text: /* vim:set ts=8 sts=4 sw=4:
   * vim600:fdm=marker fdl=1 fdc=3:
   *
   * VIM - Vi IMproved	by Bram Moolenaar
   *
   * Do ":help uganda"  in Vim to read copying and usage conditions.
   * Do ":help credits" in Vim to see a list of people who contributed.
   * See README.txt for an overview of the Vim source code.
   */
  
  /*
   * fold.c: code for folding
   */
  
  #include "vim.h"
  
  #if defined(FEAT_FOLDING) || defined(PROTO)
  
  /* local declarations. {{{1 */
  /* typedef fold_T {{{2 */
  /*
   * The toplevel folds for each window are stored in the w_folds growarray.
   * Each toplevel fold can contain an array of second level folds in the
   * fd_nested growarray.
   * The info stored in both growarrays is the same: An array of fold_T.
   */
  typedef struct
  {
      linenr_T	fd_top;		/* first line of fold; for nested fold
  				 * relative to parent */
      linenr_T	fd_len;		/* number of lines in the fold */
      garray_T	fd_nested;	/* array of nested folds */
      char	fd_flags;	/* see below */
      char	fd_small;	/* TRUE, FALSE or MAYBE: fold smaller than
  				   'foldminlines'; MAYBE applies to nested
  				   folds too */
  } fold_T;
  
  #define FD_OPEN		0	/* fold is open (nested ones can be closed) */
  #define FD_CLOSED	1	/* fold is closed */
  #define FD_LEVEL	2	/* depends on 'foldlevel' (nested folds too) */
  
  #define MAX_LEVEL	20	/* maximum fold depth */
  
  /* static functions {{{2 */
  static void newFoldLevelWin(win_T *wp);
  static int checkCloseRec(garray_T *gap, linenr_T lnum, int level);
  static int foldFind(garray_T *gap, linenr_T lnum, fold_T **fpp);
  static int foldLevelWin(win_T *wp, linenr_T lnum);
  static void checkupdate(win_T *wp);
  static void setFoldRepeat(linenr_T lnum, long count, int do_open);
  static linenr_T setManualFold(linenr_T lnum, int opening, int recurse, int *donep);
  static linenr_T setManualFoldWin(win_T *wp, linenr_T lnum, int opening, int recurse, int *donep);
  static void foldOpenNested(fold_T *fpr);
  static void deleteFoldEntry(garray_T *gap, int idx, int recursive);
  static void foldMarkAdjustRecurse(garray_T *gap, linenr_T line1, linenr_T line2, long amount, long amount_after);
  static int getDeepestNestingRecurse(garray_T *gap);
  static int check_closed(win_T *win, fold_T *fp, int *use_levelp, int level, int *maybe_smallp, linenr_T lnum_off);
  static void checkSmall(win_T *wp, fold_T *fp, linenr_T lnum_off);
  static void setSmallMaybe(garray_T *gap);
  static void foldCreateMarkers(linenr_T start, linenr_T end);
  static void foldAddMarker(linenr_T lnum, char_u *marker, int markerlen);
  static void deleteFoldMarkers(fold_T *fp, int recursive, linenr_T lnum_off);
  static void foldDelMarker(linenr_T lnum, char_u *marker, int markerlen);
  static void foldUpdateIEMS(win_T *wp, linenr_T top, linenr_T bot);
  static void parseMarker(win_T *wp);
  
  static char *e_nofold = N_("E490: No fold found");
  
  /*
   * While updating the folds lines between invalid_top and invalid_bot have an
   * undefined fold level.  Only used for the window currently being updated.
   */
  static linenr_T invalid_top = (linenr_T)0;
  static linenr_T invalid_bot = (linenr_T)0;
  
  /*
   * When using 'foldexpr' we sometimes get the level of the next line, which
   * calls foldlevel() to get the level of the current line, which hasn't been
   * stored yet.  To get around this chicken-egg problem the level of the
   * previous line is stored here when available.  prev_lnum is zero when the
   * level is not available.
   */
  static linenr_T prev_lnum = 0;
  static int prev_lnum_lvl = -1;
  
  /* Flags used for "done" argument of setManualFold. */
  #define DONE_NOTHING	0
  #define DONE_ACTION	1	/* did close or open a fold */
  #define DONE_FOLD	2	/* did find a fold */
  
  static int foldstartmarkerlen;
  static char_u *foldendmarker;
  static int foldendmarkerlen;
  
  /* Exported folding functions. {{{1 */
  /* copyFoldingState() {{{2 */
  #if defined(FEAT_WINDOWS) || defined(PROTO)
  /*
   * Copy that folding state from window "wp_from" to window "wp_to".
   */
      void
  copyFoldingState(win_T *wp_from, win_T *wp_to)
  {
      wp_to->w_fold_manual = wp_from->w_fold_manual;
      wp_to->w_foldinvalid = wp_from->w_foldinvalid;
      cloneFoldGrowArray(&wp_from->w_folds, &wp_to->w_folds);
  }
  #endif
  
  /* hasAnyFolding() {{{2 */
  /*
   * Return TRUE if there may be folded lines in the current window.
   */
      int
  hasAnyFolding(win_T *win)
  {
      /* very simple now, but can become more complex later */
      return (win->w_p_fen
  	    && (!foldmethodIsManual(win) || win->w_folds.ga_len > 0));
  }
  
  /* hasFolding() {{{2 */
  /*
   * Return TRUE if line "lnum" in the current window is part of a closed
   * fold.
   * When returning TRUE, *firstp and *lastp are set to the first and last
   * lnum of the sequence of folded lines (skipped when NULL).
   */
      int
  hasFolding(linenr_T lnum, linenr_T *firstp, linenr_T *lastp)
  {
      return hasFoldingWin(curwin, lnum, firstp, lastp, TRUE, NULL);
  }
  
  /* hasFoldingWin() {{{2 */
      int
  hasFoldingWin(
      win_T	*win,
      linenr_T	lnum,
      linenr_T	*firstp,
      linenr_T	*lastp,
      int		cache,		/* when TRUE: use cached values of window */
      foldinfo_T	*infop)		/* where to store fold info */
  {
      int		had_folded = FALSE;
      linenr_T	first = 0;
      linenr_T	last = 0;
      linenr_T	lnum_rel = lnum;
      int		x;
      fold_T	*fp;
      int		level = 0;
      int		use_level = FALSE;
      int		maybe_small = FALSE;
      garray_T	*gap;
      int		low_level = 0;
  
      checkupdate(win);
      /*
       * Return quickly when there is no folding at all in this window.
       */
      if (!hasAnyFolding(win))
      {
  	if (infop != NULL)
  	    infop->fi_level = 0;
  	return FALSE;
      }
  
      if (cache)
      {
  	/*
  	 * First look in cached info for displayed lines.  This is probably
  	 * the fastest, but it can only be used if the entry is still valid.
  	 */
  	x = find_wl_entry(win, lnum);
  	if (x >= 0)
  	{
  	    first = win->w_lines[x].wl_lnum;
  	    last = win->w_lines[x].wl_lastlnum;
  	    had_folded = win->w_lines[x].wl_folded;
  	}
      }
  
      if (first == 0)
      {
  	/*
  	 * Recursively search for a fold that contains "lnum".
  	 */
  	gap = &win->w_folds;
  	for (;;)
  	{
  	    if (!foldFind(gap, lnum_rel, &fp))
  		break;
  
  	    /* Remember lowest level of fold that starts in "lnum". */
  	    if (lnum_rel == fp->fd_top && low_level == 0)
  		low_level = level + 1;
  
  	    first += fp->fd_top;
  	    last += fp->fd_top;
  
  	    /* is this fold closed? */
  	    had_folded = check_closed(win, fp, &use_level, level,
  					       &maybe_small, lnum - lnum_rel);
  	    if (had_folded)
  	    {
  		/* Fold closed: Set last and quit loop. */
  		last += fp->fd_len - 1;
  		break;
  	    }
  
  	    /* Fold found, but it's open: Check nested folds.  Line number is
  	     * relative to containing fold. */
  	    gap = &fp->fd_nested;
  	    lnum_rel -= fp->fd_top;
  	    ++level;
  	}
      }
  
      if (!had_folded)
      {
  	if (infop != NULL)
  	{
  	    infop->fi_level = level;
  	    infop->fi_lnum = lnum - lnum_rel;
  	    infop->fi_low_level = low_level == 0 ? level : low_level;
  	}
  	return FALSE;
      }
  
      if (last > win->w_buffer->b_ml.ml_line_count)
  	last = win->w_buffer->b_ml.ml_line_count;
      if (lastp != NULL)
  	*lastp = last;
      if (firstp != NULL)
  	*firstp = first;
      if (infop != NULL)
      {
  	infop->fi_level = level + 1;
  	infop->fi_lnum = first;
  	infop->fi_low_level = low_level == 0 ? level + 1 : low_level;
      }
      return TRUE;
  }
  
  /* foldLevel() {{{2 */
  /*
   * Return fold level at line number "lnum" in the current window.
   */
      int
  foldLevel(linenr_T lnum)
  {
      /* While updating the folds lines between invalid_top and invalid_bot have
       * an undefined fold level.  Otherwise update the folds first. */
      if (invalid_top == (linenr_T)0)
  	checkupdate(curwin);
      else if (lnum == prev_lnum && prev_lnum_lvl >= 0)
  	return prev_lnum_lvl;
      else if (lnum >= invalid_top && lnum <= invalid_bot)
  	return -1;
  
      /* Return quickly when there is no folding at all in this window. */
      if (!hasAnyFolding(curwin))
  	return 0;
  
      return foldLevelWin(curwin, lnum);
  }
  
  /* lineFolded()	{{{2 */
  /*
   * Low level function to check if a line is folded.  Doesn't use any caching.
   * Return TRUE if line is folded.
   * Return FALSE if line is not folded.
   * Return MAYBE if the line is folded when next to a folded line.
   */
      int
  lineFolded(win_T *win, linenr_T lnum)
  {
      return foldedCount(win, lnum, NULL) != 0;
  }
  
  /* foldedCount() {{{2 */
  /*
   * Count the number of lines that are folded at line number "lnum".
   * Normally "lnum" is the first line of a possible fold, and the returned
   * number is the number of lines in the fold.
   * Doesn't use caching from the displayed window.
   * Returns number of folded lines from "lnum", or 0 if line is not folded.
   * When "infop" is not NULL, fills *infop with the fold level info.
   */
      long
  foldedCount(win_T *win, linenr_T lnum, foldinfo_T *infop)
  {
      linenr_T	last;
  
      if (hasFoldingWin(win, lnum, NULL, &last, FALSE, infop))
  	return (long)(last - lnum + 1);
      return 0;
  }
  
  /* foldmethodIsManual() {{{2 */
  /*
   * Return TRUE if 'foldmethod' is "manual"
   */
      int
  foldmethodIsManual(win_T *wp)
  {
      return (wp->w_p_fdm[3] == 'u');
  }
  
  /* foldmethodIsIndent() {{{2 */
  /*
   * Return TRUE if 'foldmethod' is "indent"
   */
      int
  foldmethodIsIndent(win_T *wp)
  {
      return (wp->w_p_fdm[0] == 'i');
  }
  
  /* foldmethodIsExpr() {{{2 */
  /*
   * Return TRUE if 'foldmethod' is "expr"
   */
      int
  foldmethodIsExpr(win_T *wp)
  {
      return (wp->w_p_fdm[1] == 'x');
  }
  
  /* foldmethodIsMarker() {{{2 */
  /*
   * Return TRUE if 'foldmethod' is "marker"
   */
      int
  foldmethodIsMarker(win_T *wp)
  {
      return (wp->w_p_fdm[2] == 'r');
  }
  
  /* foldmethodIsSyntax() {{{2 */
  /*
   * Return TRUE if 'foldmethod' is "syntax"
   */
      int
  foldmethodIsSyntax(win_T *wp)
  {
      return (wp->w_p_fdm[0] == 's');
  }
  
  /* foldmethodIsDiff() {{{2 */
  /*
   * Return TRUE if 'foldmethod' is "diff"
   */
      int
  foldmethodIsDiff(win_T *wp)
  {
      return (wp->w_p_fdm[0] == 'd');
  }
  
  /* closeFold() {{{2 */
  /*
   * Close fold for current window at line "lnum".
   * Repeat "count" times.
   */
      void
  closeFold(linenr_T lnum, long count)
  {
      setFoldRepeat(lnum, count, FALSE);
  }
  
  /* closeFoldRecurse() {{{2 */
  /*
   * Close fold for current window at line "lnum" recursively.
   */
      void
  closeFoldRecurse(linenr_T lnum)
  {
      (void)setManualFold(lnum, FALSE, TRUE, NULL);
  }
  
  /* opFoldRange() {{{2 */
  /*
   * Open or Close folds for current window in lines "first" to "last".
   * Used for "zo", "zO", "zc" and "zC" in Visual mode.
   */
      void
  opFoldRange(
      linenr_T	first,
      linenr_T	last,
      int		opening,	/* TRUE to open, FALSE to close */
      int		recurse,	/* TRUE to do it recursively */
      int		had_visual)	/* TRUE when Visual selection used */
  {
      int		done = DONE_NOTHING;	/* avoid error messages */
      linenr_T	lnum;
      linenr_T	lnum_next;
  
      for (lnum = first; lnum <= last; lnum = lnum_next + 1)
      {
  	lnum_next = lnum;
  	/* Opening one level only: next fold to open is after the one going to
  	 * be opened. */
  	if (opening && !recurse)
  	    (void)hasFolding(lnum, NULL, &lnum_next);
  	(void)setManualFold(lnum, opening, recurse, &done);
  	/* Closing one level only: next line to close a fold is after just
  	 * closed fold. */
  	if (!opening && !recurse)
  	    (void)hasFolding(lnum, NULL, &lnum_next);
      }
      if (done == DONE_NOTHING)
  	EMSG(_(e_nofold));
      /* Force a redraw to remove the Visual highlighting. */
      if (had_visual)
  	redraw_curbuf_later(INVERTED);
  }
  
  /* openFold() {{{2 */
  /*
   * Open fold for current window at line "lnum".
   * Repeat "count" times.
   */
      void
  openFold(linenr_T lnum, long count)
  {
      setFoldRepeat(lnum, count, TRUE);
  }
  
  /* openFoldRecurse() {{{2 */
  /*
   * Open fold for current window at line "lnum" recursively.
   */
      void
  openFoldRecurse(linenr_T lnum)
  {
      (void)setManualFold(lnum, TRUE, TRUE, NULL);
  }
  
  /* foldOpenCursor() {{{2 */
  /*
   * Open folds until the cursor line is not in a closed fold.
   */
      void
  foldOpenCursor(void)
  {
      int		done;
  
      checkupdate(curwin);
      if (hasAnyFolding(curwin))
  	for (;;)
  	{
  	    done = DONE_NOTHING;
  	    (void)setManualFold(curwin->w_cursor.lnum, TRUE, FALSE, &done);
  	    if (!(done & DONE_ACTION))
  		break;
  	}
  }
  
  /* newFoldLevel() {{{2 */
  /*
   * Set new foldlevel for current window.
   */
      void
  newFoldLevel(void)
  {
      newFoldLevelWin(curwin);
  
  #ifdef FEAT_DIFF
      if (foldmethodIsDiff(curwin) && curwin->w_p_scb)
      {
  	win_T	    *wp;
  
  	/*
  	 * Set the same foldlevel in other windows in diff mode.
  	 */
  	FOR_ALL_WINDOWS(wp)
  	{
  	    if (wp != curwin && foldmethodIsDiff(wp) && wp->w_p_scb)
  	    {
  		wp->w_p_fdl = curwin->w_p_fdl;
  		newFoldLevelWin(wp);
  	    }
  	}
      }
  #endif
  }
  
      static void
  newFoldLevelWin(win_T *wp)
  {
      fold_T	*fp;
      int		i;
  
      checkupdate(wp);
      if (wp->w_fold_manual)
      {
  	/* Set all flags for the first level of folds to FD_LEVEL.  Following
  	 * manual open/close will then change the flags to FD_OPEN or
  	 * FD_CLOSED for those folds that don't use 'foldlevel'. */
  	fp = (fold_T *)wp->w_folds.ga_data;
  	for (i = 0; i < wp->w_folds.ga_len; ++i)
  	    fp[i].fd_flags = FD_LEVEL;
  	wp->w_fold_manual = FALSE;
      }
      changed_window_setting_win(wp);
  }
  
  /* foldCheckClose() {{{2 */
  /*
   * Apply 'foldlevel' to all folds that don't contain the cursor.
   */
      void
  foldCheckClose(void)
  {
      if (*p_fcl != NUL)	/* can only be "all" right now */
      {
  	checkupdate(curwin);
  	if (checkCloseRec(&curwin->w_folds, curwin->w_cursor.lnum,
  							(int)curwin->w_p_fdl))
  	    changed_window_setting();
      }
  }
  
  /* checkCloseRec() {{{2 */
      static int
  checkCloseRec(garray_T *gap, linenr_T lnum, int level)
  {
      fold_T	*fp;
      int		retval = FALSE;
      int		i;
  
      fp = (fold_T *)gap->ga_data;
      for (i = 0; i < gap->ga_len; ++i)
      {
  	/* Only manually opened folds may need to be closed. */
  	if (fp[i].fd_flags == FD_OPEN)
  	{
  	    if (level <= 0 && (lnum < fp[i].fd_top
  				      || lnum >= fp[i].fd_top + fp[i].fd_len))
  	    {
  		fp[i].fd_flags = FD_LEVEL;
  		retval = TRUE;
  	    }
  	    else
  		retval |= checkCloseRec(&fp[i].fd_nested, lnum - fp[i].fd_top,
  								   level - 1);
  	}
      }
      return retval;
  }
  
  /* foldCreateAllowed() {{{2 */
  /*
   * Return TRUE if it's allowed to manually create or delete a fold.
   * Give an error message and return FALSE if not.
   */
      int
  foldManualAllowed(int create)
  {
      if (foldmethodIsManual(curwin) || foldmethodIsMarker(curwin))
  	return TRUE;
      if (create)
  	EMSG(_("E350: Cannot create fold with current 'foldmethod'"));
      else
  	EMSG(_("E351: Cannot delete fold with current 'foldmethod'"));
      return FALSE;
  }
  
  /* foldCreate() {{{2 */
  /*
   * Create a fold from line "start" to line "end" (inclusive) in the current
   * window.
   */
      void
  foldCreate(linenr_T start, linenr_T end)
  {
      fold_T	*fp;
      garray_T	*gap;
      garray_T	fold_ga;
      int		i, j;
      int		cont;
      int		use_level = FALSE;
      int		closed = FALSE;
      int		level = 0;
      linenr_T	start_rel = start;
      linenr_T	end_rel = end;
  
      if (start > end)
      {
  	/* reverse the range */
  	end = start_rel;
  	start = end_rel;
  	start_rel = start;
  	end_rel = end;
      }
  
      /* When 'foldmethod' is "marker" add markers, which creates the folds. */
      if (foldmethodIsMarker(curwin))
      {
  	foldCreateMarkers(start, end);
  	return;
      }
  
      checkupdate(curwin);
  
      /* Find the place to insert the new fold. */
      gap = &curwin->w_folds;
      for (;;)
      {
  	if (!foldFind(gap, start_rel, &fp))
  	    break;
  	if (fp->fd_top + fp->fd_len > end_rel)
  	{
  	    /* New fold is completely inside this fold: Go one level deeper. */
  	    gap = &fp->fd_nested;
  	    start_rel -= fp->fd_top;
  	    end_rel -= fp->fd_top;
  	    if (use_level || fp->fd_flags == FD_LEVEL)
  	    {
  		use_level = TRUE;
  		if (level >= curwin->w_p_fdl)
  		    closed = TRUE;
  	    }
  	    else if (fp->fd_flags == FD_CLOSED)
  		closed = TRUE;
  	    ++level;
  	}
  	else
  	{
  	    /* This fold and new fold overlap: Insert here and move some folds
  	     * inside the new fold. */
  	    break;
  	}
      }
  
      i = (int)(fp - (fold_T *)gap->ga_data);
      if (ga_grow(gap, 1) == OK)
      {
  	fp = (fold_T *)gap->ga_data + i;
  	ga_init2(&fold_ga, (int)sizeof(fold_T), 10);
  
  	/* Count number of folds that will be contained in the new fold. */
  	for (cont = 0; i + cont < gap->ga_len; ++cont)
  	    if (fp[cont].fd_top > end_rel)
  		break;
  	if (cont > 0 && ga_grow(&fold_ga, cont) == OK)
  	{
  	    /* If the first fold starts before the new fold, let the new fold
  	     * start there.  Otherwise the existing fold would change. */
  	    if (start_rel > fp->fd_top)
  		start_rel = fp->fd_top;
  
  	    /* When last contained fold isn't completely contained, adjust end
  	     * of new fold. */
  	    if (end_rel < fp[cont - 1].fd_top + fp[cont - 1].fd_len - 1)
  		end_rel = fp[cont - 1].fd_top + fp[cont - 1].fd_len - 1;
  	    /* Move contained folds to inside new fold. */
  	    mch_memmove(fold_ga.ga_data, fp, sizeof(fold_T) * cont);
  	    fold_ga.ga_len += cont;
  	    i += cont;
  
  	    /* Adjust line numbers in contained folds to be relative to the
  	     * new fold. */
  	    for (j = 0; j < cont; ++j)
  		((fold_T *)fold_ga.ga_data)[j].fd_top -= start_rel;
  	}
  	/* Move remaining entries to after the new fold. */
  	if (i < gap->ga_len)
  	    mch_memmove(fp + 1, (fold_T *)gap->ga_data + i,
  				     sizeof(fold_T) * (gap->ga_len - i));
  	gap->ga_len = gap->ga_len + 1 - cont;
  
  	/* insert new fold */
  	fp->fd_nested = fold_ga;
  	fp->fd_top = start_rel;
  	fp->fd_len = end_rel - start_rel + 1;
  
  	/* We want the new fold to be closed.  If it would remain open because
  	 * of using 'foldlevel', need to adjust fd_flags of containing folds.
  	 */
  	if (use_level && !closed && level < curwin->w_p_fdl)
  	    closeFold(start, 1L);
  	if (!use_level)
  	    curwin->w_fold_manual = TRUE;
  	fp->fd_flags = FD_CLOSED;
  	fp->fd_small = MAYBE;
  
  	/* redraw */
  	changed_window_setting();
      }
  }
  
  /* deleteFold() {{{2 */
  /*
   * Delete a fold at line "start" in the current window.
   * When "end" is not 0, delete all folds from "start" to "end".
   * When "recursive" is TRUE delete recursively.
   */
      void
  deleteFold(
      linenr_T	start,
      linenr_T	end,
      int		recursive,
      int		had_visual)	/* TRUE when Visual selection used */
  {
      garray_T	*gap;
      fold_T	*fp;
      garray_T	*found_ga;
      fold_T	*found_fp = NULL;
      linenr_T	found_off = 0;
      int		use_level;
      int		maybe_small = FALSE;
      int		level = 0;
      linenr_T	lnum = start;
      linenr_T	lnum_off;
      int		did_one = FALSE;
      linenr_T	first_lnum = MAXLNUM;
      linenr_T	last_lnum = 0;
  
      checkupdate(curwin);
  
      while (lnum <= end)
      {
  	/* Find the deepest fold for "start". */
  	gap = &curwin->w_folds;
  	found_ga = NULL;
  	lnum_off = 0;
  	use_level = FALSE;
  	for (;;)
  	{
  	    if (!foldFind(gap, lnum - lnum_off, &fp))
  		break;
  	    /* lnum is inside this fold, remember info */
  	    found_ga = gap;
  	    found_fp = fp;
  	    found_off = lnum_off;
  
  	    /* if "lnum" is folded, don't check nesting */
  	    if (check_closed(curwin, fp, &use_level, level,
  						      &maybe_small, lnum_off))
  		break;
  
  	    /* check nested folds */
  	    gap = &fp->fd_nested;
  	    lnum_off += fp->fd_top;
  	    ++level;
  	}
  	if (found_ga == NULL)
  	{
  	    ++lnum;
  	}
  	else
  	{
  	    lnum = found_fp->fd_top + found_fp->fd_len + found_off;
  
  	    if (foldmethodIsManual(curwin))
  		deleteFoldEntry(found_ga,
  		    (int)(found_fp - (fold_T *)found_ga->ga_data), recursive);
  	    else
  	    {
  		if (first_lnum > found_fp->fd_top + found_off)
  		    first_lnum = found_fp->fd_top + found_off;
  		if (last_lnum < lnum)
  		    last_lnum = lnum;
  		if (!did_one)
  		    parseMarker(curwin);
  		deleteFoldMarkers(found_fp, recursive, found_off);
  	    }
  	    did_one = TRUE;
  
  	    /* redraw window */
  	    changed_window_setting();
  	}
      }
      if (!did_one)
      {
  	EMSG(_(e_nofold));
  	/* Force a redraw to remove the Visual highlighting. */
  	if (had_visual)
  	    redraw_curbuf_later(INVERTED);
      }
      else
  	/* Deleting markers may make cursor column invalid. */
  	check_cursor_col();
  
      if (last_lnum > 0)
  	changed_lines(first_lnum, (colnr_T)0, last_lnum, 0L);
  }
  
  /* clearFolding() {{{2 */
  /*
   * Remove all folding for window "win".
   */
      void
  clearFolding(win_T *win)
  {
      deleteFoldRecurse(&win->w_folds);
      win->w_foldinvalid = FALSE;
  }
  
  /* foldUpdate() {{{2 */
  /*
   * Update folds for changes in the buffer of a window.
   * Note that inserted/deleted lines must have already been taken care of by
   * calling foldMarkAdjust().
   * The changes in lines from top to bot (inclusive).
   */
      void
  foldUpdate(win_T *wp, linenr_T top, linenr_T bot)
  {
      fold_T	*fp;
  
      if (disable_fold_update > 0)
  	return;
  
      /* Mark all folds from top to bot as maybe-small. */
      (void)foldFind(&wp->w_folds, top, &fp);
      while (fp < (fold_T *)wp->w_folds.ga_data + wp->w_folds.ga_len
  	    && fp->fd_top < bot)
      {
  	fp->fd_small = MAYBE;
  	++fp;
      }
  
      if (foldmethodIsIndent(wp)
  	    || foldmethodIsExpr(wp)
  	    || foldmethodIsMarker(wp)
  #ifdef FEAT_DIFF
  	    || foldmethodIsDiff(wp)
  #endif
  	    || foldmethodIsSyntax(wp))
      {
  	int save_got_int = got_int;
  
  	/* reset got_int here, otherwise it won't work */
  	got_int = FALSE;
  	foldUpdateIEMS(wp, top, bot);
  	got_int |= save_got_int;
      }
  }
  
  /* foldUpdateAll() {{{2 */
  /*
   * Update all lines in a window for folding.
   * Used when a fold setting changes or after reloading the buffer.
   * The actual updating is postponed until fold info is used, to avoid doing
   * every time a setting is changed or a syntax item is added.
   */
      void
  foldUpdateAll(win_T *win)
  {
      win->w_foldinvalid = TRUE;
      redraw_win_later(win, NOT_VALID);
  }
  
  /* foldMoveTo() {{{2 */
  /*
   * If "updown" is FALSE: Move to the start or end of the fold.
   * If "updown" is TRUE: move to fold at the same level.
   * If not moved return FAIL.
   */
      int
  foldMoveTo(
      int		updown,
      int		dir,	    /* FORWARD or BACKWARD */
      long	count)
  {
      long	n;
      int		retval = FAIL;
      linenr_T	lnum_off;
      linenr_T	lnum_found;
      linenr_T	lnum;
      int		use_level;
      int		maybe_small;
      garray_T	*gap;
      fold_T	*fp;
      int		level;
      int		last;
  
      checkupdate(curwin);
  
      /* Repeat "count" times. */
      for (n = 0; n < count; ++n)
      {
  	/* Find nested folds.  Stop when a fold is closed.  The deepest fold
  	 * that moves the cursor is used. */
  	lnum_off = 0;
  	gap = &curwin->w_folds;
  	use_level = FALSE;
  	maybe_small = FALSE;
  	lnum_found = curwin->w_cursor.lnum;
  	level = 0;
  	last = FALSE;
  	for (;;)
  	{
  	    if (!foldFind(gap, curwin->w_cursor.lnum - lnum_off, &fp))
  	    {
  		if (!updown)
  		    break;
  
  		/* When moving up, consider a fold above the cursor; when
  		 * moving down consider a fold below the cursor. */
  		if (dir == FORWARD)
  		{
  		    if (fp - (fold_T *)gap->ga_data >= gap->ga_len)
  			break;
  		    --fp;
  		}
  		else
  		{
  		    if (fp == (fold_T *)gap->ga_data)
  			break;
  		}
  		/* don't look for contained folds, they will always move
  		 * the cursor too far. */
  		last = TRUE;
  	    }
  
  	    if (!last)
  	    {
  		/* Check if this fold is closed. */
  		if (check_closed(curwin, fp, &use_level, level,
  						      &maybe_small, lnum_off))
  		    last = TRUE;
  
  		/* "[z" and "]z" stop at closed fold */
  		if (last && !updown)
  		    break;
  	    }
  
  	    if (updown)
  	    {
  		if (dir == FORWARD)
  		{
  		    /* to start of next fold if there is one */
  		    if (fp + 1 - (fold_T *)gap->ga_data < gap->ga_len)
  		    {
  			lnum = fp[1].fd_top + lnum_off;
  			if (lnum > curwin->w_cursor.lnum)
  			    lnum_found = lnum;
  		    }
  		}
  		else
  		{
  		    /* to end of previous fold if there is one */
  		    if (fp > (fold_T *)gap->ga_data)
  		    {
  			lnum = fp[-1].fd_top + lnum_off + fp[-1].fd_len - 1;
  			if (lnum < curwin->w_cursor.lnum)
  			    lnum_found = lnum;
  		    }
  		}
  	    }
  	    else
  	    {
  		/* Open fold found, set cursor to its start/end and then check
  		 * nested folds. */
  		if (dir == FORWARD)
  		{
  		    lnum = fp->fd_top + lnum_off + fp->fd_len - 1;
  		    if (lnum > curwin->w_cursor.lnum)
  			lnum_found = lnum;
  		}
  		else
  		{
  		    lnum = fp->fd_top + lnum_off;
  		    if (lnum < curwin->w_cursor.lnum)
  			lnum_found = lnum;
  		}
  	    }
  
  	    if (last)
  		break;
  
  	    /* Check nested folds (if any). */
  	    gap = &fp->fd_nested;
  	    lnum_off += fp->fd_top;
  	    ++level;
  	}
  	if (lnum_found != curwin->w_cursor.lnum)
  	{
  	    if (retval == FAIL)
  		setpcmark();
  	    curwin->w_cursor.lnum = lnum_found;
  	    curwin->w_cursor.col = 0;
  	    retval = OK;
  	}
  	else
  	    break;
      }
  
      return retval;
  }
  
  /* foldInitWin() {{{2 */
  /*
   * Init the fold info in a new window.
   */
      void
  foldInitWin(win_T *new_win)
  {
      ga_init2(&new_win->w_folds, (int)sizeof(fold_T), 10);
  }
  
  /* find_wl_entry() {{{2 */
  /*
   * Find an entry in the win->w_lines[] array for buffer line "lnum".
   * Only valid entries are considered (for entries where wl_valid is FALSE the
   * line number can be wrong).
   * Returns index of entry or -1 if not found.
   */
      int
  find_wl_entry(win_T *win, linenr_T lnum)
  {
      int		i;
  
      for (i = 0; i < win->w_lines_valid; ++i)
  	if (win->w_lines[i].wl_valid)
  	{
  	    if (lnum < win->w_lines[i].wl_lnum)
  		return -1;
  	    if (lnum <= win->w_lines[i].wl_lastlnum)
  		return i;
  	}
      return -1;
  }
  
  /* foldAdjustVisual() {{{2 */
  /*
   * Adjust the Visual area to include any fold at the start or end completely.
   */
      void
  foldAdjustVisual(void)
  {
      pos_T	*start, *end;
      char_u	*ptr;
  
      if (!VIsual_active || !hasAnyFolding(curwin))
  	return;
  
      if (ltoreq(VIsual, curwin->w_cursor))
      {
  	start = &VIsual;
  	end = &curwin->w_cursor;
      }
      else
      {
  	start = &curwin->w_cursor;
  	end = &VIsual;
      }
      if (hasFolding(start->lnum, &start->lnum, NULL))
  	start->col = 0;
      if (hasFolding(end->lnum, NULL, &end->lnum))
      {
  	ptr = ml_get(end->lnum);
  	end->col = (colnr_T)STRLEN(ptr);
  	if (end->col > 0 && *p_sel == 'o')
  	    --end->col;
  #ifdef FEAT_MBYTE
  	/* prevent cursor from moving on the trail byte */
  	if (has_mbyte)
  	    mb_adjust_cursor();
  #endif
      }
  }
  
  /* cursor_foldstart() {{{2 */
  /*
   * Move the cursor to the first line of a closed fold.
   */
      void
  foldAdjustCursor(void)
  {
      (void)hasFolding(curwin->w_cursor.lnum, &curwin->w_cursor.lnum, NULL);
  }
  
  /* Internal functions for "fold_T" {{{1 */
  /* cloneFoldGrowArray() {{{2 */
  /*
   * Will "clone" (i.e deep copy) a garray_T of folds.
   *
   * Return FAIL if the operation cannot be completed, otherwise OK.
   */
      void
  cloneFoldGrowArray(garray_T *from, garray_T *to)
  {
      int		i;
      fold_T	*from_p;
      fold_T	*to_p;
  
      ga_init2(to, from->ga_itemsize, from->ga_growsize);
      if (from->ga_len == 0 || ga_grow(to, from->ga_len) == FAIL)
  	return;
  
      from_p = (fold_T *)from->ga_data;
      to_p = (fold_T *)to->ga_data;
  
      for (i = 0; i < from->ga_len; i++)
      {
  	to_p->fd_top = from_p->fd_top;
  	to_p->fd_len = from_p->fd_len;
  	to_p->fd_flags = from_p->fd_flags;
  	to_p->fd_small = from_p->fd_small;
  	cloneFoldGrowArray(&from_p->fd_nested, &to_p->fd_nested);
  	++to->ga_len;
  	++from_p;
  	++to_p;
      }
  }
  
  /* foldFind() {{{2 */
  /*
   * Search for line "lnum" in folds of growarray "gap".
   * Set *fpp to the fold struct for the fold that contains "lnum" or
   * the first fold below it (careful: it can be beyond the end of the array!).
   * Returns FALSE when there is no fold that contains "lnum".
   */
      static int
  foldFind(garray_T *gap, linenr_T lnum, fold_T **fpp)
  {
      linenr_T	low, high;
      fold_T	*fp;
      int		i;
  
      /*
       * Perform a binary search.
       * "low" is lowest index of possible match.
       * "high" is highest index of possible match.
       */
      fp = (fold_T *)gap->ga_data;
      low = 0;
      high = gap->ga_len - 1;
      while (low <= high)
      {
  	i = (low + high) / 2;
  	if (fp[i].fd_top > lnum)
  	    /* fold below lnum, adjust high */
  	    high = i - 1;
  	else if (fp[i].fd_top + fp[i].fd_len <= lnum)
  	    /* fold above lnum, adjust low */
  	    low = i + 1;
  	else
  	{
  	    /* lnum is inside this fold */
  	    *fpp = fp + i;
  	    return TRUE;
  	}
      }
      *fpp = fp + low;
      return FALSE;
  }
  
  /* foldLevelWin() {{{2 */
  /*
   * Return fold level at line number "lnum" in window "wp".
   */
      static int
  foldLevelWin(win_T *wp, linenr_T lnum)
  {
      fold_T	*fp;
      linenr_T	lnum_rel = lnum;
      int		level =  0;
      garray_T	*gap;
  
      /* Recursively search for a fold that contains "lnum". */
      gap = &wp->w_folds;
      for (;;)
      {
  	if (!foldFind(gap, lnum_rel, &fp))
  	    break;
  	/* Check nested folds.  Line number is relative to containing fold. */
  	gap = &fp->fd_nested;
  	lnum_rel -= fp->fd_top;
  	++level;
      }
  
      return level;
  }
  
  /* checkupdate() {{{2 */
  /*
   * Check if the folds in window "wp" are invalid and update them if needed.
   */
      static void
  checkupdate(win_T *wp)
  {
      if (wp->w_foldinvalid)
      {
  	foldUpdate(wp, (linenr_T)1, (linenr_T)MAXLNUM); /* will update all */
  	wp->w_foldinvalid = FALSE;
      }
  }
  
  /* setFoldRepeat() {{{2 */
  /*
   * Open or close fold for current window at line "lnum".
   * Repeat "count" times.
   */
      static void
  setFoldRepeat(linenr_T lnum, long count, int do_open)
  {
      int		done;
      long	n;
  
      for (n = 0; n < count; ++n)
      {
  	done = DONE_NOTHING;
  	(void)setManualFold(lnum, do_open, FALSE, &done);
  	if (!(done & DONE_ACTION))
  	{
  	    /* Only give an error message when no fold could be opened. */
  	    if (n == 0 && !(done & DONE_FOLD))
  		EMSG(_(e_nofold));
  	    break;
  	}
      }
  }
  
  /* setManualFold() {{{2 */
  /*
   * Open or close the fold in the current window which contains "lnum".
   * Also does this for other windows in diff mode when needed.
   */
      static linenr_T
  setManualFold(
      linenr_T	lnum,
      int		opening,    /* TRUE when opening, FALSE when closing */
      int		recurse,    /* TRUE when closing/opening recursive */
      int		*donep)
  {
  #ifdef FEAT_DIFF
      if (foldmethodIsDiff(curwin) && curwin->w_p_scb)
      {
  	win_T	    *wp;
  	linenr_T    dlnum;
  
  	/*
  	 * Do the same operation in other windows in diff mode.  Calculate the
  	 * line number from the diffs.
  	 */
  	FOR_ALL_WINDOWS(wp)
  	{
  	    if (wp != curwin && foldmethodIsDiff(wp) && wp->w_p_scb)
  	    {
  		dlnum = diff_lnum_win(curwin->w_cursor.lnum, wp);
  		if (dlnum != 0)
  		    (void)setManualFoldWin(wp, dlnum, opening, recurse, NULL);
  	    }
  	}
      }
  #endif
  
      return setManualFoldWin(curwin, lnum, opening, recurse, donep);
  }
  
  /* setManualFoldWin() {{{2 */
  /*
   * Open or close the fold in window "wp" which contains "lnum".
   * "donep", when not NULL, points to flag that is set to DONE_FOLD when some
   * fold was found and to DONE_ACTION when some fold was opened or closed.
   * When "donep" is NULL give an error message when no fold was found for
   * "lnum", but only if "wp" is "curwin".
   * Return the line number of the next line that could be closed.
   * It's only valid when "opening" is TRUE!
   */
      static linenr_T
  setManualFoldWin(
      win_T	*wp,
      linenr_T	lnum,
      int		opening,    /* TRUE when opening, FALSE when closing */
      int		recurse,    /* TRUE when closing/opening recursive */
      int		*donep)
  {
      fold_T	*fp;
      fold_T	*fp2;
      fold_T	*found = NULL;
      int		j;
      int		level = 0;
      int		use_level = FALSE;
      int		found_fold = FALSE;
      garray_T	*gap;
      linenr_T	next = MAXLNUM;
      linenr_T	off = 0;
      int		done = 0;
  
      checkupdate(wp);
  
      /*
       * Find the fold, open or close it.
       */
      gap = &wp->w_folds;
      for (;;)
      {
  	if (!foldFind(gap, lnum, &fp))
  	{
  	    /* If there is a following fold, continue there next time. */
  	    if (fp < (fold_T *)gap->ga_data + gap->ga_len)
  		next = fp->fd_top + off;
  	    break;
  	}
  
  	/* lnum is inside this fold */
  	found_fold = TRUE;
  
  	/* If there is a following fold, continue there next time. */
  	if (fp + 1 < (fold_T *)gap->ga_data + gap->ga_len)
  	    next = fp[1].fd_top + off;
  
  	/* Change from level-dependent folding to manual. */
  	if (use_level || fp->fd_flags == FD_LEVEL)
  	{
  	    use_level = TRUE;
  	    if (level >= wp->w_p_fdl)
  		fp->fd_flags = FD_CLOSED;
  	    else
  		fp->fd_flags = FD_OPEN;
  	    fp2 = (fold_T *)fp->fd_nested.ga_data;
  	    for (j = 0; j < fp->fd_nested.ga_len; ++j)
  		fp2[j].fd_flags = FD_LEVEL;
  	}
  
  	/* Simple case: Close recursively means closing the fold. */
  	if (!opening && recurse)
  	{
  	    if (fp->fd_flags != FD_CLOSED)
  	    {
  		done |= DONE_ACTION;
  		fp->fd_flags = FD_CLOSED;
  	    }
  	}
  	else if (fp->fd_flags == FD_CLOSED)
  	{
  	    /* When opening, open topmost closed fold. */
  	    if (opening)
  	    {
  		fp->fd_flags = FD_OPEN;
  		done |= DONE_ACTION;
  		if (recurse)
  		    foldOpenNested(fp);
  	    }
  	    break;
  	}
  
  	/* fold is open, check nested folds */
  	found = fp;
  	gap = &fp->fd_nested;
  	lnum -= fp->fd_top;
  	off += fp->fd_top;
  	++level;
      }
      if (found_fold)
      {
  	/* When closing and not recurse, close deepest open fold. */
  	if (!opening && found != NULL)
  	{
  	    found->fd_flags = FD_CLOSED;
  	    done |= DONE_ACTION;
  	}
  	wp->w_fold_manual = TRUE;
  	if (done & DONE_ACTION)
  	    changed_window_setting_win(wp);
  	done |= DONE_FOLD;
      }
      else if (donep == NULL && wp == curwin)
  	EMSG(_(e_nofold));
  
      if (donep != NULL)
  	*donep |= done;
  
      return next;
  }
  
  /* foldOpenNested() {{{2 */
  /*
   * Open all nested folds in fold "fpr" recursively.
   */
      static void
  foldOpenNested(fold_T *fpr)
  {
      int		i;
      fold_T	*fp;
  
      fp = (fold_T *)fpr->fd_nested.ga_data;
      for (i = 0; i < fpr->fd_nested.ga_len; ++i)
      {
  	foldOpenNested(&fp[i]);
  	fp[i].fd_flags = FD_OPEN;
      }
  }
  
  /* deleteFoldEntry() {{{2 */
  /*
   * Delete fold "idx" from growarray "gap".
   * When "recursive" is TRUE also delete all the folds contained in it.
   * When "recursive" is FALSE contained folds are moved one level up.
   */
      static void
  deleteFoldEntry(garray_T *gap, int idx, int recursive)
  {
      fold_T	*fp;
      int		i;
      long	moved;
      fold_T	*nfp;
  
      fp = (fold_T *)gap->ga_data + idx;
      if (recursive || fp->fd_nested.ga_len == 0)
      {
  	/* recursively delete the contained folds */
  	deleteFoldRecurse(&fp->fd_nested);
  	--gap->ga_len;
  	if (idx < gap->ga_len)
  	    mch_memmove(fp, fp + 1, sizeof(fold_T) * (gap->ga_len - idx));
      }
      else
      {
  	/* Move nested folds one level up, to overwrite the fold that is
  	 * deleted. */
  	moved = fp->fd_nested.ga_len;
  	if (ga_grow(gap, (int)(moved - 1)) == OK)
  	{
  	    /* Get "fp" again, the array may have been reallocated. */
  	    fp = (fold_T *)gap->ga_data + idx;
  
  	    /* adjust fd_top and fd_flags for the moved folds */
  	    nfp = (fold_T *)fp->fd_nested.ga_data;
  	    for (i = 0; i < moved; ++i)
  	    {
  		nfp[i].fd_top += fp->fd_top;
  		if (fp->fd_flags == FD_LEVEL)
  		    nfp[i].fd_flags = FD_LEVEL;
  		if (fp->fd_small == MAYBE)
  		    nfp[i].fd_small = MAYBE;
  	    }
  
  	    /* move the existing folds down to make room */
  	    if (idx + 1 < gap->ga_len)
  		mch_memmove(fp + moved, fp + 1,
  				  sizeof(fold_T) * (gap->ga_len - (idx + 1)));
  	    /* move the contained folds one level up */
  	    mch_memmove(fp, nfp, (size_t)(sizeof(fold_T) * moved));
  	    vim_free(nfp);
  	    gap->ga_len += moved - 1;
  	}
      }
  }
  
  /* deleteFoldRecurse() {{{2 */
  /*
   * Delete nested folds in a fold.
   */
      void
  deleteFoldRecurse(garray_T *gap)
  {
      int		i;
  
      for (i = 0; i < gap->ga_len; ++i)
  	deleteFoldRecurse(&(((fold_T *)(gap->ga_data))[i].fd_nested));
      ga_clear(gap);
  }
  
  /* foldMarkAdjust() {{{2 */
  /*
   * Update line numbers of folds for inserted/deleted lines.
   */
      void
  foldMarkAdjust(
      win_T	*wp,
      linenr_T	line1,
      linenr_T	line2,
      long	amount,
      long	amount_after)
  {
      /* If deleting marks from line1 to line2, but not deleting all those
       * lines, set line2 so that only deleted lines have their folds removed. */
      if (amount == MAXLNUM && line2 >= line1 && line2 - line1 >= -amount_after)
  	line2 = line1 - amount_after - 1;
      /* If appending a line in Insert mode, it should be included in the fold
       * just above the line. */
      if ((State & INSERT) && amount == (linenr_T)1 && line2 == MAXLNUM)
  	--line1;
      foldMarkAdjustRecurse(&wp->w_folds, line1, line2, amount, amount_after);
  }
  
  /* foldMarkAdjustRecurse() {{{2 */
      static void
  foldMarkAdjustRecurse(
      garray_T	*gap,
      linenr_T	line1,
      linenr_T	line2,
      long	amount,
      long	amount_after)
  {
      fold_T	*fp;
      int		i;
      linenr_T	last;
      linenr_T	top;
  
      /* In Insert mode an inserted line at the top of a fold is considered part
       * of the fold, otherwise it isn't. */
      if ((State & INSERT) && amount == (linenr_T)1 && line2 == MAXLNUM)
  	top = line1 + 1;
      else
  	top = line1;
  
      /* Find the fold containing or just below "line1". */
      (void)foldFind(gap, line1, &fp);
  
      /*
       * Adjust all folds below "line1" that are affected.
       */
      for (i = (int)(fp - (fold_T *)gap->ga_data); i < gap->ga_len; ++i, ++fp)
      {
  	/*
  	 * Check for these situations:
  	 *	  1  2	3
  	 *	  1  2	3
  	 * line1     2	3  4  5
  	 *	     2	3  4  5
  	 *	     2	3  4  5
  	 * line2     2	3  4  5
  	 *		3     5  6
  	 *		3     5  6
  	 */
  
  	last = fp->fd_top + fp->fd_len - 1; /* last line of fold */
  
  	/* 1. fold completely above line1: nothing to do */
  	if (last < line1)
  	    continue;
  
  	/* 6. fold below line2: only adjust for amount_after */
  	if (fp->fd_top > line2)
  	{
  	    if (amount_after == 0)
  		break;
  	    fp->fd_top += amount_after;
  	}
  	else
  	{
  	    if (fp->fd_top >= top && last <= line2)
  	    {
  		/* 4. fold completely contained in range */
  		if (amount == MAXLNUM)
  		{
  		    /* Deleting lines: delete the fold completely */
  		    deleteFoldEntry(gap, i, TRUE);
  		    --i;    /* adjust index for deletion */
  		    --fp;
  		}
  		else
  		    fp->fd_top += amount;
  	    }
  	    else
  	    {
  		if (fp->fd_top < top)
  		{
  		    /* 2 or 3: need to correct nested folds too */
  		    foldMarkAdjustRecurse(&fp->fd_nested, line1 - fp->fd_top,
  				  line2 - fp->fd_top, amount, amount_after);
  		    if (last <= line2)
  		    {
  			/* 2. fold contains line1, line2 is below fold */
  			if (amount == MAXLNUM)
  			    fp->fd_len = line1 - fp->fd_top;
  			else
  			    fp->fd_len += amount;
  		    }
  		    else
  		    {
  			/* 3. fold contains line1 and line2 */
  			fp->fd_len += amount_after;
  		    }
  		}
  		else
  		{
  		    /* 5. fold is below line1 and contains line2; need to
  		     * correct nested folds too */
  		    foldMarkAdjustRecurse(&fp->fd_nested, line1 - fp->fd_top,
  				  line2 - fp->fd_top, amount,
  				  amount_after + (fp->fd_top - top));
  		    if (amount == MAXLNUM)
  		    {
  			fp->fd_len -= line2 - fp->fd_top + 1;
  			fp->fd_top = line1;
  		    }
  		    else
  		    {
  			fp->fd_len += amount_after - amount;
  			fp->fd_top += amount;
  		    }
  		}
  	    }
  	}
      }
  }
  
  /* getDeepestNesting() {{{2 */
  /*
   * Get the lowest 'foldlevel' value that makes the deepest nested fold in the
   * current window open.
   */
      int
  getDeepestNesting(void)
  {
      checkupdate(curwin);
      return getDeepestNestingRecurse(&curwin->w_folds);
  }
  
      static int
  getDeepestNestingRecurse(garray_T *gap)
  {
      int		i;
      int		level;
      int		maxlevel = 0;
      fold_T	*fp;
  
      fp = (fold_T *)gap->ga_data;
      for (i = 0; i < gap->ga_len; ++i)
      {
  	level = getDeepestNestingRecurse(&fp[i].fd_nested) + 1;
  	if (level > maxlevel)
  	    maxlevel = level;
      }
  
      return maxlevel;
  }
  
  /* check_closed() {{{2 */
  /*
   * Check if a fold is closed and update the info needed to check nested folds.
   */
      static int
  check_closed(
      win_T	*win,
      fold_T	*fp,
      int		*use_levelp,	    /* TRUE: outer fold had FD_LEVEL */
      int		level,		    /* folding depth */
      int		*maybe_smallp,	    /* TRUE: outer this had fd_small == MAYBE */
      linenr_T	lnum_off)	    /* line number offset for fp->fd_top */
  {
      int		closed = FALSE;
  
      /* Check if this fold is closed.  If the flag is FD_LEVEL this
       * fold and all folds it contains depend on 'foldlevel'. */
      if (*use_levelp || fp->fd_flags == FD_LEVEL)
      {
  	*use_levelp = TRUE;
  	if (level >= win->w_p_fdl)
  	    closed = TRUE;
      }
      else if (fp->fd_flags == FD_CLOSED)
  	closed = TRUE;
  
      /* Small fold isn't closed anyway. */
      if (fp->fd_small == MAYBE)
  	*maybe_smallp = TRUE;
      if (closed)
      {
  	if (*maybe_smallp)
  	    fp->fd_small = MAYBE;
  	checkSmall(win, fp, lnum_off);
  	if (fp->fd_small == TRUE)
  	    closed = FALSE;
      }
      return closed;
  }
  
  /* checkSmall() {{{2 */
  /*
   * Update fd_small field of fold "fp".
   */
      static void
  checkSmall(
      win_T	*wp,
      fold_T	*fp,
      linenr_T	lnum_off)	/* offset for fp->fd_top */
  {
      int		count;
      int		n;
  
      if (fp->fd_small == MAYBE)
      {
  	/* Mark any nested folds to maybe-small */
  	setSmallMaybe(&fp->fd_nested);
  
  	if (fp->fd_len > curwin->w_p_fml)
  	    fp->fd_small = FALSE;
  	else
  	{
  	    count = 0;
  	    for (n = 0; n < fp->fd_len; ++n)
  	    {
  		count += plines_win_nofold(wp, fp->fd_top + lnum_off + n);
  		if (count > curwin->w_p_fml)
  		{
  		    fp->fd_small = FALSE;
  		    return;
  		}
  	    }
  	    fp->fd_small = TRUE;
  	}
      }
  }
  
  /* setSmallMaybe() {{{2 */
  /*
   * Set small flags in "gap" to MAYBE.
   */
      static void
  setSmallMaybe(garray_T *gap)
  {
      int		i;
      fold_T	*fp;
  
      fp = (fold_T *)gap->ga_data;
      for (i = 0; i < gap->ga_len; ++i)
  	fp[i].fd_small = MAYBE;
  }
  
  /* foldCreateMarkers() {{{2 */
  /*
   * Create a fold from line "start" to line "end" (inclusive) in the current
   * window by adding markers.
   */
      static void
  foldCreateMarkers(linenr_T start, linenr_T end)
  {
      if (!curbuf->b_p_ma)
      {
  	EMSG(_(e_modifiable));
  	return;
      }
      parseMarker(curwin);
  
      foldAddMarker(start, curwin->w_p_fmr, foldstartmarkerlen);
      foldAddMarker(end, foldendmarker, foldendmarkerlen);
  
      /* Update both changes here, to avoid all folds after the start are
       * changed when the start marker is inserted and the end isn't. */
      changed_lines(start, (colnr_T)0, end, 0L);
  }
  
  /* foldAddMarker() {{{2 */
  /*
   * Add "marker[markerlen]" in 'commentstring' to line "lnum".
   */
      static void
  foldAddMarker(linenr_T lnum, char_u *marker, int markerlen)
  {
      char_u	*cms = curbuf->b_p_cms;
      char_u	*line;
      int		line_len;
      char_u	*newline;
      char_u	*p = (char_u *)strstr((char *)curbuf->b_p_cms, "%s");
  
      /* Allocate a new line: old-line + 'cms'-start + marker + 'cms'-end */
      line = ml_get(lnum);
      line_len = (int)STRLEN(line);
  
      if (u_save(lnum - 1, lnum + 1) == OK)
      {
  	newline = alloc((unsigned)(line_len + markerlen + STRLEN(cms) + 1));
  	if (newline == NULL)
  	    return;
  	STRCPY(newline, line);
  	if (p == NULL)
  	    vim_strncpy(newline + line_len, marker, markerlen);
  	else
  	{
  	    STRCPY(newline + line_len, cms);
  	    STRNCPY(newline + line_len + (p - cms), marker, markerlen);
  	    STRCPY(newline + line_len + (p - cms) + markerlen, p + 2);
  	}
  
  	ml_replace(lnum, newline, FALSE);
      }
  }
  
  /* deleteFoldMarkers() {{{2 */
  /*
   * Delete the markers for a fold, causing it to be deleted.
   */
      static void
  deleteFoldMarkers(
      fold_T	*fp,
      int		recursive,
      linenr_T	lnum_off)	/* offset for fp->fd_top */
  {
      int		i;
  
      if (recursive)
  	for (i = 0; i < fp->fd_nested.ga_len; ++i)
  	    deleteFoldMarkers((fold_T *)fp->fd_nested.ga_data + i, TRUE,
  						       lnum_off + fp->fd_top);
      foldDelMarker(fp->fd_top + lnum_off, curwin->w_p_fmr, foldstartmarkerlen);
      foldDelMarker(fp->fd_top + lnum_off + fp->fd_len - 1,
  					     foldendmarker, foldendmarkerlen);
  }
  
  /* foldDelMarker() {{{2 */
  /*
   * Delete marker "marker[markerlen]" at the end of line "lnum".
   * Delete 'commentstring' if it matches.
   * If the marker is not found, there is no error message.  Could a missing
   * close-marker.
   */
      static void
  foldDelMarker(linenr_T lnum, char_u *marker, int markerlen)
  {
      char_u	*line;
      char_u	*newline;
      char_u	*p;
      int		len;
      char_u	*cms = curbuf->b_p_cms;
      char_u	*cms2;
  
      line = ml_get(lnum);
      for (p = line; *p != NUL; ++p)
  	if (STRNCMP(p, marker, markerlen) == 0)
  	{
  	    /* Found the marker, include a digit if it's there. */
  	    len = markerlen;
  	    if (VIM_ISDIGIT(p[len]))
  		++len;
  	    if (*cms != NUL)
  	    {
  		/* Also delete 'commentstring' if it matches. */
  		cms2 = (char_u *)strstr((char *)cms, "%s");
  		if (p - line >= cms2 - cms
  			&& STRNCMP(p - (cms2 - cms), cms, cms2 - cms) == 0
  			&& STRNCMP(p + len, cms2 + 2, STRLEN(cms2 + 2)) == 0)
  		{
  		    p -= cms2 - cms;
  		    len += (int)STRLEN(cms) - 2;
  		}
  	    }
  	    if (u_save(lnum - 1, lnum + 1) == OK)
  	    {
  		/* Make new line: text-before-marker + text-after-marker */
  		newline = alloc((unsigned)(STRLEN(line) - len + 1));
  		if (newline != NULL)
  		{
  		    STRNCPY(newline, line, p - line);
  		    STRCPY(newline + (p - line), p + len);
  		    ml_replace(lnum, newline, FALSE);
  		}
  	    }
  	    break;
  	}
  }
  
  /* get_foldtext() {{{2 */
  /*
   * Return the text for a closed fold at line "lnum", with last line "lnume".
   * When 'foldtext' isn't set puts the result in "buf[51]".  Otherwise the
   * result is in allocated memory.
   */
      char_u *
  get_foldtext(
      win_T	*wp,
      linenr_T	lnum,
      linenr_T	lnume,
      foldinfo_T	*foldinfo,
      char_u	*buf)
  {
      char_u	*text = NULL;
  #ifdef FEAT_EVAL
       /* an error occurred when evaluating 'fdt' setting */
      static int	    got_fdt_error = FALSE;
      int		    save_did_emsg = did_emsg;
      static win_T    *last_wp = NULL;
      static linenr_T last_lnum = 0;
  
      if (last_wp != wp || last_wp == NULL
  					|| last_lnum > lnum || last_lnum == 0)
  	/* window changed, try evaluating foldtext setting once again */
  	got_fdt_error = FALSE;
  
      if (!got_fdt_error)
  	/* a previous error should not abort evaluating 'foldexpr' */
  	did_emsg = FALSE;
  
      if (*wp->w_p_fdt != NUL)
      {
  	char_u	dashes[MAX_LEVEL + 2];
  	win_T	*save_curwin;
  	int	level;
  	char_u	*p;
  
  	/* Set "v:foldstart" and "v:foldend". */
  	set_vim_var_nr(VV_FOLDSTART, lnum);
  	set_vim_var_nr(VV_FOLDEND, lnume);
  
  	/* Set "v:folddashes" to a string of "level" dashes. */
  	/* Set "v:foldlevel" to "level". */
  	level = foldinfo->fi_level;
  	if (level > (int)sizeof(dashes) - 1)
  	    level = (int)sizeof(dashes) - 1;
  	vim_memset(dashes, '-', (size_t)level);
  	dashes[level] = NUL;
  	set_vim_var_string(VV_FOLDDASHES, dashes, -1);
  	set_vim_var_nr(VV_FOLDLEVEL, (long)level);
  
  	/* skip evaluating foldtext on errors */
  	if (!got_fdt_error)
  	{
  	    save_curwin = curwin;
  	    curwin = wp;
  	    curbuf = wp->w_buffer;
  
  	    ++emsg_silent; /* handle exceptions, but don't display errors */
  	    text = eval_to_string_safe(wp->w_p_fdt, NULL,
  			 was_set_insecurely((char_u *)"foldtext", OPT_LOCAL));
  	    --emsg_silent;
  
  	    if (text == NULL || did_emsg)
  		got_fdt_error = TRUE;
  
  	    curwin = save_curwin;
  	    curbuf = curwin->w_buffer;
  	}
  	last_lnum = lnum;
  	last_wp   = wp;
  	set_vim_var_string(VV_FOLDDASHES, NULL, -1);
  
  	if (!did_emsg && save_did_emsg)
  	    did_emsg = save_did_emsg;
  
  	if (text != NULL)
  	{
  	    /* Replace unprintable characters, if there are any.  But
  	     * replace a TAB with a space. */
  	    for (p = text; *p != NUL; ++p)
  	    {
  # ifdef FEAT_MBYTE
  		int	len;
  
  		if (has_mbyte && (len = (*mb_ptr2len)(p)) > 1)
  		{
  		    if (!vim_isprintc((*mb_ptr2char)(p)))
  			break;
  		    p += len - 1;
  		}
  		else
  # endif
  		    if (*p == TAB)
  			*p = ' ';
  		    else if (ptr2cells(p) > 1)
  			break;
  	    }
  	    if (*p != NUL)
  	    {
  		p = transstr(text);
  		vim_free(text);
  		text = p;
  	    }
  	}
      }
      if (text == NULL)
  #endif
      {
  	sprintf((char *)buf, _("+--%3ld lines folded "),
  						    (long)(lnume - lnum + 1));
  	text = buf;
      }
      return text;
  }
  
  /* foldtext_cleanup() {{{2 */
  /*
   * Remove 'foldmarker' and 'commentstring' from "str" (in-place).
   */
      void
  foldtext_cleanup(char_u *str)
  {
      char_u	*cms_start;	/* first part or the whole comment */
      int		cms_slen = 0;	/* length of cms_start */
      char_u	*cms_end;	/* last part of the comment or NULL */
      int		cms_elen = 0;	/* length of cms_end */
      char_u	*s;
      char_u	*p;
      int		len;
      int		did1 = FALSE;
      int		did2 = FALSE;
  
      /* Ignore leading and trailing white space in 'commentstring'. */
      cms_start = skipwhite(curbuf->b_p_cms);
      cms_slen = (int)STRLEN(cms_start);
      while (cms_slen > 0 && vim_iswhite(cms_start[cms_slen - 1]))
  	--cms_slen;
  
      /* locate "%s" in 'commentstring', use the part before and after it. */
      cms_end = (char_u *)strstr((char *)cms_start, "%s");
      if (cms_end != NULL)
      {
  	cms_elen = cms_slen - (int)(cms_end - cms_start);
  	cms_slen = (int)(cms_end - cms_start);
  
  	/* exclude white space before "%s" */
  	while (cms_slen > 0 && vim_iswhite(cms_start[cms_slen - 1]))
  	    --cms_slen;
  
  	/* skip "%s" and white space after it */
  	s = skipwhite(cms_end + 2);
  	cms_elen -= (int)(s - cms_end);
  	cms_end = s;
      }
      parseMarker(curwin);
  
      for (s = str; *s != NUL; )
      {
  	len = 0;
  	if (STRNCMP(s, curwin->w_p_fmr, foldstartmarkerlen) == 0)
  	    len = foldstartmarkerlen;
  	else if (STRNCMP(s, foldendmarker, foldendmarkerlen) == 0)
  	    len = foldendmarkerlen;
  	if (len > 0)
  	{
  	    if (VIM_ISDIGIT(s[len]))
  		++len;
  
  	    /* May remove 'commentstring' start.  Useful when it's a double
  	     * quote and we already removed a double quote. */
  	    for (p = s; p > str && vim_iswhite(p[-1]); --p)
  		;
  	    if (p >= str + cms_slen
  			   && STRNCMP(p - cms_slen, cms_start, cms_slen) == 0)
  	    {
  		len += (int)(s - p) + cms_slen;
  		s = p - cms_slen;
  	    }
  	}
  	else if (cms_end != NULL)
  	{
  	    if (!did1 && cms_slen > 0 && STRNCMP(s, cms_start, cms_slen) == 0)
  	    {
  		len = cms_slen;
  		did1 = TRUE;
  	    }
  	    else if (!did2 && cms_elen > 0
  					&& STRNCMP(s, cms_end, cms_elen) == 0)
  	    {
  		len = cms_elen;
  		did2 = TRUE;
  	    }
  	}
  	if (len != 0)
  	{
  	    while (vim_iswhite(s[len]))
  		++len;
  	    STRMOVE(s, s + len);
  	}
  	else
  	{
  	    mb_ptr_adv(s);
  	}
      }
  }
  
  /* Folding by indent, expr, marker and syntax. {{{1 */
  /* Define "fline_T", passed to get fold level for a line. {{{2 */
  typedef struct
  {
      win_T	*wp;		/* window */
      linenr_T	lnum;		/* current line number */
      linenr_T	off;		/* offset between lnum and real line number */
      linenr_T	lnum_save;	/* line nr used by foldUpdateIEMSRecurse() */
      int		lvl;		/* current level (-1 for undefined) */
      int		lvl_next;	/* level used for next line */
      int		start;		/* number of folds that are forced to start at
  				   this line. */
      int		end;		/* level of fold that is forced to end below
  				   this line */
      int		had_end;	/* level of fold that is forced to end above
  				   this line (copy of "end" of prev. line) */
  } fline_T;
  
  /* Flag is set when redrawing is needed. */
  static int fold_changed;
  
  /* Function declarations. {{{2 */
  static linenr_T foldUpdateIEMSRecurse(garray_T *gap, int level, linenr_T startlnum, fline_T *flp, void (*getlevel)(fline_T *), linenr_T bot, int topflags);
  static int foldInsert(garray_T *gap, int i);
  static void foldSplit(garray_T *gap, int i, linenr_T top, linenr_T bot);
  static void foldRemove(garray_T *gap, linenr_T top, linenr_T bot);
  static void foldMerge(fold_T *fp1, garray_T *gap, fold_T *fp2);
  static void foldlevelIndent(fline_T *flp);
  #ifdef FEAT_DIFF
  static void foldlevelDiff(fline_T *flp);
  #endif
  static void foldlevelExpr(fline_T *flp);
  static void foldlevelMarker(fline_T *flp);
  static void foldlevelSyntax(fline_T *flp);
  
  /* foldUpdateIEMS() {{{2 */
  /*
   * Update the folding for window "wp", at least from lines "top" to "bot".
   * Return TRUE if any folds did change.
   */
      static void
  foldUpdateIEMS(win_T *wp, linenr_T top, linenr_T bot)
  {
      linenr_T	start;
      linenr_T	end;
      fline_T	fline;
      void	(*getlevel)(fline_T *);
      int		level;
      fold_T	*fp;
  
      /* Avoid problems when being called recursively. */
      if (invalid_top != (linenr_T)0)
  	return;
  
      if (wp->w_foldinvalid)
      {
  	/* Need to update all folds. */
  	top = 1;
  	bot = wp->w_buffer->b_ml.ml_line_count;
  	wp->w_foldinvalid = FALSE;
  
  	/* Mark all folds a maybe-small. */
  	setSmallMaybe(&wp->w_folds);
      }
  
  #ifdef FEAT_DIFF
      /* add the context for "diff" folding */
      if (foldmethodIsDiff(wp))
      {
  	if (top > diff_context)
  	    top -= diff_context;
  	else
  	    top = 1;
  	bot += diff_context;
      }
  #endif
  
      /* When deleting lines at the end of the buffer "top" can be past the end
       * of the buffer. */
      if (top > wp->w_buffer->b_ml.ml_line_count)
  	top = wp->w_buffer->b_ml.ml_line_count;
  
      fold_changed = FALSE;
      fline.wp = wp;
      fline.off = 0;
      fline.lvl = 0;
      fline.lvl_next = -1;
      fline.start = 0;
      fline.end = MAX_LEVEL + 1;
      fline.had_end = MAX_LEVEL + 1;
  
      invalid_top = top;
      invalid_bot = bot;
  
      if (foldmethodIsMarker(wp))
      {
  	getlevel = foldlevelMarker;
  
  	/* Init marker variables to speed up foldlevelMarker(). */
  	parseMarker(wp);
  
  	/* Need to get the level of the line above top, it is used if there is
  	 * no marker at the top. */
  	if (top > 1)
  	{
  	    /* Get the fold level at top - 1. */
  	    level = foldLevelWin(wp, top - 1);
  
  	    /* The fold may end just above the top, check for that. */
  	    fline.lnum = top - 1;
  	    fline.lvl = level;
  	    getlevel(&fline);
  
  	    /* If a fold started here, we already had the level, if it stops
  	     * here, we need to use lvl_next.  Could also start and end a fold
  	     * in the same line. */
  	    if (fline.lvl > level)
  		fline.lvl = level - (fline.lvl - fline.lvl_next);
  	    else
  		fline.lvl = fline.lvl_next;
  	}
  	fline.lnum = top;
  	getlevel(&fline);
      }
      else
      {
  	fline.lnum = top;
  	if (foldmethodIsExpr(wp))
  	{
  	    getlevel = foldlevelExpr;
  	    /* start one line back, because a "<1" may indicate the end of a
  	     * fold in the topline */
  	    if (top > 1)
  		--fline.lnum;
  	}
  	else if (foldmethodIsSyntax(wp))
  	    getlevel = foldlevelSyntax;
  #ifdef FEAT_DIFF
  	else if (foldmethodIsDiff(wp))
  	    getlevel = foldlevelDiff;
  #endif
  	else
  	    getlevel = foldlevelIndent;
  
  	/* Backup to a line for which the fold level is defined.  Since it's
  	 * always defined for line one, we will stop there. */
  	fline.lvl = -1;
  	for ( ; !got_int; --fline.lnum)
  	{
  	    /* Reset lvl_next each time, because it will be set to a value for
  	     * the next line, but we search backwards here. */
  	    fline.lvl_next = -1;
  	    getlevel(&fline);
  	    if (fline.lvl >= 0)
  		break;
  	}
      }
  
      /*
       * If folding is defined by the syntax, it is possible that a change in
       * one line will cause all sub-folds of the current fold to change (e.g.,
       * closing a C-style comment can cause folds in the subsequent lines to
       * appear). To take that into account we should adjust the value of "bot"
       * to point to the end of the current fold:
       */
      if (foldlevelSyntax == getlevel)
      {
  	garray_T *gap = &wp->w_folds;
  	fold_T	 *fpn = NULL;
  	int	  current_fdl = 0;
  	linenr_T  fold_start_lnum = 0;
  	linenr_T  lnum_rel = fline.lnum;
  
  	while (current_fdl < fline.lvl)
  	{
  	    if (!foldFind(gap, lnum_rel, &fpn))
  		break;
  	    ++current_fdl;
  
  	    fold_start_lnum += fpn->fd_top;
  	    gap = &fpn->fd_nested;
  	    lnum_rel -= fpn->fd_top;
  	}
  	if (fpn != NULL && current_fdl == fline.lvl)
  	{
  	    linenr_T fold_end_lnum = fold_start_lnum + fpn->fd_len;
  
  	    if (fold_end_lnum > bot)
  		bot = fold_end_lnum;
  	}
      }
  
      start = fline.lnum;
      end = bot;
      /* Do at least one line. */
      if (start > end && end < wp->w_buffer->b_ml.ml_line_count)
  	end = start;
      while (!got_int)
      {
  	/* Always stop at the end of the file ("end" can be past the end of
  	 * the file). */
  	if (fline.lnum > wp->w_buffer->b_ml.ml_line_count)
  	    break;
  	if (fline.lnum > end)
  	{
  	    /* For "marker", "expr"  and "syntax"  methods: If a change caused
  	     * a fold to be removed, we need to continue at least until where
  	     * it ended. */
  	    if (getlevel != foldlevelMarker
  		    && getlevel != foldlevelSyntax
  		    && getlevel != foldlevelExpr)
  		break;
  	    if ((start <= end
  			&& foldFind(&wp->w_folds, end, &fp)
  			&& fp->fd_top + fp->fd_len - 1 > end)
  		    || (fline.lvl == 0
  			&& foldFind(&wp->w_folds, fline.lnum, &fp)
  			&& fp->fd_top < fline.lnum))
  		end = fp->fd_top + fp->fd_len - 1;
  	    else if (getlevel == foldlevelSyntax
  		    && foldLevelWin(wp, fline.lnum) != fline.lvl)
  		/* For "syntax" method: Compare the foldlevel that the syntax
  		 * tells us to the foldlevel from the existing folds.  If they
  		 * don't match continue updating folds. */
  		end = fline.lnum;
  	    else
  		break;
  	}
  
  	/* A level 1 fold starts at a line with foldlevel > 0. */
  	if (fline.lvl > 0)
  	{
  	    invalid_top = fline.lnum;
  	    invalid_bot = end;
  	    end = foldUpdateIEMSRecurse(&wp->w_folds,
  				   1, start, &fline, getlevel, end, FD_LEVEL);
  	    start = fline.lnum;
  	}
  	else
  	{
  	    if (fline.lnum == wp->w_buffer->b_ml.ml_line_count)
  		break;
  	    ++fline.lnum;
  	    fline.lvl = fline.lvl_next;
  	    getlevel(&fline);
  	}
      }
  
      /* There can't be any folds from start until end now. */
      foldRemove(&wp->w_folds, start, end);
  
      /* If some fold changed, need to redraw and position cursor. */
      if (fold_changed && wp->w_p_fen)
  	changed_window_setting_win(wp);
  
      /* If we updated folds past "bot", need to redraw more lines.  Don't do
       * this in other situations, the changed lines will be redrawn anyway and
       * this method can cause the whole window to be updated. */
      if (end != bot)
      {
  	if (wp->w_redraw_top == 0 || wp->w_redraw_top > top)
  	    wp->w_redraw_top = top;
  	if (wp->w_redraw_bot < end)
  	    wp->w_redraw_bot = end;
      }
  
      invalid_top = (linenr_T)0;
  }
  
  /* foldUpdateIEMSRecurse() {{{2 */
  /*
   * Update a fold that starts at "flp->lnum".  At this line there is always a
   * valid foldlevel, and its level >= "level".
   * "flp" is valid for "flp->lnum" when called and it's valid when returning.
   * "flp->lnum" is set to the lnum just below the fold, if it ends before
   * "bot", it's "bot" plus one if the fold continues and it's bigger when using
   * the marker method and a text change made following folds to change.
   * When returning, "flp->lnum_save" is the line number that was used to get
   * the level when the level at "flp->lnum" is invalid.
   * Remove any folds from "startlnum" up to here at this level.
   * Recursively update nested folds.
   * Below line "bot" there are no changes in the text.
   * "flp->lnum", "flp->lnum_save" and "bot" are relative to the start of the
   * outer fold.
   * "flp->off" is the offset to the real line number in the buffer.
   *
   * All this would be a lot simpler if all folds in the range would be deleted
   * and then created again.  But we would lose all information about the
   * folds, even when making changes that don't affect the folding (e.g. "vj~").
   *
   * Returns bot, which may have been increased for lines that also need to be
   * updated as a result of a detected change in the fold.
   */
      static linenr_T
  foldUpdateIEMSRecurse(
      garray_T	*gap,
      int		level,
      linenr_T	startlnum,
      fline_T	*flp,
      void	(*getlevel)(fline_T *),
      linenr_T	bot,
      int		topflags)	/* flags used by containing fold */
  {
      linenr_T	ll;
      fold_T	*fp = NULL;
      fold_T	*fp2;
      int		lvl = level;
      linenr_T	startlnum2 = startlnum;
      linenr_T	firstlnum = flp->lnum;	/* first lnum we got */
      int		i;
      int		finish = FALSE;
      linenr_T	linecount = flp->wp->w_buffer->b_ml.ml_line_count - flp->off;
      int		concat;
  
      /*
       * If using the marker method, the start line is not the start of a fold
       * at the level we're dealing with and the level is non-zero, we must use
       * the previous fold.  But ignore a fold that starts at or below
       * startlnum, it must be deleted.
       */
      if (getlevel == foldlevelMarker && flp->start <= flp->lvl - level
  							      && flp->lvl > 0)
      {
  	(void)foldFind(gap, startlnum - 1, &fp);
  	if (fp >= ((fold_T *)gap->ga_data) + gap->ga_len
  						   || fp->fd_top >= startlnum)
  	    fp = NULL;
      }
  
      /*
       * Loop over all lines in this fold, or until "bot" is hit.
       * Handle nested folds inside of this fold.
       * "flp->lnum" is the current line.  When finding the end of the fold, it
       * is just below the end of the fold.
       * "*flp" contains the level of the line "flp->lnum" or a following one if
       * there are lines with an invalid fold level.  "flp->lnum_save" is the
       * line number that was used to get the fold level (below "flp->lnum" when
       * it has an invalid fold level).  When called the fold level is always
       * valid, thus "flp->lnum_save" is equal to "flp->lnum".
       */
      flp->lnum_save = flp->lnum;
      while (!got_int)
      {
  	/* Updating folds can be slow, check for CTRL-C. */
  	line_breakcheck();
  
  	/* Set "lvl" to the level of line "flp->lnum".  When flp->start is set
  	 * and after the first line of the fold, set the level to zero to
  	 * force the fold to end.  Do the same when had_end is set: Previous
  	 * line was marked as end of a fold. */
  	lvl = flp->lvl;
  	if (lvl > MAX_LEVEL)
  	    lvl = MAX_LEVEL;
  	if (flp->lnum > firstlnum
  		&& (level > lvl - flp->start || level >= flp->had_end))
  	    lvl = 0;
  
  	if (flp->lnum > bot && !finish && fp != NULL)
  	{
  	    /* For "marker" and "syntax" methods:
  	     * - If a change caused a nested fold to be removed, we need to
  	     *   delete it and continue at least until where it ended.
  	     * - If a change caused a nested fold to be created, or this fold
  	     *   to continue below its original end, need to finish this fold.
  	     */
  	    if (getlevel != foldlevelMarker
  		    && getlevel != foldlevelExpr
  		    && getlevel != foldlevelSyntax)
  		break;
  	    i = 0;
  	    fp2 = fp;
  	    if (lvl >= level)
  	    {
  		/* Compute how deep the folds currently are, if it's deeper
  		 * than "lvl" then some must be deleted, need to update
  		 * at least one nested fold. */
  		ll = flp->lnum - fp->fd_top;
  		while (foldFind(&fp2->fd_nested, ll, &fp2))
  		{
  		    ++i;
  		    ll -= fp2->fd_top;
  		}
  	    }
  	    if (lvl < level + i)
  	    {
  		(void)foldFind(&fp->fd_nested, flp->lnum - fp->fd_top, &fp2);
  		if (fp2 != NULL)
  		    bot = fp2->fd_top + fp2->fd_len - 1 + fp->fd_top;
  	    }
  	    else if (fp->fd_top + fp->fd_len <= flp->lnum && lvl >= level)
  		finish = TRUE;
  	    else
  		break;
  	}
  
  	/* At the start of the first nested fold and at the end of the current
  	 * fold: check if existing folds at this level, before the current
  	 * one, need to be deleted or truncated. */
  	if (fp == NULL
  		&& (lvl != level
  		    || flp->lnum_save >= bot
  		    || flp->start != 0
  		    || flp->had_end <= MAX_LEVEL
  		    || flp->lnum == linecount))
  	{
  	    /*
  	     * Remove or update folds that have lines between startlnum and
  	     * firstlnum.
  	     */
  	    while (!got_int)
  	    {
  		/* set concat to 1 if it's allowed to concatenated this fold
  		 * with a previous one that touches it. */
  		if (flp->start != 0 || flp->had_end <= MAX_LEVEL)
  		    concat = 0;
  		else
  		    concat = 1;
  
  		/* Find an existing fold to re-use.  Preferably one that
  		 * includes startlnum, otherwise one that ends just before
  		 * startlnum or starts after it. */
  		if (foldFind(gap, startlnum, &fp)
  			|| (fp < ((fold_T *)gap->ga_data) + gap->ga_len
  			    && fp->fd_top <= firstlnum)
  			|| foldFind(gap, firstlnum - concat, &fp)
  			|| (fp < ((fold_T *)gap->ga_data) + gap->ga_len
  			    && ((lvl < level && fp->fd_top < flp->lnum)
  				|| (lvl >= level
  					   && fp->fd_top <= flp->lnum_save))))
  		{
  		    if (fp->fd_top + fp->fd_len + concat > firstlnum)
  		    {
  			/* Use existing fold for the new fold.  If it starts
  			 * before where we started looking, extend it.  If it
  			 * starts at another line, update nested folds to keep
  			 * their position, compensating for the new fd_top. */
  			if (fp->fd_top >= startlnum && fp->fd_top != firstlnum)
  			{
  			    if (fp->fd_top > firstlnum)
  				/* like lines are inserted */
  				foldMarkAdjustRecurse(&fp->fd_nested,
  					(linenr_T)0, (linenr_T)MAXLNUM,
  					(long)(fp->fd_top - firstlnum), 0L);
  			    else
  				/* like lines are deleted */
  				foldMarkAdjustRecurse(&fp->fd_nested,
  					(linenr_T)0,
  					(long)(firstlnum - fp->fd_top - 1),
  					(linenr_T)MAXLNUM,
  					(long)(fp->fd_top - firstlnum));
  			    fp->fd_len += fp->fd_top - firstlnum;
  			    fp->fd_top = firstlnum;
  			    fold_changed = TRUE;
  			}
  			else if (flp->start != 0 && lvl == level
  						   && fp->fd_top != firstlnum)
  			{
  			    /* Existing fold that includes startlnum must stop
  			     * if we find the start of a new fold at the same
  			     * level.  Split it.  Delete contained folds at
  			     * this point to split them too. */
  			    foldRemove(&fp->fd_nested, flp->lnum - fp->fd_top,
  						      flp->lnum - fp->fd_top);
  			    i = (int)(fp - (fold_T *)gap->ga_data);
  			    foldSplit(gap, i, flp->lnum, flp->lnum - 1);
  			    fp = (fold_T *)gap->ga_data + i + 1;
  			    /* If using the "marker" or "syntax" method, we
  			     * need to continue until the end of the fold is
  			     * found. */
  			    if (getlevel == foldlevelMarker
  				    || getlevel == foldlevelExpr
  				    || getlevel == foldlevelSyntax)
  				finish = TRUE;
  			}
  			break;
  		    }
  		    if (fp->fd_top >= startlnum)
  		    {
  			/* A fold that starts at or after startlnum and stops
  			 * before the new fold must be deleted.  Continue
  			 * looking for the next one. */
  			deleteFoldEntry(gap,
  				     (int)(fp - (fold_T *)gap->ga_data), TRUE);
  		    }
  		    else
  		    {
  			/* A fold has some lines above startlnum, truncate it
  			 * to stop just above startlnum.  */
  			fp->fd_len = startlnum - fp->fd_top;
  			foldMarkAdjustRecurse(&fp->fd_nested,
  				(linenr_T)fp->fd_len, (linenr_T)MAXLNUM,
  						       (linenr_T)MAXLNUM, 0L);
  			fold_changed = TRUE;
  		    }
  		}
  		else
  		{
  		    /* Insert new fold.  Careful: ga_data may be NULL and it
  		     * may change! */
  		    i = (int)(fp - (fold_T *)gap->ga_data);
  		    if (foldInsert(gap, i) != OK)
  			return bot;
  		    fp = (fold_T *)gap->ga_data + i;
  		    /* The new fold continues until bot, unless we find the
  		     * end earlier. */
  		    fp->fd_top = firstlnum;
  		    fp->fd_len = bot - firstlnum + 1;
  		    /* When the containing fold is open, the new fold is open.
  		     * The new fold is closed if the fold above it is closed.
  		     * The first fold depends on the containing fold. */
  		    if (topflags == FD_OPEN)
  		    {
  			flp->wp->w_fold_manual = TRUE;
  			fp->fd_flags = FD_OPEN;
  		    }
  		    else if (i <= 0)
  		    {
  			fp->fd_flags = topflags;
  			if (topflags != FD_LEVEL)
  			    flp->wp->w_fold_manual = TRUE;
  		    }
  		    else
  			fp->fd_flags = (fp - 1)->fd_flags;
  		    fp->fd_small = MAYBE;
  		    /* If using the "marker", "expr" or "syntax" method, we
  		     * need to continue until the end of the fold is found. */
  		    if (getlevel == foldlevelMarker
  			    || getlevel == foldlevelExpr
  			    || getlevel == foldlevelSyntax)
  			finish = TRUE;
  		    fold_changed = TRUE;
  		    break;
  		}
  	    }
  	}
  
  	if (lvl < level || flp->lnum > linecount)
  	{
  	    /*
  	     * Found a line with a lower foldlevel, this fold ends just above
  	     * "flp->lnum".
  	     */
  	    break;
  	}
  
  	/*
  	 * The fold includes the line "flp->lnum" and "flp->lnum_save".
  	 * Check "fp" for safety.
  	 */
  	if (lvl > level && fp != NULL)
  	{
  	    /*
  	     * There is a nested fold, handle it recursively.
  	     */
  	    /* At least do one line (can happen when finish is TRUE). */
  	    if (bot < flp->lnum)
  		bot = flp->lnum;
  
  	    /* Line numbers in the nested fold are relative to the start of
  	     * this fold. */
  	    flp->lnum = flp->lnum_save - fp->fd_top;
  	    flp->off += fp->fd_top;
  	    i = (int)(fp - (fold_T *)gap->ga_data);
  	    bot = foldUpdateIEMSRecurse(&fp->fd_nested, level + 1,
  				       startlnum2 - fp->fd_top, flp, getlevel,
  					      bot - fp->fd_top, fp->fd_flags);
  	    fp = (fold_T *)gap->ga_data + i;
  	    flp->lnum += fp->fd_top;
  	    flp->lnum_save += fp->fd_top;
  	    flp->off -= fp->fd_top;
  	    bot += fp->fd_top;
  	    startlnum2 = flp->lnum;
  
  	    /* This fold may end at the same line, don't incr. flp->lnum. */
  	}
  	else
  	{
  	    /*
  	     * Get the level of the next line, then continue the loop to check
  	     * if it ends there.
  	     * Skip over undefined lines, to find the foldlevel after it.
  	     * For the last line in the file the foldlevel is always valid.
  	     */
  	    flp->lnum = flp->lnum_save;
  	    ll = flp->lnum + 1;
  	    while (!got_int)
  	    {
  		/* Make the previous level available to foldlevel(). */
  		prev_lnum = flp->lnum;
  		prev_lnum_lvl = flp->lvl;
  
  		if (++flp->lnum > linecount)
  		    break;
  		flp->lvl = flp->lvl_next;
  		getlevel(flp);
  		if (flp->lvl >= 0 || flp->had_end <= MAX_LEVEL)
  		    break;
  	    }
  	    prev_lnum = 0;
  	    if (flp->lnum > linecount)
  		break;
  
  	    /* leave flp->lnum_save to lnum of the line that was used to get
  	     * the level, flp->lnum to the lnum of the next line. */
  	    flp->lnum_save = flp->lnum;
  	    flp->lnum = ll;
  	}
      }
  
      if (fp == NULL)	/* only happens when got_int is set */
  	return bot;
  
      /*
       * Get here when:
       * lvl < level: the folds ends just above "flp->lnum"
       * lvl >= level: fold continues below "bot"
       */
  
      /* Current fold at least extends until lnum. */
      if (fp->fd_len < flp->lnum - fp->fd_top)
      {
  	fp->fd_len = flp->lnum - fp->fd_top;
  	fp->fd_small = MAYBE;
  	fold_changed = TRUE;
      }
  
      /* Delete contained folds from the end of the last one found until where
       * we stopped looking. */
      foldRemove(&fp->fd_nested, startlnum2 - fp->fd_top,
  						  flp->lnum - 1 - fp->fd_top);
  
      if (lvl < level)
      {
  	/* End of fold found, update the length when it got shorter. */
  	if (fp->fd_len != flp->lnum - fp->fd_top)
  	{
  	    if (fp->fd_top + fp->fd_len > bot + 1)
  	    {
  		/* fold continued below bot */
  		if (getlevel == foldlevelMarker
  			|| getlevel == foldlevelExpr
  			|| getlevel == foldlevelSyntax)
  		{
  		    /* marker method: truncate the fold and make sure the
  		     * previously included lines are processed again */
  		    bot = fp->fd_top + fp->fd_len - 1;
  		    fp->fd_len = flp->lnum - fp->fd_top;
  		}
  		else
  		{
  		    /* indent or expr method: split fold to create a new one
  		     * below bot */
  		    i = (int)(fp - (fold_T *)gap->ga_data);
  		    foldSplit(gap, i, flp->lnum, bot);
  		    fp = (fold_T *)gap->ga_data + i;
  		}
  	    }
  	    else
  		fp->fd_len = flp->lnum - fp->fd_top;
  	    fold_changed = TRUE;
  	}
      }
  
      /* delete following folds that end before the current line */
      for (;;)
      {
  	fp2 = fp + 1;
  	if (fp2 >= (fold_T *)gap->ga_data + gap->ga_len
  						  || fp2->fd_top > flp->lnum)
  	    break;
  	if (fp2->fd_top + fp2->fd_len > flp->lnum)
  	{
  	    if (fp2->fd_top < flp->lnum)
  	    {
  		/* Make fold that includes lnum start at lnum. */
  		foldMarkAdjustRecurse(&fp2->fd_nested,
  			(linenr_T)0, (long)(flp->lnum - fp2->fd_top - 1),
  			(linenr_T)MAXLNUM, (long)(fp2->fd_top - flp->lnum));
  		fp2->fd_len -= flp->lnum - fp2->fd_top;
  		fp2->fd_top = flp->lnum;
  		fold_changed = TRUE;
  	    }
  
  	    if (lvl >= level)
  	    {
  		/* merge new fold with existing fold that follows */
  		foldMerge(fp, gap, fp2);
  	    }
  	    break;
  	}
  	fold_changed = TRUE;
  	deleteFoldEntry(gap, (int)(fp2 - (fold_T *)gap->ga_data), TRUE);
      }
  
      /* Need to redraw the lines we inspected, which might be further down than
       * was asked for. */
      if (bot < flp->lnum - 1)
  	bot = flp->lnum - 1;
  
      return bot;
  }
  
  /* foldInsert() {{{2 */
  /*
   * Insert a new fold in "gap" at position "i".
   * Returns OK for success, FAIL for failure.
   */
      static int
  foldInsert(garray_T *gap, int i)
  {
      fold_T	*fp;
  
      if (ga_grow(gap, 1) != OK)
  	return FAIL;
      fp = (fold_T *)gap->ga_data + i;
      if (i < gap->ga_len)
  	mch_memmove(fp + 1, fp, sizeof(fold_T) * (gap->ga_len - i));
      ++gap->ga_len;
      ga_init2(&fp->fd_nested, (int)sizeof(fold_T), 10);
      return OK;
  }
  
  /* foldSplit() {{{2 */
  /*
   * Split the "i"th fold in "gap", which starts before "top" and ends below
   * "bot" in two pieces, one ending above "top" and the other starting below
   * "bot".
   * The caller must first have taken care of any nested folds from "top" to
   * "bot"!
   */
      static void
  foldSplit(
      garray_T	*gap,
      int		i,
      linenr_T	top,
      linenr_T	bot)
  {
      fold_T	*fp;
      fold_T	*fp2;
      garray_T	*gap1;
      garray_T	*gap2;
      int		idx;
      int		len;
  
      /* The fold continues below bot, need to split it. */
      if (foldInsert(gap, i + 1) == FAIL)
  	return;
      fp = (fold_T *)gap->ga_data + i;
      fp[1].fd_top = bot + 1;
      fp[1].fd_len = fp->fd_len - (fp[1].fd_top - fp->fd_top);
      fp[1].fd_flags = fp->fd_flags;
      fp[1].fd_small = MAYBE;
      fp->fd_small = MAYBE;
  
      /* Move nested folds below bot to new fold.  There can't be
       * any between top and bot, they have been removed by the caller. */
      gap1 = &fp->fd_nested;
      gap2 = &fp[1].fd_nested;
      (void)(foldFind(gap1, bot + 1 - fp->fd_top, &fp2));
      len = (int)((fold_T *)gap1->ga_data + gap1->ga_len - fp2);
      if (len > 0 && ga_grow(gap2, len) == OK)
      {
  	for (idx = 0; idx < len; ++idx)
  	{
  	    ((fold_T *)gap2->ga_data)[idx] = fp2[idx];
  	    ((fold_T *)gap2->ga_data)[idx].fd_top
  						 -= fp[1].fd_top - fp->fd_top;
  	}
  	gap2->ga_len = len;
  	gap1->ga_len -= len;
      }
      fp->fd_len = top - fp->fd_top;
      fold_changed = TRUE;
  }
  
  /* foldRemove() {{{2 */
  /*
   * Remove folds within the range "top" to and including "bot".
   * Check for these situations:
   *      1  2  3
   *      1  2  3
   * top     2  3  4  5
   *	   2  3  4  5
   * bot	   2  3  4  5
   *	      3     5  6
   *	      3     5  6
   *
   * 1: not changed
   * 2: truncate to stop above "top"
   * 3: split in two parts, one stops above "top", other starts below "bot".
   * 4: deleted
   * 5: made to start below "bot".
   * 6: not changed
   */
      static void
  foldRemove(garray_T *gap, linenr_T top, linenr_T bot)
  {
      fold_T	*fp = NULL;
  
      if (bot < top)
  	return;		/* nothing to do */
  
      for (;;)
      {
  	/* Find fold that includes top or a following one. */
  	if (foldFind(gap, top, &fp) && fp->fd_top < top)
  	{
  	    /* 2: or 3: need to delete nested folds */
  	    foldRemove(&fp->fd_nested, top - fp->fd_top, bot - fp->fd_top);
  	    if (fp->fd_top + fp->fd_len > bot + 1)
  	    {
  		/* 3: need to split it. */
  		foldSplit(gap, (int)(fp - (fold_T *)gap->ga_data), top, bot);
  	    }
  	    else
  	    {
  		/* 2: truncate fold at "top". */
  		fp->fd_len = top - fp->fd_top;
  	    }
  	    fold_changed = TRUE;
  	    continue;
  	}
  	if (fp >= (fold_T *)(gap->ga_data) + gap->ga_len
  		|| fp->fd_top > bot)
  	{
  	    /* 6: Found a fold below bot, can stop looking. */
  	    break;
  	}
  	if (fp->fd_top >= top)
  	{
  	    /* Found an entry below top. */
  	    fold_changed = TRUE;
  	    if (fp->fd_top + fp->fd_len - 1 > bot)
  	    {
  		/* 5: Make fold that includes bot start below bot. */
  		foldMarkAdjustRecurse(&fp->fd_nested,
  			(linenr_T)0, (long)(bot - fp->fd_top),
  			(linenr_T)MAXLNUM, (long)(fp->fd_top - bot - 1));
  		fp->fd_len -= bot - fp->fd_top + 1;
  		fp->fd_top = bot + 1;
  		break;
  	    }
  
  	    /* 4: Delete completely contained fold. */
  	    deleteFoldEntry(gap, (int)(fp - (fold_T *)gap->ga_data), TRUE);
  	}
      }
  }
  
  /* foldMerge() {{{2 */
  /*
   * Merge two adjacent folds (and the nested ones in them).
   * This only works correctly when the folds are really adjacent!  Thus "fp1"
   * must end just above "fp2".
   * The resulting fold is "fp1", nested folds are moved from "fp2" to "fp1".
   * Fold entry "fp2" in "gap" is deleted.
   */
      static void
  foldMerge(fold_T *fp1, garray_T *gap, fold_T *fp2)
  {
      fold_T	*fp3;
      fold_T	*fp4;
      int		idx;
      garray_T	*gap1 = &fp1->fd_nested;
      garray_T	*gap2 = &fp2->fd_nested;
  
      /* If the last nested fold in fp1 touches the first nested fold in fp2,
       * merge them recursively. */
      if (foldFind(gap1, fp1->fd_len - 1L, &fp3) && foldFind(gap2, 0L, &fp4))
  	foldMerge(fp3, gap2, fp4);
  
      /* Move nested folds in fp2 to the end of fp1. */
      if (gap2->ga_len > 0 && ga_grow(gap1, gap2->ga_len) == OK)
      {
  	for (idx = 0; idx < gap2->ga_len; ++idx)
  	{
  	    ((fold_T *)gap1->ga_data)[gap1->ga_len]
  					= ((fold_T *)gap2->ga_data)[idx];
  	    ((fold_T *)gap1->ga_data)[gap1->ga_len].fd_top += fp1->fd_len;
  	    ++gap1->ga_len;
  	}
  	gap2->ga_len = 0;
      }
  
      fp1->fd_len += fp2->fd_len;
      deleteFoldEntry(gap, (int)(fp2 - (fold_T *)gap->ga_data), TRUE);
      fold_changed = TRUE;
  }
  
  /* foldlevelIndent() {{{2 */
  /*
   * Low level function to get the foldlevel for the "indent" method.
   * Doesn't use any caching.
   * Returns a level of -1 if the foldlevel depends on surrounding lines.
   */
      static void
  foldlevelIndent(fline_T *flp)
  {
      char_u	*s;
      buf_T	*buf;
      linenr_T	lnum = flp->lnum + flp->off;
  
      buf = flp->wp->w_buffer;
      s = skipwhite(ml_get_buf(buf, lnum, FALSE));
  
      /* empty line or lines starting with a character in 'foldignore': level
       * depends on surrounding lines */
      if (*s == NUL || vim_strchr(flp->wp->w_p_fdi, *s) != NULL)
      {
  	/* first and last line can't be undefined, use level 0 */
  	if (lnum == 1 || lnum == buf->b_ml.ml_line_count)
  	    flp->lvl = 0;
  	else
  	    flp->lvl = -1;
      }
      else
  	flp->lvl = get_indent_buf(buf, lnum) / get_sw_value(curbuf);
      if (flp->lvl > flp->wp->w_p_fdn)
      {
  	flp->lvl = flp->wp->w_p_fdn;
  	if (flp->lvl < 0)
  	    flp->lvl = 0;
      }
  }
  
  /* foldlevelDiff() {{{2 */
  #ifdef FEAT_DIFF
  /*
   * Low level function to get the foldlevel for the "diff" method.
   * Doesn't use any caching.
   */
      static void
  foldlevelDiff(fline_T *flp)
  {
      if (diff_infold(flp->wp, flp->lnum + flp->off))
  	flp->lvl = 1;
      else
  	flp->lvl = 0;
  }
  #endif
  
  /* foldlevelExpr() {{{2 */
  /*
   * Low level function to get the foldlevel for the "expr" method.
   * Doesn't use any caching.
   * Returns a level of -1 if the foldlevel depends on surrounding lines.
   */
      static void
  foldlevelExpr(fline_T *flp)
  {
  #ifndef FEAT_EVAL
      flp->start = FALSE;
      flp->lvl = 0;
  #else
      win_T	*win;
      int		n;
      int		c;
      linenr_T	lnum = flp->lnum + flp->off;
      int		save_keytyped;
  
      win = curwin;
      curwin = flp->wp;
      curbuf = flp->wp->w_buffer;
      set_vim_var_nr(VV_LNUM, lnum);
  
      flp->start = 0;
      flp->had_end = flp->end;
      flp->end = MAX_LEVEL + 1;
      if (lnum <= 1)
  	flp->lvl = 0;
  
      /* KeyTyped may be reset to 0 when calling a function which invokes
       * do_cmdline().  To make 'foldopen' work correctly restore KeyTyped. */
      save_keytyped = KeyTyped;
      n = (int)eval_foldexpr(flp->wp->w_p_fde, &c);
      KeyTyped = save_keytyped;
  
      switch (c)
      {
  	/* "a1", "a2", .. : add to the fold level */
  	case 'a': if (flp->lvl >= 0)
  		  {
  		      flp->lvl += n;
  		      flp->lvl_next = flp->lvl;
  		  }
  		  flp->start = n;
  		  break;
  
  	/* "s1", "s2", .. : subtract from the fold level */
  	case 's': if (flp->lvl >= 0)
  		  {
  		      if (n > flp->lvl)
  			  flp->lvl_next = 0;
  		      else
  			  flp->lvl_next = flp->lvl - n;
  		      flp->end = flp->lvl_next + 1;
  		  }
  		  break;
  
  	/* ">1", ">2", .. : start a fold with a certain level */
  	case '>': flp->lvl = n;
  		  flp->lvl_next = n;
  		  flp->start = 1;
  		  break;
  
  	/* "<1", "<2", .. : end a fold with a certain level */
  	case '<': flp->lvl_next = n - 1;
  		  flp->end = n;
  		  break;
  
  	/* "=": No change in level */
  	case '=': flp->lvl_next = flp->lvl;
  		  break;
  
  	/* "-1", "0", "1", ..: set fold level */
  	default:  if (n < 0)
  		      /* Use the current level for the next line, so that "a1"
  		       * will work there. */
  		      flp->lvl_next = flp->lvl;
  		  else
  		      flp->lvl_next = n;
  		  flp->lvl = n;
  		  break;
      }
  
      /* If the level is unknown for the first or the last line in the file, use
       * level 0. */
      if (flp->lvl < 0)
      {
  	if (lnum <= 1)
  	{
  	    flp->lvl = 0;
  	    flp->lvl_next = 0;
  	}
  	if (lnum == curbuf->b_ml.ml_line_count)
  	    flp->lvl_next = 0;
      }
  
      curwin = win;
      curbuf = curwin->w_buffer;
  #endif
  }
  
  /* parseMarker() {{{2 */
  /*
   * Parse 'foldmarker' and set "foldendmarker", "foldstartmarkerlen" and
   * "foldendmarkerlen".
   * Relies on the option value to have been checked for correctness already.
   */
      static void
  parseMarker(win_T *wp)
  {
      foldendmarker = vim_strchr(wp->w_p_fmr, ',');
      foldstartmarkerlen = (int)(foldendmarker++ - wp->w_p_fmr);
      foldendmarkerlen = (int)STRLEN(foldendmarker);
  }
  
  /* foldlevelMarker() {{{2 */
  /*
   * Low level function to get the foldlevel for the "marker" method.
   * "foldendmarker", "foldstartmarkerlen" and "foldendmarkerlen" must have been
   * set before calling this.
   * Requires that flp->lvl is set to the fold level of the previous line!
   * Careful: This means you can't call this function twice on the same line.
   * Doesn't use any caching.
   * Sets flp->start when a start marker was found.
   */
      static void
  foldlevelMarker(fline_T *flp)
  {
      char_u	*startmarker;
      int		cstart;
      int		cend;
      int		start_lvl = flp->lvl;
      char_u	*s;
      int		n;
  
      /* cache a few values for speed */
      startmarker = flp->wp->w_p_fmr;
      cstart = *startmarker;
      ++startmarker;
      cend = *foldendmarker;
  
      /* Default: no start found, next level is same as current level */
      flp->start = 0;
      flp->lvl_next = flp->lvl;
  
      s = ml_get_buf(flp->wp->w_buffer, flp->lnum + flp->off, FALSE);
      while (*s)
      {
  	if (*s == cstart
  		  && STRNCMP(s + 1, startmarker, foldstartmarkerlen - 1) == 0)
  	{
  	    /* found startmarker: set flp->lvl */
  	    s += foldstartmarkerlen;
  	    if (VIM_ISDIGIT(*s))
  	    {
  		n = atoi((char *)s);
  		if (n > 0)
  		{
  		    flp->lvl = n;
  		    flp->lvl_next = n;
  		    if (n <= start_lvl)
  			flp->start = 1;
  		    else
  			flp->start = n - start_lvl;
  		}
  	    }
  	    else
  	    {
  		++flp->lvl;
  		++flp->lvl_next;
  		++flp->start;
  	    }
  	}
  	else if (*s == cend
  	      && STRNCMP(s + 1, foldendmarker + 1, foldendmarkerlen - 1) == 0)
  	{
  	    /* found endmarker: set flp->lvl_next */
  	    s += foldendmarkerlen;
  	    if (VIM_ISDIGIT(*s))
  	    {
  		n = atoi((char *)s);
  		if (n > 0)
  		{
  		    flp->lvl = n;
  		    flp->lvl_next = n - 1;
  		    /* never start a fold with an end marker */
  		    if (flp->lvl_next > start_lvl)
  			flp->lvl_next = start_lvl;
  		}
  	    }
  	    else
  		--flp->lvl_next;
  	}
  	else
  	    mb_ptr_adv(s);
      }
  
      /* The level can't go negative, must be missing a start marker. */
      if (flp->lvl_next < 0)
  	flp->lvl_next = 0;
  }
  
  /* foldlevelSyntax() {{{2 */
  /*
   * Low level function to get the foldlevel for the "syntax" method.
   * Doesn't use any caching.
   */
      static void
  foldlevelSyntax(fline_T *flp)
  {
  #ifndef FEAT_SYN_HL
      flp->start = 0;
      flp->lvl = 0;
  #else
      linenr_T	lnum = flp->lnum + flp->off;
      int		n;
  
      /* Use the maximum fold level at the start of this line and the next. */
      flp->lvl = syn_get_foldlevel(flp->wp, lnum);
      flp->start = 0;
      if (lnum < flp->wp->w_buffer->b_ml.ml_line_count)
      {
  	n = syn_get_foldlevel(flp->wp, lnum + 1);
  	if (n > flp->lvl)
  	{
  	    flp->start = n - flp->lvl;	/* fold(s) start here */
  	    flp->lvl = n;
  	}
      }
  #endif
  }
  
  /* functions for storing the fold state in a View {{{1 */
  /* put_folds() {{{2 */
  #if defined(FEAT_SESSION) || defined(PROTO)
  static int put_folds_recurse(FILE *fd, garray_T *gap, linenr_T off);
  static int put_foldopen_recurse(FILE *fd, win_T *wp, garray_T *gap, linenr_T off);
  static int put_fold_open_close(FILE *fd, fold_T *fp, linenr_T off);
  
  /*
   * Write commands to "fd" to restore the manual folds in window "wp".
   * Return FAIL if writing fails.
   */
      int
  put_folds(FILE *fd, win_T *wp)
  {
      if (foldmethodIsManual(wp))
      {
  	if (put_line(fd, "silent! normal! zE") == FAIL
  		|| put_folds_recurse(fd, &wp->w_folds, (linenr_T)0) == FAIL)
  	    return FAIL;
      }
  
      /* If some folds are manually opened/closed, need to restore that. */
      if (wp->w_fold_manual)
  	return put_foldopen_recurse(fd, wp, &wp->w_folds, (linenr_T)0);
  
      return OK;
  }
  
  /* put_folds_recurse() {{{2 */
  /*
   * Write commands to "fd" to recreate manually created folds.
   * Returns FAIL when writing failed.
   */
      static int
  put_folds_recurse(FILE *fd, garray_T *gap, linenr_T off)
  {
      int		i;
      fold_T	*fp;
  
      fp = (fold_T *)gap->ga_data;
      for (i = 0; i < gap->ga_len; i++)
      {
  	/* Do nested folds first, they will be created closed. */
  	if (put_folds_recurse(fd, &fp->fd_nested, off + fp->fd_top) == FAIL)
  	    return FAIL;
  	if (fprintf(fd, "%ld,%ldfold", fp->fd_top + off,
  					fp->fd_top + off + fp->fd_len - 1) < 0
  		|| put_eol(fd) == FAIL)
  	    return FAIL;
  	++fp;
      }
      return OK;
  }
  
  /* put_foldopen_recurse() {{{2 */
  /*
   * Write commands to "fd" to open and close manually opened/closed folds.
   * Returns FAIL when writing failed.
   */
      static int
  put_foldopen_recurse(
      FILE	*fd,
      win_T	*wp,
      garray_T	*gap,
      linenr_T	off)
  {
      int		i;
      int		level;
      fold_T	*fp;
  
      fp = (fold_T *)gap->ga_data;
      for (i = 0; i < gap->ga_len; i++)
      {
  	if (fp->fd_flags != FD_LEVEL)
  	{
  	    if (fp->fd_nested.ga_len > 0)
  	    {
  		/* open nested folds while this fold is open */
  		if (fprintf(fd, "%ld", fp->fd_top + off) < 0
  			|| put_eol(fd) == FAIL
  			|| put_line(fd, "normal! zo") == FAIL)
  		    return FAIL;
  		if (put_foldopen_recurse(fd, wp, &fp->fd_nested,
  							     off + fp->fd_top)
  			== FAIL)
  		    return FAIL;
  		/* close the parent when needed */
  		if (fp->fd_flags == FD_CLOSED)
  		{
  		    if (put_fold_open_close(fd, fp, off) == FAIL)
  			return FAIL;
  		}
  	    }
  	    else
  	    {
  		/* Open or close the leaf according to the window foldlevel.
  		 * Do not close a leaf that is already closed, as it will close
  		 * the parent. */
  		level = foldLevelWin(wp, off + fp->fd_top);
  		if ((fp->fd_flags == FD_CLOSED && wp->w_p_fdl >= level)
  			|| (fp->fd_flags != FD_CLOSED && wp->w_p_fdl < level))
  		if (put_fold_open_close(fd, fp, off) == FAIL)
  		    return FAIL;
  	    }
  	}
  	++fp;
      }
  
      return OK;
  }
  
  /* put_fold_open_close() {{{2 */
  /*
   * Write the open or close command to "fd".
   * Returns FAIL when writing failed.
   */
      static int
  put_fold_open_close(FILE *fd, fold_T *fp, linenr_T off)
  {
      if (fprintf(fd, "%ld", fp->fd_top + off) < 0
  	    || put_eol(fd) == FAIL
  	    || fprintf(fd, "normal! z%c",
  			   fp->fd_flags == FD_CLOSED ? 'c' : 'o') < 0
  	    || put_eol(fd) == FAIL)
  	return FAIL;
  
      return OK;
  }
  #endif /* FEAT_SESSION */
  
  /* }}}1 */
  #endif /* defined(FEAT_FOLDING) || defined(PROTO) */
  