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

[Adam McKee]

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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