view src/fold.c @ 34219:a0a4a774117b v9.1.0058

patch 9.1.0058: Cannot map Super Keys in GTK UI Commit: https://github.com/vim/vim/commit/92e90a1e102825aa9149262cacfc991264db05df Author: Casey Tucker <dctucker@hotmail.com> Date: Thu Jan 25 22:44:00 2024 +0100 patch 9.1.0058: Cannot map Super Keys in GTK UI Problem: Cannot map Super Keys in GTK UI (Casey Tucker) Solution: Enable Super Key mappings in GTK using <D-Key> (Casey Tucker) As a developer who works in both Mac and Linux using the same keyboard, it can be frustrating having to remember different key combinations or having to rely on system utilities to remap keys. This change allows `<D-z>` `<D-x>` `<D-c>` `<D-v>` etc. to be recognized by the `map` commands, along with the `<D-S-...>` shifted variants. ```vimrc if has('gui_gtk') nnoremap <D-z> u nnoremap <D-S-Z> <C-r> vnoremap <D-x> "+d vnoremap <D-c> "+y cnoremap <D-v> <C-R>+ inoremap <D-v> <C-o>"+gP nnoremap <D-v> "+P vnoremap <D-v> "-d"+P nnoremap <D-s> :w<CR> inoremap <D-s> <C-o>:w<CR> nnoremap <D-w> :q<CR> nnoremap <D-q> :qa<CR> nnoremap <D-t> :tabe<CR> nnoremap <D-S-T> :vs#<CR><C-w>T nnoremap <D-a> ggVG vnoremap <D-a> <ESC>ggVG inoremap <D-a> <ESC>ggVG nnoremap <D-f> / nnoremap <D-g> n nnoremap <D-S-G> N vnoremap <D-x> "+x endif ``` closes: #12698 Signed-off-by: Casey Tucker <dctucker@hotmail.com> Signed-off-by: Christian Brabandt <cb@256bit.org>
author Christian Brabandt <cb@256bit.org>
date Thu, 25 Jan 2024 23:00:03 +0100
parents 48955338edb1
children 9e093c96dff6
line wrap: on
line source

/* vi:set ts=8 sts=4 sw=4 noet:
 * 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);

/*
 * 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

/*
 * 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);
}

// 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
#ifdef FEAT_EVAL
/*
 * Return fold level at line number "lnum" in the current window.
 */
    static 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);
}
#endif

// 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[0] != NUL && 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[0] != NUL && wp->w_p_fdm[1] == 'x');
}

// foldmethodIsMarker() {{{2
/*
 * Return TRUE if 'foldmethod' is "marker"
 */
    int
foldmethodIsMarker(win_T *wp)
{
    return (wp->w_p_fdm[0] != NUL && 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_no_fold_found));
    // Force a redraw to remove the Visual highlighting.
    if (had_visual)
	redraw_curbuf_later(UPD_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)
	return;

    // 'foldclose' 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(_(e_cannot_create_fold_with_current_foldmethod));
    else
	emsg(_(e_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;
    if (gap->ga_len == 0)
	i = 0;
    else
    {
	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;
	    }
	}
	if (gap->ga_len == 0)
	    i = 0;
	else
	    i = (int)(fp - (fold_T *)gap->ga_data);
    }

    if (ga_grow(gap, 1) == FAIL)
	return;

    fp = (fold_T *)gap->ga_data + i;
    ga_init2(&fold_ga, 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_no_fold_found));
	// Force a redraw to remove the Visual highlighting.
	if (had_visual)
	    redraw_curbuf_later(UPD_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;
#ifdef FEAT_DIFF
    if (need_diff_redraw)
	// will update later
	return;
#endif

    if (wp->w_folds.ga_len > 0)
    {
	linenr_T	maybe_small_start = top;
	linenr_T	maybe_small_end = bot;

	// Mark all folds from top to bot (or bot to top) as maybe-small.
	if (top > bot)
	{
	    maybe_small_start = bot;
	    maybe_small_end = top;
	}
	(void)foldFind(&wp->w_folds, maybe_small_start, &fp);
	while (fp < (fold_T *)wp->w_folds.ga_data + wp->w_folds.ga_len
		&& fp->fd_top <= maybe_small_end)
	{
	    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, UPD_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;
	if (gap->ga_len == 0)
	    break;
	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 || gap->ga_len == 0)
		    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, 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_POS(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))
	return;

    ptr = ml_get(end->lnum);
    end->col = (colnr_T)STRLEN(ptr);
    if (end->col > 0 && *p_sel == 'o')
	--end->col;
    // prevent cursor from moving on the trail byte
    if (has_mbyte)
	mb_adjust_cursor();
}

// 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;

    if (gap->ga_len == 0)
    {
	*fpp = NULL;
	return FALSE;
    }

    /*
     * 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)
	return;

    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_no_fold_found));
	    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 != NULL && 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_no_fold_found));

    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 & MODE_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;

    if (gap->ga_len == 0)
	return;

    // In Insert mode an inserted line at the top of a fold is considered part
    // of the fold, otherwise it isn't.
    if ((State & MODE_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
		    if (amount == MAXLNUM)
		    {
			foldMarkAdjustRecurse(&fp->fd_nested,
				  0,
				  line2 - fp->fd_top,
				  amount,
				  amount_after + (fp->fd_top - top));
			fp->fd_len -= line2 - fp->fd_top + 1;
			fp->fd_top = line1;
		    }
		    else
		    {
			foldMarkAdjustRecurse(&fp->fd_nested,
				  0,
				  line2 - fp->fd_top,
				  amount,
				  amount_after - amount);
			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)
	return;

    // 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_cannot_make_changes_modifiable_is_off));
	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");
    int		line_is_comment = FALSE;

    // 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)
	return;

    // Check if the line ends with an unclosed comment
    (void)skip_comment(line, FALSE, FALSE, &line_is_comment);
    newline = alloc(line_len + markerlen + STRLEN(cms) + 1);
    if (newline == NULL)
	return;
    STRCPY(newline, line);
    // Append the marker to the end of the line
    if (p == NULL || line_is_comment)
	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 be 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;

    // end marker may be missing and fold extends below the last line
    if (lnum > curbuf->b_ml.ml_line_count)
	return;
    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(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[FOLD_TEXT_LEN]".
 * 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];
	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)
	{
	    win_T   *save_curwin = curwin;
	    sctx_T  saved_sctx = current_sctx;

	    curwin = wp;
	    curbuf = wp->w_buffer;
	    current_sctx = wp->w_p_script_ctx[WV_FDT];

	    ++emsg_off; // handle exceptions, but don't display errors
	    text = eval_to_string_safe(wp->w_p_fdt,
			   was_set_insecurely((char_u *)"foldtext", OPT_LOCAL),
			   TRUE, TRUE);
	    --emsg_off;

	    if (text == NULL || did_emsg)
		got_fdt_error = TRUE;

	    curwin = save_curwin;
	    curbuf = curwin->w_buffer;
	    current_sctx = saved_sctx;
	}
	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)
	    {
		int	len;

		if (has_mbyte && (len = (*mb_ptr2len)(p)) > 1)
		{
		    if (!vim_isprintc((*mb_ptr2char)(p)))
			break;
		    p += len - 1;
		}
		else
		    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
    {
	long count = (long)(lnume - lnum + 1);

	vim_snprintf((char *)buf, FOLD_TEXT_LEN,
		     NGETTEXT("+--%3ld line folded ",
					       "+--%3ld lines folded ", count),
		     count);
	text = buf;
    }
    return text;
}

// foldtext_cleanup() {{{2
#ifdef FEAT_EVAL
/*
 * Remove 'foldmarker' and 'commentstring' from "str" (in-place).
 */
    static 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);
	}
    }
}
#endif

// 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 as 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;
	    // Start one line back, because if the line above "top" has an
	    // undefined fold level, folding it relies on the line under it,
	    // which is "top".
	    if (top > 1)
		--fline.lnum;
	}

	// 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 != NULL && (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 concatenate 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 (gap->ga_len > 0 && (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 == firstlnum)
			{
			    // have found a fold beginning where we want
			}
			else if (fp->fd_top >= startlnum)
			{
			    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;
			    fp->fd_small = MAYBE;
			    fold_changed = TRUE;
			}
			else if ((flp->start != 0 && lvl == level)
						     || firstlnum != startlnum)
			{
			    linenr_T breakstart;
			    linenr_T breakend;

			    /*
			     * Before there was a fold spanning from above
			     * startlnum to below firstlnum. This fold is valid
			     * above startlnum (because we are not updating
			     * that range), but there should now be a break in
			     * it.
			     * If the break is because we are now forced to
			     * start a new fold at the level "level" at line
			     * fline->lnum, then we need to split the fold at
			     * fline->lnum.
			     * If the break is because the range
			     * [startlnum, firstlnum) is now at a lower indent
			     * than "level", we need to split the fold in this
			     * range.
			     * Any splits have to be done recursively.
			     */
			    if (firstlnum != startlnum)
			    {
				breakstart = startlnum;
				breakend = firstlnum;
			    }
			    else
			    {
				breakstart = flp->lnum;
				breakend = flp->lnum;
			    }
			    foldRemove(&fp->fd_nested, breakstart - fp->fd_top,
						      breakend - fp->fd_top);
			    i = (int)(fp - (fold_T *)gap->ga_data);
			    foldSplit(gap, i, breakstart, breakend - 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;
			}

			if (fp->fd_top == startlnum && concat)
			{
			    i = (int)(fp - (fold_T *)gap->ga_data);
			    if (i != 0)
			    {
				fp2 = fp - 1;
				if (fp2->fd_top + fp2->fd_len == fp->fd_top)
				{
				    foldMerge(fp2, gap, fp);
				    fp = fp2;
				}
			    }
			}
			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,
				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!
		    if (gap->ga_len == 0)
			i = 0;
		    else
			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;
    }
    else if (fp->fd_top + fp->fd_len > linecount)
	// running into the end of the buffer (deleted last line)
	fp->fd_len = linecount - fp->fd_top + 1;

    // 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 - 1 > bot)
	    {
		// 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) == FAIL)
	return FAIL;
    fp = (fold_T *)gap->ga_data + i;
    if (gap->ga_len > 0 && i < gap->ga_len)
	mch_memmove(fp + 1, fp, sizeof(fold_T) * (gap->ga_len - i));
    ++gap->ga_len;
    ga_init2(&fp->fd_nested, 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);
    if (fp2 != NULL)
    {
	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

    while (gap->ga_len > 0)
    {
	// 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 - 1 > bot)
	    {
		// 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);
	}
    }
}

// foldReverseOrder() {{{2
    static void
foldReverseOrder(garray_T *gap, linenr_T start_arg, linenr_T end_arg)
{
    fold_T *left, *right;
    fold_T tmp;
    linenr_T start = start_arg;
    linenr_T end = end_arg;

    for (; start < end; start++, end--)
    {
	left = (fold_T *)gap->ga_data + start;
	right = (fold_T *)gap->ga_data + end;
	tmp  = *left;
	*left = *right;
	*right = tmp;
    }
}

// foldMoveRange() {{{2
/*
 * Move folds within the inclusive range "line1" to "line2" to after "dest"
 * requires "line1" <= "line2" <= "dest"
 *
 * There are the following situations for the first fold at or below line1 - 1.
 *       1  2  3  4
 *       1  2  3  4
 * line1    2  3  4
 *          2  3  4  5  6  7
 * line2       3  4  5  6  7
 *             3  4     6  7  8  9
 * dest           4        7  8  9
 *                4        7  8    10
 *                4        7  8    10
 *
 * In the following descriptions, "moved" means moving in the buffer, *and* in
 * the fold array.
 * Meanwhile, "shifted" just means moving in the buffer.
 * 1. not changed
 * 2. truncated above line1
 * 3. length reduced by  line2 - line1, folds starting between the end of 3 and
 *    dest are truncated and shifted up
 * 4. internal folds moved (from [line1, line2] to dest)
 * 5. moved to dest.
 * 6. truncated below line2 and moved.
 * 7. length reduced by line2 - dest, folds starting between line2 and dest are
 *    removed, top is moved down by move_len.
 * 8. truncated below dest and shifted up.
 * 9. shifted up
 * 10. not changed
 */

    static void
truncate_fold(fold_T *fp, linenr_T end)
{
    end += 1;
    foldRemove(&fp->fd_nested, end - fp->fd_top, MAXLNUM);
    fp->fd_len = end - fp->fd_top;
}

#define fold_end(fp) ((fp)->fd_top + (fp)->fd_len - 1)
#define valid_fold(fp, gap) ((gap)->ga_len > 0 && (fp) < ((fold_T *)(gap)->ga_data + (gap)->ga_len))
#define fold_index(fp, gap) ((size_t)((fp) - ((fold_T *)(gap)->ga_data)))

    void
foldMoveRange(garray_T *gap, linenr_T line1, linenr_T line2, linenr_T dest)
{
    fold_T *fp;
    linenr_T range_len = line2 - line1 + 1;
    linenr_T move_len = dest - line2;
    int at_start = foldFind(gap, line1 - 1, &fp);
    size_t move_start = 0, move_end = 0, dest_index = 0;

    if (at_start)
    {
	if (fold_end(fp) > dest)
	{
	    // Case 4
	   // don't have to change this fold, but have to move nested folds.
	    foldMoveRange(&fp->fd_nested, line1 - fp->fd_top, line2 -
		    fp->fd_top, dest - fp->fd_top);
	    return;
	}
	else if (fold_end(fp) > line2)
	{
	    // Case 3
	    // Remove nested folds between line1 and line2 & reduce the
	    // length of fold by "range_len".
	    // Folds after this one must be dealt with.
	    foldMarkAdjustRecurse(&fp->fd_nested, line1 - fp->fd_top, line2 -
		    fp->fd_top, MAXLNUM, -range_len);
	    fp->fd_len -= range_len;
	}
	else
	    // Case 2 truncate fold, folds after this one must be dealt with.
	    truncate_fold(fp, line1 - 1);

	// Look at the next fold, and treat that one as if it were the first
	// after  "line1" (because now it is).
	fp = fp + 1;
    }

    if (!valid_fold(fp, gap) || fp->fd_top > dest)
    {
	// Case 10
	// No folds after "line1" and before "dest"
	return;
    }
    else if (fp->fd_top > line2)
    {
	for (; valid_fold(fp, gap) && fold_end(fp) <= dest; fp++)
	// Case 9. (for all case 9's) -- shift up.
	    fp->fd_top -= range_len;

	if (valid_fold(fp, gap) && fp->fd_top <= dest)
	{
	    // Case 8. -- ensure truncated at dest, shift up
	    truncate_fold(fp, dest);
	    fp->fd_top -= range_len;
	}
	return;
    }
    else if (fold_end(fp) > dest)
    {
	// Case 7 -- remove nested folds and shrink
	foldMarkAdjustRecurse(&fp->fd_nested, line2 + 1 - fp->fd_top, dest -
		fp->fd_top, MAXLNUM, -move_len);
	fp->fd_len -= move_len;
	fp->fd_top += move_len;
	return;
    }

    // Case 5 or 6
    // changes rely on whether there are folds between the end of
    // this fold and "dest".
    move_start = fold_index(fp, gap);

    for (; valid_fold(fp, gap) && fp->fd_top <= dest; fp++)
    {
	if (fp->fd_top <= line2)
	{
	    // 1. 2. or 3.
	    if (fold_end(fp) > line2)
		// 2. or 3., truncate before moving
		truncate_fold(fp, line2);

	    fp->fd_top += move_len;
	    continue;
	}

	// Record index of the first fold after the moved range.
	if (move_end == 0)
	    move_end = fold_index(fp, gap);

	if (fold_end(fp) > dest)
	    truncate_fold(fp, dest);

	fp->fd_top -= range_len;
    }

    dest_index = fold_index(fp, gap);

    /*
     * All folds are now correct, but not necessarily in the correct order.  We
     * must swap folds in the range [move_end, dest_index) with those in the
     * range [move_start, move_end).
     */
    if (move_end == 0)
	// There are no folds after those moved, hence no folds have been moved
	// out of order.
	return;
    foldReverseOrder(gap, (linenr_T)move_start, (linenr_T)dest_index - 1);
    foldReverseOrder(gap, (linenr_T)move_start,
			   (linenr_T)(move_start + dest_index - move_end - 1));
    foldReverseOrder(gap, (linenr_T)(move_start + dest_index - move_end),
						   (linenr_T)(dest_index - 1));
}
#undef fold_end
#undef valid_fold
#undef fold_index

// 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(buf);
    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 = eval_foldexpr(flp->wp, &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 '<': // To prevent an unexpected start of a new fold, the next
		  // level must not exceed the level of the current fold.
		  flp->lvl_next = MIN(flp->lvl, 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
		|| put_line(fd, "let &fdl = &fdl") == 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)

#if defined(FEAT_EVAL) || defined(PROTO)

/*
 * "foldclosed()" and "foldclosedend()" functions
 */
    static void
foldclosed_both(
    typval_T	*argvars UNUSED,
    typval_T	*rettv,
    int		end UNUSED)
{
# ifdef FEAT_FOLDING
    linenr_T	lnum;
    linenr_T	first, last;

    if (in_vim9script() && check_for_lnum_arg(argvars, 0) == FAIL)
	return;

    lnum = tv_get_lnum(argvars);
    if (lnum >= 1 && lnum <= curbuf->b_ml.ml_line_count)
    {
	if (hasFoldingWin(curwin, lnum, &first, &last, FALSE, NULL))
	{
	    if (end)
		rettv->vval.v_number = (varnumber_T)last;
	    else
		rettv->vval.v_number = (varnumber_T)first;
	    return;
	}
    }
#endif
    rettv->vval.v_number = -1;
}

/*
 * "foldclosed()" function
 */
    void
f_foldclosed(typval_T *argvars, typval_T *rettv)
{
    foldclosed_both(argvars, rettv, FALSE);
}

/*
 * "foldclosedend()" function
 */
    void
f_foldclosedend(typval_T *argvars, typval_T *rettv)
{
    foldclosed_both(argvars, rettv, TRUE);
}

/*
 * "foldlevel()" function
 */
    void
f_foldlevel(typval_T *argvars UNUSED, typval_T *rettv UNUSED)
{
# ifdef FEAT_FOLDING
    linenr_T	lnum;

    if (in_vim9script() && check_for_lnum_arg(argvars, 0) == FAIL)
	return;

    lnum = tv_get_lnum(argvars);
    if (lnum >= 1 && lnum <= curbuf->b_ml.ml_line_count)
	rettv->vval.v_number = foldLevel(lnum);
# endif
}

/*
 * "foldtext()" function
 */
    void
f_foldtext(typval_T *argvars UNUSED, typval_T *rettv)
{
# ifdef FEAT_FOLDING
    linenr_T	foldstart;
    linenr_T	foldend;
    char_u	*dashes;
    linenr_T	lnum;
    char_u	*s;
    char_u	*r;
    int		len;
    char	*txt;
    long	count;
# endif

    rettv->v_type = VAR_STRING;
    rettv->vval.v_string = NULL;
# ifdef FEAT_FOLDING
    foldstart = (linenr_T)get_vim_var_nr(VV_FOLDSTART);
    foldend = (linenr_T)get_vim_var_nr(VV_FOLDEND);
    dashes = get_vim_var_str(VV_FOLDDASHES);
    if (foldstart > 0 && foldend <= curbuf->b_ml.ml_line_count
	    && dashes != NULL)
    {
	// Find first non-empty line in the fold.
	for (lnum = foldstart; lnum < foldend; ++lnum)
	    if (!linewhite(lnum))
		break;

	// Find interesting text in this line.
	s = skipwhite(ml_get(lnum));
	// skip C comment-start
	if (s[0] == '/' && (s[1] == '*' || s[1] == '/'))
	{
	    s = skipwhite(s + 2);
	    if (*skipwhite(s) == NUL
			    && lnum + 1 < (linenr_T)get_vim_var_nr(VV_FOLDEND))
	    {
		s = skipwhite(ml_get(lnum + 1));
		if (*s == '*')
		    s = skipwhite(s + 1);
	    }
	}
	count = (long)(foldend - foldstart + 1);
	txt = NGETTEXT("+-%s%3ld line: ", "+-%s%3ld lines: ", count);
	r = alloc(STRLEN(txt)
		    + STRLEN(dashes)	    // for %s
		    + 20		    // for %3ld
		    + STRLEN(s));	    // concatenated
	if (r != NULL)
	{
	    sprintf((char *)r, txt, dashes, count);
	    len = (int)STRLEN(r);
	    STRCAT(r, s);
	    // remove 'foldmarker' and 'commentstring'
	    foldtext_cleanup(r + len);
	    rettv->vval.v_string = r;
	}
    }
# endif
}

/*
 * "foldtextresult(lnum)" function
 */
    void
f_foldtextresult(typval_T *argvars UNUSED, typval_T *rettv)
{
# ifdef FEAT_FOLDING
    linenr_T	lnum;
    char_u	*text;
    char_u	buf[FOLD_TEXT_LEN];
    foldinfo_T  foldinfo;
    int		fold_count;
    static int	entered = FALSE;
# endif

    rettv->v_type = VAR_STRING;
    rettv->vval.v_string = NULL;

    if (in_vim9script() && check_for_lnum_arg(argvars, 0) == FAIL)
	return;

# ifdef FEAT_FOLDING
    if (entered)
	return; // reject recursive use
    entered = TRUE;

    lnum = tv_get_lnum(argvars);
    // treat illegal types and illegal string values for {lnum} the same
    if (lnum < 0)
	lnum = 0;
    fold_count = foldedCount(curwin, lnum, &foldinfo);
    if (fold_count > 0)
    {
	text = get_foldtext(curwin, lnum, lnum + fold_count - 1,
							       &foldinfo, buf);
	if (text == buf)
	    text = vim_strsave(text);
	rettv->vval.v_string = text;
    }

    entered = FALSE;
# endif
}

#endif // FEAT_EVAL