vim-airline/autoload/airline/extensions/tabline.vim

" MIT License. Copyright (c) 2013 Bailey Ling.
" vim: et ts=2 sts=2 sw=2

let s:formatter = get(g:, 'airline#extensions#tabline#formatter', 'default')
let s:excludes = get(g:, 'airline#extensions#tabline#excludes', [])
let s:tab_nr_type = get(g:, 'airline#extensions#tabline#tab_nr_type', 0)
let s:show_buffers = get(g:, 'airline#extensions#tabline#show_buffers', 1)

let s:builder_context = {
      \ 'active'        : 1,
      \ 'left_sep'      : get(g:, 'airline#extensions#tabline#left_sep'     , ' '),
      \ 'left_alt_sep'  : get(g:, 'airline#extensions#tabline#left_alt_sep' , '|'),
      \ 'right_sep'     : get(g:, 'airline#extensions#tabline#right_sep'    , g:airline_right_sep),
      \ 'right_alt_sep' : get(g:, 'airline#extensions#tabline#right_alt_sep', g:airline_right_alt_sep),
      \ }

let s:buf_min_count = get(g:, 'airline#extensions#tabline#buffer_min_count', 0)
let s:tab_min_count = get(g:, 'airline#extensions#tabline#tab_min_count', 0)

function! airline#extensions#tabline#init(ext)
  if has('gui_running')
    set guioptions-=e
  endif

  set tabline=%!airline#extensions#tabline#get()

  if s:buf_min_count <= 0 && s:tab_min_count <= 0
    set showtabline=2
  else
    if s:show_buffers == 1
      autocmd BufEnter * call <sid>on_buf_enter(s:buf_min_count, len(s:get_buffer_list()))
    else
      autocmd BufEnter * call <sid>on_buf_enter(s:tab_min_count, tabpagenr('$'))
    endif
  endif

  call a:ext.add_theme_func('airline#extensions#tabline#load_theme')
endfunction

function! airline#extensions#tabline#load_theme(palette)
  let colors    = get(a:palette, 'tabline', {})
  let l:tab     = get(colors, 'airline_tab', a:palette.normal.airline_b)
  let l:tabsel  = get(colors, 'airline_tabsel', a:palette.normal.airline_a)
  let l:tabtype = get(colors, 'airline_tabtype', a:palette.visual.airline_a)
  let l:tabfill = get(colors, 'airline_tabfill', a:palette.normal.airline_c)
  let l:tabmod  = get(colors, 'airline_tabmod', a:palette.insert.airline_a)
  let l:tabhid  = get(colors, 'airline_tabhid', a:palette.normal.airline_c)
  call airline#highlighter#exec('airline_tab', l:tab)
  call airline#highlighter#exec('airline_tabsel', l:tabsel)
  call airline#highlighter#exec('airline_tabtype', l:tabtype)
  call airline#highlighter#exec('airline_tabfill', l:tabfill)
  call airline#highlighter#exec('airline_tabmod', l:tabmod)
  call airline#highlighter#exec('airline_tabhid', l:tabhid)
endfunction

function! s:on_buf_enter(min_count, total_count)
  if a:total_count >= a:min_count
    if &showtabline != 2
      set showtabline=2
    endif
  else
    if &showtabline != 0
      set showtabline=0
    endif
  endif
endfunction

function! airline#extensions#tabline#get()
  if s:show_buffers && tabpagenr('$') == 1
    return s:get_buffers()
  else
    return s:get_tabs()
  endif
endfunction

function! airline#extensions#tabline#title(n)
  let buflist = tabpagebuflist(a:n)
  let winnr = tabpagewinnr(a:n)
  return airline#extensions#tabline#get_buffer_name(buflist[winnr - 1])
endfunction

function! airline#extensions#tabline#get_buffer_name(nr)
  return airline#extensions#tabline#formatters#{s:formatter}(a:nr, get(s:, 'current_buffer_list', []))
endfunction

function! s:get_buffer_list()
  let buffers = []
  let cur = bufnr('%')
  for nr in range(1, bufnr('$'))
    if buflisted(nr) && bufexists(nr)
      for ex in s:excludes
        if match(bufname(nr), ex)
          continue
        endif
      endfor
      if getbufvar(nr, 'current_syntax') == 'qf'
        continue
      endif
      call add(buffers, nr)
    endif
  endfor

  let s:current_buffer_list = buffers
  return buffers
endfunction

function! s:get_visible_buffers()
  let buffers = s:get_buffer_list()
  let cur = bufnr('%')

  let total_width = 0
  let max_width = 0

  for nr in buffers
    let width = len(airline#extensions#tabline#get_buffer_name(nr)) + 4
    let total_width += width
    let max_width = max([max_width, width])
  endfor

  " only show current and surrounding buffers if there are too many buffers
  let position  = index(buffers, cur)
  if total_width > winwidth(0) && position > -1
    let buf_count = len(buffers)

    " determine how many buffers to show based on the longest buffer width,
    " use one on the right side and put the rest on the left
    let buf_max   = winwidth(0) / max_width
    let buf_right = 1
    let buf_left  = max([0, buf_max - buf_right])

    let start = max([0, position - buf_left])
    let end   = min([buf_count, position + buf_right])

    " fill up available space on the right
    if position < buf_left
      let end += (buf_left - position)
    endif

    " fill up available space on the left
    if end > buf_count - 1 - buf_right
      let start -= max([0, buf_right - (buf_count - 1 - position)])
    endif

    let buffers = eval('buffers[' . start . ':' . end . ']')

    if start > 0
      call insert(buffers, -1, 0)
    endif

    if end < buf_count - 1
      call add(buffers, -1)
    endif
  endif

  return buffers
endfunction

function! s:get_buffers()
  let b = airline#builder#new(s:builder_context)
  let cur = bufnr('%')
  let tab_bufs = tabpagebuflist(tabpagenr())
  for nr in s:get_visible_buffers()
    if nr < 0
      call b.add_raw('%#airline_tabhid#...')
      continue
    endif
    if cur == nr
      if g:airline_detect_modified && getbufvar(nr, '&modified')
        let group = 'airline_tabmod'
      else
        let group = 'airline_tabsel'
      endif
    else
      if index(tab_bufs, nr) > -1
        let group = 'airline_tab'
      else
        let group = 'airline_tabhid'
      endif
    endif
    call b.add_section(group, '%( %{airline#extensions#tabline#get_buffer_name('.nr.')} %)')
  endfor

  call b.add_section('airline_tabfill', '')
  call b.split()
  call b.add_section('airline_tabtype', ' buffers ')
  return b.build()
endfunction

function! s:get_tabs()
  let b = airline#builder#new(s:builder_context)
  for i in range(1, tabpagenr('$'))
    if i == tabpagenr()
      let group = 'airline_tabsel'
      if g:airline_detect_modified
        for bi in tabpagebuflist(i)
          if getbufvar(bi, '&modified')
            let group = 'airline_tabmod'
          endif
        endfor
      endif
    else
      let group = 'airline_tab'
    endif
    let val = '%('
    if s:tab_nr_type == 0
      let val .= ' %{len(tabpagebuflist('.i.'))}'
    else
      let val .= (g:airline_symbols.space).i
    endif
    call b.add_section(group, val.'%'.i.'T %{airline#extensions#tabline#title('.i.')} %)')
  endfor
  call b.add_raw('%T')
  call b.add_section('airline_tabfill', '')
  call b.split()
  call b.add_section('airline_tab', ' %999XX ')
  call b.add_section('airline_tabtype', ' tabs ')
  return b.build()
endfunction