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Re: Best way to get buffer changes in a program?


From: Thorsten Jolitz
Subject: Re: Best way to get buffer changes in a program?
Date: Tue, 18 Mar 2014 17:44:49 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux)

Thorsten Jolitz <address@hidden> writes:

> Andreas Röhler <address@hidden> writes:
>
>> Am 18.03.2014 01:02, schrieb Thorsten Jolitz:
>>>
>>> Hi List,
>>>
>>> there are many ways to track and visualize changes in Emacs (see
>>> e.g. http://www.emacswiki.org/emacs/TrackChanges).
>>>
>>> However, I would like to get non-interactively a list of lines (or
>>> positions) in the buffer that changed after the last command - how to I
>>> do that? Is is somehow possible to determine in a program that calls
>>> other functions that insert text which new lines have been inserted
>>> (when
>>> a buffer increased in size after a command was executed)?
>>>
>>> Thanks in advance for any hints.
>>>
>>
>> You could start from ediff-regions-... running at alist of functions -
>> all that against a list of original buffers.
>
> Thanks for bringing me on the right track, after quite a lot of research in
> the ediff libraries I found this low-level non-interactive function that
> gives me the line numbers I need:
>
> ,-------------------------------------------------------------------------
> | ;; Run the diff program on FILE1 and FILE2 and put the output in
> | ;; DIFF-BUFFER Return the size of DIFF-BUFFER The return code isn't used
> | ;; in the program at present.
> | 
> | (defun ediff-make-diff2-buffer (diff-buffer file1 file2) ...)
> `-------------------------------------------------------------------------

Just for the record, although I doubt that this is a frequently
requested functionality, this is what I finally came up with to get the
line numbers of the lines that are in file A but not in file B. 

#+begin_src emacs-lisp

(defun omm-get-diff-lines (buf-or-file1 buf-or-file2 &optional 
exec-diff-program)
  "Get line-number of added lines in diff of file args.

BUF-OR-FILE1 should be the file (or its visiting buffer) where
new lines have been added, BUF-OR-FILE2 the smaller original
file (or its visiting buffer).

Optional string argument EXEC-DIFF-PROGRAM defaults to \"diff\"
and should be an executable shell-command."
  (let* ((file1 (cond
                 ((file-readable-p buf-or-file1)
                  buffer-or-file1)
                 ((file-readable-p
                   (buffer-file-name (get-buffer buf-or-file1)))
                  (buffer-file-name (get-buffer buf-or-file1)))
                 (t (error
                     "%s not a file (visiting buffer)"
                     buf-or-file1))))
         (file2 (cond
                 ((file-readable-p buf-or-file2)
                  buffer-or-file2)
                 ((file-readable-p
                   (buffer-file-name (get-buffer buf-or-file2)))
                  (buffer-file-name (get-buffer buf-or-file2)))
                 (t (error
                     "%s not a file (visiting buffer)"
                     buf-or-file2))))
         (diff-prg (or (org-string-nw-p exec-diff-program)
                       "diff"))
         (diff-lst (split-string
                    (shell-command-to-string
                     (format "%s %s %s" diff-prg file1 file2))
                    "\\(---\\|^<.*$\\|^>.*\\|\\\n\\)")))
    (mapcar (lambda (--pair)
              (split-string (cadr --pair) ","))
            (mapcar (lambda (--diff)
                      (split-string --diff "a"))
                    (setq diff-lst
                          (remove-if
                           (lambda (--strg)
                             (or (not (org-string-nw-p --strg))
                                 (not (member
                                       "a"
                                       (split-string --strg "")))))
                           diff-lst))))))
#+end_src

-- 
cheers,
Thorsten




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