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>

4 files changed, 428 insertions, 335 deletions

diff --git a/runtime/autoload/tohtml.vim b/runtime/autoload/tohtml.vim
index 1086347473..d2722a4021 100644
--- a/runtime/autoload/tohtml.vim
+++ b/runtime/autoload/tohtml.vim
@@ -1,6 +1,6 @@
 " Vim autoload file for the tohtml plugin.
 " Maintainer: Ben Fritz <fritzophrenic@gmail.com>
-" Last Change: 2023 Jan 01
+" Last Change: 2023 Sep 03
 "
 " Additional contributors:
 "
@@ -307,7 +307,7 @@ func! tohtml#Convert2HTML(line1, line2) "{{{
     let g:html_diff_win_num = 0
     for window in win_list
       " switch to the next buffer to convert
-      exe ":" . bufwinnr(window) . "wincmd w"
+      exe ":" .. bufwinnr(window) .. "wincmd w"
 
       " figure out whether current charset and encoding will work, if not
       " default to UTF-8
@@ -355,7 +355,7 @@ func! tohtml#Diff2HTML(win_list, buf_list) "{{{
   if !s:settings.no_doc
     if s:settings.use_xhtml
       if s:settings.encoding != ""
-	let xml_line = "<?xml version=\"1.0\" encoding=\"" . s:settings.encoding . "\"?>"
+	let xml_line = "<?xml version=\"1.0\" encoding=\"" .. s:settings.encoding .. "\"?>"
       else
 	let xml_line = "<?xml version=\"1.0\"?>"
       endif
@@ -387,34 +387,34 @@ func! tohtml#Diff2HTML(win_list, buf_list) "{{{
     " contained in XML information
     if s:settings.encoding != "" && !s:settings.use_xhtml
       if s:html5
-	call add(html, '<meta charset="' . s:settings.encoding . '"' . tag_close)
+	call add(html, '<meta charset="' .. s:settings.encoding .. '"' .. tag_close)
       else
-	call add(html, "<meta http-equiv=\"content-type\" content=\"text/html; charset=" . s:settings.encoding . '"' . tag_close)
+	call add(html, "<meta http-equiv=\"content-type\" content=\"text/html; charset=" .. s:settings.encoding .. '"' .. tag_close)
       endif
     endif
 
     call add(html, '<title>diff</title>')
-    call add(html, '<meta name="Generator" content="Vim/'.v:version/100.'.'.v:version%100.'"'.tag_close)
-    call add(html, '<meta name="plugin-version" content="'.g:loaded_2html_plugin.'"'.tag_close)
+    call add(html, '<meta name="Generator" content="Vim/'..v:version/100..'.'..v:version%100..'"'..tag_close)
+    call add(html, '<meta name="plugin-version" content="'..g:loaded_2html_plugin..'"'..tag_close)
     call add(html, '<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.
-	  \ '"'.tag_close)
+	  \ ',prevent_copy='..s:settings.prevent_copy.
+	  \ ',use_input_for_pc='..s:settings.use_input_for_pc.
+	  \ '"'..tag_close)
     call add(html, '<meta name="colorscheme" content="'.
 	  \ (exists('g:colors_name')
 	  \ ? g:colors_name
-	  \ : 'none'). '"'.tag_close)
+	  \ : 'none').. '"'..tag_close)
 
     call add(html, '</head>')
     let body_line_num = len(html)
-    call add(html, '<body'.(s:settings.line_ids ? ' onload="JumpToLine();"' : '').'>')
+    call add(html, '<body'..(s:settings.line_ids ? ' onload="JumpToLine();"' : '')..'>')
   endif
-  call add(html, "<table ".(s:settings.use_css? "" : "border='1' width='100%' ")."id='vimCodeElement".s:settings.id_suffix."'>")
+  call add(html, "<table "..(s:settings.use_css? "" : "border='1' width='100%' ").."id='vimCodeElement"..s:settings.id_suffix.."'>")
 
   call add(html, '<tr>')
   for buf in a:win_list
-    call add(html, '<th>'.bufname(buf).'</th>')
+    call add(html, '<th>'..bufname(buf)..'</th>')
   endfor
   call add(html, '</tr><tr>')
 
@@ -423,7 +423,7 @@ func! tohtml#Diff2HTML(win_list, buf_list) "{{{
 
   for buf in a:buf_list
     let temp = []
-    exe bufwinnr(buf) . 'wincmd w'
+    exe bufwinnr(buf) .. 'wincmd w'
 
     " If text is folded because of user foldmethod settings, etc. we don't want
     " to act on everything in a fold by mistake.
@@ -526,16 +526,16 @@ func! tohtml#Diff2HTML(win_list, buf_list) "{{{
   endif
 
   let i = 1
-  let name = "Diff" . (s:settings.use_xhtml ? ".xhtml" : ".html")
+  let name = "Diff" .. (s:settings.use_xhtml ? ".xhtml" : ".html")
   " Find an unused file name if current file name is already in use
   while filereadable(name)
-    let name = substitute(name, '\d*\.x\?html$', '', '') . i . '.' . fnamemodify(copy(name), ":t:e")
+    let name = substitute(name, '\d*\.x\?html$', '', '') .. i .. '.' .. fnamemodify(copy(name), ":t:e")
     let i += 1
   endwhile
 
   let s:ei_sav = &eventignore
   set eventignore+=FileType
-  exe "topleft new " . name
+  exe "topleft new " .. name
   let &eventignore=s:ei_sav
   unlet s:ei_sav
 
@@ -601,7 +601,7 @@ func! tohtml#Diff2HTML(win_list, buf_list) "{{{
 		\ "",
 		\ "  /* 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')",
 		\ "    {",
@@ -640,7 +640,7 @@ func! tohtml#Diff2HTML(win_list, buf_list) "{{{
 	call append(style_start, [
 	      \  "  function toggleFold(objID)",
 	      \  "  {",
-	      \  "    for (win_num = 1; win_num <= ".len(a:buf_list)."; win_num++)",
+	      \  "    for (win_num = 1; win_num <= "..len(a:buf_list).."; win_num++)",
 	      \  "    {",
 	      \  "      var fold;",
 	      \  '      fold = document.getElementById("win"+win_num+objID);',
@@ -660,7 +660,7 @@ func! tohtml#Diff2HTML(win_list, buf_list) "{{{
       if s:uses_script
 	" insert script tag if needed
 	call append(style_start, [
-	      \ "<script" . (s:html5 ? "" : " type='text/javascript'") . ">",
+	      \ "<script" .. (s:html5 ? "" : " type='text/javascript'") .. ">",
 	      \ s:settings.use_xhtml ? '//<![CDATA[' : "<!--"])
       endif
 
@@ -671,14 +671,14 @@ func! tohtml#Diff2HTML(win_list, buf_list) "{{{
       " is pretty useless for really long lines. {{{
       if s:settings.use_css
 	call append(style_start,
-	      \ ['<style' . (s:html5 ? '' : 'type="text/css"') . '>']+
+	      \ ['<style' .. (s:html5 ? '' : 'type="text/css"') .. '>']+
 	      \ style+
 	      \ [ s:settings.use_xhtml ? '' : '<!--',
 	      \   'table { table-layout: fixed; }',
 	      \   'html, body, table, tbody { width: 100%; margin: 0; padding: 0; }',
 	      \   'table, td, th { border: 1px solid; }',
 	      \   'td { vertical-align: top; }',
-	      \   'th, td { width: '.printf("%.1f",100.0/len(a:win_list)).'%; }',
+	      \   'th, td { width: '..printf("%.1f",100.0/len(a:win_list))..'%; }',
 	      \   'td div { overflow: auto; }',
 	      \   s:settings.use_xhtml ? '' : '-->',
 	      \   '</style>'
@@ -694,7 +694,7 @@ endfunc "}}}
 " Gets a single user option and sets it in the passed-in Dict, or gives it the
 " default value if the option doesn't actually exist.
 func! tohtml#GetOption(settings, option, default) "{{{
-  if exists('g:html_'.a:option)
+  if exists('g:html_'..a:option)
     let a:settings[a:option] = g:html_{a:option}
   else
     let a:settings[a:option] = a:default
@@ -713,10 +713,11 @@ func! tohtml#GetUserSettings() "{{{
     let user_settings = {}
 
     " Define the correct option if the old option name exists and we haven't
-    " already defined the correct one. Maybe I'll put out a warning message about
-    " this sometime and remove the old option entirely at some even later time,
-    " but for now just silently accept the old option.
+    " already defined the correct one.
     if exists('g:use_xhtml') && !exists("g:html_use_xhtml")
+      echohl WarningMsg
+      echomsg "Warning: g:use_xhtml is deprecated, use g:html_use_xhtml"
+      echohl None
       let g:html_use_xhtml = g:use_xhtml
     endif
 
@@ -739,7 +740,7 @@ func! tohtml#GetUserSettings() "{{{
     call tohtml#GetOption(user_settings,      'whole_filler', 0 )
     call tohtml#GetOption(user_settings,         'use_xhtml', 0 )
     call tohtml#GetOption(user_settings,          'line_ids', user_settings.number_lines )
-    call tohtml#GetOption(user_settings, 'use_input_for_pc', 'fallback')
+    call tohtml#GetOption(user_settings, 'use_input_for_pc', 'none')
     " }}}
     
     " override those settings that need it {{{
@@ -854,16 +855,16 @@ func! tohtml#GetUserSettings() "{{{
     if user_settings.use_css
       if exists("g:html_prevent_copy")
 	if user_settings.dynamic_folds && !user_settings.no_foldcolumn && g:html_prevent_copy =~# 'f'
-	  let user_settings.prevent_copy .= 'f'
+	  let user_settings.prevent_copy ..= 'f'
 	endif
 	if user_settings.number_lines && g:html_prevent_copy =~# 'n'
-	  let user_settings.prevent_copy .= 'n'
+	  let user_settings.prevent_copy ..= 'n'
 	endif
 	if &diff && g:html_prevent_copy =~# 'd'
-	  let user_settings.prevent_copy .= 'd'
+	  let user_settings.prevent_copy ..= 'd'
 	endif
 	if !user_settings.ignore_folding && g:html_prevent_copy =~# 't'
-	  let user_settings.prevent_copy .= 't'
+	  let user_settings.prevent_copy ..= 't'
 	endif
       else
 	let user_settings.prevent_copy = ""
@@ -875,10 +876,10 @@ func! tohtml#GetUserSettings() "{{{
 
     " enforce valid values for use_input_for_pc
     if user_settings.use_input_for_pc !~# 'fallback\|none\|all'
-      let user_settings.use_input_for_pc = 'fallback'
+      let user_settings.use_input_for_pc = 'none'
       echohl WarningMsg
-      echomsg '2html: "' . g:html_use_input_for_pc . '" is not valid for g:html_use_input_for_pc'
-      echomsg '2html: defaulting to "' . user_settings.use_input_for_pc . '"'
+      echomsg '2html: "' .. g:html_use_input_for_pc .. '" is not valid for g:html_use_input_for_pc'
+      echomsg '2html: defaulting to "' .. user_settings.use_input_for_pc .. '"'
       echohl None
       sleep 3
     endif
diff --git a/runtime/doc/syntax.txt b/runtime/doc/syntax.txt
index 29a12396d4..6a20734a60 100644
--- a/runtime/doc/syntax.txt
+++ b/runtime/doc/syntax.txt
@@ -596,7 +596,7 @@ The method used to prevent copying in the generated page depends on the value
 of |g:html_use_input_for_pc|.
 
 						    *g:html_use_input_for_pc*
-Default: "fallback"
+Default: "none"
 If |g:html_prevent_copy| is non-empty, then:
 
 When "all", read-only <input> elements are used in place of normal text for
diff --git a/runtime/plugin/tohtml.vim b/runtime/plugin/tohtml.vim
index 0369313f08..56eb2c15bf 100644
--- a/runtime/plugin/tohtml.vim
+++ b/runtime/plugin/tohtml.vim
@@ -1,6 +1,6 @@
 " Vim plugin for converting a syntax highlighted file to HTML.
 " Maintainer: Ben Fritz <fritzophrenic@gmail.com>
-" Last Change: 2023 Jan 01
+" Last Change: 2023 Sep 07
 "
 " The core of the code is in $VIMRUNTIME/autoload/tohtml.vim and
 " $VIMRUNTIME/syntax/2html.vim
@@ -8,11 +8,29 @@
 if exists('g:loaded_2html_plugin')
   finish
 endif
-let g:loaded_2html_plugin = 'vim9.0_v1'
+let g:loaded_2html_plugin = 'vim9.0_v2'
 
 "
 " Changelog: {{{
-"   9.0_v1  (this version): - Implement g:html_no_doc and g:html_no_modeline
+"   9.0_v2  (this version): - Warn if using deprecated g:use_xhtml option
+"                           - Change default g:html_use_input_for_pc to "none"
+"                             instead of "fallback". All modern browsers support
+"                             the "user-select: none" and "content:" CSS
+"                             properties so the older method relying on extra
+"                             markup and unspecified browser/app clipboard
+"                             handling is only needed in rare special cases.
+"                           - Fix SourceForge issue #33: generate diff filler
+"                             correctly when new lines have been added to or
+"                             removed from end of buffer.
+"                           - Fix SourceForge issue #32/Vim Github issue #8547:
+"                             use translated highlight ID for styling the
+"                             special-use group names (e.g. LineNr) used
+"                             directly by name in the 2html processing.
+"                           - Fix SourceForge issue #26, refactoring to use
+"                             :let-heredoc style string assignment and
+"                             additional fixes for ".." vs. "." style string
+"                             concatenation. Requires Vim v8.1.1354 or higher.
+"   9.0_v1  (Vim 9.0.1275): - Implement g:html_no_doc and g:html_no_modeline
 "                             for diff mode. Add tests.
 "           (Vim 9.0.1122): NOTE: no version string update for this version!
 "                           - Bugfix for variable name in g:html_no_doc
@@ -21,7 +39,8 @@ let g:loaded_2html_plugin = 'vim9.0_v1'
 "                             and g:html_no_modeline (partially included in Vim
 "                             runtime prior to version string update).
 "                           - Updates for new Vim9 string append style (i.e. use
-"                             ".." instead of ".")
+"                             ".." instead of "."). Requires Vim version
+"                             8.1.1114 or higher.
 "
 "   8.1 updates: {{{
 "   8.1_v2  (Vim 8.1.2312): - Fix SourceForge issue #19: fix calculation of tab
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: under