Re: awesome feature (yet to be added?)

["Andreas Röhler" <andreas.roehler@online.de>]

On 30.05.2014 23:35, Thorsten Jolitz wrote:
> Davis Herring <herring@lanl.gov> writes:
>
>>> Judging by the uptake.  We are the only two to think this is useful.  :)
>
> No, I would really like to see a generic `invert-comment' function in
> Emacs. My use case is outorg.el that converts programming language buffers
> (structured the outshine way, i.e. with outcommented Org-mode headers)
> temporarily to org-mode for text editing and then back to the
> programming major-mode.
>
> That means all the comment sections of the source file are uncommented
> when converting to Org, and outcommented again when converting back to
> the original major-mode. I do this linewise, and in fact outorg can't
> handle those special multiline comments like in C or Java.
>
> A robust generic (= major-mode agnostic) `invert-comment' function as
> part of Emacs that knows how to handle multiline comments too would come
> very handy.
>
>> I thought about implementing `invert-comment' a few years ago, but I
>> wasn't sure what to do about code like this:
>>
>>    /* old_implementation_prepare (); */
>>    /* old_implementation_go (); */
>>
>>    new_implementation_prepare ();
>>    /* The new implementation needs a buffer allocated. */
>>    char *p = malloc (new_implementation_size ());
>>    new_implementation_go (p);
>
> IMO such a function should only act on comments that start at the
> beginning of line, indented comments should remain untouched.
>
>> What to do about the actual comment embedded in the "new" code?
>>
>>    x = foo () + /* bar () + */ baz ();
>>    quux (x, x + 1);     /* quux now accounts for bar internally */
>>
>> What does it mean to toggle commented-ness here?
>
> Again, IMO these comments should remain untouched. E.g. when converting
> source files to org-mode, code section are enclosed in source-blocks
>
> #+begin_src lang
>    x = foo () + /* bar () + */ baz ();
>   quux (x, x + 1);     /* quux now accounts for bar internally */
> #+end_src
>
> and the embedded comments clearly belong to the code.
>
>> Your idea of markers likely works out better than "toggle the comments"
>> because of cases like these.
>
> It would indeed be very useful if there is a way to further act on the
> region/line that was inverted after the function has done its job. So
> returning start/end position, set markers or running a hook or so would
> be nice.
>
> There were quite a lot of proposals in this thread. Any chance that this
> is actually outdiscussed and included in Emacs any time soon?
>

AFAIU instrumenting `comment-dwim' should provide all you need here.

Grüße,

Andreas