2009-05-26

tracking changes

It's sometimes nice to see the changes you've made to a file. If the file is under version control, you can use the 'diff'-features of the version control system of course; or you can use diff-buffer-with-file to compare your buffer with the version on disk. That obviously only. works when you haven't saved the file yet.

Anyway, a bit easier, straighforward way may be to use highlight-changes-mode. With that mode, emacs can give a special color to parts of the text that you have changed. 

;; higlight changes in documents
(global-highlight-changes-mode t)
(setq highlight-changes-visibility-initial-state nil); initially hide

The last line tells me that the changes should not be visible unless I want to see them.

I defined a key binding (F6) so I can easily toggle between visible/invisible changes: 

;; toggle visibility
(global-set-key (kbd "<f6>")      'highlight-changes-visible-mode) ;; changes
;; remove the change-highlight in region
(global-set-key (kbd "S-<f6>")    'highlight-changes-remove-highlight)

With this last keybinding S-<f6> (Shift-F6), I can remove the change-indication of the current region (selection). Here are some other useful keybindings to quickly jump between various changes: 

;; alt-pgup/pgdown jump to the previous/next change

;; if you're not already using it for something else...
(global-set-key (kbd "<M-prior>") 'highlight-changes-next-change)
(global-set-key (kbd "<M-next>")  'highlight-changes-previous-change)

Another interesting thing you can do is M-x highlight-compare-with-file.

The only remaining problem with highlight-changes-mode is that the default colors are, well, hideous. But of course, that can easily be fixed by changing the faces: 

(set-face-foreground 'highlight-changes nil)
(set-face-background 'highlight-changes "#382f2f")
(set-face-foreground 'highlight-changes-delete nil)
(set-face-background 'highlight-changes-delete "#916868")

Or adding to your color-scheme: 

(highlight-changes ((t (:foreground nil :background "#382f2f"))))
(highlight-changes-delete ((t (:foreground nil :background "#916868"))))

Now, with these color changes, the foreground stays the same, only the background changes a bit. I am using a dark theme, you might want to change the colors to fit in with your theme.

There are some more features - for example, to rotate through changes of different age. For such things I prefer to use a version control system, but you might want to check it out.

Tracking changes can be quite useful. And, unlike some word-processing software, emacs does not hide your highly embarrassing modifications somewhere in your document…

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12 comments:

  1. UnknownMay 27, 2009 at 10:41 AM

    nice. may i know what color scheme were you using taking that screenshot above? could you share with it?

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  2. zzktMay 27, 2009 at 3:43 PM

    Thanks for the tip. One small correction, the line (global-highlight-changes-mode t) should read (global-highlight-changes t)

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  3. djcbMay 27, 2009 at 4:12 PM

    @zzkt: well, in my emacs 23, 'global-highlight-changes-mode' is the preferred one. 'global-highlight-changes' is an alias for backward compatibility.

    So, indeed for emacs <= 23.1, you might need 'global-highlight-changes' instead.

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  4. AnonymousMay 28, 2009 at 12:54 AM

    Sorry a beginner question..where do you put this code?

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  5. djcbMay 28, 2009 at 8:52 AM

    @Anonymous: ignore that last part about 'adding to your color-scheme'

    all the other things should go to your ~/.emacs (~/.emacs means 'the file called .emacs, which is located in your homedir)

    Also see: http://emacs-fu.blogspot.com/2008/12/emacs.html

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  6. AnonymousMay 30, 2009 at 2:30 AM

    Thanks, and if you are using xemacs then, do you put these in init.el?

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  7. djcbMay 30, 2009 at 12:21 PM

    @Anonymous: haven't used Xemacs in ages, but I think it would be: ~/.xemacs/init.el

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  8. AnonymousJune 12, 2009 at 3:06 PM

    Should the second

    (set-face-foreground 'highlight-changes nil)

    have been

    (set-face-foreground 'highlight-changes-delete nil)
    ?

    My .emacs is almost a mirror of the emacs-fu postings :)

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  9. djcbJune 12, 2009 at 3:17 PM

    @dave:good catch,eagle-eyed. copy-paste... i won't update right now, to avoid spamming planet.emacsen.org...

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  10. djcbJune 19, 2009 at 2:46 PM

    updated; fixed the mistake that dave found, and some small other things.

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  11. ssislandsFebruary 5, 2010 at 3:35 PM

    Hi, just found this after a long trek of Googling. My only remaining issue is I want the changes still being highlighted even after I save and reopen my file, do you have any ideas? Thanks a lot.

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  12. AnonymousFebruary 24, 2010 at 6:20 AM

    thank you.. it was a great help to find how the highlight-changes-mode can be controlled .

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