bug#13949: 24.3.50; `fill-paragraph' should not always put the buffer as modified

[Andreas Röhler]

Am 14.03.2013 18:53, schrieb Eli Zaretskii:
> > From: Stefan Monnier <monnier@iro.umontreal.ca>
> > Cc: Eli Zaretskii <eliz@gnu.org>,  13949@debbugs.gnu.org
> > Date: Thu, 14 Mar 2013 09:38:08 -0400
> >
> > > Well, since the `fill-paragraph' command at step #4 leaved the buffer
> > > with the same contents, flagging the buffer as modified was
> > > unnecessary in this case.
> >
> > AFAIK there are two ways to go about it:
> > - compare the sha1 of the paragraph before and after filling and reset
> >    buffer-modified-p if it shows the text hasn't changed.
>
> This has the disadvantage of scanning the entire buffer, which might
> increase paging and memory pressure in general.
>
> > - change fill.el so that filling paragraph doesn't just "unfill whole
> >    paragraph + fill whole paragraph" but instead goes line by line, and
> >    only modifies the text where there's a need to.
>
> But it sounds like Dani wants this behavior not only for
> fill-paragraph, but for any command that can potentially modify the
> buffer, but actually doesn't.  This would require to compute sha1
> before and after every command that might change the buffer.

If fill-paragraph is at stake only, store paragraph in a string at beginning and
compare the result should be enough to reset the modify flag if justified.

Andreas