Vim: Foldtext contain all content, instead of only the first line

Question

Would like to have all content of the folded block, instead of only the first line.

My current foldsettings are:

set foldmethod=marker
set foldmarker={,}

Example how my data is structured:

{
  cows
  pigs
  chickens
}

Current folds look like:

+--  5 lines: ---------------------------

Ideally folds look like:

{  cows  pigs  chickens  } --------------

Have searched on the net for a while, unfortunately didn't succeed.

Answer 1

The option foldtext defines a expression, that is evaluated to create the text displayed for a closed fold. By default this is set to the build in function foldtext().

You can create a custom function, to create the text displayed on a closed fold. The documentation :help fold-foldtext contains an example. Note that the resulting text is truncated to fit window width.

Answer 2

An example of probably what you want:

set foldmethod=marker
set foldmarker={,}

set foldtext=MyFoldText()
fu! MyFoldText()
    let lineNr = v:foldstart
    let text = ""
    while (strlen(text) < winwidth(0) - v:foldlevel - 2) && lineNr <= v:foldend
        let text .= getline(lineNr).' '
        let lineNr += 1
    endwhile

    let text = v:folddashes . text
    if strlen(text) > winwidth(0) - 5 
        let text = strpart(text, 0, winwidth(0) - 5).' … }'
    endif
    return text
endfu

It is not 100% bulletproof, probably will make your vim slow. I could make it more generic (you see there are some figures I manually hardcoded) but I will leave it for you to tinker.