Re: highlight-changes-rotate-faces sets buffer modified flag

[Reindert-Jan Ekker]

On Wed, 9 May 2007, martin rudalics wrote:

> > Hi,
> >
> > Turning off highlight-changes-mode sets the buffer-modified state as well.
>
> This could be handled as with `highlight-changes-rotate-faces'.
> Unfortunately, switching `highlight-changes-mode' off will leave
> `buffer-undo-list' cluttered with all sorts of remnants that make sense
> iff the mode is on.  You could try as follows: Switch the mode on, do
> some changes, rotate colors, switch it off, undo changes.  Changed text
> may get highlighted although the mode is off.

This does not seem to be a problem in my case. Looking at the value of 
buffer-undo-list after turning of highlight-changes-mode does show some 
face changes, but undo-ing these does not cause any text to become 
highlighted again.

> > By the way, I do not have a lot of experience with emacs lisp. Regarding
> > buffer-undo-list: would it be correct to just remove the front element
> > of the list in the advice I wrote?
>
> Better not record the change in the first place by temporarily binding
> `buffer-undo-list' to t during the buffer change.

So this is an improved version of my advice:

(defadvice highlight-changes-rotate-faces (around around-rotate-faces)
  (let ((was-modified (buffer-modified-p))
        (saved-undo-list buffer-undo-list)
        (buffer-undo-list t))
    ad-do-it
    (setq buffer-undo-list saved-undo-list)
    (unless was-modified
      (set-buffer-modified-p nil))))
(ad-activate 'highlight-changes-rotate-faces)

> BTW, am I correct that you run `highlight-changes-rotate-faces'
> interactively and not in `write-file-functions'?  In the latter case
> setting the buffer-modified flag should get shadowed by the saving
> primitive.

Actually, I am trying to write a hook that calls 
highlight-changes-rotate-faces on the right buffers whenever I do a 
subversion commit with psvn.

Reindert