Automatically fitting a quickfix window height, consider a long line as many lines. based in http://vim.wikia.com/wiki/Automatically_fitting_a_quickfix_window_height

AdjustWindowHeight.vim

    au FileType qf call AdjustWindowHeight(3, 10)
    function! AdjustWindowHeight(minheight, maxheight)
        let l = 1
        let n_lines = 0
        let w_width = winwidth(0)
        while l <= line('$')
            " number to float for division
            let l_len = strlen(getline(l)) + 0.0
            let line_width = l_len/w_width
            let n_lines += float2nr(ceil(line_width))
            let l += 1
        endw
        exe max([min([n_lines, a:maxheight]), a:minheight]) . "wincmd _"
    endfunction

The loop should/can stop also already, if line('$') >= a:maxheight (and if n_lines is >= a:maxheight).

Because if there are 1000 lines, but maxheight is 10, you can just set it to 10).