new file mode 100644
--- /dev/null
+++ b/src/change.c
@@ -0,0 +1,2165 @@
+/* vi:set ts=8 sts=4 sw=4 noet:
+ *
+ * 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.
+ */
+
+/*
+ * change.c: functions related to changing text
+ */
+
+#include "vim.h"
+
+/*
+ * If the file is readonly, give a warning message with the first change.
+ * Don't do this for autocommands.
+ * Doesn't use emsg(), because it flushes the macro buffer.
+ * If we have undone all changes b_changed will be FALSE, but "b_did_warn"
+ * will be TRUE.
+ * "col" is the column for the message; non-zero when in insert mode and
+ * 'showmode' is on.
+ * Careful: may trigger autocommands that reload the buffer.
+ */
+    void
+change_warning(int col)
+{
+    static char *w_readonly = N_("W10: Warning: Changing a readonly file");
+
+    if (curbuf->b_did_warn == FALSE
+	    && curbufIsChanged() == 0
+	    && !autocmd_busy
+	    && curbuf->b_p_ro)
+    {
+	++curbuf_lock;
+	apply_autocmds(EVENT_FILECHANGEDRO, NULL, NULL, FALSE, curbuf);
+	--curbuf_lock;
+	if (!curbuf->b_p_ro)
+	    return;
+
+	// Do what msg() does, but with a column offset if the warning should
+	// be after the mode message.
+	msg_start();
+	if (msg_row == Rows - 1)
+	    msg_col = col;
+	msg_source(HL_ATTR(HLF_W));
+	msg_puts_attr(_(w_readonly), HL_ATTR(HLF_W) | MSG_HIST);
+#ifdef FEAT_EVAL
+	set_vim_var_string(VV_WARNINGMSG, (char_u *)_(w_readonly), -1);
+#endif
+	msg_clr_eos();
+	(void)msg_end();
+	if (msg_silent == 0 && !silent_mode
+#ifdef FEAT_EVAL
+		&& time_for_testing != 1
+#endif
+		)
+	{
+	    out_flush();
+	    ui_delay(1000L, TRUE); // give the user time to think about it
+	}
+	curbuf->b_did_warn = TRUE;
+	redraw_cmdline = FALSE;	// don't redraw and erase the message
+	if (msg_row < Rows - 1)
+	    showmode();
+    }
+}
+
+/*
+ * Call this function when something in the current buffer is changed.
+ *
+ * Most often called through changed_bytes() and changed_lines(), which also
+ * mark the area of the display to be redrawn.
+ *
+ * Careful: may trigger autocommands that reload the buffer.
+ */
+    void
+changed(void)
+{
+#if defined(FEAT_XIM) && defined(FEAT_GUI_GTK)
+    if (p_imst == IM_ON_THE_SPOT)
+    {
+	// The text of the preediting area is inserted, but this doesn't
+	// mean a change of the buffer yet.  That is delayed until the
+	// text is committed. (this means preedit becomes empty)
+	if (im_is_preediting() && !xim_changed_while_preediting)
+	    return;
+	xim_changed_while_preediting = FALSE;
+    }
+#endif
+
+    if (!curbuf->b_changed)
+    {
+	int	save_msg_scroll = msg_scroll;
+
+	// Give a warning about changing a read-only file.  This may also
+	// check-out the file, thus change "curbuf"!
+	change_warning(0);
+
+	// Create a swap file if that is wanted.
+	// Don't do this for "nofile" and "nowrite" buffer types.
+	if (curbuf->b_may_swap
+#ifdef FEAT_QUICKFIX
+		&& !bt_dontwrite(curbuf)
+#endif
+		)
+	{
+	    int save_need_wait_return = need_wait_return;
+
+	    need_wait_return = FALSE;
+	    ml_open_file(curbuf);
+
+	    // The ml_open_file() can cause an ATTENTION message.
+	    // Wait two seconds, to make sure the user reads this unexpected
+	    // message.  Since we could be anywhere, call wait_return() now,
+	    // and don't let the emsg() set msg_scroll.
+	    if (need_wait_return && emsg_silent == 0)
+	    {
+		out_flush();
+		ui_delay(2000L, TRUE);
+		wait_return(TRUE);
+		msg_scroll = save_msg_scroll;
+	    }
+	    else
+		need_wait_return = save_need_wait_return;
+	}
+	changed_internal();
+    }
+    ++CHANGEDTICK(curbuf);
+
+#ifdef FEAT_SEARCH_EXTRA
+    // If a pattern is highlighted, the position may now be invalid.
+    highlight_match = FALSE;
+#endif
+}
+
+/*
+ * Internal part of changed(), no user interaction.
+ * Also used for recovery.
+ */
+    void
+changed_internal(void)
+{
+    curbuf->b_changed = TRUE;
+    ml_setflags(curbuf);
+    check_status(curbuf);
+    redraw_tabline = TRUE;
+#ifdef FEAT_TITLE
+    need_maketitle = TRUE;	    // set window title later
+#endif
+}
+
+/*
+ * Common code for when a change was made.
+ * See changed_lines() for the arguments.
+ * Careful: may trigger autocommands that reload the buffer.
+ */
+    static void
+changed_common(
+    linenr_T	lnum,
+    colnr_T	col,
+    linenr_T	lnume,
+    long	xtra)
+{
+    win_T	*wp;
+    tabpage_T	*tp;
+    int		i;
+#ifdef FEAT_JUMPLIST
+    int		cols;
+    pos_T	*p;
+    int		add;
+#endif
+
+    // mark the buffer as modified
+    changed();
+
+#ifdef FEAT_DIFF
+    if (curwin->w_p_diff && diff_internal())
+	curtab->tp_diff_update = TRUE;
+#endif
+
+    // set the '. mark
+    if (!cmdmod.keepjumps)
+    {
+	curbuf->b_last_change.lnum = lnum;
+	curbuf->b_last_change.col = col;
+
+#ifdef FEAT_JUMPLIST
+	// Create a new entry if a new undo-able change was started or we
+	// don't have an entry yet.
+	if (curbuf->b_new_change || curbuf->b_changelistlen == 0)
+	{
+	    if (curbuf->b_changelistlen == 0)
+		add = TRUE;
+	    else
+	    {
+		// Don't create a new entry when the line number is the same
+		// as the last one and the column is not too far away.  Avoids
+		// creating many entries for typing "xxxxx".
+		p = &curbuf->b_changelist[curbuf->b_changelistlen - 1];
+		if (p->lnum != lnum)
+		    add = TRUE;
+		else
+		{
+		    cols = comp_textwidth(FALSE);
+		    if (cols == 0)
+			cols = 79;
+		    add = (p->col + cols < col || col + cols < p->col);
+		}
+	    }
+	    if (add)
+	    {
+		// This is the first of a new sequence of undo-able changes
+		// and it's at some distance of the last change.  Use a new
+		// position in the changelist.
+		curbuf->b_new_change = FALSE;
+
+		if (curbuf->b_changelistlen == JUMPLISTSIZE)
+		{
+		    // changelist is full: remove oldest entry
+		    curbuf->b_changelistlen = JUMPLISTSIZE - 1;
+		    mch_memmove(curbuf->b_changelist, curbuf->b_changelist + 1,
+					  sizeof(pos_T) * (JUMPLISTSIZE - 1));
+		    FOR_ALL_TAB_WINDOWS(tp, wp)
+		    {
+			// Correct position in changelist for other windows on
+			// this buffer.
+			if (wp->w_buffer == curbuf && wp->w_changelistidx > 0)
+			    --wp->w_changelistidx;
+		    }
+		}
+		FOR_ALL_TAB_WINDOWS(tp, wp)
+		{
+		    // For other windows, if the position in the changelist is
+		    // at the end it stays at the end.
+		    if (wp->w_buffer == curbuf
+			    && wp->w_changelistidx == curbuf->b_changelistlen)
+			++wp->w_changelistidx;
+		}
+		++curbuf->b_changelistlen;
+	    }
+	}
+	curbuf->b_changelist[curbuf->b_changelistlen - 1] =
+							curbuf->b_last_change;
+	// The current window is always after the last change, so that "g,"
+	// takes you back to it.
+	curwin->w_changelistidx = curbuf->b_changelistlen;
+#endif
+    }
+
+    FOR_ALL_TAB_WINDOWS(tp, wp)
+    {
+	if (wp->w_buffer == curbuf)
+	{
+	    // Mark this window to be redrawn later.
+	    if (wp->w_redr_type < VALID)
+		wp->w_redr_type = VALID;
+
+	    // Check if a change in the buffer has invalidated the cached
+	    // values for the cursor.
+#ifdef FEAT_FOLDING
+	    // Update the folds for this window.  Can't postpone this, because
+	    // a following operator might work on the whole fold: ">>dd".
+	    foldUpdate(wp, lnum, lnume + xtra - 1);
+
+	    // The change may cause lines above or below the change to become
+	    // included in a fold.  Set lnum/lnume to the first/last line that
+	    // might be displayed differently.
+	    // Set w_cline_folded here as an efficient way to update it when
+	    // inserting lines just above a closed fold.
+	    i = hasFoldingWin(wp, lnum, &lnum, NULL, FALSE, NULL);
+	    if (wp->w_cursor.lnum == lnum)
+		wp->w_cline_folded = i;
+	    i = hasFoldingWin(wp, lnume, NULL, &lnume, FALSE, NULL);
+	    if (wp->w_cursor.lnum == lnume)
+		wp->w_cline_folded = i;
+
+	    // If the changed line is in a range of previously folded lines,
+	    // compare with the first line in that range.
+	    if (wp->w_cursor.lnum <= lnum)
+	    {
+		i = find_wl_entry(wp, lnum);
+		if (i >= 0 && wp->w_cursor.lnum > wp->w_lines[i].wl_lnum)
+		    changed_line_abv_curs_win(wp);
+	    }
+#endif
+
+	    if (wp->w_cursor.lnum > lnum)
+		changed_line_abv_curs_win(wp);
+	    else if (wp->w_cursor.lnum == lnum && wp->w_cursor.col >= col)
+		changed_cline_bef_curs_win(wp);
+	    if (wp->w_botline >= lnum)
+	    {
+		// Assume that botline doesn't change (inserted lines make
+		// other lines scroll down below botline).
+		approximate_botline_win(wp);
+	    }
+
+	    // Check if any w_lines[] entries have become invalid.
+	    // For entries below the change: Correct the lnums for
+	    // inserted/deleted lines.  Makes it possible to stop displaying
+	    // after the change.
+	    for (i = 0; i < wp->w_lines_valid; ++i)
+		if (wp->w_lines[i].wl_valid)
+		{
+		    if (wp->w_lines[i].wl_lnum >= lnum)
+		    {
+			if (wp->w_lines[i].wl_lnum < lnume)
+			{
+			    // line included in change
+			    wp->w_lines[i].wl_valid = FALSE;
+			}
+			else if (xtra != 0)
+			{
+			    // line below change
+			    wp->w_lines[i].wl_lnum += xtra;
+#ifdef FEAT_FOLDING
+			    wp->w_lines[i].wl_lastlnum += xtra;
+#endif
+			}
+		    }
+#ifdef FEAT_FOLDING
+		    else if (wp->w_lines[i].wl_lastlnum >= lnum)
+		    {
+			// change somewhere inside this range of folded lines,
+			// may need to be redrawn
+			wp->w_lines[i].wl_valid = FALSE;
+		    }
+#endif
+		}
+
+#ifdef FEAT_FOLDING
+	    // Take care of side effects for setting w_topline when folds have
+	    // changed.  Esp. when the buffer was changed in another window.
+	    if (hasAnyFolding(wp))
+		set_topline(wp, wp->w_topline);
+#endif
+	    // relative numbering may require updating more
+	    if (wp->w_p_rnu)
+		redraw_win_later(wp, SOME_VALID);
+	}
+    }
+
+    // Call update_screen() later, which checks out what needs to be redrawn,
+    // since it notices b_mod_set and then uses b_mod_*.
+    if (must_redraw < VALID)
+	must_redraw = VALID;
+
+    // when the cursor line is changed always trigger CursorMoved
+    if (lnum <= curwin->w_cursor.lnum
+		 && lnume + (xtra < 0 ? -xtra : xtra) > curwin->w_cursor.lnum)
+	last_cursormoved.lnum = 0;
+}
+
+    static void
+changedOneline(buf_T *buf, linenr_T lnum)
+{
+    if (buf->b_mod_set)
+    {
+	// find the maximum area that must be redisplayed
+	if (lnum < buf->b_mod_top)
+	    buf->b_mod_top = lnum;
+	else if (lnum >= buf->b_mod_bot)
+	    buf->b_mod_bot = lnum + 1;
+    }
+    else
+    {
+	// set the area that must be redisplayed to one line
+	buf->b_mod_set = TRUE;
+	buf->b_mod_top = lnum;
+	buf->b_mod_bot = lnum + 1;
+	buf->b_mod_xlines = 0;
+    }
+}
+
+/*
+ * Changed bytes within a single line for the current buffer.
+ * - marks the windows on this buffer to be redisplayed
+ * - marks the buffer changed by calling changed()
+ * - invalidates cached values
+ * Careful: may trigger autocommands that reload the buffer.
+ */
+    void
+changed_bytes(linenr_T lnum, colnr_T col)
+{
+    changedOneline(curbuf, lnum);
+    changed_common(lnum, col, lnum + 1, 0L);
+
+#ifdef FEAT_DIFF
+    // Diff highlighting in other diff windows may need to be updated too.
+    if (curwin->w_p_diff)
+    {
+	win_T	    *wp;
+	linenr_T    wlnum;
+
+	FOR_ALL_WINDOWS(wp)
+	    if (wp->w_p_diff && wp != curwin)
+	    {
+		redraw_win_later(wp, VALID);
+		wlnum = diff_lnum_win(lnum, wp);
+		if (wlnum > 0)
+		    changedOneline(wp->w_buffer, wlnum);
+	    }
+    }
+#endif
+}
+
+/*
+ * Like changed_bytes() but also adjust text properties for "added" bytes.
+ * When "added" is negative text was deleted.
+ */
+    void
+inserted_bytes(linenr_T lnum, colnr_T col, int added UNUSED)
+{
+    changed_bytes(lnum, col);
+
+#ifdef FEAT_TEXT_PROP
+    if (curbuf->b_has_textprop && added != 0)
+	adjust_prop_columns(lnum, col, added);
+#endif
+}
+
+/*
+ * Appended "count" lines below line "lnum" in the current buffer.
+ * Must be called AFTER the change and after mark_adjust().
+ * Takes care of marking the buffer to be redrawn and sets the changed flag.
+ */
+    void
+appended_lines(linenr_T lnum, long count)
+{
+    changed_lines(lnum + 1, 0, lnum + 1, count);
+}
+
+/*
+ * Like appended_lines(), but adjust marks first.
+ */
+    void
+appended_lines_mark(linenr_T lnum, long count)
+{
+    // Skip mark_adjust when adding a line after the last one, there can't
+    // be marks there. But it's still needed in diff mode.
+    if (lnum + count < curbuf->b_ml.ml_line_count
+#ifdef FEAT_DIFF
+	    || curwin->w_p_diff
+#endif
+	)
+	mark_adjust(lnum + 1, (linenr_T)MAXLNUM, count, 0L);
+    changed_lines(lnum + 1, 0, lnum + 1, count);
+}
+
+/*
+ * Deleted "count" lines at line "lnum" in the current buffer.
+ * Must be called AFTER the change and after mark_adjust().
+ * Takes care of marking the buffer to be redrawn and sets the changed flag.
+ */
+    void
+deleted_lines(linenr_T lnum, long count)
+{
+    changed_lines(lnum, 0, lnum + count, -count);
+}
+
+/*
+ * Like deleted_lines(), but adjust marks first.
+ * Make sure the cursor is on a valid line before calling, a GUI callback may
+ * be triggered to display the cursor.
+ */
+    void
+deleted_lines_mark(linenr_T lnum, long count)
+{
+    mark_adjust(lnum, (linenr_T)(lnum + count - 1), (long)MAXLNUM, -count);
+    changed_lines(lnum, 0, lnum + count, -count);
+}
+
+/*
+ * Marks the area to be redrawn after a change.
+ */
+    static void
+changed_lines_buf(
+    buf_T	*buf,
+    linenr_T	lnum,	    // first line with change
+    linenr_T	lnume,	    // line below last changed line
+    long	xtra)	    // number of extra lines (negative when deleting)
+{
+    if (buf->b_mod_set)
+    {
+	// find the maximum area that must be redisplayed
+	if (lnum < buf->b_mod_top)
+	    buf->b_mod_top = lnum;
+	if (lnum < buf->b_mod_bot)
+	{
+	    // adjust old bot position for xtra lines
+	    buf->b_mod_bot += xtra;
+	    if (buf->b_mod_bot < lnum)
+		buf->b_mod_bot = lnum;
+	}
+	if (lnume + xtra > buf->b_mod_bot)
+	    buf->b_mod_bot = lnume + xtra;
+	buf->b_mod_xlines += xtra;
+    }
+    else
+    {
+	// set the area that must be redisplayed
+	buf->b_mod_set = TRUE;
+	buf->b_mod_top = lnum;
+	buf->b_mod_bot = lnume + xtra;
+	buf->b_mod_xlines = xtra;
+    }
+}
+
+/*
+ * Changed lines for the current buffer.
+ * Must be called AFTER the change and after mark_adjust().
+ * - mark the buffer changed by calling changed()
+ * - mark the windows on this buffer to be redisplayed
+ * - invalidate cached values
+ * "lnum" is the first line that needs displaying, "lnume" the first line
+ * below the changed lines (BEFORE the change).
+ * When only inserting lines, "lnum" and "lnume" are equal.
+ * Takes care of calling changed() and updating b_mod_*.
+ * Careful: may trigger autocommands that reload the buffer.
+ */
+    void
+changed_lines(
+    linenr_T	lnum,	    // first line with change
+    colnr_T	col,	    // column in first line with change
+    linenr_T	lnume,	    // line below last changed line
+    long	xtra)	    // number of extra lines (negative when deleting)
+{
+    changed_lines_buf(curbuf, lnum, lnume, xtra);
+
+#ifdef FEAT_DIFF
+    if (xtra == 0 && curwin->w_p_diff && !diff_internal())
+    {
+	// When the number of lines doesn't change then mark_adjust() isn't
+	// called and other diff buffers still need to be marked for
+	// displaying.
+	win_T	    *wp;
+	linenr_T    wlnum;
+
+	FOR_ALL_WINDOWS(wp)
+	    if (wp->w_p_diff && wp != curwin)
+	    {
+		redraw_win_later(wp, VALID);
+		wlnum = diff_lnum_win(lnum, wp);
+		if (wlnum > 0)
+		    changed_lines_buf(wp->w_buffer, wlnum,
+						    lnume - lnum + wlnum, 0L);
+	    }
+    }
+#endif
+
+    changed_common(lnum, col, lnume, xtra);
+}
+
+/*
+ * Called when the changed flag must be reset for buffer "buf".
+ * When "ff" is TRUE also reset 'fileformat'.
+ */
+    void
+unchanged(buf_T *buf, int ff)
+{
+    if (buf->b_changed || (ff && file_ff_differs(buf, FALSE)))
+    {
+	buf->b_changed = 0;
+	ml_setflags(buf);
+	if (ff)
+	    save_file_ff(buf);
+	check_status(buf);
+	redraw_tabline = TRUE;
+#ifdef FEAT_TITLE
+	need_maketitle = TRUE;	    // set window title later
+#endif
+    }
+    ++CHANGEDTICK(buf);
+#ifdef FEAT_NETBEANS_INTG
+    netbeans_unmodified(buf);
+#endif
+}
+
+/*
+ * Insert string "p" at the cursor position.  Stops at a NUL byte.
+ * Handles Replace mode and multi-byte characters.
+ */
+    void
+ins_bytes(char_u *p)
+{
+    ins_bytes_len(p, (int)STRLEN(p));
+}
+
+/*
+ * Insert string "p" with length "len" at the cursor position.
+ * Handles Replace mode and multi-byte characters.
+ */
+    void
+ins_bytes_len(char_u *p, int len)
+{
+    int		i;
+    int		n;
+
+    if (has_mbyte)
+	for (i = 0; i < len; i += n)
+	{
+	    if (enc_utf8)
+		// avoid reading past p[len]
+		n = utfc_ptr2len_len(p + i, len - i);
+	    else
+		n = (*mb_ptr2len)(p + i);
+	    ins_char_bytes(p + i, n);
+	}
+    else
+	for (i = 0; i < len; ++i)
+	    ins_char(p[i]);
+}
+
+/*
+ * Insert or replace a single character at the cursor position.
+ * When in REPLACE or VREPLACE mode, replace any existing character.
+ * Caller must have prepared for undo.
+ * For multi-byte characters we get the whole character, the caller must
+ * convert bytes to a character.
+ */
+    void
+ins_char(int c)
+{
+    char_u	buf[MB_MAXBYTES + 1];
+    int		n = (*mb_char2bytes)(c, buf);
+
+    // When "c" is 0x100, 0x200, etc. we don't want to insert a NUL byte.
+    // Happens for CTRL-Vu9900.
+    if (buf[0] == 0)
+	buf[0] = '\n';
+
+    ins_char_bytes(buf, n);
+}
+
+    void
+ins_char_bytes(char_u *buf, int charlen)
+{
+    int		c = buf[0];
+    int		newlen;		// nr of bytes inserted
+    int		oldlen;		// nr of bytes deleted (0 when not replacing)
+    char_u	*p;
+    char_u	*newp;
+    char_u	*oldp;
+    int		linelen;	// length of old line including NUL
+    colnr_T	col;
+    linenr_T	lnum = curwin->w_cursor.lnum;
+    int		i;
+
+    // Break tabs if needed.
+    if (virtual_active() && curwin->w_cursor.coladd > 0)
+	coladvance_force(getviscol());
+
+    col = curwin->w_cursor.col;
+    oldp = ml_get(lnum);
+    linelen = (int)STRLEN(oldp) + 1;
+
+    // The lengths default to the values for when not replacing.
+    oldlen = 0;
+    newlen = charlen;
+
+    if (State & REPLACE_FLAG)
+    {
+	if (State & VREPLACE_FLAG)
+	{
+	    colnr_T	new_vcol = 0;   // init for GCC
+	    colnr_T	vcol;
+	    int		old_list;
+
+	    // Disable 'list' temporarily, unless 'cpo' contains the 'L' flag.
+	    // Returns the old value of list, so when finished,
+	    // curwin->w_p_list should be set back to this.
+	    old_list = curwin->w_p_list;
+	    if (old_list && vim_strchr(p_cpo, CPO_LISTWM) == NULL)
+		curwin->w_p_list = FALSE;
+
+	    // In virtual replace mode each character may replace one or more
+	    // characters (zero if it's a TAB).  Count the number of bytes to
+	    // be deleted to make room for the new character, counting screen
+	    // cells.  May result in adding spaces to fill a gap.
+	    getvcol(curwin, &curwin->w_cursor, NULL, &vcol, NULL);
+	    new_vcol = vcol + chartabsize(buf, vcol);
+	    while (oldp[col + oldlen] != NUL && vcol < new_vcol)
+	    {
+		vcol += chartabsize(oldp + col + oldlen, vcol);
+		// Don't need to remove a TAB that takes us to the right
+		// position.
+		if (vcol > new_vcol && oldp[col + oldlen] == TAB)
+		    break;
+		oldlen += (*mb_ptr2len)(oldp + col + oldlen);
+		// Deleted a bit too much, insert spaces.
+		if (vcol > new_vcol)
+		    newlen += vcol - new_vcol;
+	    }
+	    curwin->w_p_list = old_list;
+	}
+	else if (oldp[col] != NUL)
+	{
+	    // normal replace
+	    oldlen = (*mb_ptr2len)(oldp + col);
+	}
+
+
+	// Push the replaced bytes onto the replace stack, so that they can be
+	// put back when BS is used.  The bytes of a multi-byte character are
+	// done the other way around, so that the first byte is popped off
+	// first (it tells the byte length of the character).
+	replace_push(NUL);
+	for (i = 0; i < oldlen; ++i)
+	{
+	    if (has_mbyte)
+		i += replace_push_mb(oldp + col + i) - 1;
+	    else
+		replace_push(oldp[col + i]);
+	}
+    }
+
+    newp = alloc_check((unsigned)(linelen + newlen - oldlen));
+    if (newp == NULL)
+	return;
+
+    // Copy bytes before the cursor.
+    if (col > 0)
+	mch_memmove(newp, oldp, (size_t)col);
+
+    // Copy bytes after the changed character(s).
+    p = newp + col;
+    if (linelen > col + oldlen)
+	mch_memmove(p + newlen, oldp + col + oldlen,
+					    (size_t)(linelen - col - oldlen));
+
+    // Insert or overwrite the new character.
+    mch_memmove(p, buf, charlen);
+    i = charlen;
+
+    // Fill with spaces when necessary.
+    while (i < newlen)
+	p[i++] = ' ';
+
+    // Replace the line in the buffer.
+    ml_replace(lnum, newp, FALSE);
+
+    // mark the buffer as changed and prepare for displaying
+    inserted_bytes(lnum, col, newlen - oldlen);
+
+    // If we're in Insert or Replace mode and 'showmatch' is set, then briefly
+    // show the match for right parens and braces.
+    if (p_sm && (State & INSERT)
+	    && msg_silent == 0
+#ifdef FEAT_INS_EXPAND
+	    && !ins_compl_active()
+#endif
+       )
+    {
+	if (has_mbyte)
+	    showmatch(mb_ptr2char(buf));
+	else
+	    showmatch(c);
+    }
+
+#ifdef FEAT_RIGHTLEFT
+    if (!p_ri || (State & REPLACE_FLAG))
+#endif
+    {
+	// Normal insert: move cursor right
+	curwin->w_cursor.col += charlen;
+    }
+
+    // TODO: should try to update w_row here, to avoid recomputing it later.
+}
+
+/*
+ * Insert a string at the cursor position.
+ * Note: Does NOT handle Replace mode.
+ * Caller must have prepared for undo.
+ */
+    void
+ins_str(char_u *s)
+{
+    char_u	*oldp, *newp;
+    int		newlen = (int)STRLEN(s);
+    int		oldlen;
+    colnr_T	col;
+    linenr_T	lnum = curwin->w_cursor.lnum;
+
+    if (virtual_active() && curwin->w_cursor.coladd > 0)
+	coladvance_force(getviscol());
+
+    col = curwin->w_cursor.col;
+    oldp = ml_get(lnum);
+    oldlen = (int)STRLEN(oldp);
+
+    newp = alloc_check((unsigned)(oldlen + newlen + 1));
+    if (newp == NULL)
+	return;
+    if (col > 0)
+	mch_memmove(newp, oldp, (size_t)col);
+    mch_memmove(newp + col, s, (size_t)newlen);
+    mch_memmove(newp + col + newlen, oldp + col, (size_t)(oldlen - col + 1));
+    ml_replace(lnum, newp, FALSE);
+    inserted_bytes(lnum, col, newlen);
+    curwin->w_cursor.col += newlen;
+}
+
+/*
+ * Delete one character under the cursor.
+ * If "fixpos" is TRUE, don't leave the cursor on the NUL after the line.
+ * Caller must have prepared for undo.
+ *
+ * return FAIL for failure, OK otherwise
+ */
+    int
+del_char(int fixpos)
+{
+    if (has_mbyte)
+    {
+	// Make sure the cursor is at the start of a character.
+	mb_adjust_cursor();
+	if (*ml_get_cursor() == NUL)
+	    return FAIL;
+	return del_chars(1L, fixpos);
+    }
+    return del_bytes(1L, fixpos, TRUE);
+}
+
+/*
+ * Like del_bytes(), but delete characters instead of bytes.
+ */
+    int
+del_chars(long count, int fixpos)
+{
+    long	bytes = 0;
+    long	i;
+    char_u	*p;
+    int		l;
+
+    p = ml_get_cursor();
+    for (i = 0; i < count && *p != NUL; ++i)
+    {
+	l = (*mb_ptr2len)(p);
+	bytes += l;
+	p += l;
+    }
+    return del_bytes(bytes, fixpos, TRUE);
+}
+
+/*
+ * Delete "count" bytes under the cursor.
+ * If "fixpos" is TRUE, don't leave the cursor on the NUL after the line.
+ * Caller must have prepared for undo.
+ *
+ * Return FAIL for failure, OK otherwise.
+ */
+    int
+del_bytes(
+    long	count,
+    int		fixpos_arg,
+    int		use_delcombine UNUSED)	    // 'delcombine' option applies
+{
+    char_u	*oldp, *newp;
+    colnr_T	oldlen;
+    colnr_T	newlen;
+    linenr_T	lnum = curwin->w_cursor.lnum;
+    colnr_T	col = curwin->w_cursor.col;
+    int		alloc_newp;
+    long	movelen;
+    int		fixpos = fixpos_arg;
+
+    oldp = ml_get(lnum);
+    oldlen = (int)STRLEN(oldp);
+
+    // Can't do anything when the cursor is on the NUL after the line.
+    if (col >= oldlen)
+	return FAIL;
+
+    // If "count" is zero there is nothing to do.
+    if (count == 0)
+	return OK;
+
+    // If "count" is negative the caller must be doing something wrong.
+    if (count < 1)
+    {
+	siemsg("E950: Invalid count for del_bytes(): %ld", count);
+	return FAIL;
+    }
+
+    // If 'delcombine' is set and deleting (less than) one character, only
+    // delete the last combining character.
+    if (p_deco && use_delcombine && enc_utf8
+					 && utfc_ptr2len(oldp + col) >= count)
+    {
+	int	cc[MAX_MCO];
+	int	n;
+
+	(void)utfc_ptr2char(oldp + col, cc);
+	if (cc[0] != NUL)
+	{
+	    // Find the last composing char, there can be several.
+	    n = col;
+	    do
+	    {
+		col = n;
+		count = utf_ptr2len(oldp + n);
+		n += count;
+	    } while (UTF_COMPOSINGLIKE(oldp + col, oldp + n));
+	    fixpos = 0;
+	}
+    }
+
+    // When count is too big, reduce it.
+    movelen = (long)oldlen - (long)col - count + 1; // includes trailing NUL
+    if (movelen <= 1)
+    {
+	// If we just took off the last character of a non-blank line, and
+	// fixpos is TRUE, we don't want to end up positioned at the NUL,
+	// unless "restart_edit" is set or 'virtualedit' contains "onemore".
+	if (col > 0 && fixpos && restart_edit == 0
+					      && (ve_flags & VE_ONEMORE) == 0)
+	{
+	    --curwin->w_cursor.col;
+	    curwin->w_cursor.coladd = 0;
+	    if (has_mbyte)
+		curwin->w_cursor.col -=
+			    (*mb_head_off)(oldp, oldp + curwin->w_cursor.col);
+	}
+	count = oldlen - col;
+	movelen = 1;
+    }
+    newlen = oldlen - count;
+
+    // If the old line has been allocated the deletion can be done in the
+    // existing line. Otherwise a new line has to be allocated
+    // Can't do this when using Netbeans, because we would need to invoke
+    // netbeans_removed(), which deallocates the line.  Let ml_replace() take
+    // care of notifying Netbeans.
+#ifdef FEAT_NETBEANS_INTG
+    if (netbeans_active())
+	alloc_newp = TRUE;
+    else
+#endif
+	alloc_newp = !ml_line_alloced();    // check if oldp was allocated
+    if (!alloc_newp)
+	newp = oldp;			    // use same allocated memory
+    else
+    {					    // need to allocate a new line
+	newp = alloc((unsigned)(newlen + 1));
+	if (newp == NULL)
+	    return FAIL;
+	mch_memmove(newp, oldp, (size_t)col);
+    }
+    mch_memmove(newp + col, oldp + col + count, (size_t)movelen);
+    if (alloc_newp)
+	ml_replace(lnum, newp, FALSE);
+#ifdef FEAT_TEXT_PROP
+    else
+    {
+	// Also move any following text properties.
+	if (oldlen + 1 < curbuf->b_ml.ml_line_len)
+	    mch_memmove(newp + newlen + 1, oldp + oldlen + 1,
+			       (size_t)curbuf->b_ml.ml_line_len - oldlen - 1);
+	curbuf->b_ml.ml_line_len -= count;
+    }
+#endif
+
+    // mark the buffer as changed and prepare for displaying
+    inserted_bytes(lnum, curwin->w_cursor.col, -count);
+
+    return OK;
+}
+
+/*
+ * Copy the indent from ptr to the current line (and fill to size)
+ * Leaves the cursor on the first non-blank in the line.
+ * Returns TRUE if the line was changed.
+ */
+    static int
+copy_indent(int size, char_u *src)
+{
+    char_u	*p = NULL;
+    char_u	*line = NULL;
+    char_u	*s;
+    int		todo;
+    int		ind_len;
+    int		line_len = 0;
+    int		tab_pad;
+    int		ind_done;
+    int		round;
+#ifdef FEAT_VARTABS
+    int		ind_col;
+#endif
+
+    // Round 1: compute the number of characters needed for the indent
+    // Round 2: copy the characters.
+    for (round = 1; round <= 2; ++round)
+    {
+	todo = size;
+	ind_len = 0;
+	ind_done = 0;
+#ifdef FEAT_VARTABS
+	ind_col = 0;
+#endif
+	s = src;
+
+	// Count/copy the usable portion of the source line
+	while (todo > 0 && VIM_ISWHITE(*s))
+	{
+	    if (*s == TAB)
+	    {
+#ifdef FEAT_VARTABS
+		tab_pad = tabstop_padding(ind_done, curbuf->b_p_ts,
+							curbuf->b_p_vts_array);
+#else
+		tab_pad = (int)curbuf->b_p_ts
+					   - (ind_done % (int)curbuf->b_p_ts);
+#endif
+		// Stop if this tab will overshoot the target
+		if (todo < tab_pad)
+		    break;
+		todo -= tab_pad;
+		ind_done += tab_pad;
+#ifdef FEAT_VARTABS
+		ind_col += tab_pad;
+#endif
+	    }
+	    else
+	    {
+		--todo;
+		++ind_done;
+#ifdef FEAT_VARTABS
+		++ind_col;
+#endif
+	    }
+	    ++ind_len;
+	    if (p != NULL)
+		*p++ = *s;
+	    ++s;
+	}
+
+	// Fill to next tabstop with a tab, if possible
+#ifdef FEAT_VARTABS
+	tab_pad = tabstop_padding(ind_done, curbuf->b_p_ts,
+							curbuf->b_p_vts_array);
+#else
+	tab_pad = (int)curbuf->b_p_ts - (ind_done % (int)curbuf->b_p_ts);
+#endif
+	if (todo >= tab_pad && !curbuf->b_p_et)
+	{
+	    todo -= tab_pad;
+	    ++ind_len;
+#ifdef FEAT_VARTABS
+	    ind_col += tab_pad;
+#endif
+	    if (p != NULL)
+		*p++ = TAB;
+	}
+
+	// Add tabs required for indent
+	if (!curbuf->b_p_et)
+	{
+#ifdef FEAT_VARTABS
+	    for (;;)
+	    {
+		tab_pad = tabstop_padding(ind_col, curbuf->b_p_ts,
+							curbuf->b_p_vts_array);
+		if (todo < tab_pad)
+		    break;
+		todo -= tab_pad;
+		++ind_len;
+		ind_col += tab_pad;
+		if (p != NULL)
+		    *p++ = TAB;
+	    }
+#else
+	    while (todo >= (int)curbuf->b_p_ts)
+	    {
+		todo -= (int)curbuf->b_p_ts;
+		++ind_len;
+		if (p != NULL)
+		    *p++ = TAB;
+	    }
+#endif
+	}
+
+	// Count/add spaces required for indent
+	while (todo > 0)
+	{
+	    --todo;
+	    ++ind_len;
+	    if (p != NULL)
+		*p++ = ' ';
+	}
+
+	if (p == NULL)
+	{
+	    // Allocate memory for the result: the copied indent, new indent
+	    // and the rest of the line.
+	    line_len = (int)STRLEN(ml_get_curline()) + 1;
+	    line = alloc(ind_len + line_len);
+	    if (line == NULL)
+		return FALSE;
+	    p = line;
+	}
+    }
+
+    // Append the original line
+    mch_memmove(p, ml_get_curline(), (size_t)line_len);
+
+    // Replace the line
+    ml_replace(curwin->w_cursor.lnum, line, FALSE);
+
+    // Put the cursor after the indent.
+    curwin->w_cursor.col = ind_len;
+    return TRUE;
+}
+
+/*
+ * open_line: Add a new line below or above the current line.
+ *
+ * For VREPLACE mode, we only add a new line when we get to the end of the
+ * file, otherwise we just start replacing the next line.
+ *
+ * Caller must take care of undo.  Since VREPLACE may affect any number of
+ * lines however, it may call u_save_cursor() again when starting to change a
+ * new line.
+ * "flags": OPENLINE_DELSPACES	delete spaces after cursor
+ *	    OPENLINE_DO_COM	format comments
+ *	    OPENLINE_KEEPTRAIL	keep trailing spaces
+ *	    OPENLINE_MARKFIX	adjust mark positions after the line break
+ *	    OPENLINE_COM_LIST	format comments with list or 2nd line indent
+ *
+ * "second_line_indent": indent for after ^^D in Insert mode or if flag
+ *			  OPENLINE_COM_LIST
+ *
+ * Return OK for success, FAIL for failure
+ */
+    int
+open_line(
+    int		dir,		// FORWARD or BACKWARD
+    int		flags,
+    int		second_line_indent)
+{
+    char_u	*saved_line;		// copy of the original line
+    char_u	*next_line = NULL;	// copy of the next line
+    char_u	*p_extra = NULL;	// what goes to next line
+    int		less_cols = 0;		// less columns for mark in new line
+    int		less_cols_off = 0;	// columns to skip for mark adjust
+    pos_T	old_cursor;		// old cursor position
+    int		newcol = 0;		// new cursor column
+    int		newindent = 0;		// auto-indent of the new line
+    int		n;
+    int		trunc_line = FALSE;	// truncate current line afterwards
+    int		retval = FAIL;		// return value
+#ifdef FEAT_COMMENTS
+    int		extra_len = 0;		// length of p_extra string
+    int		lead_len;		// length of comment leader
+    char_u	*lead_flags;	// position in 'comments' for comment leader
+    char_u	*leader = NULL;		// copy of comment leader
+#endif
+    char_u	*allocated = NULL;	// allocated memory
+    char_u	*p;
+    int		saved_char = NUL;	// init for GCC
+#if defined(FEAT_SMARTINDENT) || defined(FEAT_COMMENTS)
+    pos_T	*pos;
+#endif
+#ifdef FEAT_SMARTINDENT
+    int		do_si = (!p_paste && curbuf->b_p_si
+# ifdef FEAT_CINDENT
+					&& !curbuf->b_p_cin
+# endif
+# ifdef FEAT_EVAL
+					&& *curbuf->b_p_inde == NUL
+# endif
+			);
+    int		no_si = FALSE;		// reset did_si afterwards
+    int		first_char = NUL;	// init for GCC
+#endif
+#if defined(FEAT_LISP) || defined(FEAT_CINDENT)
+    int		vreplace_mode;
+#endif
+    int		did_append;		// appended a new line
+    int		saved_pi = curbuf->b_p_pi; // copy of preserveindent setting
+
+    // make a copy of the current line so we can mess with it
+    saved_line = vim_strsave(ml_get_curline());
+    if (saved_line == NULL)	    /* out of memory! */
+	return FALSE;
+
+    if (State & VREPLACE_FLAG)
+    {
+	// With VREPLACE we make a copy of the next line, which we will be
+	// starting to replace.  First make the new line empty and let vim play
+	// with the indenting and comment leader to its heart's content.  Then
+	// we grab what it ended up putting on the new line, put back the
+	// original line, and call ins_char() to put each new character onto
+	// the line, replacing what was there before and pushing the right
+	// stuff onto the replace stack.  -- webb.
+	if (curwin->w_cursor.lnum < orig_line_count)
+	    next_line = vim_strsave(ml_get(curwin->w_cursor.lnum + 1));
+	else
+	    next_line = vim_strsave((char_u *)"");
+	if (next_line == NULL)	    // out of memory!
+	    goto theend;
+
+	// In VREPLACE mode, a NL replaces the rest of the line, and starts
+	// replacing the next line, so push all of the characters left on the
+	// line onto the replace stack.  We'll push any other characters that
+	// might be replaced at the start of the next line (due to autoindent
+	// etc) a bit later.
+	replace_push(NUL);  // Call twice because BS over NL expects it
+	replace_push(NUL);
+	p = saved_line + curwin->w_cursor.col;
+	while (*p != NUL)
+	{
+	    if (has_mbyte)
+		p += replace_push_mb(p);
+	    else
+		replace_push(*p++);
+	}
+	saved_line[curwin->w_cursor.col] = NUL;
+    }
+
+    if ((State & INSERT) && !(State & VREPLACE_FLAG))
+    {
+	p_extra = saved_line + curwin->w_cursor.col;
+#ifdef FEAT_SMARTINDENT
+	if (do_si)		// need first char after new line break
+	{
+	    p = skipwhite(p_extra);
+	    first_char = *p;
+	}
+#endif
+#ifdef FEAT_COMMENTS
+	extra_len = (int)STRLEN(p_extra);
+#endif
+	saved_char = *p_extra;
+	*p_extra = NUL;
+    }
+
+    u_clearline();		// cannot do "U" command when adding lines
+#ifdef FEAT_SMARTINDENT
+    did_si = FALSE;
+#endif
+    ai_col = 0;
+
+    // If we just did an auto-indent, then we didn't type anything on
+    // the prior line, and it should be truncated.  Do this even if 'ai' is not
+    // set because automatically inserting a comment leader also sets did_ai.
+    if (dir == FORWARD && did_ai)
+	trunc_line = TRUE;
+
+    // If 'autoindent' and/or 'smartindent' is set, try to figure out what
+    // indent to use for the new line.
+    if (curbuf->b_p_ai
+#ifdef FEAT_SMARTINDENT
+			|| do_si
+#endif
+					    )
+    {
+	// count white space on current line
+#ifdef FEAT_VARTABS
+	newindent = get_indent_str_vtab(saved_line, curbuf->b_p_ts,
+						 curbuf->b_p_vts_array, FALSE);
+#else
+	newindent = get_indent_str(saved_line, (int)curbuf->b_p_ts, FALSE);
+#endif
+	if (newindent == 0 && !(flags & OPENLINE_COM_LIST))
+	    newindent = second_line_indent; // for ^^D command in insert mode
+
+#ifdef FEAT_SMARTINDENT
+	// Do smart indenting.
+	// In insert/replace mode (only when dir == FORWARD)
+	// we may move some text to the next line. If it starts with '{'
+	// don't add an indent. Fixes inserting a NL before '{' in line
+	//	"if (condition) {"
+	if (!trunc_line && do_si && *saved_line != NUL
+				    && (p_extra == NULL || first_char != '{'))
+	{
+	    char_u  *ptr;
+	    char_u  last_char;
+
+	    old_cursor = curwin->w_cursor;
+	    ptr = saved_line;
+# ifdef FEAT_COMMENTS
+	    if (flags & OPENLINE_DO_COM)
+		lead_len = get_leader_len(ptr, NULL, FALSE, TRUE);
+	    else
+		lead_len = 0;
+# endif
+	    if (dir == FORWARD)
+	    {
+		// Skip preprocessor directives, unless they are
+		// recognised as comments.
+		if (
+# ifdef FEAT_COMMENTS
+			lead_len == 0 &&
+# endif
+			ptr[0] == '#')
+		{
+		    while (ptr[0] == '#' && curwin->w_cursor.lnum > 1)
+			ptr = ml_get(--curwin->w_cursor.lnum);
+		    newindent = get_indent();
+		}
+# ifdef FEAT_COMMENTS
+		if (flags & OPENLINE_DO_COM)
+		    lead_len = get_leader_len(ptr, NULL, FALSE, TRUE);
+		else
+		    lead_len = 0;
+		if (lead_len > 0)
+		{
+		    // This case gets the following right:
+		    //	    /*
+		    //	     * A comment (read '\' as '/').
+		    //	     */
+		    // #define IN_THE_WAY
+		    //	    This should line up here;
+		    p = skipwhite(ptr);
+		    if (p[0] == '/' && p[1] == '*')
+			p++;
+		    if (p[0] == '*')
+		    {
+			for (p++; *p; p++)
+			{
+			    if (p[0] == '/' && p[-1] == '*')
+			    {
+				// End of C comment, indent should line up
+				// with the line containing the start of
+				// the comment
+				curwin->w_cursor.col = (colnr_T)(p - ptr);
+				if ((pos = findmatch(NULL, NUL)) != NULL)
+				{
+				    curwin->w_cursor.lnum = pos->lnum;
+				    newindent = get_indent();
+				}
+			    }
+			}
+		    }
+		}
+		else	// Not a comment line
+# endif
+		{
+		    // Find last non-blank in line
+		    p = ptr + STRLEN(ptr) - 1;
+		    while (p > ptr && VIM_ISWHITE(*p))
+			--p;
+		    last_char = *p;
+
+		    // find the character just before the '{' or ';'
+		    if (last_char == '{' || last_char == ';')
+		    {
+			if (p > ptr)
+			    --p;
+			while (p > ptr && VIM_ISWHITE(*p))
+			    --p;
+		    }
+		    // Try to catch lines that are split over multiple
+		    // lines.  eg:
+		    //	    if (condition &&
+		    //			condition) {
+		    //		Should line up here!
+		    //	    }
+		    if (*p == ')')
+		    {
+			curwin->w_cursor.col = (colnr_T)(p - ptr);
+			if ((pos = findmatch(NULL, '(')) != NULL)
+			{
+			    curwin->w_cursor.lnum = pos->lnum;
+			    newindent = get_indent();
+			    ptr = ml_get_curline();
+			}
+		    }
+		    // If last character is '{' do indent, without
+		    // checking for "if" and the like.
+		    if (last_char == '{')
+		    {
+			did_si = TRUE;	// do indent
+			no_si = TRUE;	// don't delete it when '{' typed
+		    }
+		    // Look for "if" and the like, use 'cinwords'.
+		    // Don't do this if the previous line ended in ';' or
+		    // '}'.
+		    else if (last_char != ';' && last_char != '}'
+						       && cin_is_cinword(ptr))
+			did_si = TRUE;
+		}
+	    }
+	    else // dir == BACKWARD
+	    {
+		// Skip preprocessor directives, unless they are
+		// recognised as comments.
+		if (
+# ifdef FEAT_COMMENTS
+			lead_len == 0 &&
+# endif
+			ptr[0] == '#')
+		{
+		    int was_backslashed = FALSE;
+
+		    while ((ptr[0] == '#' || was_backslashed) &&
+			 curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count)
+		    {
+			if (*ptr && ptr[STRLEN(ptr) - 1] == '\\')
+			    was_backslashed = TRUE;
+			else
+			    was_backslashed = FALSE;
+			ptr = ml_get(++curwin->w_cursor.lnum);
+		    }
+		    if (was_backslashed)
+			newindent = 0;	    // Got to end of file
+		    else
+			newindent = get_indent();
+		}
+		p = skipwhite(ptr);
+		if (*p == '}')	    // if line starts with '}': do indent
+		    did_si = TRUE;
+		else		    // can delete indent when '{' typed
+		    can_si_back = TRUE;
+	    }
+	    curwin->w_cursor = old_cursor;
+	}
+	if (do_si)
+	    can_si = TRUE;
+#endif // FEAT_SMARTINDENT
+
+	did_ai = TRUE;
+    }
+
+#ifdef FEAT_COMMENTS
+    // Find out if the current line starts with a comment leader.
+    // This may then be inserted in front of the new line.
+    end_comment_pending = NUL;
+    if (flags & OPENLINE_DO_COM)
+	lead_len = get_leader_len(saved_line, &lead_flags,
+							dir == BACKWARD, TRUE);
+    else
+	lead_len = 0;
+    if (lead_len > 0)
+    {
+	char_u	*lead_repl = NULL;	    // replaces comment leader
+	int	lead_repl_len = 0;	    // length of *lead_repl
+	char_u	lead_middle[COM_MAX_LEN];   // middle-comment string
+	char_u	lead_end[COM_MAX_LEN];	    // end-comment string
+	char_u	*comment_end = NULL;	    // where lead_end has been found
+	int	extra_space = FALSE;	    // append extra space
+	int	current_flag;
+	int	require_blank = FALSE;	    // requires blank after middle
+	char_u	*p2;
+
+	// If the comment leader has the start, middle or end flag, it may not
+	// be used or may be replaced with the middle leader.
+	for (p = lead_flags; *p && *p != ':'; ++p)
+	{
+	    if (*p == COM_BLANK)
+	    {
+		require_blank = TRUE;
+		continue;
+	    }
+	    if (*p == COM_START || *p == COM_MIDDLE)
+	    {
+		current_flag = *p;
+		if (*p == COM_START)
+		{
+		    // Doing "O" on a start of comment does not insert leader.
+		    if (dir == BACKWARD)
+		    {
+			lead_len = 0;
+			break;
+		    }
+
+		    // find start of middle part
+		    (void)copy_option_part(&p, lead_middle, COM_MAX_LEN, ",");
+		    require_blank = FALSE;
+		}
+
+		// Isolate the strings of the middle and end leader.
+		while (*p && p[-1] != ':')	/* find end of middle flags */
+		{
+		    if (*p == COM_BLANK)
+			require_blank = TRUE;
+		    ++p;
+		}
+		(void)copy_option_part(&p, lead_middle, COM_MAX_LEN, ",");
+
+		while (*p && p[-1] != ':')	// find end of end flags
+		{
+		    // Check whether we allow automatic ending of comments
+		    if (*p == COM_AUTO_END)
+			end_comment_pending = -1; // means we want to set it
+		    ++p;
+		}
+		n = copy_option_part(&p, lead_end, COM_MAX_LEN, ",");
+
+		if (end_comment_pending == -1)	// we can set it now
+		    end_comment_pending = lead_end[n - 1];
+
+		// If the end of the comment is in the same line, don't use
+		// the comment leader.
+		if (dir == FORWARD)
+		{
+		    for (p = saved_line + lead_len; *p; ++p)
+			if (STRNCMP(p, lead_end, n) == 0)
+			{
+			    comment_end = p;
+			    lead_len = 0;
+			    break;
+			}
+		}
+
+		// Doing "o" on a start of comment inserts the middle leader.
+		if (lead_len > 0)
+		{
+		    if (current_flag == COM_START)
+		    {
+			lead_repl = lead_middle;
+			lead_repl_len = (int)STRLEN(lead_middle);
+		    }
+
+		    // If we have hit RETURN immediately after the start
+		    // comment leader, then put a space after the middle
+		    // comment leader on the next line.
+		    if (!VIM_ISWHITE(saved_line[lead_len - 1])
+			    && ((p_extra != NULL
+				    && (int)curwin->w_cursor.col == lead_len)
+				|| (p_extra == NULL
+				    && saved_line[lead_len] == NUL)
+				|| require_blank))
+			extra_space = TRUE;
+		}
+		break;
+	    }
+	    if (*p == COM_END)
+	    {
+		// Doing "o" on the end of a comment does not insert leader.
+		// Remember where the end is, might want to use it to find the
+		// start (for C-comments).
+		if (dir == FORWARD)
+		{
+		    comment_end = skipwhite(saved_line);
+		    lead_len = 0;
+		    break;
+		}
+
+		// Doing "O" on the end of a comment inserts the middle leader.
+		// Find the string for the middle leader, searching backwards.
+		while (p > curbuf->b_p_com && *p != ',')
+		    --p;
+		for (lead_repl = p; lead_repl > curbuf->b_p_com
+					 && lead_repl[-1] != ':'; --lead_repl)
+		    ;
+		lead_repl_len = (int)(p - lead_repl);
+
+		// We can probably always add an extra space when doing "O" on
+		// the comment-end
+		extra_space = TRUE;
+
+		// Check whether we allow automatic ending of comments
+		for (p2 = p; *p2 && *p2 != ':'; p2++)
+		{
+		    if (*p2 == COM_AUTO_END)
+			end_comment_pending = -1; // means we want to set it
+		}
+		if (end_comment_pending == -1)
+		{
+		    // Find last character in end-comment string
+		    while (*p2 && *p2 != ',')
+			p2++;
+		    end_comment_pending = p2[-1];
+		}
+		break;
+	    }
+	    if (*p == COM_FIRST)
+	    {
+		// Comment leader for first line only:	Don't repeat leader
+		// when using "O", blank out leader when using "o".
+		if (dir == BACKWARD)
+		    lead_len = 0;
+		else
+		{
+		    lead_repl = (char_u *)"";
+		    lead_repl_len = 0;
+		}
+		break;
+	    }
+	}
+	if (lead_len)
+	{
+	    // allocate buffer (may concatenate p_extra later)
+	    leader = alloc(lead_len + lead_repl_len + extra_space + extra_len
+		     + (second_line_indent > 0 ? second_line_indent : 0) + 1);
+	    allocated = leader;		    // remember to free it later
+
+	    if (leader == NULL)
+		lead_len = 0;
+	    else
+	    {
+		vim_strncpy(leader, saved_line, lead_len);
+
+		// Replace leader with lead_repl, right or left adjusted
+		if (lead_repl != NULL)
+		{
+		    int		c = 0;
+		    int		off = 0;
+
+		    for (p = lead_flags; *p != NUL && *p != ':'; )
+		    {
+			if (*p == COM_RIGHT || *p == COM_LEFT)
+			    c = *p++;
+			else if (VIM_ISDIGIT(*p) || *p == '-')
+			    off = getdigits(&p);
+			else
+			    ++p;
+		    }
+		    if (c == COM_RIGHT)    // right adjusted leader
+		    {
+			// find last non-white in the leader to line up with
+			for (p = leader + lead_len - 1; p > leader
+						      && VIM_ISWHITE(*p); --p)
+			    ;
+			++p;
+
+			// Compute the length of the replaced characters in
+			// screen characters, not bytes.
+			{
+			    int	    repl_size = vim_strnsize(lead_repl,
+							       lead_repl_len);
+			    int	    old_size = 0;
+			    char_u  *endp = p;
+			    int	    l;
+
+			    while (old_size < repl_size && p > leader)
+			    {
+				MB_PTR_BACK(leader, p);
+				old_size += ptr2cells(p);
+			    }
+			    l = lead_repl_len - (int)(endp - p);
+			    if (l != 0)
+				mch_memmove(endp + l, endp,
+					(size_t)((leader + lead_len) - endp));
+			    lead_len += l;
+			}
+			mch_memmove(p, lead_repl, (size_t)lead_repl_len);
+			if (p + lead_repl_len > leader + lead_len)
+			    p[lead_repl_len] = NUL;
+
+			// blank-out any other chars from the old leader.
+			while (--p >= leader)
+			{
+			    int l = mb_head_off(leader, p);
+
+			    if (l > 1)
+			    {
+				p -= l;
+				if (ptr2cells(p) > 1)
+				{
+				    p[1] = ' ';
+				    --l;
+				}
+				mch_memmove(p + 1, p + l + 1,
+				   (size_t)((leader + lead_len) - (p + l + 1)));
+				lead_len -= l;
+				*p = ' ';
+			    }
+			    else if (!VIM_ISWHITE(*p))
+				*p = ' ';
+			}
+		    }
+		    else	// left adjusted leader
+		    {
+			p = skipwhite(leader);
+
+			// Compute the length of the replaced characters in
+			// screen characters, not bytes. Move the part that is
+			// not to be overwritten.
+			{
+			    int	    repl_size = vim_strnsize(lead_repl,
+							       lead_repl_len);
+			    int	    i;
+			    int	    l;
+
+			    for (i = 0; i < lead_len && p[i] != NUL; i += l)
+			    {
+				l = (*mb_ptr2len)(p + i);
+				if (vim_strnsize(p, i + l) > repl_size)
+				    break;
+			    }
+			    if (i != lead_repl_len)
+			    {
+				mch_memmove(p + lead_repl_len, p + i,
+				       (size_t)(lead_len - i - (p - leader)));
+				lead_len += lead_repl_len - i;
+			    }
+			}
+			mch_memmove(p, lead_repl, (size_t)lead_repl_len);
+
+			// Replace any remaining non-white chars in the old
+			// leader by spaces.  Keep Tabs, the indent must
+			// remain the same.
+			for (p += lead_repl_len; p < leader + lead_len; ++p)
+			    if (!VIM_ISWHITE(*p))
+			    {
+				// Don't put a space before a TAB.
+				if (p + 1 < leader + lead_len && p[1] == TAB)
+				{
+				    --lead_len;
+				    mch_memmove(p, p + 1,
+						     (leader + lead_len) - p);
+				}
+				else
+				{
+				    int	    l = (*mb_ptr2len)(p);
+
+				    if (l > 1)
+				    {
+					if (ptr2cells(p) > 1)
+					{
+					    // Replace a double-wide char with
+					    // two spaces
+					    --l;
+					    *p++ = ' ';
+					}
+					mch_memmove(p + 1, p + l,
+						     (leader + lead_len) - p);
+					lead_len -= l - 1;
+				    }
+				    *p = ' ';
+				}
+			    }
+			*p = NUL;
+		    }
+
+		    // Recompute the indent, it may have changed.
+		    if (curbuf->b_p_ai
+#ifdef FEAT_SMARTINDENT
+					|| do_si
+#endif
+							   )
+#ifdef FEAT_VARTABS
+			newindent = get_indent_str_vtab(leader, curbuf->b_p_ts,
+						 curbuf->b_p_vts_array, FALSE);
+#else
+			newindent = get_indent_str(leader,
+						   (int)curbuf->b_p_ts, FALSE);
+#endif
+
+		    // Add the indent offset
+		    if (newindent + off < 0)
+		    {
+			off = -newindent;
+			newindent = 0;
+		    }
+		    else
+			newindent += off;
+
+		    // Correct trailing spaces for the shift, so that
+		    // alignment remains equal.
+		    while (off > 0 && lead_len > 0
+					       && leader[lead_len - 1] == ' ')
+		    {
+			// Don't do it when there is a tab before the space
+			if (vim_strchr(skipwhite(leader), '\t') != NULL)
+			    break;
+			--lead_len;
+			--off;
+		    }
+
+		    // If the leader ends in white space, don't add an
+		    // extra space
+		    if (lead_len > 0 && VIM_ISWHITE(leader[lead_len - 1]))
+			extra_space = FALSE;
+		    leader[lead_len] = NUL;
+		}
+
+		if (extra_space)
+		{
+		    leader[lead_len++] = ' ';
+		    leader[lead_len] = NUL;
+		}
+
+		newcol = lead_len;
+
+		// if a new indent will be set below, remove the indent that
+		// is in the comment leader
+		if (newindent
+#ifdef FEAT_SMARTINDENT
+				|| did_si
+#endif
+					   )
+		{
+		    while (lead_len && VIM_ISWHITE(*leader))
+		    {
+			--lead_len;
+			--newcol;
+			++leader;
+		    }
+		}
+
+	    }
+#ifdef FEAT_SMARTINDENT
+	    did_si = can_si = FALSE;
+#endif
+	}
+	else if (comment_end != NULL)
+	{
+	    // We have finished a comment, so we don't use the leader.
+	    // If this was a C-comment and 'ai' or 'si' is set do a normal
+	    // indent to align with the line containing the start of the
+	    // comment.
+	    if (comment_end[0] == '*' && comment_end[1] == '/' &&
+			(curbuf->b_p_ai
+#ifdef FEAT_SMARTINDENT
+					|| do_si
+#endif
+							   ))
+	    {
+		old_cursor = curwin->w_cursor;
+		curwin->w_cursor.col = (colnr_T)(comment_end - saved_line);
+		if ((pos = findmatch(NULL, NUL)) != NULL)
+		{
+		    curwin->w_cursor.lnum = pos->lnum;
+		    newindent = get_indent();
+		}
+		curwin->w_cursor = old_cursor;
+	    }
+	}
+    }
+#endif
+
+    // (State == INSERT || State == REPLACE), only when dir == FORWARD
+    if (p_extra != NULL)
+    {
+	*p_extra = saved_char;		// restore char that NUL replaced
+
+	// When 'ai' set or "flags" has OPENLINE_DELSPACES, skip to the first
+	// non-blank.
+	//
+	// When in REPLACE mode, put the deleted blanks on the replace stack,
+	// preceded by a NUL, so they can be put back when a BS is entered.
+	if (REPLACE_NORMAL(State))
+	    replace_push(NUL);	    /* end of extra blanks */
+	if (curbuf->b_p_ai || (flags & OPENLINE_DELSPACES))
+	{
+	    while ((*p_extra == ' ' || *p_extra == '\t')
+		    && (!enc_utf8
+			       || !utf_iscomposing(utf_ptr2char(p_extra + 1))))
+	    {
+		if (REPLACE_NORMAL(State))
+		    replace_push(*p_extra);
+		++p_extra;
+		++less_cols_off;
+	    }
+	}
+
+	// columns for marks adjusted for removed columns
+	less_cols = (int)(p_extra - saved_line);
+    }
+
+    if (p_extra == NULL)
+	p_extra = (char_u *)"";		    // append empty line
+
+#ifdef FEAT_COMMENTS
+    // concatenate leader and p_extra, if there is a leader
+    if (lead_len)
+    {
+	if (flags & OPENLINE_COM_LIST && second_line_indent > 0)
+	{
+	    int i;
+	    int padding = second_line_indent
+					  - (newindent + (int)STRLEN(leader));
+
+	    // Here whitespace is inserted after the comment char.
+	    // Below, set_indent(newindent, SIN_INSERT) will insert the
+	    // whitespace needed before the comment char.
+	    for (i = 0; i < padding; i++)
+	    {
+		STRCAT(leader, " ");
+		less_cols--;
+		newcol++;
+	    }
+	}
+	STRCAT(leader, p_extra);
+	p_extra = leader;
+	did_ai = TRUE;	    // So truncating blanks works with comments
+	less_cols -= lead_len;
+    }
+    else
+	end_comment_pending = NUL;  // turns out there was no leader
+#endif
+
+    old_cursor = curwin->w_cursor;
+    if (dir == BACKWARD)
+	--curwin->w_cursor.lnum;
+    if (!(State & VREPLACE_FLAG) || old_cursor.lnum >= orig_line_count)
+    {
+	if (ml_append(curwin->w_cursor.lnum, p_extra, (colnr_T)0, FALSE)
+								      == FAIL)
+	    goto theend;
+	// Postpone calling changed_lines(), because it would mess up folding
+	// with markers.
+	// Skip mark_adjust when adding a line after the last one, there can't
+	// be marks there. But still needed in diff mode.
+	if (curwin->w_cursor.lnum + 1 < curbuf->b_ml.ml_line_count
+#ifdef FEAT_DIFF
+		|| curwin->w_p_diff
+#endif
+	    )
+	    mark_adjust(curwin->w_cursor.lnum + 1, (linenr_T)MAXLNUM, 1L, 0L);
+	did_append = TRUE;
+    }
+    else
+    {
+	// In VREPLACE mode we are starting to replace the next line.
+	curwin->w_cursor.lnum++;
+	if (curwin->w_cursor.lnum >= Insstart.lnum + vr_lines_changed)
+	{
+	    // In case we NL to a new line, BS to the previous one, and NL
+	    // again, we don't want to save the new line for undo twice.
+	    (void)u_save_cursor();		    /* errors are ignored! */
+	    vr_lines_changed++;
+	}
+	ml_replace(curwin->w_cursor.lnum, p_extra, TRUE);
+	changed_bytes(curwin->w_cursor.lnum, 0);
+	curwin->w_cursor.lnum--;
+	did_append = FALSE;
+    }
+
+    if (newindent
+#ifdef FEAT_SMARTINDENT
+		    || did_si
+#endif
+				)
+    {
+	++curwin->w_cursor.lnum;
+#ifdef FEAT_SMARTINDENT
+	if (did_si)
+	{
+	    int sw = (int)get_sw_value(curbuf);
+
+	    if (p_sr)
+		newindent -= newindent % sw;
+	    newindent += sw;
+	}
+#endif
+	// Copy the indent
+	if (curbuf->b_p_ci)
+	{
+	    (void)copy_indent(newindent, saved_line);
+
+	    // Set the 'preserveindent' option so that any further screwing
+	    // with the line doesn't entirely destroy our efforts to preserve
+	    // it.  It gets restored at the function end.
+	    curbuf->b_p_pi = TRUE;
+	}
+	else
+	    (void)set_indent(newindent, SIN_INSERT);
+	less_cols -= curwin->w_cursor.col;
+
+	ai_col = curwin->w_cursor.col;
+
+	// In REPLACE mode, for each character in the new indent, there must
+	// be a NUL on the replace stack, for when it is deleted with BS
+	if (REPLACE_NORMAL(State))
+	    for (n = 0; n < (int)curwin->w_cursor.col; ++n)
+		replace_push(NUL);
+	newcol += curwin->w_cursor.col;
+#ifdef FEAT_SMARTINDENT
+	if (no_si)
+	    did_si = FALSE;
+#endif
+    }
+
+#ifdef FEAT_COMMENTS
+    // In REPLACE mode, for each character in the extra leader, there must be
+    // a NUL on the replace stack, for when it is deleted with BS.
+    if (REPLACE_NORMAL(State))
+	while (lead_len-- > 0)
+	    replace_push(NUL);
+#endif
+
+    curwin->w_cursor = old_cursor;
+
+    if (dir == FORWARD)
+    {
+	if (trunc_line || (State & INSERT))
+	{
+	    // truncate current line at cursor
+	    saved_line[curwin->w_cursor.col] = NUL;
+	    // Remove trailing white space, unless OPENLINE_KEEPTRAIL used.
+	    if (trunc_line && !(flags & OPENLINE_KEEPTRAIL))
+		truncate_spaces(saved_line);
+	    ml_replace(curwin->w_cursor.lnum, saved_line, FALSE);
+	    saved_line = NULL;
+	    if (did_append)
+	    {
+		changed_lines(curwin->w_cursor.lnum, curwin->w_cursor.col,
+					       curwin->w_cursor.lnum + 1, 1L);
+		did_append = FALSE;
+
+		// Move marks after the line break to the new line.
+		if (flags & OPENLINE_MARKFIX)
+		    mark_col_adjust(curwin->w_cursor.lnum,
+					 curwin->w_cursor.col + less_cols_off,
+						      1L, (long)-less_cols, 0);
+	    }
+	    else
+		changed_bytes(curwin->w_cursor.lnum, curwin->w_cursor.col);
+	}
+
+	// Put the cursor on the new line.  Careful: the scrollup() above may
+	// have moved w_cursor, we must use old_cursor.
+	curwin->w_cursor.lnum = old_cursor.lnum + 1;
+    }
+    if (did_append)
+	changed_lines(curwin->w_cursor.lnum, 0, curwin->w_cursor.lnum, 1L);
+
+    curwin->w_cursor.col = newcol;
+    curwin->w_cursor.coladd = 0;
+
+#if defined(FEAT_LISP) || defined(FEAT_CINDENT)
+    // In VREPLACE mode, we are handling the replace stack ourselves, so stop
+    // fixthisline() from doing it (via change_indent()) by telling it we're in
+    // normal INSERT mode.
+    if (State & VREPLACE_FLAG)
+    {
+	vreplace_mode = State;	// So we know to put things right later
+	State = INSERT;
+    }
+    else
+	vreplace_mode = 0;
+#endif
+#ifdef FEAT_LISP
+    // May do lisp indenting.
+    if (!p_paste
+# ifdef FEAT_COMMENTS
+	    && leader == NULL
+# endif
+	    && curbuf->b_p_lisp
+	    && curbuf->b_p_ai)
+    {
+	fixthisline(get_lisp_indent);
+	ai_col = (colnr_T)getwhitecols_curline();
+    }
+#endif
+#ifdef FEAT_CINDENT
+    // May do indenting after opening a new line.
+    if (!p_paste
+	    && (curbuf->b_p_cin
+#  ifdef FEAT_EVAL
+		    || *curbuf->b_p_inde != NUL
+#  endif
+		)
+	    && in_cinkeys(dir == FORWARD
+		? KEY_OPEN_FORW
+		: KEY_OPEN_BACK, ' ', linewhite(curwin->w_cursor.lnum)))
+    {
+	do_c_expr_indent();
+	ai_col = (colnr_T)getwhitecols_curline();
+    }
+#endif
+#if defined(FEAT_LISP) || defined(FEAT_CINDENT)
+    if (vreplace_mode != 0)
+	State = vreplace_mode;
+#endif
+
+    // Finally, VREPLACE gets the stuff on the new line, then puts back the
+    // original line, and inserts the new stuff char by char, pushing old stuff
+    // onto the replace stack (via ins_char()).
+    if (State & VREPLACE_FLAG)
+    {
+	// Put new line in p_extra
+	p_extra = vim_strsave(ml_get_curline());
+	if (p_extra == NULL)
+	    goto theend;
+
+	// Put back original line
+	ml_replace(curwin->w_cursor.lnum, next_line, FALSE);
+
+	// Insert new stuff into line again
+	curwin->w_cursor.col = 0;
+	curwin->w_cursor.coladd = 0;
+	ins_bytes(p_extra);	// will call changed_bytes()
+	vim_free(p_extra);
+	next_line = NULL;
+    }
+
+    retval = OK;		// success!
+theend:
+    curbuf->b_p_pi = saved_pi;
+    vim_free(saved_line);
+    vim_free(next_line);
+    vim_free(allocated);
+    return retval;
+}
+
+/*
+ * Delete from cursor to end of line.
+ * Caller must have prepared for undo.
+ * If "fixpos" is TRUE fix the cursor position when done.
+ *
+ * Return FAIL for failure, OK otherwise.
+ */
+    int
+truncate_line(int fixpos)
+{
+    char_u	*newp;
+    linenr_T	lnum = curwin->w_cursor.lnum;
+    colnr_T	col = curwin->w_cursor.col;
+
+    if (col == 0)
+	newp = vim_strsave((char_u *)"");
+    else
+	newp = vim_strnsave(ml_get(lnum), col);
+
+    if (newp == NULL)
+	return FAIL;
+
+    ml_replace(lnum, newp, FALSE);
+
+    // mark the buffer as changed and prepare for displaying
+    changed_bytes(lnum, curwin->w_cursor.col);
+
+    // If "fixpos" is TRUE we don't want to end up positioned at the NUL.
+    if (fixpos && curwin->w_cursor.col > 0)
+	--curwin->w_cursor.col;
+
+    return OK;
+}
+
+/*
+ * Delete "nlines" lines at the cursor.
+ * Saves the lines for undo first if "undo" is TRUE.
+ */
+    void
+del_lines(long nlines,	int undo)
+{
+    long	n;
+    linenr_T	first = curwin->w_cursor.lnum;
+
+    if (nlines <= 0)
+	return;
+
+    // save the deleted lines for undo
+    if (undo && u_savedel(first, nlines) == FAIL)
+	return;
+
+    for (n = 0; n < nlines; )
+    {
+	if (curbuf->b_ml.ml_flags & ML_EMPTY)	    // nothing to delete
+	    break;
+
+	ml_delete(first, TRUE);
+	++n;
+
+	// If we delete the last line in the file, stop
+	if (first > curbuf->b_ml.ml_line_count)
+	    break;
+    }
+
+    // Correct the cursor position before calling deleted_lines_mark(), it may
+    // trigger a callback to display the cursor.
+    curwin->w_cursor.col = 0;
+    check_cursor_lnum();
+
+    // adjust marks, mark the buffer as changed and prepare for displaying
+    deleted_lines_mark(first, n);
+}

new file mode 100644
--- /dev/null
+++ b/src/proto/change.pro
@@ -0,0 +1,24 @@
+/* change.c */
+void change_warning(int col);
+void changed(void);
+void changed_internal(void);
+void changed_bytes(linenr_T lnum, colnr_T col);
+void inserted_bytes(linenr_T lnum, colnr_T col, int added);
+void appended_lines(linenr_T lnum, long count);
+void appended_lines_mark(linenr_T lnum, long count);
+void deleted_lines(linenr_T lnum, long count);
+void deleted_lines_mark(linenr_T lnum, long count);
+void changed_lines(linenr_T lnum, colnr_T col, linenr_T lnume, long xtra);
+void unchanged(buf_T *buf, int ff);
+void ins_bytes(char_u *p);
+void ins_bytes_len(char_u *p, int len);
+void ins_char(int c);
+void ins_char_bytes(char_u *buf, int charlen);
+void ins_str(char_u *s);
+int del_char(int fixpos);
+int del_chars(long count, int fixpos);
+int del_bytes(long count, int fixpos_arg, int use_delcombine);
+int open_line(int dir, int flags, int second_line_indent);
+int truncate_line(int fixpos);
+void del_lines(long nlines, int undo);
+/* vim: set ft=c : */