au! CursorHold *.[ch] nested call PreviewWord()
func PreviewWord()
  if &previewwindow			" don't do this in the preview window
    return
  endif
  let w = expand("<cword>")		" get the word under cursor
  if w =~ '\a'			" if the word contains a letter

    " Delete any existing highlight before showing another tag
    silent! wincmd P			" jump to preview window
    if &previewwindow			" if we really get there...
      match none			" delete existing highlight
      wincmd p			" back to old window
    endif

    " Try displaying a matching tag for the word under the cursor
    try
       exe "ptag " . w
    catch
      return
    endtry

    silent! wincmd P			" jump to preview window
    if &previewwindow		" if we really get there...
	 if has("folding")
	   silent! .foldopen		" don't want a closed fold
	 endif
	 call search("$", "b")		" to end of previous line
	 let w = substitute(w, '\\', '\\\\', "")
	 call search('\<\V' . w . '\>')	" position cursor on match
	 " Add a match highlight to the word at this position
      hi previewWord term=bold ctermbg=green guibg=green
	 exe 'match previewWord "\%' . line(".") . 'l\%' . col(".") . 'c\k*"'
      wincmd p			" back to old window
    endif
  endif
endfun