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

[Daniel Jasper]

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.
>
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>
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