Change the text in folds

Question

I noticed that fold texts can show useful information. They usually show something like

+-- 5 lines: <div id="header-inner">--------------------------------------------

Is it possible to change the text in those lines? I noticed that something is possible in foldexpr but would it be possible to completely redesign folds?
e.g.
+ <div id="header-inner"> : "possible comment from line above" : row 27 : length 5

thank you

Answer 1

There are a few things I don't understand from your question, such as which foldmethod you are using, or what the number of "rows" refers to, but here's a custom foldtext function that should do roughly what you want:

function! MyFoldText()
    let nl = v:foldend - v:foldstart + 1
    let comment = substitute(getline(v:foldstart),"^ *","",1)
    let linetext = substitute(getline(v:foldstart+1),"^ *","",1)
    let txt = '+ ' . linetext . ' : "' . comment . '" : length ' . nl
    return txt
endfunction
set foldtext=MyFoldText()

Explanation:

1. Find the number of lines contained by the fold.
2. Get the "comment" from the line before the first folded line (and remove leading spaces).
3. Get the text from the first line of the fold (and remove leading spaces).
4. Assemble the above information into the returned foldtext, with appropriate formatting.

Hope this helps. It should be easily tailored to your needs.