allow to show the statusline on top

This is an experimental feature that allows to display the statusline in
the tabline. It might still be a bit rough, but seems to work so far.

Remaining problem:
- Mode changes are not immediately detected, only after moving the
  cursor

fixes #1388
closes #1867

CHANGELOG.md

@@ -6,6 +6,9 @@ This is the Changelog for the vim-airline project.
 - New features
   - Extensions:
     - [Defx](https://github.com/Shougo/defx.nvim) support
+  - Improvements
+    - The statusline can be configured to be shown on top (in the tabline)
+      Set the `g:airline_statusline_ontop` to enable this experimental feature.
 
 ## [0.10] - 2018-12-15
 - New features

autoload/airline.vim

@@ -180,7 +180,8 @@ function! s:invoke_funcrefs(context, funcrefs)
   if err == 1
     let a:context.line = builder.build()
     let s:contexts[a:context.winnr] = a:context
-    call setwinvar(a:context.winnr, '&statusline', '%!airline#statusline('.a:context.winnr.')')
+    let option = get(g:, 'airline_statusline_ontop', 0) ? '&tabline' : '&statusline'
+    call setwinvar(a:context.winnr, option, '%!airline#statusline('.a:context.winnr.')')
   endif
 endfunction
 
@@ -190,7 +191,6 @@ function! airline#statusline(winnr)
   if has_key(s:contexts, a:winnr)
     return '%{airline#check_mode('.a:winnr.')}'.s:contexts[a:winnr].line
   endif
-
   " in rare circumstances this happens...see #276
   return ''
 endfunction

autoload/airline/extensions/branch.vim

@@ -88,7 +88,8 @@ function! s:update_git_branch()
 
   let s:vcs_config['git'].branch = exists("*FugitiveHead") ?
         \ FugitiveHead(s:sha1size) : fugitive#head(s:sha1size)
-  if s:vcs_config['git'].branch is# 'master' && winwidth(0) < 81
+  if s:vcs_config['git'].branch is# 'master' &&
+        \ airline#util#winwidth() < 81
     " Shorten default a bit
     let s:vcs_config['git'].branch='mas'
   endif

autoload/airline/extensions/default.vim

@@ -19,7 +19,7 @@ let s:layout = get(g:, 'airline#extensions#default#layout', [
 
 function! s:get_section(winnr, key, ...)
   if has_key(s:section_truncate_width, a:key)
-    if winwidth(a:winnr) < s:section_truncate_width[a:key]
+    if airline#util#winwidth(a:winnr) < s:section_truncate_width[a:key]
       return ''
     endif
   endif

autoload/airline/extensions/hunks.vim

@@ -66,7 +66,7 @@ function! airline#extensions#hunks#get_hunks()
   " Cache values, so that it isn't called too often
   if exists("b:airline_hunks") &&
     \ get(b:,  'airline_changenr', 0) == b:changedtick &&
-    \ winwidth(0) == get(s:, 'airline_winwidth', 0) &&
+    \ airline#util#winwidth() == get(s:, 'airline_winwidth', 0) &&
     \ get(b:, 'source_func', '') isnot# 's:get_hunks_signify' &&
     \ get(b:, 'source_func', '') isnot# 's:get_hunks_gitgutter' &&
     \ get(b:, 'source_func', '') isnot# 's:get_hunks_empty' &&
@@ -77,14 +77,14 @@ function! airline#extensions#hunks#get_hunks()
   let string = ''
   if !empty(hunks)
     for i in [0, 1, 2]
-      if (s:non_zero_only == 0 && winwidth(0) > 100) || hunks[i] > 0
+      if (s:non_zero_only == 0 && airline#util#winwidth() > 100) || hunks[i] > 0
         let string .= printf('%s%s ', s:hunk_symbols[i], hunks[i])
       endif
     endfor
   endif
   let b:airline_hunks = string
   let b:airline_changenr = b:changedtick
-  let s:airline_winwidth = winwidth(0)
+  let s:airline_winwidth = airline#util#winwidth()
   return string
 endfunction
 

autoload/airline/extensions/nrrwrgn.vim

@@ -19,7 +19,7 @@ function! airline#extensions#nrrwrgn#apply(...)
       let dict=nrrwrgn#NrrwRgnStatus()
       let vmode = { 'v': 'Char ', 'V': 'Line ', '': 'Block '}
       let mode = dict.visual ? vmode[dict.visual] : vmode['V']
-      let winwidth = winwidth(0)
+      let winwidth = airline#util#winwidth()
       if winwidth < 80
         let mode = mode[0]
       endif

autoload/airline/extensions/po.vim

@@ -13,7 +13,7 @@ function! airline#extensions#po#shorten()
       let b:airline_po_stats = b:airline_po_stats[0:(w:displayed_po_limit - 2)].(&encoding==?'utf-8' ? '…' : '.'). ']'
     endif
   endif
-  if strlen(get(b:, 'airline_po_stats', '')) >= 30 && winwidth(0) < 150
+  if strlen(get(b:, 'airline_po_stats', '')) >= 30 && airline#util#winwidth() < 150
     let fuzzy = ''
     let untranslated = ''
     let messages = ''
@@ -35,8 +35,8 @@ endfunction
 
 function! airline#extensions#po#on_winenter()
   " only reset cache, if the window size changed
-  if get(b:, 'airline_winwidth', 0) != winwidth(0)
-    let b:airline_winwidth = winwidth(0)
+  if get(b:, 'airline_winwidth', 0) != airline#util#winwidth()
+    let b:airline_winwidth = airline#util#winwidth()
     " needs re-formatting
     unlet! b:airline_po_stats
   endif

autoload/airline/extensions/tabline.vim

@@ -33,6 +33,11 @@ function! s:toggle_off()
 endfunction
 
 function! s:toggle_on()
+  if get(g:, 'airline_statusline_ontop', 0)
+    call airline#extensions#tabline#enable()
+    let &tabline='%!airline#statusline('.winnr().')'
+    return
+  endif
   call airline#extensions#tabline#autoshow#on()
   call airline#extensions#tabline#tabs#on()
   call airline#extensions#tabline#buffers#on()
@@ -58,12 +63,25 @@ function! s:update_tabline()
     return
   endif
   call airline#util#doautocmd('BufMRUChange')
+  call airline#extensions#tabline#redraw()
+endfunction
+
+function! airline#extensions#tabline#redraw()
   " sometimes, the tabline is not correctly updated see #1580
   " so force redraw here
   if exists(":redrawtabline") == 2
     redrawtabline
   else
-    let &tabline = &tabline
+  " Have to set a property equal to itself to get airline to re-eval.
+  " Setting `let &tabline=&tabline` destroys the cursor position so we
+  " need something less invasive.
+    let &ro = &ro
+  endif
+endfunction
+
+function! airline#extensions#tabline#enable()
+  if &lines > 3
+    set showtabline=2
   endif
 endfunction
 

autoload/airline/extensions/tabline/autoshow.vim

@@ -24,9 +24,7 @@ function! airline#extensions#tabline#autoshow#on()
   augroup airline_tabline_autoshow
     autocmd!
     if s:buf_min_count <= 0 && s:tab_min_count <= 1
-      if &lines > 3
-        set showtabline=2
-      endif
+      call airline#extensions#tabline#enable()
     else
       if s:show_buffers == 1
         autocmd BufEnter  * call <sid>show_tabline(s:buf_min_count, len(airline#extensions#tabline#buflist#list()))

autoload/airline/extensions/wordcount/formatters/default.vim

@@ -24,7 +24,7 @@ else
 endif
 
 function! airline#extensions#wordcount#formatters#default#to_string(wordcount)
-  if winwidth(0) >= 80
+  if airline#util#winwidth() >= 80
     if a:wordcount > 999
       " Format number according to locale, e.g. German: 1.245 or English: 1,245
       let wordcount = substitute(a:wordcount, '\d\@<=\(\(\d\{3\}\)\+\)$', s:decimal_group.'&', 'g')

autoload/airline/init.vim

@@ -194,7 +194,7 @@ function! airline#init#sections()
     let g:airline_section_y = airline#section#create_right(['ffenc'])
   endif
   if !exists('g:airline_section_z')
-    if winwidth(0) > 80
+    if airline#util#winwidth() > 80
       let g:airline_section_z = airline#section#create(['windowswap', 'obsession', '%3p%%'.spc, 'linenr', 'maxlinenr', spc.':%3v'])
     else
       let g:airline_section_z = airline#section#create(['%3p%%'.spc, 'linenr',  ':%3v'])

autoload/airline/parts.vim

@@ -67,9 +67,10 @@ endfunction
 function! airline#parts#spell()
   let spelllang = g:airline_detect_spelllang ? printf(" [%s]", toupper(substitute(&spelllang, ',', '/', 'g'))) : ''
   if g:airline_detect_spell && &spell
-    if winwidth(0) >= 90
+    let winwidth = airline#util#winwidth()
+    if winwidth >= 90
       return g:airline_symbols.spell . spelllang
-    elseif winwidth(0) >= 70
+    elseif winwidth >= 70
       return g:airline_symbols.spell
     else
       return split(g:airline_symbols.spell, '\zs')[0]
@@ -99,7 +100,9 @@ function! airline#parts#readonly()
 endfunction
 
 function! airline#parts#filetype()
-  return winwidth(0) < 90 && strlen(&filetype) > 3 ? matchstr(&filetype, '...'). (&encoding is? 'utf-8' ? '…' : '>') : &filetype
+  return (airline#util#winwidth() < 90 && strlen(&filetype) > 3)
+        \ ? matchstr(&filetype, '...'). (&encoding is? 'utf-8' ? '…' : '>')
+        \ : &filetype
 endfunction
 
 function! airline#parts#ffenc()

autoload/airline/util.vim

@@ -1,17 +1,26 @@
 " MIT License. Copyright (c) 2013-2018 Bailey Ling et al.
 " vim: et ts=2 sts=2 sw=2
 
-" TODO: Try to cache winwidth(0) function
-" e.g. store winwidth per window and access that, only update it, if the size
-" actually changed.
 scriptencoding utf-8
 
 call airline#init#bootstrap()
 let s:spc = g:airline_symbols.space
 let s:nomodeline = (v:version > 703 || (v:version == 703 && has("patch438"))) ? '<nomodeline>' : ''
 
+" TODO: Try to cache winwidth(0) function
+" e.g. store winwidth per window and access that, only update it, if the size
+" actually changed.
+function! airline#util#winwidth(...)
+  let nr = get(a:000, 0, 0)
+  if get(g:, 'airline_statusline_ontop', 0)
+    return &columns
+  else
+    return winwidth(nr)
+  endif
+endfunction
+
 function! airline#util#shorten(text, winwidth, minwidth, ...)
-  if winwidth(0) < a:winwidth && len(split(a:text, '\zs')) > a:minwidth
+  if airline#util#winwidth() < a:winwidth && len(split(a:text, '\zs')) > a:minwidth
     if get(a:000, 0, 0)
       " shorten from tail
       return '…'.matchstr(a:text, '.\{'.a:minwidth.'}$')
@@ -25,14 +34,14 @@ function! airline#util#shorten(text, winwidth, minwidth, ...)
 endfunction
 
 function! airline#util#wrap(text, minwidth)
-  if a:minwidth > 0 && winwidth(0) < a:minwidth
+  if a:minwidth > 0 && airline#util#winwidth() < a:minwidth
     return ''
   endif
   return a:text
 endfunction
 
 function! airline#util#append(text, minwidth)
-  if a:minwidth > 0 && winwidth(0) < a:minwidth
+  if a:minwidth > 0 && airline#util#winwidth() < a:minwidth
     return ''
   endif
   let prefix = s:spc == "\ua0" ? s:spc : s:spc.s:spc
@@ -46,7 +55,7 @@ function! airline#util#warning(msg)
 endfunction
 
 function! airline#util#prepend(text, minwidth)
-  if a:minwidth > 0 && winwidth(0) < a:minwidth
+  if a:minwidth > 0 && airline#util#winwidth() < a:minwidth
     return ''
   endif
   return empty(a:text) ? '' : a:text.s:spc.g:airline_right_alt_sep.s:spc

doc/airline.txt

@@ -228,10 +228,19 @@ values):
 <
 * configure the fileformat output
   By default, it will display something like 'utf-8[unix]', however, you can
-  skip displaying it, if the output matches a configured string. To do so,
-  set >
+  skip displaying it, if the output matches a configured string. To do so, set >
   let g:airline#parts#ffenc#skip_expected_string='utf-8[unix]'
 <
+* Display the statusline in the tabline (first top line): >
+  let g:airline_statusline_ontop = 1
+< 
+  Setting this option, allows to use the statusline option to be used by
+  a custom function or another plugin, since airline won't change it.
+
+  Note: This setting is experimental and works on a best effort approach.
+  Updating the statusline might not always happen as fast as needed, but that
+  is a limitation, that comes from Vim. airline tries to force an update if
+  needed, but it might not always work as expected.
 ==============================================================================
 COMMANDS                                                  *airline-commands*
 

plugin/airline.vim

@@ -57,6 +57,19 @@ function! s:on_window_changed()
   call airline#update_statusline()
 endfunction
 
+function! s:on_cursor_moved()
+  if winnr() != s:active_winnr
+    call <sid>on_window_changed()
+  endif
+  call <sid>update_tabline()
+endfunction
+
+function! s:update_tabline()
+  if get(g:, 'airline_statusline_ontop', 0)
+    call airline#extensions#tabline#redraw()
+  endif
+endfunction
+
 function! s:on_colorscheme_changed()
   call s:init()
   unlet! g:airline#highlighter#normal_fg_hi
@@ -84,11 +97,15 @@ function! s:airline_toggle()
     if exists("s:stl")
       let &stl = s:stl
     endif
+    if exists("s:tal")
+      let [&tal, &showtabline] = s:tal
+    endif
     call airline#highlighter#reset_hlcache()
 
     call airline#util#doautocmd('AirlineToggledOff')
   else
     let s:stl = &statusline
+    let s:tal = [&tabline, &showtabline]
     augroup airline
       autocmd!
 
@@ -113,10 +130,7 @@ function! s:airline_toggle()
         autocmd CompleteDone * call <sid>on_window_changed()
       endif
       " non-trivial number of external plugins use eventignore=all, so we need to account for that
-      autocmd CursorMoved *
-            \   if winnr() != s:active_winnr
-            \ |   call <sid>on_window_changed()
-            \ | endif
+      autocmd CursorMoved * call <sid>on_cursor_moved()
 
       autocmd VimResized * unlet! w:airline_lastmode | :call <sid>airline_refresh()
       if exists('*timer_start') && exists('*funcref')
@@ -137,6 +151,11 @@ function! s:airline_toggle()
       autocmd BufWritePost */autoload/airline/themes/*.vim
             \ exec 'source '.split(globpath(&rtp, 'autoload/airline/themes/'.g:airline_theme.'.vim', 1), "\n")[0]
             \ | call airline#load_theme()
+
+      if get(g:, 'airline_statusline_ontop', 0)
+        " Force update of tabline more often
+        autocmd InsertEnter,InsertLeave,CursorMovedI * :call <sid>update_tabline()
+      endif
     augroup END
 
     if &laststatus < 2
@@ -174,6 +193,7 @@ function! s:airline_refresh()
   call airline#highlighter#reset_hlcache()
   call airline#load_theme()
   call airline#update_statusline()
+  call s:update_tabline()
 endfunction
 
 function! s:FocusGainedHandler(timer)