From a2f298ba8fc6e7e971ad9d1ba90469cbab8f04fa Mon Sep 17 00:00:00 2001
From: Christian Brabandt <cb@256bit.org>
Date: Sat, 8 May 2021 13:36:55 +0200
Subject: [PATCH] vim9: Rewrite highlighter in Vim9 Script

This is the one script, that is usually causing the most slow down.
Converting it to Vim9 Script should keep vim responsive and the users
happy. Hopefully that works now.
---
 autoload/airline.vim             |   2 +-
 autoload/airline/highlighter.vim | 952 +++++++++++++++++++++----------
 autoload/airline/msdos.vim       |  56 +-
 3 files changed, 695 insertions(+), 315 deletions(-)

diff --git a/autoload/airline.vim b/autoload/airline.vim
index 60a4dc05..cd02cf5c 100644
--- a/autoload/airline.vim
+++ b/autoload/airline.vim
@@ -261,7 +261,7 @@ function! airline#check_mode(winnr)
 
   let mode_string = join(mode)
   if get(w:, 'airline_lastmode', '') != mode_string
-    call airline#highlighter#highlight_modified_inactive(string(context.bufnr))
+    call airline#highlighter#highlight_modified_inactive(context.bufnr)
     call airline#highlighter#highlight(mode, string(context.bufnr))
     call airline#util#doautocmd('AirlineModeChanged')
     let w:airline_lastmode = mode_string
diff --git a/autoload/airline/highlighter.vim b/autoload/airline/highlighter.vim
index 3de3174b..348a8426 100644
--- a/autoload/airline/highlighter.vim
+++ b/autoload/airline/highlighter.vim
@@ -1,5 +1,5 @@
 " MIT License. Copyright (c) 2013-2021 Bailey Ling Christian Brabandt et al.
-" vim: et ts=2 sts=2 sw=2
+" vim: et ts=2 sts=2 sw=2 et
 
 scriptencoding utf-8
 
@@ -13,318 +13,674 @@ let s:separators = {}
 let s:accents = {}
 let s:hl_groups = {}
 
-function! s:gui2cui(rgb, fallback) abort
-  if a:rgb == ''
-    return a:fallback
-  elseif match(a:rgb, '^\%(NONE\|[fb]g\)$') > -1
-    return a:rgb
-  elseif a:rgb[0] !~ '#'
-    " a:rgb contains colorname
-    return a:rgb
-  endif
-  let rgb = map(split(a:rgb[1:], '..\zs'), '0 + ("0x".v:val)')
-  return airline#msdos#round_msdos_colors(rgb)
-endfunction
+if !exists(":def") || (exists(":def") && get(g:, "airline_experimental", 0) == 0)
 
-function! s:group_not_done(list, name) abort
-  if index(a:list, a:name) == -1
-    call add(a:list, a:name)
-    return 1
-  else
-    if &vbs
-      echomsg printf("airline: group: %s already done, skipping", a:name)
+  " Legacy Vimscript implementation
+  function! s:gui2cui(rgb, fallback) abort
+    if a:rgb == ''
+      return a:fallback
+    elseif match(a:rgb, '^\%(NONE\|[fb]g\)$') > -1
+      return a:rgb
+    elseif a:rgb[0] !~ '#'
+      " a:rgb contains colorname
+      return a:rgb
     endif
-    return 0
-  endif
-endfu
+    let rgb = map(split(a:rgb[1:], '..\zs'), '0 + ("0x".v:val)')
+    return airline#msdos#round_msdos_colors(rgb)
+  endfunction
 
-function! s:get_syn(group, what, mode) abort
-  let color = ''
-  if hlexists(a:group)
-    let color = synIDattr(synIDtrans(hlID(a:group)), a:what, a:mode)
-  endif
-  if empty(color) || color == -1
-    " should always exist
-    let color = synIDattr(synIDtrans(hlID('Normal')), a:what, a:mode)
-    " however, just in case
-    if empty(color) || color == -1
-      let color = 'NONE'
-    endif
-  endif
-  return color
-endfunction
-
-function! s:get_array(guifg, guibg, ctermfg, ctermbg, opts) abort
-  return [ a:guifg, a:guibg, a:ctermfg, a:ctermbg, empty(a:opts) ? '' : join(a:opts, ',') ]
-endfunction
-
-function! airline#highlighter#reset_hlcache() abort
-  let s:hl_groups = {}
-endfunction
-
-function! airline#highlighter#get_highlight(group, ...) abort
-  " only check for the cterm reverse attribute
-  " TODO: do we need to check all modes (gui, term, as well)?
-  let reverse = synIDattr(synIDtrans(hlID(a:group)), 'reverse', 'cterm')
-  if get(g:, 'airline_highlighting_cache', 0) && has_key(s:hl_groups, a:group)
-    let res = s:hl_groups[a:group]
-    return reverse ? [ res[1], res[0], res[3], res[2], res[4] ] : res
-  else
-    let ctermfg = s:get_syn(a:group, 'fg', 'cterm')
-    let ctermbg = s:get_syn(a:group, 'bg', 'cterm')
-    let guifg = s:get_syn(a:group, 'fg', 'gui')
-    let guibg = s:get_syn(a:group, 'bg', 'gui')
-    let bold = synIDattr(synIDtrans(hlID(a:group)), 'bold')
-    if reverse
-      let res = s:get_array(guibg, guifg, ctermbg, ctermfg, bold ? ['bold'] : a:000)
+  function! s:group_not_done(list, name) abort
+    if index(a:list, a:name) == -1
+      call add(a:list, a:name)
+      return 1
     else
-      let res = s:get_array(guifg, guibg, ctermfg, ctermbg, bold ? ['bold'] : a:000)
+      if &vbs
+        echomsg printf("airline: group: %s already done, skipping", a:name)
+      endif
+      return 0
     endif
-  endif
-  let s:hl_groups[a:group] = res
-  return res
-endfunction
+  endfu
 
-function! airline#highlighter#get_highlight2(fg, bg, ...) abort
-  let guifg = s:get_syn(a:fg[0], a:fg[1], 'gui')
-  let guibg = s:get_syn(a:bg[0], a:bg[1], 'gui')
-  let ctermfg = s:get_syn(a:fg[0], a:fg[1], 'cterm')
-  let ctermbg = s:get_syn(a:bg[0], a:bg[1], 'cterm')
-  return s:get_array(guifg, guibg, ctermfg, ctermbg, a:000)
-endfunction
-
-function! s:hl_group_exists(group) abort
-  if !hlexists(a:group)
-    return 0
-  elseif empty(synIDattr(hlID(a:group), 'fg'))
-    return 0
-  endif
-  return 1
-endfunction
-
-function! airline#highlighter#exec(group, colors) abort
-  if pumvisible()
-    return
-  endif
-  let colors = a:colors
-  if s:is_win32term
-    let colors[2] = s:gui2cui(get(colors, 0, ''), get(colors, 2, ''))
-    let colors[3] = s:gui2cui(get(colors, 1, ''), get(colors, 3, ''))
-  endif
-  let old_hi = airline#highlighter#get_highlight(a:group)
-  if len(colors) == 4
-    call add(colors, '')
-  endif
-  let new_hi = [colors[0], colors[1], printf('%s', colors[2]), printf('%s', colors[3]), colors[4]]
-  let colors = s:CheckDefined(colors)
-  if old_hi != new_hi || !s:hl_group_exists(a:group)
-    let cmd = printf('hi %s%s', a:group, s:GetHiCmd(colors))
-    try
-      exe cmd
-    catch /^Vim\%((\a\+)\)\=:E421:/ " color definition not found
-      let group=matchstr(v:exception, '\w\+\ze=')
-      let color=matchstr(v:exception, '=\zs\w\+')
-      let cmd=substitute(cmd, color, 'grey', 'g')
-      exe cmd
-      call airline#util#warning('color definition for group ' . a:group . ' not found, using grey as fallback')
-    endtry
-    if has_key(s:hl_groups, a:group)
-      let s:hl_groups[a:group] = colors
+  function! s:get_syn(group, what, mode) abort
+    let color = ''
+    if hlexists(a:group)
+      let color = synIDattr(synIDtrans(hlID(a:group)), a:what, a:mode)
     endif
-  endif
-endfunction
+    if empty(color) || color == -1
+      " should always exist
+      let color = synIDattr(synIDtrans(hlID('Normal')), a:what, a:mode)
+      " however, just in case
+      if empty(color) || color == -1
+        let color = 'NONE'
+      endif
+    endif
+    return color
+  endfunction
 
-function! s:CheckDefined(colors) abort
-  " Checks, whether the definition of the colors is valid and is not empty or NONE
-  " e.g. if the colors would expand to this:
-  " hi airline_c ctermfg=NONE ctermbg=NONE
-  " that means to clear that highlighting group, therefore, fallback to Normal
-  " highlighting group for the cterm values
+  function! s:get_array(guifg, guibg, ctermfg, ctermbg, opts) abort
+    return [ a:guifg, a:guibg, a:ctermfg, a:ctermbg, empty(a:opts) ? '' : join(a:opts, ',') ]
+  endfunction
 
-  " This only works, if the Normal highlighting group is actually defined, so
-  " return early, if it has been cleared
-  if !exists("g:airline#highlighter#normal_fg_hi")
-    let g:airline#highlighter#normal_fg_hi = synIDattr(synIDtrans(hlID('Normal')), 'fg', 'cterm')
-  endif
-  if empty(g:airline#highlighter#normal_fg_hi) || g:airline#highlighter#normal_fg_hi < 0
-    return a:colors
-  endif
+  function! airline#highlighter#reset_hlcache() abort
+    let s:hl_groups = {}
+  endfunction
 
-  for val in a:colors
-    if !empty(val) && val !=# 'NONE'
+  function! airline#highlighter#get_highlight(group, ...) abort
+    " only check for the cterm reverse attribute
+    " TODO: do we need to check all modes (gui, term, as well)?
+    let reverse = synIDattr(synIDtrans(hlID(a:group)), 'reverse', 'cterm')
+    if get(g:, 'airline_highlighting_cache', 0) && has_key(s:hl_groups, a:group)
+      let res = s:hl_groups[a:group]
+      return reverse ? [ res[1], res[0], res[3], res[2], res[4] ] : res
+    else
+      let ctermfg = s:get_syn(a:group, 'fg', 'cterm')
+      let ctermbg = s:get_syn(a:group, 'bg', 'cterm')
+      let guifg = s:get_syn(a:group, 'fg', 'gui')
+      let guibg = s:get_syn(a:group, 'bg', 'gui')
+      let bold = synIDattr(synIDtrans(hlID(a:group)), 'bold')
+      if reverse
+        let res = s:get_array(guibg, guifg, ctermbg, ctermfg, bold ? ['bold'] : a:000)
+      else
+        let res = s:get_array(guifg, guibg, ctermfg, ctermbg, bold ? ['bold'] : a:000)
+      endif
+    endif
+    let s:hl_groups[a:group] = res
+    return res
+  endfunction
+
+  function! airline#highlighter#get_highlight2(fg, bg, ...) abort
+    let guifg = s:get_syn(a:fg[0], a:fg[1], 'gui')
+    let guibg = s:get_syn(a:bg[0], a:bg[1], 'gui')
+    let ctermfg = s:get_syn(a:fg[0], a:fg[1], 'cterm')
+    let ctermbg = s:get_syn(a:bg[0], a:bg[1], 'cterm')
+    return s:get_array(guifg, guibg, ctermfg, ctermbg, a:000)
+  endfunction
+
+  function! s:hl_group_exists(group) abort
+    if !hlexists(a:group)
+      return 0
+    elseif empty(synIDattr(synIDtrans(hlID(a:group)), 'fg'))
+      return 0
+    endif
+    return 1
+  endfunction
+
+  function! s:CheckDefined(colors) abort
+    " Checks, whether the definition of the colors is valid and is not empty or NONE
+    " e.g. if the colors would expand to this:
+    " hi airline_c ctermfg=NONE ctermbg=NONE
+    " that means to clear that highlighting group, therefore, fallback to Normal
+    " highlighting group for the cterm values
+
+    " This only works, if the Normal highlighting group is actually defined, so
+    " return early, if it has been cleared
+    if !exists("g:airline#highlighter#normal_fg_hi")
+      let g:airline#highlighter#normal_fg_hi = synIDattr(synIDtrans(hlID('Normal')), 'fg', 'cterm')
+    endif
+    if empty(g:airline#highlighter#normal_fg_hi) || g:airline#highlighter#normal_fg_hi < 0
       return a:colors
     endif
-  endfor
-  " this adds the bold attribute to the term argument of the :hi command,
-  " but at least this makes sure, the group will be defined
-  let fg = g:airline#highlighter#normal_fg_hi
-  let bg = synIDattr(synIDtrans(hlID('Normal')), 'bg', 'cterm')
-  if bg < 0
-    " in case there is no background color defined for Normal
-    let bg = a:colors[3]
-  endif
-  return a:colors[0:1] + [fg, bg] + [a:colors[4]]
-endfunction
 
-function! s:GetHiCmd(list) abort
-  " a:list needs to have 5 items!
-  let res = ''
-  let i = -1
-  while i < 4
-    let i += 1
-    let item = get(a:list, i, '')
-    if item is ''
-      continue
+    for val in a:colors
+      if !empty(val) && val !=# 'NONE'
+        return a:colors
+      endif
+    endfor
+    " this adds the bold attribute to the term argument of the :hi command,
+    " but at least this makes sure, the group will be defined
+    let fg = g:airline#highlighter#normal_fg_hi
+    let bg = synIDattr(synIDtrans(hlID('Normal')), 'bg', 'cterm')
+    if empty(bg) || bg < 0
+      " in case there is no background color defined for Normal
+      let bg = a:colors[3]
     endif
-    if i == 0
-      let res .= ' guifg='.item
-    elseif i == 1
-      let res .= ' guibg='.item
-    elseif i == 2
-      let res .= ' ctermfg='.item
-    elseif i == 3
-      let res .= ' ctermbg='.item
-    elseif i == 4
-      let res .= printf(' gui=%s cterm=%s term=%s', item, item, item)
-    endif
-  endwhile
-  return res
-endfunction
+    return a:colors[0:1] + [fg, bg] + [a:colors[4]]
+  endfunction
 
-function! s:exec_separator(dict, from, to, inverse, suffix) abort
-  if pumvisible()
-    return
-  endif
-  let group = a:from.'_to_'.a:to.a:suffix
-  let l:from = airline#themes#get_highlight(a:from.a:suffix)
-  let l:to = airline#themes#get_highlight(a:to.a:suffix)
-  if a:inverse
-    let colors = [ l:from[1], l:to[1], l:from[3], l:to[3] ]
-  else
-    let colors = [ l:to[1], l:from[1], l:to[3], l:from[3] ]
-  endif
-  let a:dict[group] = colors
-  call airline#highlighter#exec(group, colors)
-endfunction
-
-function! airline#highlighter#load_theme() abort
-  if pumvisible()
-    return
-  endif
-  for winnr in filter(range(1, winnr('$')), 'v:val != winnr()')
-    call airline#highlighter#highlight_modified_inactive(winbufnr(winnr))
-  endfor
-  call airline#highlighter#highlight(['inactive'])
-  if getbufvar( bufnr('%'), '&modified'  )
-    call airline#highlighter#highlight(['normal', 'modified'])
-  else
-    call airline#highlighter#highlight(['normal'])
-  endif
-endfunction
-
-function! airline#highlighter#add_separator(from, to, inverse) abort
-  let s:separators[a:from.a:to] = [a:from, a:to, a:inverse]
-  call <sid>exec_separator({}, a:from, a:to, a:inverse, '')
-endfunction
-
-function! airline#highlighter#add_accent(accent) abort
-  let s:accents[a:accent] = 1
-endfunction
-
-function! airline#highlighter#highlight_modified_inactive(bufnr) abort
-  if getbufvar(a:bufnr, '&modified')
-    let colors = exists('g:airline#themes#{g:airline_theme}#palette.inactive_modified.airline_c')
-          \ ? g:airline#themes#{g:airline_theme}#palette.inactive_modified.airline_c : []
-  else
-    let colors = exists('g:airline#themes#{g:airline_theme}#palette.inactive.airline_c')
-          \ ? g:airline#themes#{g:airline_theme}#palette.inactive.airline_c : []
-  endif
-
-  if !empty(colors)
-    call airline#highlighter#exec('airline_c'.(a:bufnr).'_inactive', colors)
-  endif
-endfunction
-
-function! airline#highlighter#highlight(modes, ...) abort
-  let bufnr = a:0 ? a:1 : ''
-  let p = g:airline#themes#{g:airline_theme}#palette
-
-  " draw the base mode, followed by any overrides
-  let mapped = map(a:modes, 'v:val == a:modes[0] ? v:val : a:modes[0]."_".v:val')
-  let suffix = a:modes[0] == 'inactive' ? '_inactive' : ''
-  let airline_grouplist = []
-  let buffers_in_tabpage = sort(tabpagebuflist())
-  if exists("*uniq")
-    let buffers_in_tabpage = uniq(buffers_in_tabpage)
-  endif
-  " mapped might be something like ['normal', 'normal_modified']
-  " if a group is in both modes available, only define the second
-  " that is how this was done previously overwrite the previous definition
-  for mode in reverse(mapped)
-    if exists('g:airline#themes#{g:airline_theme}#palette[mode]')
-      let dict = g:airline#themes#{g:airline_theme}#palette[mode]
-      for kvp in items(dict)
-        let mode_colors = kvp[1]
-        let name = kvp[0]
-        if name is# 'airline_c' && !empty(bufnr) && suffix is# '_inactive'
-          let name = 'airline_c'.bufnr
-        endif
-        " do not re-create highlighting for buffers that are no longer visible
-        " in the current tabpage
-        if name =~# 'airline_c\d\+'
-          let bnr = matchstr(name, 'airline_c\zs\d\+') + 0
-          if bnr > 0 && index(buffers_in_tabpage, bnr) == -1
-            continue
-          endif
-        elseif (name =~# '_to_') || (name[0:10] is# 'airline_tab' && !empty(suffix))
-          " group will be redefined below at exec_separator
-          " or is not needed for tabline with '_inactive' suffix
-          " since active flag is 1 for builder)
-          continue
-        endif
-        if s:group_not_done(airline_grouplist, name.suffix)
-          call airline#highlighter#exec(name.suffix, mode_colors)
-        endif
-
-        if !has_key(p, 'accents') 
-          " work around a broken installation
-          " shouldn't actually happen, p should always contain accents
-          continue
-        endif
-
-        for accent in keys(s:accents)
-          if !has_key(p.accents, accent)
-            continue
-          endif
-          let colors = copy(mode_colors)
-          if p.accents[accent][0] != ''
-            let colors[0] = p.accents[accent][0]
-          endif
-          if p.accents[accent][2] != ''
-            let colors[2] = p.accents[accent][2]
-          endif
-          if len(colors) >= 5
-            let colors[4] = get(p.accents[accent], 4, '')
-          else
-            call add(colors, get(p.accents[accent], 4, ''))
-          endif
-          if s:group_not_done(airline_grouplist, name.suffix.'_'.accent)
-            call airline#highlighter#exec(name.suffix.'_'.accent, colors)
-          endif
-        endfor
-      endfor
-
-      if empty(s:separators)
-        " nothing to be done
+  function! s:GetHiCmd(list) abort
+    " a:list needs to have 5 items!
+    let res = ''
+    let i = -1
+    while i < 4
+      let i += 1
+      let item = get(a:list, i, '')
+      if item is ''
         continue
       endif
-      " TODO: optimize this
-      for sep in items(s:separators)
-        " we cannot check, that the group already exists, else the separators
-        " might not be correctly defined. But perhaps we can skip above groups
-        " that match the '_to_' name, because they would be redefined here...
-        call <sid>exec_separator(dict, sep[1][0], sep[1][1], sep[1][2], suffix)
-      endfor
+      if i == 0
+        let res .= ' guifg='.item
+      elseif i == 1
+        let res .= ' guibg='.item
+      elseif i == 2
+        let res .= ' ctermfg='.item
+      elseif i == 3
+        let res .= ' ctermbg='.item
+      elseif i == 4
+        let res .= printf(' gui=%s cterm=%s term=%s', item, item, item)
+      endif
+    endwhile
+    return res
+  endfunction
+
+  function! airline#highlighter#load_theme() abort
+    if pumvisible()
+      return
     endif
-  endfor
-endfunction
+    for winnr in filter(range(1, winnr('$')), 'v:val != winnr()')
+      call airline#highlighter#highlight_modified_inactive(winbufnr(winnr))
+    endfor
+    call airline#highlighter#highlight(['inactive'])
+    if getbufvar( bufnr('%'), '&modified'  )
+      call airline#highlighter#highlight(['normal', 'modified'])
+    else
+      call airline#highlighter#highlight(['normal'])
+    endif
+  endfunction
+
+  function! airline#highlighter#add_accent(accent) abort
+    let s:accents[a:accent] = 1
+  endfunction
+
+  function! airline#highlighter#add_separator(from, to, inverse) abort
+    let s:separators[a:from.a:to] = [a:from, a:to, a:inverse]
+    call <sid>exec_separator({}, a:from, a:to, a:inverse, '')
+  endfunction
+
+  function! s:exec_separator(dict, from, to, inverse, suffix) abort
+    if pumvisible()
+      return
+    endif
+    let group = a:from.'_to_'.a:to.a:suffix
+    let l:from = airline#themes#get_highlight(a:from.a:suffix)
+    let l:to = airline#themes#get_highlight(a:to.a:suffix)
+    if a:inverse
+      let colors = [ l:from[1], l:to[1], l:from[3], l:to[3] ]
+    else
+      let colors = [ l:to[1], l:from[1], l:to[3], l:from[3] ]
+    endif
+    let a:dict[group] = colors
+    call airline#highlighter#exec(group, colors)
+  endfunction
+
+  function! airline#highlighter#highlight_modified_inactive(bufnr) abort
+    if getbufvar(a:bufnr, '&modified')
+      let colors = exists('g:airline#themes#{g:airline_theme}#palette.inactive_modified.airline_c')
+            \ ? g:airline#themes#{g:airline_theme}#palette.inactive_modified.airline_c : []
+    else
+      let colors = exists('g:airline#themes#{g:airline_theme}#palette.inactive.airline_c')
+            \ ? g:airline#themes#{g:airline_theme}#palette.inactive.airline_c : []
+    endif
+
+    if !empty(colors)
+      call airline#highlighter#exec('airline_c'.(a:bufnr).'_inactive', colors)
+    endif
+  endfunction
+
+  function! airline#highlighter#exec(group, colors) abort
+    if pumvisible()
+      return
+    endif
+    let colors = a:colors
+    if len(colors) == 4
+      call add(colors, '')
+    endif
+    " colors should always be string values
+    let colors = map(copy(colors), 'type(v:val) != type("") ? string(v:val) : v:val')
+    if s:is_win32term
+      let colors[2] = s:gui2cui(get(colors, 0, ''), get(colors, 2, ''))
+      let colors[3] = s:gui2cui(get(colors, 1, ''), get(colors, 3, ''))
+    endif
+    let old_hi = airline#highlighter#get_highlight(a:group)
+    let new_hi = [colors[0], colors[1], printf('%s', colors[2]), printf('%s', colors[3]), colors[4]]
+    let colors = s:CheckDefined(colors)
+    if old_hi != new_hi || !s:hl_group_exists(a:group)
+      let cmd = printf('hi %s%s', a:group, s:GetHiCmd(colors))
+      try
+        exe cmd
+      catch /^Vim\%((\a\+)\)\=:E421:/ " color definition not found
+        let group=matchstr(v:exception, '\w\+\ze=')
+        let color=matchstr(v:exception, '=\zs\w\+')
+        let cmd=substitute(cmd, color, 'grey', 'g')
+        exe cmd
+        call airline#util#warning('color definition for group ' . a:group . ' not found, using grey as fallback')
+      catch
+        call airline#util#warning('Error when running command: '. cmd)
+      endtry
+      if has_key(s:hl_groups, a:group)
+        let s:hl_groups[a:group] = colors
+      endif
+    endif
+  endfunction
+
+  function! airline#highlighter#highlight(modes, ...) abort
+    let bufnr = a:0 ? a:1 : ''
+    let p = g:airline#themes#{g:airline_theme}#palette
+
+    " draw the base mode, followed by any overrides
+    let mapped = map(a:modes, 'v:val == a:modes[0] ? v:val : a:modes[0]."_".v:val')
+    let suffix = a:modes[0] == 'inactive' ? '_inactive' : ''
+    let airline_grouplist = []
+    let buffers_in_tabpage = sort(tabpagebuflist())
+    if exists("*uniq")
+      let buffers_in_tabpage = uniq(buffers_in_tabpage)
+    endif
+    " mapped might be something like ['normal', 'normal_modified']
+    " if a group is in both modes available, only define the second
+    " that is how this was done previously overwrite the previous definition
+    for mode in reverse(mapped)
+      if exists('g:airline#themes#{g:airline_theme}#palette[mode]')
+        let dict = g:airline#themes#{g:airline_theme}#palette[mode]
+        for kvp in items(dict)
+          let mode_colors = kvp[1]
+          let name = kvp[0]
+          if name is# 'airline_c' && !empty(bufnr) && suffix is# '_inactive'
+            let name = 'airline_c'.bufnr
+          endif
+          " do not re-create highlighting for buffers that are no longer visible
+          " in the current tabpage
+          if name =~# 'airline_c\d\+'
+            let bnr = matchstr(name, 'airline_c\zs\d\+') + 0
+            if bnr > 0 && index(buffers_in_tabpage, bnr) == -1
+              continue
+            endif
+          elseif (name =~# '_to_') || (name[0:10] is# 'airline_tab' && !empty(suffix))
+            " group will be redefined below at exec_separator
+            " or is not needed for tabline with '_inactive' suffix
+            " since active flag is 1 for builder)
+            continue
+          endif
+          if s:group_not_done(airline_grouplist, name.suffix)
+            call airline#highlighter#exec(name.suffix, mode_colors)
+          endif
+
+          if !has_key(p, 'accents')
+            " work around a broken installation
+            " shouldn't actually happen, p should always contain accents
+            continue
+          endif
+
+          for accent in keys(s:accents)
+            if !has_key(p.accents, accent)
+              continue
+            endif
+            let colors = copy(mode_colors)
+            if p.accents[accent][0] != ''
+              let colors[0] = p.accents[accent][0]
+            endif
+            if p.accents[accent][2] != ''
+              let colors[2] = p.accents[accent][2]
+            endif
+            if len(colors) >= 5
+              let colors[4] = get(p.accents[accent], 4, '')
+            else
+              call add(colors, get(p.accents[accent], 4, ''))
+            endif
+            if s:group_not_done(airline_grouplist, name.suffix.'_'.accent)
+              call airline#highlighter#exec(name.suffix.'_'.accent, colors)
+            endif
+          endfor
+        endfor
+
+        if empty(s:separators)
+          " nothing to be done
+          continue
+        endif
+        " TODO: optimize this
+        for sep in items(s:separators)
+          " we cannot check, that the group already exists, else the separators
+          " might not be correctly defined. But perhaps we can skip above groups
+          " that match the '_to_' name, because they would be redefined here...
+          call <sid>exec_separator(dict, sep[1][0], sep[1][1], sep[1][2], suffix)
+        endfor
+      endif
+    endfor
+  endfunction
+
+  " End legacy VimScript
+  finish
+
+else
+
+  " This is using Vim9 script
+
+  def s:gui2cui(rgb: string, fallback: string): string
+    if empty(rgb)
+      return fallback
+    elseif match(rgb, '^\%(NONE\|[fb]g\)$') > -1
+      return rgb
+    elseif rgb !~ '#'
+      # rgb contains colorname
+      return rgb
+    endif
+    var _rgb = []
+    _rgb = mapnew(split(rgb[1 : ], '..\zs'), (_, v) => ('0x' .. v)->str2nr(16))
+    return airline#msdos#round_msdos_colors(_rgb)
+  enddef
+
+  def s:group_not_done(list: list<string>, name: string): bool
+    if index(list, name) == -1
+      add(list, name)
+      return true
+    else
+      if &vbs
+        :echomsg printf("airline: group: %s already done, skipping", name)
+      endif
+      return false
+    endif
+  enddef
+
+  def s:get_syn(group: string, what: string, mode: string): string
+    var color = ''
+    if hlexists(group)
+      color = hlID(group)->synIDtrans()->synIDattr(what, mode)
+    endif
+    if empty(color) || str2nr(color) == -1
+      # Normal highlighting group should always exist
+      color = hlID('Normal')->synIDtrans()->synIDattr(what, mode)
+      # however, just in case
+      if empty(color) || str2nr(color) == -1
+        color = 'NONE'
+      endif
+    endif
+    return color
+  enddef
+
+  def s:get_array(guifg: string, guibg: string, ctermfg: string, ctermbg: string, opts: list<string>): list<string>
+    return [ guifg, guibg, ctermfg, ctermbg, empty(opts) ? '' : join(opts, ',') ]
+  enddef
+
+  def airline#highlighter#reset_hlcache(): void
+    s:hl_groups = {}
+  enddef
+
+  def airline#highlighter#get_highlight(group: string, rest: list<string> = ['']): list<string>
+    # only check for the cterm reverse attribute
+    # TODO: do we need to check all modes (gui, term, as well)?
+    var reverse = false
+    var bold = false
+    var property: string
+    var res = []
+    var ctermfg: string
+    var ctermbg: string
+    var guifg: string
+    var guibg: string
+    property = hlID(group)->synIDtrans()->synIDattr('reverse', 'cterm')
+    if !empty(property) && property->str2nr()
+      reverse = true
+    endif
+    if get(g:, 'airline_highlighting_cache', 0) && has_key(s:hl_groups, group)
+      res = s:hl_groups[group]
+      return reverse ? [ res[1], res[0], res[3], res[2], res[4] ] : res
+    else
+      ctermfg = s:get_syn(group, 'fg', 'cterm')
+      ctermbg = s:get_syn(group, 'bg', 'cterm')
+      guifg = s:get_syn(group, 'fg', 'gui')
+      guibg = s:get_syn(group, 'bg', 'gui')
+      property = hlID(group)->synIDtrans()->synIDattr('bold')
+      if !empty(property) && property->str2nr()
+        bold = true
+      endif
+      if reverse
+        res = s:get_array(guibg, guifg, ctermbg, ctermfg, bold ? ['bold'] : rest)
+      else
+        res = s:get_array(guifg, guibg, ctermfg, ctermbg, bold ? ['bold'] : rest)
+      endif
+    endif
+    s:hl_groups[group] = res
+    return res
+  enddef
+
+  def airline#highlighter#get_highlight2(fg: list<string>, bg: list<string>, rest1: string = '', rest2: string = '', rest3: string = ''): list<string>
+    var guifg = s:get_syn(fg[0], fg[1], 'gui')
+    var guibg = s:get_syn(bg[0], bg[1], 'gui')
+    var ctermfg = s:get_syn(fg[0], fg[1], 'cterm')
+    var ctermbg = s:get_syn(bg[0], bg[1], 'cterm')
+    var rest = [ rest1, rest2, rest3 ]
+    return s:get_array(guifg, guibg, ctermfg, ctermbg, filter(rest, (_, v) => !empty(v)))
+  enddef
+
+  def s:hl_group_exists(group: string): bool
+    if !hlexists(group)
+      return false
+    elseif hlID(group)->synIDtrans()->synIDattr('fg')->empty()
+      return false
+    endif
+    return true
+  enddef
+
+  def s:CheckDefined(colors: list<any>): list<any>
+    # Checks, whether the definition of the colors is valid and is not empty or NONE
+    # e.g. if the colors would expand to this:
+    # hi airline_c ctermfg=NONE ctermbg=NONE
+    # that means to clear that highlighting group, therefore, fallback to Normal
+    # highlighting group for the cterm values
+
+    # This only works, if the Normal highlighting group is actually defined,
+    # so return early, if it has been cleared
+    if !exists("g:airline#highlighter#normal_fg_hi")
+      g:airline#highlighter#normal_fg_hi = hlID('Normal')->synIDtrans()->synIDattr('fg', 'cterm')
+    endif
+    if empty(g:airline#highlighter#normal_fg_hi) || str2nr(g:airline#highlighter#normal_fg_hi) < 0
+      return colors
+    endif
+
+    for val in colors
+      if !empty(val) && val !=# 'NONE'
+        return colors
+      endif
+    endfor
+    # this adds the bold attribute to the term argument of the :hi command,
+    # but at least this makes sure, the group will be defined
+    var fg = g:airline#highlighter#normal_fg_hi
+    var bg = hlID('Normal')->synIDtrans()->synIDattr('bg', 'cterm')
+    if empty(bg) || str2nr(bg) < 0
+      # in case there is no background color defined for Normal
+      bg = colors[3]
+    endif
+    return colors[ 0 : 1 ] + [fg, bg] + [colors[4]]
+  enddef
+
+  def s:GetHiCmd(list: list<string>): string
+    # list needs to have 5 items!
+    var res: string
+    var i = -1
+    var item: string
+    while i < 4
+      i += 1
+      item = get(list, i, '')
+      if item is ''
+        continue
+      endif
+      if i == 0
+        res ..= ' guifg=' .. item
+      elseif i == 1
+        res ..= ' guibg=' .. item
+      elseif i == 2
+        res ..= ' ctermfg=' .. item
+      elseif i == 3
+        res ..= ' ctermbg=' .. item
+      elseif i == 4
+        res ..= printf(' gui=%s cterm=%s term=%s', item, item, item)
+      endif
+    endwhile
+    return res
+  enddef
+
+  def airline#highlighter#load_theme(): void
+    if pumvisible()
+      return
+    endif
+    for winnr in filter(range(1, winnr('$')), (_, v) => v != winnr())
+      airline#highlighter#highlight_modified_inactive(winbufnr(winnr))
+    endfor
+    airline#highlighter#highlight(['inactive'])
+    if getbufvar( bufnr('%'), '&modified'  )
+      airline#highlighter#highlight(['normal', 'modified'])
+    else
+      airline#highlighter#highlight(['normal'])
+    endif
+  enddef
+
+  def airline#highlighter#add_accent(accent: string): void
+    s:accents[accent] = 1
+  enddef
+
+  def airline#highlighter#add_separator(from: string, to: string, inverse: bool): void
+    s:separators[from .. to] = [from, to, inverse]
+    s:exec_separator({}, from, to, inverse, '')
+  enddef
+
+  def s:exec_separator(dict: dict<any>, from_arg: string, to_arg: string, inverse: bool, suffix: string): void
+    if pumvisible()
+      return
+    endif
+    var group = from_arg .. '_to_' .. to_arg .. suffix
+    var from = mapnew(airline#themes#get_highlight(from_arg .. suffix), (_, v) => type(v) != type('') ? string(v) : v)
+    var colors = []
+    var to = mapnew(airline#themes#get_highlight(to_arg .. suffix), (_, v) => type(v) != type('') ? string(v) : v)
+    if inverse
+      colors = [ from[1], to[1], from[3], to[3] ]
+    else
+      colors = [ to[1], from[1], to[3], from[3] ]
+    endif
+    dict[group] = colors
+    airline#highlighter#exec(group, colors)
+  enddef
+
+  def airline#highlighter#highlight_modified_inactive(bufnr: number): void
+    var colors: list<any>
+    var dict1  = eval('g:airline#themes#' .. g:airline_theme .. '#palette')->get('inactive_modified', {})
+    var dict2  = eval('g:airline#themes#' .. g:airline_theme .. '#palette')->get('inactive', {})
+
+    if empty(dict2)
+      return
+    endif
+
+    if getbufvar(bufnr, '&modified')
+      colors = get(dict1, 'airline_c', [])
+    else
+      colors = get(dict2, 'airline_c', [])
+    endif
+    if !empty(colors)
+      airline#highlighter#exec('airline_c' .. bufnr .. '_inactive', colors)
+    endif
+  enddef
+
+  def airline#highlighter#exec(group: string, clrs: list<any>): void
+    if pumvisible()
+      return
+    endif
+    var colors: list<string> = mapnew(copy(clrs), (_, v) => type(v) != type('') ? string(v) : v)
+    if len(colors) == 4
+      add(colors, '')
+    endif
+    if s:is_win32term
+      colors[2] = s:gui2cui(get(colors, 0, ''), get(colors, 2, ''))
+      colors[3] = s:gui2cui(get(colors, 1, ''), get(colors, 3, ''))
+    endif
+    var old_hi: list<string> = airline#highlighter#get_highlight(group)
+    var new_hi: list<string> = colors
+    if old_hi != new_hi || !s:hl_group_exists(group)
+      var cmd = printf('hi %s%s', group, s:GetHiCmd(colors))
+      try
+        :exe cmd
+      catch /^Vim\%((\a\+)\)\=:E421:/
+        var grp = matchstr(v:exception, '\w\+\ze=')
+        var clr = matchstr(v:exception, '=\zs\w\+')
+        cmd = substitute(cmd, clr, 'grey', 'g')
+        :exe cmd
+        airline#util#warning('color ' .. clr .. ' definition for group ' .. grp .. ' not found, using grey as fallback')
+      catch
+        airline#util#warning('Error when running command: ' .. cmd)
+      endtry
+      if has_key(s:hl_groups, group)
+        s:hl_groups[group] = colors
+      endif
+    endif
+  enddef
+
+  def airline#highlighter#highlight(modes: list<string>, bufnr: string = ''): void
+    var p: dict<any> = eval('g:airline#themes#' .. g:airline_theme .. '#palette')
+
+    # draw the base mode, followed by any overrides
+    var mapped = map(modes, (_, v) => v == modes[0] ? v : modes[0] .. "_" .. v)
+    var suffix = ''
+    if modes[0] == 'inactive'
+      suffix = '_inactive'
+    endif
+    var airline_grouplist = []
+    var dict: dict<any>
+    var bnr: number = 0
+
+    var buffers_in_tabpage: list<number> = uniq(sort(tabpagebuflist()))
+    # mapped might be something like ['normal', 'normal_modified']
+    # if a group is in both modes available, only define the second
+    # that is how this was done previously overwrite the previous definition
+    for mode in reverse(mapped)
+      if exists('g:airline#themes#' .. g:airline_theme .. '#palette.' .. mode)
+        dict = eval('g:airline#themes#' .. g:airline_theme .. '#palette.' .. mode)
+        for kvp in items(dict)
+          var mode_colors = kvp[1]
+          var name = kvp[0]
+          if name == 'airline_c' && !empty(bufnr) && suffix == '_inactive'
+            name = 'airline_c' .. bufnr
+          endif
+          # do not re-create highlighting for buffers that are no longer visible
+          # in the current tabpage
+          if name =~# 'airline_c\d\+'
+            bnr = matchstr(name, 'airline_c\zs\d\+')->str2nr()
+            if bnr > 0 && index(buffers_in_tabpage, bnr) == -1
+              continue
+            endif
+          elseif (name =~ '_to_') || (name[ 0 : 10 ] == 'airline_tab' && !empty(suffix))
+            # group will be redefined below at exec_separator
+            # or is not needed for tabline with '_inactive' suffix
+            # since active flag is 1 for builder)
+            continue
+          endif
+          if s:group_not_done(airline_grouplist, name .. suffix)
+            airline#highlighter#exec(name .. suffix, mode_colors)
+          endif
+
+          if !has_key(p, 'accents')
+            # shouldn't actually happen, p should always contain accents
+            continue
+          endif
+
+          for accent in keys(s:accents)
+            if !has_key(p.accents, accent)
+              continue
+            endif
+            var colors = copy(mode_colors)
+            if p.accents[accent][0] != ''
+                colors[0] = p.accents[accent][0]
+            endif
+            if type(get(p.accents[accent], 2, '')) == type('')
+              colors[2] = get(p.accents[accent], 2, '')
+            else
+              colors[2] = string(p.accents[accent][2])
+            endif
+            if len(colors) >= 5
+              colors[4] = get(p.accents[accent], 4, '')
+            else
+              add(colors, get(p.accents[accent], 4, ''))
+            endif
+            if s:group_not_done(airline_grouplist, name .. suffix .. '_' .. accent)
+              airline#highlighter#exec(name .. suffix .. '_' .. accent, colors)
+            endif
+          endfor
+        endfor
+
+        if empty(s:separators)
+          continue
+        endif
+        for sep in items(s:separators)
+          # we cannot check, that the group already exists, else the separators
+          # might not be correctly defined. But perhaps we can skip above groups
+          # that match the '_to_' name, because they would be redefined here...
+          s:exec_separator(dict, sep[1][0], sep[1][1], sep[1][2], suffix)
+        endfor
+      endif
+    endfor
+	enddef
+endif
diff --git a/autoload/airline/msdos.vim b/autoload/airline/msdos.vim
index 571b86ef..ebafdc7c 100644
--- a/autoload/airline/msdos.vim
+++ b/autoload/airline/msdos.vim
@@ -41,19 +41,43 @@ let s:basic16 = [
   \ [ 0xFF, 0xFF, 0xFF ]
   \ ]
 
-function! airline#msdos#round_msdos_colors(rgblist)
-  " Check for values from MSDOS 16 color terminal
-  let best = []
-  let min  = 100000
-  let list = s:basic16
-  for value in list
-    let t = abs(value[0] - a:rgblist[0]) +
-          \ abs(value[1] - a:rgblist[1]) +
-          \ abs(value[2] - a:rgblist[2])
-    if min > t
-      let min = t
-      let best = value
-    endif
-  endfor
-  return index(s:basic16, best)
-endfunction
+if !exists(":def") || (exists(":def") && get(g:, "airline_experimental", 0) == 0)
+
+	function! airline#msdos#round_msdos_colors(rgblist)
+		" Check for values from MSDOS 16 color terminal
+		let best = []
+		let min  = 100000
+		let list = s:basic16
+		for value in list
+			let t = abs(value[0] - a:rgblist[0]) +
+						\ abs(value[1] - a:rgblist[1]) +
+						\ abs(value[2] - a:rgblist[2])
+			if min > t
+				let min = t
+				let best = value
+			endif
+		endfor
+		return index(s:basic16, best)
+	endfunction
+
+	finish
+
+else
+
+  def airline#msdos#round_msdos_colors(rgblist: list<number>): string
+    # Check for values from MSDOS 16 color terminal
+    var best = []
+    var min  = 100000
+    var t = 0
+    for value in s:basic16
+      t = abs(value[0] - rgblist[0]) +
+          abs(value[1] - rgblist[1]) +
+          abs(value[2] - rgblist[2])
+      if min > t
+        min = t
+        best = value
+      endif
+    endfor
+    return string(index(s:basic16, best))
+  enddef
+endif