runtime(tohtml): Update TOhtml to version 9.0v2 (#13050)

Modified behavior:
  - Change default value of g:html_use_input_for_pc from "fallback" to
    "none". This means with default settings, only the standards-based
    method to make special text unselectable is used. The old method
    relying on unspecified browser behavior for <input> tags is now only
    used if a user specifically enables it.
  - Officially deprecate g:use_xhtml option (in favor of
    g:html_use_xhtml) by issuing a warning message when used.

Bugfixes:
  - Fix issue #8547: LineNr and other special highlight groups did not
    get proper style rules defined when using "hi link".
  - Fix that diff filler was not properly added for deleted lines at the
    end of a buffer.

Other:
  - Refactored function definitions from long lists of strings to use
    :let-heredoc variable assignment instead.
  - Corrected deprecated "." string concatenation operator to ".."
    operator in more places.


Signed-off-by: Christian Brabandt <cb@256bit.org>

1 files changed, 368 insertions, 295 deletions

diff --git a/runtime/syntax/2html.vim b/runtime/syntax/2html.vim
index 69780cffef..f3ce8bed8d 100644
--- a/runtime/syntax/2html.vim
+++ b/runtime/syntax/2html.vim
@@ -1,6 +1,6 @@
 " Vim syntax support file
 " Maintainer: Ben Fritz <fritzophrenic@gmail.com>
-" Last Change: 2023 Jan 01
+" Last Change: 2023 Sep 05
 "
 " Additional contributors:
 "
@@ -32,9 +32,9 @@ let s:end=line('$')
 " Font
 if exists("g:html_font")
   if type(g:html_font) == type([])
-    let s:htmlfont = "'". join(g:html_font,"','") . "', monospace"
+    let s:htmlfont = "'".. join(g:html_font,"','") .. "', monospace"
   else
-    let s:htmlfont = "'". g:html_font . "', monospace"
+    let s:htmlfont = "'".. g:html_font .. "', monospace"
   endif
 else
   let s:htmlfont = "monospace"
@@ -221,8 +221,8 @@ else
 endif
 
 " Find out the background and foreground color for use later
-let s:fgc = s:HtmlColor(synIDattr(hlID("Normal"), "fg#", s:whatterm))
-let s:bgc = s:HtmlColor(synIDattr(hlID("Normal"), "bg#", s:whatterm))
+let s:fgc = s:HtmlColor(synIDattr(hlID("Normal")->synIDtrans(), "fg#", s:whatterm))
+let s:bgc = s:HtmlColor(synIDattr(hlID("Normal")->synIDtrans(), "bg#", s:whatterm))
 if s:fgc == ""
   let s:fgc = ( &background == "dark" ? "#ffffff" : "#000000" )
 endif
@@ -234,41 +234,43 @@ if !s:settings.use_css
   " Return opening HTML tag for given highlight id
   function! s:HtmlOpening(id, extra_attrs)
     let a = ""
-    if synIDattr(a:id, "inverse")
+    let translated_ID = synIDtrans(a:id)
+    if synIDattr(translated_ID, "inverse")
       " For inverse, we always must set both colors (and exchange them)
-      let x = s:HtmlColor(synIDattr(a:id, "fg#", s:whatterm))
-      let a = a . '<span '.a:extra_attrs.'style="background-color: ' . ( x != "" ? x : s:fgc ) . '">'
-      let x = s:HtmlColor(synIDattr(a:id, "bg#", s:whatterm))
-      let a = a . '<font color="' . ( x != "" ? x : s:bgc ) . '">'
+      let x = s:HtmlColor(synIDattr(translated_ID, "fg#", s:whatterm))
+      let a = a .. '<span '..a:extra_attrs..'style="background-color: ' .. ( x != "" ? x : s:fgc ) .. '">'
+      let x = s:HtmlColor(synIDattr(translated_ID, "bg#", s:whatterm))
+      let a = a .. '<font color="' .. ( x != "" ? x : s:bgc ) .. '">'
     else
-      let x = s:HtmlColor(synIDattr(a:id, "bg#", s:whatterm))
+      let x = s:HtmlColor(synIDattr(translated_ID, "bg#", s:whatterm))
       if x != ""
-	let a = a . '<span '.a:extra_attrs.'style="background-color: ' . x . '">'
+	let a = a .. '<span '..a:extra_attrs..'style="background-color: ' .. x .. '">'
       elseif !empty(a:extra_attrs)
-	let a = a . '<span '.a:extra_attrs.'>'
+	let a = a .. '<span '..a:extra_attrs..'>'
       endif
-      let x = s:HtmlColor(synIDattr(a:id, "fg#", s:whatterm))
-      if x != "" | let a = a . '<font color="' . x . '">' | endif
+      let x = s:HtmlColor(synIDattr(translated_ID, "fg#", s:whatterm))
+      if x != "" | let a = a .. '<font color="' .. x .. '">' | endif
     endif
-    if synIDattr(a:id, "bold") | let a = a . "<b>" | endif
-    if synIDattr(a:id, "italic") | let a = a . "<i>" | endif
-    if synIDattr(a:id, "underline") | let a = a . "<u>" | endif
+    if synIDattr(translated_ID, "bold") | let a = a .. "<b>" | endif
+    if synIDattr(translated_ID, "italic") | let a = a .. "<i>" | endif
+    if synIDattr(translated_ID, "underline") | let a = a .. "<u>" | endif
     return a
   endfun
 
   " Return closing HTML tag for given highlight id
   function! s:HtmlClosing(id, has_extra_attrs)
     let a = ""
-    if synIDattr(a:id, "underline") | let a = a . "</u>" | endif
-    if synIDattr(a:id, "italic") | let a = a . "</i>" | endif
-    if synIDattr(a:id, "bold") | let a = a . "</b>" | endif
-    if synIDattr(a:id, "inverse")
-      let a = a . '</font></span>'
+    let translated_ID = synIDtrans(a:id)
+    if synIDattr(translated_ID, "underline") | let a = a .. "</u>" | endif
+    if synIDattr(translated_ID, "italic") | let a = a .. "</i>" | endif
+    if synIDattr(translated_ID, "bold") | let a = a .. "</b>" | endif
+    if synIDattr(translated_ID, "inverse")
+      let a = a .. '</font></span>'
     else
-      let x = s:HtmlColor(synIDattr(a:id, "fg#", s:whatterm))
-      if x != "" | let a = a . '</font>' | endif
-      let x = s:HtmlColor(synIDattr(a:id, "bg#", s:whatterm))
-      if x != "" || a:has_extra_attrs | let a = a . '</span>' | endif
+      let x = s:HtmlColor(synIDattr(translated_ID, "fg#", s:whatterm))
+      if x != "" | let a = a .. '</font>' | endif
+      let x = s:HtmlColor(synIDattr(translated_ID, "bg#", s:whatterm))
+      if x != "" || a:has_extra_attrs | let a = a .. '</span>' | endif
     endif
     return a
   endfun
@@ -286,84 +288,102 @@ if s:settings.use_css
   " save CSS to a list of rules to add to the output at the end of processing
 
   " first, get the style names we need
-  let wrapperfunc_lines = [
-	\ 'function! s:BuildStyleWrapper(style_id, diff_style_id, extra_attrs, text, make_unselectable, unformatted)',
-	\ '',
-	\ '  let l:style_name = synIDattr(a:style_id, "name", s:whatterm)'
-	\ ]
+  let s:wrapperfunc_lines = []
+  call add(s:wrapperfunc_lines, [])
+  let s:wrapperfunc_lines[-1] =<< trim ENDLET
+	function! s:BuildStyleWrapper(style_id, diff_style_id, extra_attrs, text, make_unselectable, unformatted)
+	
+	  let l:style_name = synIDattr(a:style_id, "name", s:whatterm)
+  ENDLET
   if &diff
-    let wrapperfunc_lines += [
-	\ '  let l:diff_style_name = synIDattr(a:diff_style_id, "name", s:whatterm)']
-
-  " Add normal groups and diff groups to separate lists so we can order them to
-  " allow diff highlight to override normal highlight
-
-  " if primary style IS a diff style, grab it from the diff cache instead
-  " (always succeeds because we pre-populate it)
-  let wrapperfunc_lines += [
-	\ '',
-	\ '  if a:style_id == s:DIFF_D_ID || a:style_id == s:DIFF_A_ID ||'.
-	\ '          a:style_id == s:DIFF_C_ID || a:style_id == s:DIFF_T_ID',
-	\ '    let l:saved_style = get(s:diffstylelist,a:style_id)',
-	\ '  else'
-	\ ]
+    call add(s:wrapperfunc_lines, [])
+    let s:wrapperfunc_lines[-1] =<< trim ENDLET
+	  let l:diff_style_name = synIDattr(a:diff_style_id, "name", s:whatterm)
+    ENDLET
+
+    " Add normal groups and diff groups to separate lists so we can order them to
+    " allow diff highlight to override normal highlight
+
+    " if primary style IS a diff style, grab it from the diff cache instead
+    " (always succeeds because we pre-populate it)
+    call add(s:wrapperfunc_lines, [])
+    let s:wrapperfunc_lines[-1] =<< trim ENDLET
+
+	  if a:style_id == s:DIFF_D_ID || a:style_id == s:DIFF_A_ID || a:style_id == s:DIFF_C_ID || a:style_id == s:DIFF_T_ID
+	    let l:saved_style = get(s:diffstylelist,a:style_id)
+	  else
+    ENDLET
   endif
 
   " get primary style info from cache or build it on the fly if not found
-  let wrapperfunc_lines += [
-	\ '    let l:saved_style = get(s:stylelist,a:style_id)',
-	\ '    if type(l:saved_style) == type(0)',
-	\ '      unlet l:saved_style',
-	\ '      let l:saved_style = s:CSS1(a:style_id)',
-	\ '      if l:saved_style != ""',
-	\ '        let l:saved_style = "." . l:style_name . " { " . l:saved_style . "}"',
-	\ '      endif',
-	\ '      let s:stylelist[a:style_id]= l:saved_style',
-	\ '    endif'
-	\ ]
+  call add(s:wrapperfunc_lines, [])
+  let s:wrapperfunc_lines[-1] =<< trim ENDLET
+	    let l:saved_style = get(s:stylelist,a:style_id)
+	    if type(l:saved_style) == type(0)
+	      unlet l:saved_style
+	      let l:saved_style = s:CSS1(a:style_id)
+	      if l:saved_style != ""
+	        let l:saved_style = "." .. l:style_name .. " { " .. l:saved_style .. "}"
+	      endif
+	      let s:stylelist[a:style_id] = l:saved_style
+	    endif
+  ENDLET
   if &diff
-    let wrapperfunc_lines += [ '  endif' ]
+    call add(s:wrapperfunc_lines, [])
+    let s:wrapperfunc_lines[-1] =<< trim ENDLET
+	  endif
+    ENDLET
   endif
+" Ignore this comment, just bypassing a highlighting issue: if
 
   " Build the wrapper tags around the text. It turns out that caching these
   " gives pretty much zero performance gain and adds a lot of logic.
 
-  let wrapperfunc_lines += [
-	\ '',
-	\ '  if l:saved_style == "" && empty(a:extra_attrs)'
-	\ ]
+  call add(s:wrapperfunc_lines, [])
+  let s:wrapperfunc_lines[-1] =<< trim ENDLET
+
+	  if l:saved_style == "" && empty(a:extra_attrs)
+  ENDLET
   if &diff
-    let wrapperfunc_lines += [
-	\ '    if a:diff_style_id <= 0'
-	\ ]
+    call add(s:wrapperfunc_lines, [])
+    let s:wrapperfunc_lines[-1] =<< trim ENDLET
+	    if a:diff_style_id <= 0
+    ENDLET
   endif
   " no surroundings if neither primary nor diff style has any info
-  let wrapperfunc_lines += [
-	\ '       return a:text'
-	\ ]
+  call add(s:wrapperfunc_lines, [])
+  let s:wrapperfunc_lines[-1] =<< trim ENDLET
+	      return a:text
+  ENDLET
   if &diff
     " no primary style, but diff style
-    let wrapperfunc_lines += [
-	\ '     else',
-	\ '       return "<span class=\"" .l:diff_style_name . "\">".a:text."</span>"',
-	\ '     endif'
-	\ ]
+    call add(s:wrapperfunc_lines, [])
+    let s:wrapperfunc_lines[-1] =<< trim ENDLET
+	    else
+	      return '<span class="' ..l:diff_style_name .. '">'..a:text.."</span>"
+	    endif
+    ENDLET
   endif
+  " Ignore this comment, just bypassing a highlighting issue: if
+
   " open tag for non-empty primary style
-  let wrapperfunc_lines += [
-	\ '  else']
+  call add(s:wrapperfunc_lines, [])
+  let s:wrapperfunc_lines[-1] =<< trim ENDLET
+	  else
+  ENDLET
   " non-empty primary style. handle either empty or non-empty diff style.
   "
   " separate the two classes by a space to apply them both if there is a diff
   " style name, unless the primary style is empty, then just use the diff style
   " name
-  let diffstyle =
-	  \ (&diff ? '(a:diff_style_id <= 0 ? "" : " ". l:diff_style_name) .'
-	  \        : "")
+  let s:diffstyle =
+	  \ (&diff ? '(a:diff_style_id <= 0 ? "" : " " .. l:diff_style_name)..'
+	  \        : '')
   if s:settings.prevent_copy == ""
-    let wrapperfunc_lines += [
-	  \ '    return "<span ".a:extra_attrs."class=\"" . l:style_name .'.diffstyle.'"\">".a:text."</span>"'
-	  \ ]
+    call add(s:wrapperfunc_lines, [])
+    let s:wrapperfunc_lines[-1] =<< trim eval ENDLET
+	    return "<span "..a:extra_attrs..'class="' .. l:style_name ..{s:diffstyle}'">'..a:text.."</span>"
+    ENDLET
   else
 
     " New method: use generated content in the CSS. The only thing needed here
@@ -388,59 +408,76 @@ if s:settings.use_css
     " Note, if maxlength property needs to be added in the future, it will need
     " to use strchars(), because HTML specifies that the maxlength parameter
     " uses the number of unique codepoints for its limit.
-    let wrapperfunc_lines += [
-	  \   '    if a:make_unselectable',
-	  \   '      return "<span ".a:extra_attrs."class=\"" . l:style_name .'.diffstyle.'"\"'
-	  \ ]
+    call add(s:wrapperfunc_lines, [])
+    let s:wrapperfunc_lines[-1] =<< trim eval ENDLET
+	    if a:make_unselectable
+	      let return_span = "<span "..a:extra_attrs..'class="' .. l:style_name ..{s:diffstyle}'"'
+    ENDLET
     if s:settings.use_input_for_pc !=# 'all'
-      let wrapperfunc_lines[-1] .= ' " . "data-" . l:style_name . "-content=\"".a:text."\"'
+      call add(s:wrapperfunc_lines, [])
+      let s:wrapperfunc_lines[-1] =<< trim ENDLET
+	      let return_span ..= " data-" .. l:style_name .. '-content="'..a:text..'"'
+      ENDLET
     endif
-    let wrapperfunc_lines[-1] .= '>'
+    call add(s:wrapperfunc_lines, [])
+    let s:wrapperfunc_lines[-1] =<< trim ENDLET
+	      let return_span ..= '>'
+    ENDLET
     if s:settings.use_input_for_pc !=# 'none'
-      let wrapperfunc_lines[-1] .=
-	    \                '<input'.s:unselInputType.' class=\"" . l:style_name .'.diffstyle.'"\"'.
-	    \                 ' value=\"".substitute(a:unformatted,''\s\+$'',"","")."\"'.
-	    \                 ' onselect=''this.blur(); return false;'''.
-	    \                 ' onmousedown=''this.blur(); return false;'''.
-	    \                 ' onclick=''this.blur(); return false;'''.
-	    \                 ' readonly=''readonly'''.
-	    \                 ' size=\"".strwidth(a:unformatted)."\"'.
-	    \                 (s:settings.use_xhtml ? '/' : '').'>'
+      call add(s:wrapperfunc_lines, [])
+      let s:wrapperfunc_lines[-1] =<< trim eval ENDLET
+	      let return_span ..=   '<input'..s:unselInputType..' class="' .. l:style_name ..{s:diffstyle}'"'
+	      let return_span ..=   ' value="'..substitute(a:unformatted,'\s\+$',"","")..'"'
+	      let return_span ..=   " onselect='this.blur(); return false;'"
+	      let return_span ..=   " onmousedown='this.blur(); return false;'"
+	      let return_span ..=   " onclick='this.blur(); return false;'"
+	      let return_span ..=   " readonly='readonly'"
+	      let return_span ..=   ' size="'..strwidth(a:unformatted)..'"'
+	      let return_span ..=   (s:settings.use_xhtml ? '/>' : '>')
+      ENDLET
     endif
-    let wrapperfunc_lines[-1] .= '</span>"'
-    let wrapperfunc_lines += [
-	  \ '    else',
-	  \ '      return "<span ".a:extra_attrs."class=\"" . l:style_name .'. diffstyle .'"\">".a:text."</span>"'
-	  \ ]
+    call add(s:wrapperfunc_lines, [])
+    let s:wrapperfunc_lines[-1] =<< trim eval ENDLET
+	      return return_span..'</span>'
+	    else
+	      return "<span "..a:extra_attrs..'class="' .. l:style_name .. {s:diffstyle}'">'..a:text.."</span>"
+	    endif
+    ENDLET
   endif
-  let wrapperfunc_lines += [
-	\ '  endif',
-	\ 'endfun'
-	\ ]
+  call add(s:wrapperfunc_lines, [])
+  let s:wrapperfunc_lines[-1] =<< trim ENDLET
+	  endif
+	endfun
+  ENDLET
 else
   " Non-CSS method just needs the wrapper.
   "
   " Functions used to get opening/closing automatically return null strings if
   " no styles exist.
   if &diff
-    let wrapperfunc_lines = [
-	  \ 'function! s:BuildStyleWrapper(style_id, diff_style_id, extra_attrs, text, unusedarg, unusedarg2)',
-	  \ '  return s:HtmlOpening(a:style_id, a:extra_attrs).(a:diff_style_id <= 0 ? "" :'.
-	  \                                     's:HtmlOpening(a:diff_style_id, "")).a:text.'.
-	  \   '(a:diff_style_id <= 0 ? "" : s:HtmlClosing(a:diff_style_id, 0)).s:HtmlClosing(a:style_id, !empty(a:extra_attrs))',
-	  \ 'endfun'
-	  \ ]
+    let s:wrapperfunc_lines =<< trim ENDLET
+	function! s:BuildStyleWrapper(style_id, diff_style_id, extra_attrs, text, unusedarg, unusedarg2)
+	  if a:diff_style_id <= 0
+	    let l:diff_opening = s:HtmlOpening(a:diff_style_id, "")
+	    let l:diff_closing = s:HtmlClosing(a:diff_style_id, 0)
+	  else
+	    let l:diff_opening = ""
+	    let l:diff_closing = ""
+	  endif
+	  return s:HtmlOpening(a:style_id, a:extra_attrs)..l:diff_opening..a:text..l:diff_closing..s:HtmlClosing(a:style_id, !empty(a:extra_attrs))
+	endfun
+    ENDLET
   else
-    let wrapperfunc_lines = [
-	  \ 'function! s:BuildStyleWrapper(style_id, diff_style_id, extra_attrs, text, unusedarg, unusedarg2)',
-	  \ '  return s:HtmlOpening(a:style_id, a:extra_attrs).a:text.s:HtmlClosing(a:style_id, !empty(a:extra_attrs))',
-	  \ 'endfun'
-	  \ ]
+    let s:wrapperfunc_lines =<< trim ENDLET
+	function! s:BuildStyleWrapper(style_id, diff_style_id, extra_attrs, text, unusedarg, unusedarg2)
+	  return s:HtmlOpening(a:style_id, a:extra_attrs)..a:text..s:HtmlClosing(a:style_id, !empty(a:extra_attrs))
+	endfun
+    ENDLET
   endif
 endif
 
 " create the function we built line by line above
-exec join(wrapperfunc_lines, "\n")
+exec join(flatten(s:wrapperfunc_lines), "\n")
 
 let s:diff_mode = &diff
 
@@ -471,7 +508,7 @@ function! s:HtmlFormat(text, style_id, diff_style_id, extra_attrs, make_unselect
 
   " Replace double spaces, leading spaces, and trailing spaces if needed
   if ' ' != s:HtmlSpace
-    let formatted = substitute(formatted, '  ', s:HtmlSpace . s:HtmlSpace, 'g')
+    let formatted = substitute(formatted, '  ', s:HtmlSpace .. s:HtmlSpace, 'g')
     let formatted = substitute(formatted, '^ ', s:HtmlSpace, 'g')
     let formatted = substitute(formatted, ' \+$', s:HtmlSpace, 'g')
   endif
@@ -487,7 +524,7 @@ if s:settings.prevent_copy =~# 'n'
     if s:settings.line_ids
       function! s:HtmlFormat_n(text, style_id, diff_style_id, lnr)
 	if a:lnr > 0
-	  return s:HtmlFormat(a:text, a:style_id, a:diff_style_id, 'id="'.(exists('g:html_diff_win_num') ? 'W'.g:html_diff_win_num : "").'L'.a:lnr.s:settings.id_suffix.'" ', 1)
+	  return s:HtmlFormat(a:text, a:style_id, a:diff_style_id, 'id="'..(exists('g:html_diff_win_num') ? 'W'..g:html_diff_win_num : "")..'L'..a:lnr..s:settings.id_suffix..'" ', 1)
 	else
 	  return s:HtmlFormat(a:text, a:style_id, a:diff_style_id, "", 1)
 	endif
@@ -503,14 +540,14 @@ if s:settings.prevent_copy =~# 'n'
     " always be non-zero, however we don't want to use the <input> because that
     " won't work as nice for empty text
     function! s:HtmlFormat_n(text, style_id, diff_style_id, lnr)
-      return s:HtmlFormat(a:text, a:style_id, a:diff_style_id, 'id="'.(exists('g:html_diff_win_num') ? 'W'.g:html_diff_win_num : "").'L'.a:lnr.s:settings.id_suffix.'" ', 0)
+      return s:HtmlFormat(a:text, a:style_id, a:diff_style_id, 'id="'..(exists('g:html_diff_win_num') ? 'W'..g:html_diff_win_num : "")..'L'..a:lnr..s:settings.id_suffix..'" ', 0)
     endfun
   endif
 else
   if s:settings.line_ids
     function! s:HtmlFormat_n(text, style_id, diff_style_id, lnr)
       if a:lnr > 0
-	return s:HtmlFormat(a:text, a:style_id, a:diff_style_id, 'id="'.(exists('g:html_diff_win_num') ? 'W'.g:html_diff_win_num : "").'L'.a:lnr.s:settings.id_suffix.'" ', 0)
+	return s:HtmlFormat(a:text, a:style_id, a:diff_style_id, 'id="'..(exists('g:html_diff_win_num') ? 'W'..g:html_diff_win_num : "")..'L'..a:lnr..s:settings.id_suffix..'" ', 0)
       else
 	return s:HtmlFormat(a:text, a:style_id, a:diff_style_id, "", 0)
       endif
@@ -535,8 +572,8 @@ if s:settings.prevent_copy =~# 'f'
     " Simply space-pad to the desired width inside the generated content (note
     " that the FoldColumn definition includes a whitespace:pre rule)
     function! s:FoldColumn_build(char, len, numfill, char2, class, click)
-      return "<a href='#' class='".a:class."' onclick='".a:click."' data-FoldColumn-content='".
-	    \ repeat(a:char, a:len).a:char2.repeat(' ', a:numfill).
+      return "<a href='#' class='"..a:class.."' onclick='"..a:click.."' data-FoldColumn-content='".
+	    \ repeat(a:char, a:len)..a:char2..repeat(' ', a:numfill).
 	    \ "'></a>"
     endfun
     function! s:FoldColumn_fill()
@@ -554,35 +591,38 @@ if s:settings.prevent_copy =~# 'f'
     "
     " Note, 'exec' commands do not recognize line continuations, so must
     " concatenate lines rather than continue them.
-    let build_fun_lines = [
-	  \ 'function! s:FoldColumn_build(char, len, numfill, char2, class, click)',
-	  \ '  let l:input_open = "<input readonly=''readonly''".s:unselInputType.'.
-	  \ '          " onselect=''this.blur(); return false;''".'.
-	  \ '          " onmousedown=''this.blur(); ".a:click." return false;''".'.
-	  \ '          " onclick=''return false;'' size=''".'.
-	  \ '          string(a:len + (empty(a:char2) ? 0 : 1) + a:numfill) .'.
-	  \ '          "'' "',
-	  \ '  let l:common_attrs = "class=''FoldColumn'' value=''"',
-	  \ '  let l:input_close = (s:settings.use_xhtml ? "'' />" : "''>")'
-	  \ ]
+    let s:build_fun_lines = []
+    call add(s:build_fun_lines, [])
+    let s:build_fun_lines[-1] =<< trim ENDLET
+	  function! s:FoldColumn_build(char, len, numfill, char2, class, click)
+	    let l:input_open = "<input readonly='readonly'"..s:unselInputType
+	    let l:input_open ..= " onselect='this.blur(); return false;'"
+	    let l:input_open ..= " onmousedown='this.blur(); "..a:click.." return false;'"
+	    let l:input_open ..= " onclick='return false;' size='"
+	    let l:input_open ..= string(a:len + (empty(a:char2) ? 0 : 1) + a:numfill) .. "' "
+	    let l:common_attrs = "class='FoldColumn' value='"
+	    let l:input_close = (s:settings.use_xhtml ? "' />" : "'>")
+	    let l:return_span = "<span class='"..a:class.."'>"
+	    let l:return_span ..= l:input_open..l:common_attrs..repeat(a:char, a:len)..(a:char2)
+	    let l:return_span ..= l:input_close
+    ENDLET
     if s:settings.use_input_for_pc ==# 'fallback'
-      let build_fun_lines += [
-	    \ '  let l:gen_content_link ='.
-	    \ '          "<a href=''#'' class=''FoldColumn'' onclick=''".a:click."'' data-FoldColumn-content=''".'.
-	    \ '          repeat(a:char, a:len).a:char2.repeat('' '', a:numfill).'.
-	    \ '          "''></a>"'
-	    \ ]
+      call add(s:build_fun_lines, [])
+      let s:build_fun_lines[-1] =<< trim ENDLET
+	    let l:return_span ..= "<a href='#' class='FoldColumn' onclick='"..a:click.."'"
+	    let l:return_span ..= " data-FoldColumn-content='"
+	    let l:return_span ..= repeat(a:char, a:len)..a:char2..repeat(' ', a:numfill)
+	    let l:return_span ..= "'></a>"
+      ENDLET
     endif
-    let build_fun_lines += [
-	  \ '  return "<span class=''".a:class."''>".'.
-	  \ '          l:input_open.l:common_attrs.repeat(a:char, a:len).(a:char2).'.
-	  \ '          l:input_close.'.
-	  \ (s:settings.use_input_for_pc ==# 'fallback' ? 'l:gen_content_link.' : "").
-	  \ '          "</span>"',
-	  \ 'endfun'
-	  \ ]
+    call add(s:build_fun_lines, [])
+    let s:build_fun_lines[-1] =<< trim ENDLET
+	    let l:return_span ..= "</span>"
+	    return l:return_span
+	  endfun
+    ENDLET
     " create the function we built line by line above
-    exec join(build_fun_lines, "\n")
+    exec join(flatten(s:build_fun_lines), "\n")
 
     function! s:FoldColumn_fill()
       return s:FoldColumn_build(' ', s:foldcolumn, 0, '', 'FoldColumn', '')
@@ -592,8 +632,8 @@ else
   " For normal fold columns, simply space-pad to the desired width (note that
   " the FoldColumn definition includes a whitespace:pre rule)
   function! s:FoldColumn_build(char, len, numfill, char2, class, click)
-    return "<a href='#' class='".a:class."' onclick='".a:click."'>".
-	  \ repeat(a:char, a:len).a:char2.repeat(' ', a:numfill).
+    return "<a href='#' class='"..a:class.."' onclick='"..a:click.."'>".
+	  \ repeat(a:char, a:len)..a:char2..repeat(' ', a:numfill).
 	  \ "</a>"
   endfun
   function! s:FoldColumn_fill()
@@ -625,29 +665,30 @@ endif
 " Return CSS style describing given highlight id (can be empty)
 function! s:CSS1(id)
   let a = ""
-  if synIDattr(a:id, "inverse")
+  let translated_ID = synIDtrans(a:id)
+  if synIDattr(translated_ID, "inverse")
     " For inverse, we always must set both colors (and exchange them)
-    let x = s:HtmlColor(synIDattr(a:id, "bg#", s:whatterm))
-    let a = a . "color: " . ( x != "" ? x : s:bgc ) . "; "
-    let x = s:HtmlColor(synIDattr(a:id, "fg#", s:whatterm))
-    let a = a . "background-color: " . ( x != "" ? x : s:fgc ) . "; "
+    let x = s:HtmlColor(synIDattr(translated_ID, "bg#", s:whatterm))
+    let a = a .. "color: " .. ( x != "" ? x : s:bgc ) .. "; "
+    let x = s:HtmlColor(synIDattr(translated_ID, "fg#", s:whatterm))
+    let a = a .. "background-color: " .. ( x != "" ? x : s:fgc ) .. "; "
   else
-    let x = s:HtmlColor(synIDattr(a:id, "fg#", s:whatterm))
-    if x != "" | let a = a . "color: " . x . "; " | endif
-    let x = s:HtmlColor(synIDattr(a:id, "bg#", s:whatterm))
+    let x = s:HtmlColor(synIDattr(translated_ID, "fg#", s:whatterm))
+    if x != "" | let a = a .. "color: " .. x .. "; " | endif
+    let x = s:HtmlColor(synIDattr(translated_ID, "bg#", s:whatterm))
     if x != ""
-      let a = a . "background-color: " . x . "; "
+      let a = a .. "background-color: " .. x .. "; "
       " stupid hack because almost every browser seems to have at least one font
       " which shows 1px gaps between lines which have background
-      let a = a . "padding-bottom: 1px; "
-    elseif (a:id == s:FOLDED_ID || a:id == s:LINENR_ID || a:id == s:FOLD_C_ID) && !empty(s:settings.prevent_copy)
+      let a = a .. "padding-bottom: 1px; "
+    elseif (translated_ID == s:FOLDED_ID || translated_ID == s:LINENR_ID || translated_ID == s:FOLD_C_ID) && !empty(s:settings.prevent_copy)
       " input elements default to a different color than the rest of the page
-      let a = a . "background-color: " . s:bgc . "; "
+      let a = a .. "background-color: " .. s:bgc .. "; "
     endif
   endif
-  if synIDattr(a:id, "bold") | let a = a . "font-weight: bold; " | endif
-  if synIDattr(a:id, "italic") | let a = a . "font-style: italic; " | endif
-  if synIDattr(a:id, "underline") | let a = a . "text-decoration: underline; " | endif
+  if synIDattr(translated_ID, "bold") | let a = a .. "font-weight: bold; " | endif
+  if synIDattr(translated_ID, "italic") | let a = a .. "font-style: italic; " | endif
+  if synIDattr(translated_ID, "underline") | let a = a .. "text-decoration: underline; " | endif
   return a
 endfun
 
@@ -720,7 +761,7 @@ if exists("g:loaded_2html_plugin")
   let s:pluginversion = g:loaded_2html_plugin
 else
   if !exists("g:unloaded_tohtml_plugin")
-    let s:main_plugin_path = expand("<sfile>:p:h:h")."/plugin/tohtml.vim"
+    let s:main_plugin_path = expand("<sfile>:p:h:h").."/plugin/tohtml.vim"
     if filereadable(s:main_plugin_path)
       let s:lines = readfile(s:main_plugin_path, "", 20)
       call filter(s:lines, 'v:val =~ "loaded_2html_plugin = "')
@@ -743,12 +784,12 @@ let s:orgbufnr = winbufnr(0)
 let s:origwin_stl = &l:stl
 if expand("%") == ""
   if exists('g:html_diff_win_num')
-    exec 'new Untitled_win'.g:html_diff_win_num.'.'.(s:settings.use_xhtml ? 'x' : '').'html'
+    exec 'new Untitled_win'..g:html_diff_win_num..'.'.(s:settings.use_xhtml ? 'xhtml' : 'html')
   else
-    exec 'new Untitled.'.(s:settings.use_xhtml ? 'x' : '').'html'
+    exec 'new Untitled.'..(s:settings.use_xhtml ? 'xhtml' : 'html')
   endif
 else
-  exec 'new %.'.(s:settings.use_xhtml ? 'x' : '').'html'
+  exec 'new %.'..(s:settings.use_xhtml ? 'xhtml' : 'html')
 endif
 
 " Resize the new window to very small in order to make it draw faster
@@ -795,7 +836,7 @@ let s:lines = []
 
 if s:settings.use_xhtml
   if s:settings.encoding != ""
-    call add(s:lines, "<?xml version=\"1.0\" encoding=\"" . s:settings.encoding . "\"?>")
+    call add(s:lines, "<?xml version=\"1.0\" encoding=\"" .. s:settings.encoding .. "\"?>")
   else
     call add(s:lines, "<?xml version=\"1.0\"?>")
   endif
@@ -808,9 +849,9 @@ let s:HtmlSpace = ' '
 let s:LeadingSpace = ' '
 let s:HtmlEndline = ''
 if s:settings.no_pre
-  let s:HtmlEndline = '<br' . s:tag_close
+  let s:HtmlEndline = '<br' .. s:tag_close
   let s:LeadingSpace = s:settings.use_xhtml ? '&#160;' : '&nbsp;'
-  let s:HtmlSpace = '\' . s:LeadingSpace
+  let s:HtmlSpace = '\' .. s:LeadingSpace
 endif
 
 " HTML header, with the title and generator ;-). Left free space for the CSS,
@@ -823,30 +864,30 @@ if !s:settings.no_doc
   " contained in XML information (to avoid haggling over content type)
   if s:settings.encoding != "" && !s:settings.use_xhtml
     if s:html5
-      call add(s:lines, '<meta charset="' . s:settings.encoding . '"' . s:tag_close)
+      call add(s:lines, '<meta charset="' .. s:settings.encoding .. '"' .. s:tag_close)
     else
-      call add(s:lines, "<meta http-equiv=\"content-type\" content=\"text/html; charset=" . s:settings.encoding . '"' . s:tag_close)
+      call add(s:lines, "<meta http-equiv=\"content-type\" content=\"text/html; charset=" .. s:settings.encoding .. '"' .. s:tag_close)
     endif
   endif
   call extend(s:lines, [
-	\ ("<title>".expand("%:p:~")."</title>"),
-	\ ("<meta name=\"Generator\" content=\"Vim/".v:version/100.".".v:version%100.'"'.s:tag_close),
-	\ ("<meta name=\"plugin-version\" content=\"".s:pluginversion.'"'.s:tag_close)
+	\ ("<title>"..expand("%:p:~").."</title>"),
+	\ ("<meta name=\"Generator\" content=\"Vim/"..v:version/100.."."..v:version%100..'"'..s:tag_close),
+	\ ("<meta name=\"plugin-version\" content=\""..s:pluginversion..'"'..s:tag_close)
 	\ ])
-  call add(s:lines, '<meta name="syntax" content="'.s:current_syntax.'"'.s:tag_close)
-  call add(s:lines, '<meta name="settings" content="'.
-	\ join(filter(keys(s:settings),'s:settings[v:val]'),',').
-	\ ',prevent_copy='.s:settings.prevent_copy.
-	\ ',use_input_for_pc='.s:settings.use_input_for_pc.
-	\ '"'.s:tag_close)
-  call add(s:lines, '<meta name="colorscheme" content="'.
+  call add(s:lines, '<meta name="syntax" content="'..s:current_syntax..'"'..s:tag_close)
+  call add(s:lines, '<meta name="settings" content="'..
+	\ join(filter(keys(s:settings),'s:settings[v:val]'),',')..
+	\ ',prevent_copy='..s:settings.prevent_copy..
+	\ ',use_input_for_pc='..s:settings.use_input_for_pc..
+	\ '"'..s:tag_close)
+  call add(s:lines, '<meta name="colorscheme" content="'..
 	\ (exists('g:colors_name')
 	\ ? g:colors_name
-	\ : 'none'). '"'.s:tag_close)
+	\ : 'none').. '"'..s:tag_close)
 
   if s:settings.use_css
     call extend(s:lines, [
-	  \ "<style" . (s:html5 ? "" : " type=\"text/css\"") . ">",
+	  \ "<style" .. (s:html5 ? "" : " type=\"text/css\"") .. ">",
 	  \ s:settings.use_xhtml ? "" : "<!--"])
     let s:ieonly = []
     if s:settings.dynamic_folds
@@ -921,7 +962,7 @@ if !s:settings.no_doc
   if s:uses_script
     call extend(s:lines, [
 	  \ "",
-	  \ "<script" . (s:html5 ? "" : " type='text/javascript'") . ">",
+	  \ "<script" .. (s:html5 ? "" : " type='text/javascript'") .. ">",
 	  \ s:settings.use_xhtml ? '//<![CDATA[' : "<!--"])
   endif
 
@@ -968,7 +1009,7 @@ if !s:settings.no_doc
 	    \ "",
 	    \ "  /* navigate upwards in the DOM tree to open all folds containing the line */",
 	    \ "  var node = lineElem;",
-	    \ "  while (node && node.id != 'vimCodeElement".s:settings.id_suffix."')",
+	    \ "  while (node && node.id != 'vimCodeElement"..s:settings.id_suffix.."')",
 	    \ "  {",
 	    \ "    if (node.className == 'closed-fold')",
 	    \ "    {",
@@ -1003,7 +1044,7 @@ if !s:settings.no_doc
   endif
 
   call extend(s:lines, ["</head>",
-	\ "<body".(s:settings.line_ids ? " onload='JumpToLine();'" : "").">"])
+	\ "<body"..(s:settings.line_ids ? " onload='JumpToLine();'" : "")..">"])
 endif
 
 if s:settings.no_pre
@@ -1015,20 +1056,20 @@ else
   call extend(s:lines, ["<pre id='vimCodeElement" .. s:settings.id_suffix .. "'>"])
 endif
 
-exe s:orgwin . "wincmd w"
+exe s:orgwin .. "wincmd w"
 
 " caches of style data
 " initialize to include line numbers if using them
 if s:settings.number_lines
-  let s:stylelist = { s:LINENR_ID : ".LineNr { " . s:CSS1( s:LINENR_ID ) . "}" }
+  let s:stylelist = { s:LINENR_ID : ".LineNr { " .. s:CSS1( s:LINENR_ID ) .. "}" }
 else
   let s:stylelist = {}
 endif
 let s:diffstylelist = {
-      \   s:DIFF_A_ID : ".DiffAdd { " . s:CSS1( s:DIFF_A_ID ) . "}",
-      \   s:DIFF_C_ID : ".DiffChange { " . s:CSS1( s:DIFF_C_ID ) . "}",
-      \   s:DIFF_D_ID : ".DiffDelete { " . s:CSS1( s:DIFF_D_ID ) . "}",
-      \   s:DIFF_T_ID : ".DiffText { " . s:CSS1( s:DIFF_T_ID ) . "}"
+      \   s:DIFF_A_ID : ".DiffAdd { " .. s:CSS1( s:DIFF_A_ID ) .. "}",
+      \   s:DIFF_C_ID : ".DiffChange { " .. s:CSS1( s:DIFF_C_ID ) .. "}",
+      \   s:DIFF_D_ID : ".DiffDelete { " .. s:CSS1( s:DIFF_D_ID ) .. "}",
+      \   s:DIFF_T_ID : ".DiffText { " .. s:CSS1( s:DIFF_T_ID ) .. "}"
       \ }
 
 " set up progress bar in the status line
@@ -1046,17 +1087,17 @@ if !s:settings.no_progress
        \ g:colors_name != s:last_colors_name
       let s:last_colors_name = exists("g:colors_name") ? g:colors_name : "none"
 
-      let l:diffatr = synIDattr(hlID("DiffDelete"), "reverse", s:whatterm) ? "fg#" : "bg#"
-      let l:stlatr = synIDattr(hlID("StatusLine"), "reverse", s:whatterm) ? "fg#" : "bg#"
+      let l:diffatr = synIDattr(hlID("DiffDelete")->synIDtrans(), "reverse", s:whatterm) ? "fg#" : "bg#"
+      let l:stlatr = synIDattr(hlID("StatusLine")->synIDtrans(), "reverse", s:whatterm) ? "fg#" : "bg#"
 
-      let l:progbar_color = synIDattr(hlID("DiffDelete"), l:diffatr, s:whatterm)
-      let l:stl_color = synIDattr(hlID("StatusLine"), l:stlatr, s:whatterm)
+      let l:progbar_color = synIDattr(hlID("DiffDelete")->synIDtrans(), l:diffatr, s:whatterm)
+      let l:stl_color = synIDattr(hlID("StatusLine")->synIDtrans(), l:stlatr, s:whatterm)
 
       if "" == l:progbar_color
-	let l:progbar_color = synIDattr(hlID("DiffDelete"), "reverse", s:whatterm) ? s:fgc : s:bgc
+	let l:progbar_color = synIDattr(hlID("DiffDelete")->synIDtrans(), "reverse", s:whatterm) ? s:fgc : s:bgc
       endif
       if "" == l:stl_color
-	let l:stl_color = synIDattr(hlID("StatusLine"), "reverse", s:whatterm) ? s:fgc : s:bgc
+	let l:stl_color = synIDattr(hlID("StatusLine")->synIDtrans(), "reverse", s:whatterm) ? s:fgc : s:bgc
       endif
 
       if l:progbar_color == l:stl_color
@@ -1086,13 +1127,13 @@ if !s:settings.no_progress
 	endif
 	echomsg "diff detected progbar color set to" l:progbar_color
       endif
-      exe "hi TOhtmlProgress_auto" s:whatterm."bg=".l:progbar_color
+      exe "hi TOhtmlProgress_auto" s:whatterm.."bg="..l:progbar_color
     endif
   endfun
 
   func! s:ProgressBar(title, max_value, winnr)
     let pgb=copy(s:progressbar)
-    let pgb.title = a:title.' '
+    let pgb.title = a:title..' '
     let pgb.max_value = a:max_value
     let pgb.winnr = a:winnr
     let pgb.cur_value = 0
@@ -1194,6 +1235,66 @@ if !s:settings.no_progress
   call s:SetProgbarColor()
 endif
 
+let s:build_fun_lines = []
+call add(s:build_fun_lines, [])
+let s:build_fun_lines[-1] =<< trim ENDLET
+    func! s:Add_diff_fill(lnum)
+      let l:filler = diff_filler(a:lnum)
+      if l:filler > 0
+	let l:to_insert = l:filler
+	while l:to_insert > 0
+	  let l:new = repeat(s:difffillchar, 3)
+
+	  if l:to_insert > 2 && l:to_insert < l:filler && !s:settings.whole_filler
+	    let l:new = l:new .. " " .. l:filler .. " inserted lines "
+	    let l:to_insert = 2
+	  endif
+ENDLET
+call add(s:build_fun_lines, [])
+if !s:settings.no_pre
+  let s:build_fun_lines[-1] =<< trim ENDLET
+	  " HTML line wrapping is off--go ahead and fill to the margin
+	  " TODO: what about when CSS wrapping is turned on?
+	  let l:new = l:new .. repeat(s:difffillchar, &columns - strlen(l:new) - s:margin)
+  ENDLET
+else
+  let s:build_fun_lines[-1] =<< trim ENDLET
+	  let l:new = l:new .. repeat(s:difffillchar, 3)
+  ENDLET
+endif
+call add(s:build_fun_lines, [])
+let s:build_fun_lines[-1] =<< trim ENDLET
+	let l:new = s:HtmlFormat_d(l:new, s:DIFF_D_ID, 0)
+ENDLET
+if s:settings.number_lines
+  call add(s:build_fun_lines, [])
+  let s:build_fun_lines[-1] =<< trim ENDLET
+	  " Indent if line numbering is on. Indent gets style of line number
+	  " column.
+	  let l:new = s:HtmlFormat_n(repeat(' ', s:margin), s:LINENR_ID, 0, 0) .. l:new
+  ENDLET
+endif
+if s:settings.dynamic_folds && !s:settings.no_foldcolumn 
+  call add(s:build_fun_lines, [])
+  let s:build_fun_lines[-1] =<< trim ENDLET
+	  if s:foldcolumn > 0
+	    " Indent for foldcolumn if there is one. Assume it's empty, there should
+	    " not be a fold for deleted lines in diff mode.
+	    let l:new = s:FoldColumn_fill() .. l:new
+	  endif
+  ENDLET
+endif
+" Ignore this comment, just bypassing a highlighting issue: if
+call add(s:build_fun_lines, [])
+let s:build_fun_lines[-1] =<< trim ENDLET
+	call add(s:lines, l:new..s:HtmlEndline)
+	let l:to_insert = l:to_insert - 1
+      endwhile
+    endif
+  endfun
+ENDLET
+exec join(flatten(s:build_fun_lines), "\n")
+
 " First do some preprocessing for dynamic folding. Do this for the entire file
 " so we don't accidentally start within a closed fold or something.
 let s:allfolds = []
@@ -1220,7 +1321,7 @@ if s:settings.dynamic_folds
       let s:newfold = {'firstline': s:lnum, 'lastline': foldclosedend(s:lnum), 'level': s:level,'type': "closed-fold"}
       call add(s:allfolds, s:newfold)
       " open the fold so we can find any contained folds
-      execute s:lnum."foldopen"
+      execute s:lnum.."foldopen"
     else
       if !s:settings.no_progress
 	call s:pgb.incr()
@@ -1252,7 +1353,7 @@ if s:settings.dynamic_folds
 	call add(s:allfolds, s:newfold)
       endif
       " open the fold so we can find any contained folds
-      execute s:lnum."foldopen"
+      execute s:lnum.."foldopen"
     else
       if !s:settings.no_progress
 	call s:pgb.incr()
@@ -1339,7 +1440,7 @@ if s:settings.dynamic_folds
   " Note that only when a start and an end line is specified will a fold
   " containing the current range ever be removed.
   while leveladjust > 0
-    exe g:html_start_line."foldopen"
+    exe g:html_start_line.."foldopen"
     let leveladjust -= 1
   endwhile
 endif
@@ -1399,47 +1500,11 @@ endif
 while s:lnum <= s:end
 
   " If there are filler lines for diff mode, show these above the line.
-  let s:filler = diff_filler(s:lnum)
-  if s:filler > 0
-    let s:n = s:filler
-    while s:n > 0
-      let s:new = repeat(s:difffillchar, 3)
-
-      if s:n > 2 && s:n < s:filler && !s:settings.whole_filler
-	let s:new = s:new . " " . s:filler . " inserted lines "
-	let s:n = 2
-      endif
-
-      if !s:settings.no_pre
-	" HTML line wrapping is off--go ahead and fill to the margin
-	" TODO: what about when CSS wrapping is turned on?
-	let s:new = s:new . repeat(s:difffillchar, &columns - strlen(s:new) - s:margin)
-      else
-	let s:new = s:new . repeat(s:difffillchar, 3)
-      endif
-
-      let s:new = s:HtmlFormat_d(s:new, s:DIFF_D_ID, 0)
-      if s:settings.number_lines
-	" Indent if line numbering is on. Indent gets style of line number
-	" column.
-	let s:new = s:HtmlFormat_n(repeat(' ', s:margin), s:LINENR_ID, 0, 0) . s:new
-      endif
-      if s:settings.dynamic_folds && !s:settings.no_foldcolumn && s:foldcolumn > 0
-	" Indent for foldcolumn if there is one. Assume it's empty, there should
-	" not be a fold for deleted lines in diff mode.