Change what vim displays when there is a fold

Question

When I create a fold with zfap, vim displays something like:

+--  15 lines: myFunctionPrototype :: Test -> Test -> Bool 

However, I would like vim not to display this number of lines. I find this distracting, and not adding sufficient information in my case.

I'd prefer:

+-- : myFunctionPrototype :: Test -> Test -> Bool

or even better:

+-- myFunctionPrototype :: Test -> Test -> Bool

Is there a way to suppress the line count, or a way to modify what vim displays when there's a fold that I could put in my vimrc ?

Answer 1

The text that is displayed for a closed fold is determined by the 'foldtext' option. See

:help 'foldtext'
:help fold-foldtext

The latter topic has a few examples of ways to get different text. As another, simple example,

:set foldtext=v:folddashes

will result in a line of only dashes (actually hyphens) across the full width of the window.

Answer 2

to put in .vimrc:

set foldtext=MyFoldText()
function MyFoldText()
  let line = getline(v:foldstart)
  let sub = substitute(line, '/\*\|\*/\|{{{\d\=', '', 'g')
  return v:folddashes . sub
endfunction

MyFoldText is now the function that is responsible for displaying some text, when some lines have been folded.