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diff --git a/runtime/indent/pov.vim b/runtime/indent/pov.vim
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+" Vim indent file
+" Language: PoV-Ray Scene Description Language
+" Maintainer: David Necas (Yeti) <yeti@physics.muni.cz>
+" Last Change: 2017 Jun 13
+"              2022 April: b:undo_indent added by Doug Kearns
+" URI: http://trific.ath.cx/Ftp/vim/indent/pov.vim
+
+" Only load this indent file when no other was loaded.
+if exists("b:did_indent")
+  finish
+endif
+let b:did_indent = 1
+
+" Some preliminary settings.
+setlocal nolisp " Make sure lisp indenting doesn't supersede us.
+
+setlocal indentexpr=GetPoVRayIndent()
+setlocal indentkeys+==else,=end,0]
+
+let b:undo_indent = "setl inde< indk< lisp<"
+
+" Only define the function once.
+if exists("*GetPoVRayIndent")
+  finish
+endif
+
+" Counts matches of a regexp <rexp> in line number <line>.
+" Doesn't count matches inside strings and comments (as defined by current
+" syntax).
+function! s:MatchCount(line, rexp)
+  let str = getline(a:line)
+  let i = 0
+  let n = 0
+  while i >= 0
+    let i = matchend(str, a:rexp, i)
+    if i >= 0 && synIDattr(synID(a:line, i, 0), "name") !~? "string\|comment"
+      let n = n + 1
+    endif
+  endwhile
+  return n
+endfunction
+
+" The main function.  Returns indent amount.
+function GetPoVRayIndent()
+  " If we are inside a comment (may be nested in obscure ways), give up
+  if synIDattr(synID(v:lnum, indent(v:lnum)+1, 0), "name") =~? "string\|comment"
+    return -1
+  endif
+
+  " Search backwards for the first non-empty, non-comment line.
+  let plnum = prevnonblank(v:lnum - 1)
+  let plind = indent(plnum)
+  while plnum > 0 && synIDattr(synID(plnum, plind+1, 0), "name") =~? "comment"
+    let plnum = prevnonblank(plnum - 1)
+    let plind = indent(plnum)
+  endwhile
+
+  " Start indenting from zero
+  if plnum == 0
+    return 0
+  endif
+
+  " Analyse previous nonempty line.
+  let chg = 0
+  let chg = chg + s:MatchCount(plnum, '[[{(]')
+  let chg = chg + s:MatchCount(plnum, '#\s*\%(if\|ifdef\|ifndef\|switch\|while\|macro\|else\)\>')
+  let chg = chg - s:MatchCount(plnum, '#\s*end\>')
+  let chg = chg - s:MatchCount(plnum, '[]})]')
+  " Dirty hack for people writing #if and #else on the same line.
+  let chg = chg - s:MatchCount(plnum, '#\s*\%(if\|ifdef\|ifndef\|switch\)\>.*#\s*else\>')
+  " When chg > 0, then we opened groups and we should indent more, but when
+  " chg < 0, we closed groups and this already affected the previous line,
+  " so we should not dedent.  And when everything else fails, scream.
+  let chg = chg > 0 ? chg : 0
+
+  " Analyse current line
+  " FIXME: If we have to dedent, we should try to find the indentation of the
+  " opening line.
+  let cur = s:MatchCount(v:lnum, '^\s*\%(#\s*\%(end\|else\)\>\|[]})]\)')
+  if cur > 0
+    let final = plind + (chg - cur) * shiftwidth()
+  else
+    let final = plind + chg * shiftwidth()
+  endif
+
+  return final < 0 ? 0 : final
+endfunction