1 files changed, 76 insertions, 1 deletions
diff --git a/ftplugin/help.vim b/ftplugin/help.vim
index 5e9a4aa0..bb6d43e8 100644
--- a/ftplugin/help.vim
+++ b/ftplugin/help.vim
@@ -15,11 +15,86 @@ set cpo&vim
 
 let b:undo_ftplugin = "setl fo< tw< cole< cocu< keywordprg<"
 
-setlocal formatoptions+=tcroql textwidth=78 keywordprg=:help
+setlocal formatoptions+=tcroql textwidth=78
 if has("conceal")
   setlocal cole=2 cocu=nc
 endif
 
+" Prefer Vim help instead of manpages.
+setlocal keywordprg=:help
+
+if !exists('g:no_plugin_maps')
+  function! s:show_toc() abort
+    let bufname = bufname('%')
+    let info = getloclist(0, {'winid': 1})
+    if !empty(info) && getwinvar(info.winid, 'qf_toc') ==# bufname
+      lopen
+      return
+    endif
+
+    let toc = []
+    let lnum = 2
+    let last_line = line('$') - 1
+    let last_added = 0
+    let has_section = 0
+    let has_sub_section = 0
+
+    while lnum && lnum <= last_line
+      let level = 0
+      let add_text = ''
+      let text = getline(lnum)
+
+      if text =~# '^=\+$' && lnum + 1 < last_line
+        " A de-facto section heading.  Other headings are inferred.
+        let has_section = 1
+        let has_sub_section = 0
+        let lnum = nextnonblank(lnum + 1)
+        let text = getline(lnum)
+        let add_text = text
+        while add_text =~# '\*[^*]\+\*\s*$'
+          let add_text = matchstr(add_text, '.*\ze\*[^*]\+\*\s*$')
+        endwhile
+      elseif text =~# '^[A-Z0-9][-A-ZA-Z0-9 .][-A-Z0-9 .():]*\%([ \t]\+\*.\+\*\)\?$'
+        " Any line that's yelling is important.
+        let has_sub_section = 1
+        let level = has_section
+        let add_text = matchstr(text, '.\{-}\ze\s*\%([ \t]\+\*.\+\*\)\?$')
+      elseif text =~# '\~$'
+            \ && matchstr(text, '^\s*\zs.\{-}\ze\s*\~$') !~# '\t\|\s\{2,}'
+            \ && getline(lnum - 1) =~# '^\s*<\?$\|^\s*\*.*\*$'
+            \ && getline(lnum + 1) =~# '^\s*>\?$\|^\s*\*.*\*$'
+        " These lines could be headers or code examples.  We only want the
+        " ones that have subsequent lines at the same indent or more.
+        let l = nextnonblank(lnum + 1)
+        if getline(l) =~# '\*[^*]\+\*$'
+          " Ignore tag lines
+          let l = nextnonblank(l + 1)
+        endif
+
+        if indent(lnum) <= indent(l)
+          let level = has_section + has_sub_section
+          let add_text = matchstr(text, '\S.*')
+        endif
+      endif
+
+      let add_text = substitute(add_text, '\s\+$', '', 'g')
+      if !empty(add_text) && last_added != lnum
+        let last_added = lnum
+        call add(toc, {'bufnr': bufnr('%'), 'lnum': lnum,
+              \ 'text': repeat('  ', level) . add_text})
+      endif
+      let lnum = nextnonblank(lnum + 1)
+    endwhile
+
+    call setloclist(0, toc, ' ')
+    call setloclist(0, [], 'a', {'title': 'Help TOC'})
+    lopen
+    let w:qf_toc = bufname
+  endfunction
+
+  nnoremap <silent><buffer> gO :call <sid>show_toc()<cr>
+endif
+
 let &cpo = s:cpo_save
 unlet s:cpo_save