Re: Diff could also show the changes within lines

[Michael Heerdegen]

"Sebastien Vauban" <sva-news@mygooglest.com>
writes:

> I did, in a minimal Emacs configuration:
>
> (load-theme 'leuven t)
>
> ;; mode for viewing/editing context diffs
> (with-eval-after-load "diff-mode"
>
>   (defun my-diff-make-fine-diffs ()
>     "Enable Diff Auto Refine mode."
>     (interactive)
>     (message ">>> BEGIN <<<")
>     (let (diff-auto-refine-mode)
>       (condition-case nil
>           (save-excursion
>             (goto-char (point-min))
>             (while (not (eobp))
>               (diff-hunk-next)
>               (diff-refine-hunk)
>               (message ">> I've refined the next hunk... <<")))
>         (error nil))
>       (run-at-time 0.0 nil
>                    (lambda ()
>                      (if (eq major-mode 'diff-mode)
>                          ;; put back the cursor only if still in a Diff buffer
>                          ;; after the delay
>                          (goto-char (point-min))))))
>     (message ">>> END <<<"))
>
>   (defun my--diff-make-fine-diffs-if-necessary ()
>     "Auto-refine only the regions of 14,000 bytes or less."
>     ;; check for auto-refine limit
>     (unless (> (buffer-size) 14000)
>       (my-diff-make-fine-diffs)))
>
>   (add-hook 'diff-mode-hook
>             'my--diff-make-fine-diffs-if-necessary))
>
> Weirdly enough, it does not work when done automatically, well when done
> interactively...
>
> In *all* cases, I see (in the *Messages* buffer):
>
> >>> BEGIN <<<
> >> I've refined the next hunk... << [2 times]
> >>> END <<<
>
> ... so, even when done by the hook, I see those messages, as if the
> refining was done, but it's not visible in the Diff buffer, as you can
> see on http://screencast.com/t/e7et4xeO.
>
> When Edebugging, or when going to the *vc-diff* buffer and calling M-x
> my-diff-make-fine-diffs, the same messages appear in the *Messages*
> buffer, but the buffer is well colored differently, as you can see on
> http://screencast.com/t/K2VdxlF2fMld.

My guess is that diff-mode-hook is not a good place to push your
function to.  Maybe it is called too early, and the effect is somehow
reverted later.  You may try something like

(advice-add
 'vc-diff :after
 (lambda (&rest _)
   (my--diff-make-fine-diffs-if-necessary)))

I wonder if that work's.

> So, I don't understand anything anymore... and don't know how to
> proceed to further debug this...

Have you already tried to (debug-on-entry 'my-diff-make-fine-diffs)?  I
wonder how the buffer looks like after `my-diff-make-fine-diffs' is
done.  You may try to find out what is going on later.

> Side (though important) question: when Edebugging, as soon as I step
> through the function, the *vc-diff* buffer disappears from my
> sight.  I always have to switch to it, and check what changed, to see
> what's going on.  Is there a way to make the buffer (on which the code
> is applied) stay visible during the stepping session?

I think it is best to display it just in a different frame after
starting edebug.  Yes, it is very aggressive in capturing frames.


Regards,

Michael.