Thursday, April 1, 2010

Re: Why is there no :foldupdate?

Christian Brabandt wrote:

> > sometimes I am using fold expressions to simply hide away unwanted
> > parts. Usually this boils down to
> > :set fdm=expr fde=getline(v:lnum)!~getreg('/',1)
> >
> > While this works fine, it is only limited to whatever was in register @/
> > when this setting was entered. Now this leaves an interesting question:
> > When are 'foldexpr' reevaluated (are they at all)? Reading :h fold.txt
> > does not mentioned when the fold expressions are reevaluated and folds
> > are updated (or I might have missed it).
> >
> > Now the obvious cure to this is to reenter the foldexpression. So if I
> > am searching for a different term, I need to enter
> > :set fde=getline(v:lnum)!~getreg('/',1)
> > and the folds will be updated.
> >
> > Of course, I could define my own :Foldupdate like this:
> > :com! Foldupdate :exe "set fde=".&fde
> >
> > But this looks so fundamental, that I am wondering, whether I am the
> > only one who is missing :foldupdate. Does anybody else think so? Or am I
> > missing something obvious?
> >
> > PS: Looking at the source, it does not seem too hard, to define an extra
> > :foldupdate command. Does that sound like a reasonable idea? I could
> > prepare a patch for this, if there is interest.
> >
> > regards,
> > Christian
> >
> > (Actually, I'd really like an RegisterChanged autocommand event, which
> > could trigger an :foldupdate)
>
> Ok, here is a patch, that implements :foldupdate as ex command and zU as
> normal mode command.
>
> Here is the testcase:
> go to the vim-Src directory and execute the attached vim-script:
>
> chrisbra t41:~/vim/src [1296]% ./vim -u NONE -N -S foldupdate.vim eval.c
>
> Note, how the folding will be wrong, after the second search command
> (and I have found no way to refresh the folding. zx and zX do not work,
> though its description led me believe it could have. Well actually I
> found one way: filtering the whole buffer through cat will also update
> the folding)
>
> When recompiling vim with the patch, the folding will be updated, when
> :foldupdate is called.

Thanks! Feedback welcome.

One remark: in the help, add a bit more information about when this would
be needed, why the folds are not updated automatically.

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