" Enable folding for ftrace function_graph traces.
  "
  " To use, :source this file while viewing a function_graph trace, or use vim's
  " -S option to load from the command-line together with a trace.  You can then
  " use the usual vim fold commands, such as "za", to open and close nested
  " functions.  While closed, a fold will show the total time taken for a call,
  " as would normally appear on the line with the closing brace.  Folded
  " functions will not include finish_task_switch(), so folding should remain
  " relatively sane even through a context switch.
  "
  " Note that this will almost certainly only work well with a
  " single-CPU trace (e.g. trace-cmd report --cpu 1).
  
  function! FunctionGraphFoldExpr(lnum)
    let line = getline(a:lnum)
    if line[-1:] == '{'
      if line =~ 'finish_task_switch() {$'
        return '>1'
      endif
      return 'a1'
    elseif line[-1:] == '}'
      return 's1'
    else
      return '='
    endif
  endfunction
  
  function! FunctionGraphFoldText()
    let s = split(getline(v:foldstart), '|', 1)
    if getline(v:foldend+1) =~ 'finish_task_switch() {$'
      let s[2] = ' task switch  '
    else
      let e = split(getline(v:foldend), '|', 1)
      let s[2] = e[2]
    endif
    return join(s, '|')
  endfunction
  
  setlocal foldexpr=FunctionGraphFoldExpr(v:lnum)
  setlocal foldtext=FunctionGraphFoldText()
  setlocal foldcolumn=12
  setlocal foldmethod=expr