits to undo

On Sunday, November 9, 2014 8:19:54 AM UTC-5, Ben Fritz wrote:
>On Saturday, November 8, 2014 9:35:12 PM UTC-6, AndyHancock wrote:
>> I have undolevels set to 1000, which is easily exceeded if each
>> keystroke is a count of 1.
>>
>> Sigh.
>>
>> I will look into persistence. I thank you for the educational
>> material in your post.
>
> Actually each keystroke is definitely NOT a count of 1. If you type
> "d3w" to delete 3 words, that's a single change. If you type "aHello
> world! I'm writing text!<Esc>" to insert two sentences, that's still
> only one change in terms of undolevels.
>
> You *may* be reaching 1000 changes, in which case you can always set
> undolevels higher in your .vimrc.
>
> But more likely, you're hitting one of these scenarios:
> * You don't have persistent undo turned on
> * The file was modified outside of Vim
> * You overwrote the file from Vim with a :w! or :saveas! when you
> were editing a different file
> * You reloaded the file in Vim and it is a big file
>
> In the first case, just put "set undofile" in your .vimrc. If you do
> this, Vim saves the current undo tree to a file when exiting, and
> reloads it the next time you edit that file.
>
> In the second case, even if persistent undo is turned on, Vim will
> not have undo information for the file. Undo files are only used if
> the file contents match what they were when the undo file was
> created.
>
> The third case is a special case of the undo file not matching, so
> the original file's saved undo tree will not work. And the new undo
> tree applies to the buffer you've been editing, not the original
> file, so that also won't work.
>
> In the final case, Vim can discard the undo tree when you reload a
> file (for example using ":e!" to discard changes instead of
> ":earlier 1f"). But, Vim will add the reload to the undo tree as
> long as the file is short enough. You can change what "short enough"
> means using the 'undoreload' option (default 10000 lines).

Ben,

Thanks for that explanation. I just started to delve into the help pages and found that undo is far more sophisticated than I've ever suspected. Some reading there for sure.

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