[cfe-dev] clang-format emacs integration: window-start dislocation when formatting-before-save

[Daniel Jasper]

Yes, we are about to do that. I just need someone with actual elisp
knowledge to review the patch ;-).

On Wed, Jan 7, 2015 at 9:34 AM, Adam McKee <Adam.Matthew.McKee at gmail.com>
wrote:

> Johann's clang-format.el is now working great for me.  For some reason,
> the XML library in my emacs 23.4 (from Debian wheezy) was complaining about
> multiple root tags in the XML from clang-format, but when I upgraded to
> emacs 24.4 that problem disappeared.  It's strange because a) there were
> not multiple root tags, and b) Johann tested with the same version of emacs
> from wheezy and that worked for him.  Despite that little mystery, from my
> point of view all's well that ends well.
>
> For thoroughness, after upgrading my emacs, I also re-tested the
> clang-format.el from clang-format-3.6, and I still had the same problem
> with window-starts getting moved to the start of the buffer when doing "C-x
> s" (save-some-buffers).
>
> Maybe Johann's clang-format.el should be adopted into clang-format?
>
> On Tue, Jan 6, 2015 at 11:54 AM, Johann Klähn <kljohann at gmail.com> wrote:
>
>> I have a prototype[1] that does adjustments via single edit operations
>> based on the '-output-replacements-xml' option (instead of replacing
>> the whole buffer; this would be similar to the difflib-approach, I
>> guess?). But when using this option the JSON-header containing the
>> '-cursor' information is not returned, so I have to rely on markers
>> inserted into the buffer to keep the cursor position. On the upside
>> this allows me to track the cursor per-window.
>>
>> [1] https://github.com/kljohann/clang-format.el/tree/xml
>>
>> On Sat, Jan 3, 2015 at 9:31 AM, Daniel Jasper <djasper at google.com> wrote:
>> > I have not heard of this problem before, but I am also not personally
>> using
>> > emacs. Adding Johann Klähn, who has just proposed improvements to the
>> emacs
>> > integration. Maybe he has experienced this problem, too.
>> >
>> > I think the "right" solution here might be what we do for the vim
>> > integration. Instead of replacing the entire buffer, we just compute a
>> diff
>> > and only apply the diff chunks individually. This makes fiddling with
>> the
>> > window starts completely unnecessary.
>> >
>> > On Fri, Jan 2, 2015 at 2:41 AM, Adam McKee <
>> Adam.Matthew.McKee at gmail.com>
>> > wrote:
>> >>
>> >> As I wrote earlier, I've put this in my ~/.emacs to format my C++
>> buffers
>> >> before they're saved:
>> >>
>> >> (add-hook 'c++-mode-hook
>> >>     (lambda()
>> >>         (add-hook 'before-save-hook 'clang-format-buffer)))
>> >>
>> >> This worked fine when saving individual files with "C-x C-s".
>> However, I
>> >> encountered a problem when using "C-x s" (save-some-buffers) where the
>> >> window-start would be moved to the very first line, and the point
>> would be
>> >> moved to the left margin on the middle line in the window.  In
>> >> clang-format.el, I added some debug messages to show what's happening
>> with
>> >> the calls to goto-char() and set-window-start().  What I found is that
>> >> there's nothing wrong with those calls in the (save-some-buffers)
>> case, and
>> >> they are the exact same as in the case where I save the buffer
>> individually
>> >> with "C-x C-s".  Despite (clang-format-buffer) doing apparently the
>> same
>> >> thing in both cases, with (save-some-buffers) _something_ is moving
>> >> window-start to the start of the file, which is not acceptable.
>> >>
>> >> I don't see a problem with clang-format.el to be fixed, and I don't
>> know
>> >> how to proceed with this any more, so here I just wanted to give an
>> account
>> >> of my experience with this, in the hope that it could be useful.
>> >>
>> >> What I've done to my clang-format.el for now is to remove the loop at
>> the
>> >> end of the function that restores the window-starts of the windows
>> showing
>> >> the formatted buffer.  The result of that is still is slightly
>> disorienting
>> >> because the line containing the point is centered on the screen (if
>> >> possible), but it's far better than having the window-start moved to
>> the
>> >> first line.
>> >>
>> >> Clang-formatting before save must be quite a common practice, so is
>> anyone
>> >> doing so _not_ seeing the same window-start dislocation problem with
>> >> (save-some-buffers)?  If I can duplicate an emacs setup that doesn't
>> have
>> >> this problem, that would help.
>> >>
>> >> _______________________________________________
>> >> cfe-dev mailing list
>> >> cfe-dev at cs.uiuc.edu
>> >> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev
>> >>
>> >
>>
>
>
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