Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> The problem here is how aborting changes is implemented in wdired: undo
>> is disabled and original code just copies entire buffer and pastes it back
>> when changes are aborted.
>
> I think you should be able to leave this part of the code completely unchanged.

Yes; and for the simplicity it will be so.

>> I would like to skip copying entire buffer into buffer-string as
>> wdired does originally.
>
> Any particular reason for that?  It should be very fast, even for very
> large directories.

Just for efficiency; it copies entire buffer which can be quite big
memory wise; but indeed it seems to be very fast, and I guess for the
simplicity of implementation it can be left as is :-).

>> I agree with you, but I am not sure how to implement it. My hack was
>> literally less than a 5 minute change, I just removed loops and changed
>> mode name so I can abort it properly.
>
> I'd start with the following:
> When converting to wdired, instead of calling `wdired-preprocess-files`, use
>
>     (add-hook 'before-change-functions #'wdired--preprocess-lines nil t)
>
> and then turn `wdired-preprocess-files` into `wdired--preprocess-lines`,
> which will `get-text-property` of the first char of each line in the
> region to see if it's already been marked as `read-only`.  If yes,
> do nothing and if not, do what the old code did on that line.

I tested, and currently I don't see any noticable slowdowns, even on
that large directory. Dropping into wdired seems to be quite reactive
and I can start editing any file name immidiately.

However I can't seem to be able to get it work with permissions; I am
not sure why. I have checked that wdired-allow-to-change-permissions is t.

I have attached code as a separate file (I worked so). I can make a
patch for wdired.el later, if you or someone can give me a tip why text
props for permissions are not changing as they should.