Re: Partial wdired (edit just filename at the point)

[Stefan Monnier]

> Never used 'before-change-function, so I didn't think about it :).
>
> Sure, as a strategy it sounds good indeed, but I am not sure I
> understand how to apply that hook in this case. Docs says it is called
> before any buffer mdification, but I am not sure what it means: before
> every key-press in this case or what is ment with buffer modification here?

Not "before a key press" because it can't know you're about to press
a key, and even if it knows, it can't easily know what that command
will do.

So instead it's done at the beginning of those ELisp primitives that
modify a buffer, like `delete-region`, or `insert`.

It can be called several times in a single command, depending on what
the command does, so it's best to optimize function placed on this hook
such that they are usually very cheap.

>> This way entering `wdired` should be instantaneous but you can still
>> edit any line you like.  The actual edits would be slightly slowed down,
>> but that shouldn't be nearly as problematic.
>
> I agree it shouldn't be noticable; it is how the implementation I
> attached works; it is just that I do it explicitly with a "manual"
> call to function that change properties just for the line at the point.

Yes, I understand, but I think we can have our cake and eat it too: be
super-fast when editing only a single line yet without having to tell
Emacs in advance whether we plan to edit only a single line or all
the lines.


        Stefan