Adding upstream version 2:9.0.1378.upstream/2%9.0.1378upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3633 insertions, 0 deletions

diff --git a/src/move.c b/src/move.c
new file mode 100644
index 0000000..0550ef5
--- /dev/null
+++ b/src/move.c
@@ -0,0 +1,3633 @@
+/* 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.
+ */
+/*
+ * move.c: Functions for moving the cursor and scrolling text.
+ *
+ * There are two ways to move the cursor:
+ * 1. Move the cursor directly, the text is scrolled to keep the cursor in the
+ *    window.
+ * 2. Scroll the text, the cursor is moved into the text visible in the
+ *    window.
+ * The 'scrolloff' option makes this a bit complicated.
+ */
+
+#include "vim.h"
+
+static int scrolljump_value(void);
+static int check_top_offset(void);
+static void curs_rows(win_T *wp);
+
+typedef struct
+{
+    linenr_T	    lnum;	// line number
+#ifdef FEAT_DIFF
+    int		    fill;	// filler lines
+#endif
+    int		    height;	// height of added line
+} lineoff_T;
+
+static void topline_back(lineoff_T *lp);
+static void botline_forw(lineoff_T *lp);
+
+/*
+ * Reduce "n" for the screen lines skipped with "wp->w_skipcol".
+ */
+    static int
+adjust_plines_for_skipcol(win_T *wp, int n)
+{
+    if (wp->w_skipcol == 0)
+	return n;
+
+    int off = 0;
+    int width = wp->w_width - win_col_off(wp);
+    if (wp->w_skipcol >= width)
+    {
+	++off;
+	int skip = wp->w_skipcol - width;
+	width += win_col_off2(wp);
+	while (skip >= width)
+	{
+	    ++off;
+	    skip -= width;
+	}
+    }
+    wp->w_valid &= ~VALID_WROW;
+    return n - off;
+}
+
+/*
+ * Return how many lines "lnum" will take on the screen, taking into account
+ * whether it is the first line, whether w_skipcol is non-zero and limiting to
+ * the window height.
+ */
+    static int
+plines_correct_topline(win_T *wp, linenr_T lnum)
+{
+    int n;
+#ifdef FEAT_DIFF
+    if (lnum == wp->w_topline)
+	n = plines_win_nofill(wp, lnum, FALSE) + wp->w_topfill;
+    else
+#endif
+	n = plines_win(wp, lnum, FALSE);
+    if (lnum == wp->w_topline)
+	n = adjust_plines_for_skipcol(wp, n);
+    if (n > wp->w_height)
+	n = wp->w_height;
+    return n;
+}
+
+/*
+ * Compute wp->w_botline for the current wp->w_topline.  Can be called after
+ * wp->w_topline changed.
+ */
+    static void
+comp_botline(win_T *wp)
+{
+    int		n;
+    linenr_T	lnum;
+    int		done;
+#ifdef FEAT_FOLDING
+    linenr_T    last;
+    int		folded;
+#endif
+
+    /*
+     * If w_cline_row is valid, start there.
+     * Otherwise have to start at w_topline.
+     */
+    check_cursor_moved(wp);
+    if (wp->w_valid & VALID_CROW)
+    {
+	lnum = wp->w_cursor.lnum;
+	done = wp->w_cline_row;
+    }
+    else
+    {
+	lnum = wp->w_topline;
+	done = 0;
+    }
+
+    for ( ; lnum <= wp->w_buffer->b_ml.ml_line_count; ++lnum)
+    {
+#ifdef FEAT_FOLDING
+	last = lnum;
+	folded = FALSE;
+	if (hasFoldingWin(wp, lnum, NULL, &last, TRUE, NULL))
+	{
+	    n = 1;
+	    folded = TRUE;
+	}
+	else
+#endif
+	{
+	    n = plines_correct_topline(wp, lnum);
+	}
+	if (
+#ifdef FEAT_FOLDING
+		lnum <= wp->w_cursor.lnum && last >= wp->w_cursor.lnum
+#else
+		lnum == wp->w_cursor.lnum
+#endif
+	   )
+	{
+	    wp->w_cline_row = done;
+	    wp->w_cline_height = n;
+#ifdef FEAT_FOLDING
+	    wp->w_cline_folded = folded;
+#endif
+	    redraw_for_cursorline(wp);
+	    wp->w_valid |= (VALID_CROW|VALID_CHEIGHT);
+	}
+	if (done + n > wp->w_height)
+	    break;
+	done += n;
+#ifdef FEAT_FOLDING
+	lnum = last;
+#endif
+    }
+
+    // wp->w_botline is the line that is just below the window
+    wp->w_botline = lnum;
+    wp->w_valid |= VALID_BOTLINE|VALID_BOTLINE_AP;
+
+    set_empty_rows(wp, done);
+}
+
+/*
+ * Redraw when w_cline_row changes and 'relativenumber' or 'cursorline' is
+ * set.
+ */
+    void
+redraw_for_cursorline(win_T *wp)
+{
+    if ((wp->w_p_rnu
+#ifdef FEAT_SYN_HL
+		|| wp->w_p_cul
+#endif
+		)
+	    && (wp->w_valid & VALID_CROW) == 0
+	    && !pum_visible())
+    {
+	// win_line() will redraw the number column and cursorline only.
+	redraw_win_later(wp, UPD_VALID);
+    }
+}
+
+#ifdef FEAT_SYN_HL
+/*
+ * Redraw when w_virtcol changes and 'cursorcolumn' is set or 'cursorlineopt'
+ * contains "screenline".
+ */
+    static void
+redraw_for_cursorcolumn(win_T *wp)
+{
+    if ((wp->w_valid & VALID_VIRTCOL) == 0 && !pum_visible())
+    {
+	// When 'cursorcolumn' is set need to redraw with UPD_SOME_VALID.
+	if (wp->w_p_cuc)
+	    redraw_win_later(wp, UPD_SOME_VALID);
+	// When 'cursorlineopt' contains "screenline" need to redraw with
+	// UPD_VALID.
+	else if (wp->w_p_cul && (wp->w_p_culopt_flags & CULOPT_SCRLINE))
+	    redraw_win_later(wp, UPD_VALID);
+    }
+}
+#endif
+
+/*
+ * Calculates how much overlap the smoothscroll marker "<<<" overlaps with
+ * buffer text for curwin.
+ * Parameter "extra2" should be the padding on the 2nd line, not the first
+ * line.
+ * Returns the number of columns of overlap with buffer text, excluding the
+ * extra padding on the ledge.
+ */
+    static int
+smoothscroll_marker_overlap(int extra2)
+{
+#if defined(FEAT_LINEBREAK)
+    // We don't draw the <<< marker when in showbreak mode, thus no need to
+    // account for it.  See wlv_screen_line().
+    if (*get_showbreak_value(curwin) != NUL)
+	return 0;
+#endif
+    return extra2 > 3 ? 0 : 3 - extra2;
+}
+
+/*
+ * Calculates the skipcol offset for window "wp" given how many
+ * physical lines we want to scroll down.
+ */
+    static int
+skipcol_from_plines(win_T *wp, int plines_off)
+{
+    int width1 = wp->w_width - win_col_off(wp);
+
+    int skipcol = 0;
+    if (plines_off > 0)
+	skipcol += width1;
+    if (plines_off > 1)
+	skipcol += (width1 + win_col_off2(wp)) * (plines_off - 1);
+    return skipcol;
+}
+
+/*
+ * Set curwin->s_skipcol to zero and redraw later if needed.
+ */
+    static void
+reset_skipcol(void)
+{
+    if (curwin->w_skipcol == 0)
+	return;
+
+    curwin->w_skipcol = 0;
+
+    // Should use the least expensive way that displays all that changed.
+    // UPD_NOT_VALID is too expensive, UPD_REDRAW_TOP does not redraw
+    // enough when the top line gets another screen line.
+    redraw_later(UPD_SOME_VALID);
+}
+
+/*
+ * Update curwin->w_topline and redraw if necessary.
+ * Used to update the screen before printing a message.
+ */
+    void
+update_topline_redraw(void)
+{
+    update_topline();
+    if (must_redraw)
+	update_screen(0);
+}
+
+/*
+ * Update curwin->w_topline to move the cursor onto the screen.
+ */
+    void
+update_topline(void)
+{
+    long	line_count;
+    int		halfheight;
+    int		n;
+    linenr_T	old_topline;
+#ifdef FEAT_DIFF
+    int		old_topfill;
+#endif
+#ifdef FEAT_FOLDING
+    linenr_T	lnum;
+#endif
+    int		check_topline = FALSE;
+    int		check_botline = FALSE;
+    long	*so_ptr = curwin->w_p_so >= 0 ? &curwin->w_p_so : &p_so;
+    int		save_so = *so_ptr;
+
+    // Cursor is updated instead when this is TRUE for 'splitkeep'.
+    if (skip_update_topline)
+	return;
+
+    // If there is no valid screen and when the window height is zero just use
+    // the cursor line.
+    if (!screen_valid(TRUE) || curwin->w_height == 0)
+    {
+	check_cursor_lnum();
+	curwin->w_topline = curwin->w_cursor.lnum;
+	curwin->w_botline = curwin->w_topline;
+	curwin->w_scbind_pos = 1;
+	return;
+    }
+
+    check_cursor_moved(curwin);
+    if (curwin->w_valid & VALID_TOPLINE)
+	return;
+
+    // When dragging with the mouse, don't scroll that quickly
+    if (mouse_dragging > 0)
+	*so_ptr = mouse_dragging - 1;
+
+    old_topline = curwin->w_topline;
+#ifdef FEAT_DIFF
+    old_topfill = curwin->w_topfill;
+#endif
+
+    /*
+     * If the buffer is empty, always set topline to 1.
+     */
+    if (BUFEMPTY())		// special case - file is empty
+    {
+	if (curwin->w_topline != 1)
+	    redraw_later(UPD_NOT_VALID);
+	curwin->w_topline = 1;
+	curwin->w_botline = 2;
+	curwin->w_valid |= VALID_BOTLINE|VALID_BOTLINE_AP;
+	curwin->w_scbind_pos = 1;
+    }
+
+    /*
+     * If the cursor is above or near the top of the window, scroll the window
+     * to show the line the cursor is in, with 'scrolloff' context.
+     */
+    else
+    {
+	if (curwin->w_topline > 1 || curwin->w_skipcol > 0)
+	{
+	    // If the cursor is above topline, scrolling is always needed.
+	    // If the cursor is far below topline and there is no folding,
+	    // scrolling down is never needed.
+	    if (curwin->w_cursor.lnum < curwin->w_topline)
+		check_topline = TRUE;
+	    else if (check_top_offset())
+		check_topline = TRUE;
+	    else if (curwin->w_cursor.lnum == curwin->w_topline)
+	    {
+		colnr_T vcol;
+
+		// Check that the cursor position is visible.  Add columns for
+		// the smoothscroll marker "<<<" displayed in the top-left if
+		// needed.
+		getvvcol(curwin, &curwin->w_cursor, &vcol, NULL, NULL);
+		int smoothscroll_overlap = smoothscroll_marker_overlap(
+					 curwin_col_off() - curwin_col_off2());
+		if (curwin->w_skipcol + smoothscroll_overlap > vcol)
+		    check_topline = TRUE;
+	    }
+	}
+#ifdef FEAT_DIFF
+	    // Check if there are more filler lines than allowed.
+	if (!check_topline && curwin->w_topfill > diff_check_fill(curwin,
+							   curwin->w_topline))
+	    check_topline = TRUE;
+#endif
+
+	if (check_topline)
+	{
+	    halfheight = curwin->w_height / 2 - 1;
+	    if (halfheight < 2)
+		halfheight = 2;
+
+#ifdef FEAT_FOLDING
+	    if (hasAnyFolding(curwin))
+	    {
+		// Count the number of logical lines between the cursor and
+		// topline + scrolloff (approximation of how much will be
+		// scrolled).
+		n = 0;
+		for (lnum = curwin->w_cursor.lnum;
+				    lnum < curwin->w_topline + *so_ptr; ++lnum)
+		{
+		    ++n;
+		    // stop at end of file or when we know we are far off
+		    if (lnum >= curbuf->b_ml.ml_line_count || n >= halfheight)
+			break;
+		    (void)hasFolding(lnum, NULL, &lnum);
+		}
+	    }
+	    else
+#endif
+		n = curwin->w_topline + *so_ptr - curwin->w_cursor.lnum;
+
+	    // If we weren't very close to begin with, we scroll to put the
+	    // cursor in the middle of the window.  Otherwise put the cursor
+	    // near the top of the window.
+	    if (n >= halfheight)
+		scroll_cursor_halfway(FALSE, FALSE);
+	    else
+	    {
+		scroll_cursor_top(scrolljump_value(), FALSE);
+		check_botline = TRUE;
+	    }
+	}
+
+	else
+	{
+#ifdef FEAT_FOLDING
+	    // Make sure topline is the first line of a fold.
+	    (void)hasFolding(curwin->w_topline, &curwin->w_topline, NULL);
+#endif
+	    check_botline = TRUE;
+	}
+    }
+
+    /*
+     * If the cursor is below the bottom of the window, scroll the window
+     * to put the cursor on the window.
+     * When w_botline is invalid, recompute it first, to avoid a redraw later.
+     * If w_botline was approximated, we might need a redraw later in a few
+     * cases, but we don't want to spend (a lot of) time recomputing w_botline
+     * for every small change.
+     */
+    if (check_botline)
+    {
+	if (!(curwin->w_valid & VALID_BOTLINE_AP))
+	    validate_botline();
+
+	if (curwin->w_botline <= curbuf->b_ml.ml_line_count)
+	{
+	    if (curwin->w_cursor.lnum < curwin->w_botline)
+	    {
+	      if (((long)curwin->w_cursor.lnum
+					   >= (long)curwin->w_botline - *so_ptr
+#ifdef FEAT_FOLDING
+			|| hasAnyFolding(curwin)
+#endif
+			))
+	      {
+		lineoff_T	loff;
+
+		// Cursor is (a few lines) above botline, check if there are
+		// 'scrolloff' window lines below the cursor.  If not, need to
+		// scroll.
+		n = curwin->w_empty_rows;
+		loff.lnum = curwin->w_cursor.lnum;
+#ifdef FEAT_FOLDING
+		// In a fold go to its last line.
+		(void)hasFolding(loff.lnum, NULL, &loff.lnum);
+#endif
+#ifdef FEAT_DIFF
+		loff.fill = 0;
+		n += curwin->w_filler_rows;
+#endif
+		loff.height = 0;
+		while (loff.lnum < curwin->w_botline
+#ifdef FEAT_DIFF
+			&& (loff.lnum + 1 < curwin->w_botline || loff.fill == 0)
+#endif
+			)
+		{
+		    n += loff.height;
+		    if (n >= *so_ptr)
+			break;
+		    botline_forw(&loff);
+		}
+		if (n >= *so_ptr)
+		    // sufficient context, no need to scroll
+		    check_botline = FALSE;
+	      }
+	      else
+		  // sufficient context, no need to scroll
+		  check_botline = FALSE;
+	    }
+	    if (check_botline)
+	    {
+#ifdef FEAT_FOLDING
+		if (hasAnyFolding(curwin))
+		{
+		    // Count the number of logical lines between the cursor and
+		    // botline - scrolloff (approximation of how much will be
+		    // scrolled).
+		    line_count = 0;
+		    for (lnum = curwin->w_cursor.lnum;
+				   lnum >= curwin->w_botline - *so_ptr; --lnum)
+		    {
+			++line_count;
+			// stop at end of file or when we know we are far off
+			if (lnum <= 0 || line_count > curwin->w_height + 1)
+			    break;
+			(void)hasFolding(lnum, &lnum, NULL);
+		    }
+		}
+		else
+#endif
+		    line_count = curwin->w_cursor.lnum - curwin->w_botline
+								 + 1 + *so_ptr;
+		if (line_count <= curwin->w_height + 1)
+		    scroll_cursor_bot(scrolljump_value(), FALSE);
+		else
+		    scroll_cursor_halfway(FALSE, FALSE);
+	    }
+	}
+    }
+    curwin->w_valid |= VALID_TOPLINE;
+
+    /*
+     * Need to redraw when topline changed.
+     */
+    if (curwin->w_topline != old_topline
+#ifdef FEAT_DIFF
+	    || curwin->w_topfill != old_topfill
+#endif
+	    )
+    {
+	dollar_vcol = -1;
+	redraw_later(UPD_VALID);
+	reset_skipcol();
+
+	// May need to set w_skipcol when cursor in w_topline.
+	if (curwin->w_cursor.lnum == curwin->w_topline)
+	    validate_cursor();
+    }
+
+    *so_ptr = save_so;
+}
+
+/*
+ * Return the scrolljump value to use for the current window.
+ * When 'scrolljump' is positive use it as-is.
+ * When 'scrolljump' is negative use it as a percentage of the window height.
+ */
+    static int
+scrolljump_value(void)
+{
+    if (p_sj >= 0)
+	return (int)p_sj;
+    return (curwin->w_height * -p_sj) / 100;
+}
+
+/*
+ * Return TRUE when there are not 'scrolloff' lines above the cursor for the
+ * current window.
+ */
+    static int
+check_top_offset(void)
+{
+    lineoff_T	loff;
+    int		n;
+    long	so = get_scrolloff_value();
+
+    if (curwin->w_cursor.lnum < curwin->w_topline + so
+#ifdef FEAT_FOLDING
+		    || hasAnyFolding(curwin)
+#endif
+	    )
+    {
+	loff.lnum = curwin->w_cursor.lnum;
+#ifdef FEAT_DIFF
+	loff.fill = 0;
+	n = curwin->w_topfill;	    // always have this context
+#else
+	n = 0;
+#endif
+	// Count the visible screen lines above the cursor line.
+	while (n < so)
+	{
+	    topline_back(&loff);
+	    // Stop when included a line above the window.
+	    if (loff.lnum < curwin->w_topline
+#ifdef FEAT_DIFF
+		    || (loff.lnum == curwin->w_topline && loff.fill > 0)
+#endif
+		    )
+		break;
+	    n += loff.height;
+	}
+	if (n < so)
+	    return TRUE;
+    }
+    return FALSE;
+}
+
+/*
+ * Update w_curswant.
+ */
+    void
+update_curswant_force(void)
+{
+    validate_virtcol();
+    curwin->w_curswant = curwin->w_virtcol
+#ifdef FEAT_PROP_POPUP
+	- curwin->w_virtcol_first_char
+#endif
+	;
+    curwin->w_set_curswant = FALSE;
+}
+
+/*
+ * Update w_curswant if w_set_curswant is set.
+ */
+    void
+update_curswant(void)
+{
+    if (curwin->w_set_curswant)
+	update_curswant_force();
+}
+
+/*
+ * Check if the cursor has moved.  Set the w_valid flag accordingly.
+ */
+    void
+check_cursor_moved(win_T *wp)
+{
+    if (wp->w_cursor.lnum != wp->w_valid_cursor.lnum)
+    {
+	wp->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL
+				      |VALID_CHEIGHT|VALID_CROW|VALID_TOPLINE
+				      |VALID_BOTLINE|VALID_BOTLINE_AP);
+	wp->w_valid_cursor = wp->w_cursor;
+	wp->w_valid_leftcol = wp->w_leftcol;
+	wp->w_valid_skipcol = wp->w_skipcol;
+    }
+    else if (wp->w_skipcol != wp->w_valid_skipcol)
+    {
+	wp->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL
+				      |VALID_CHEIGHT|VALID_CROW
+				      |VALID_BOTLINE|VALID_BOTLINE_AP);
+	wp->w_valid_cursor = wp->w_cursor;
+	wp->w_valid_leftcol = wp->w_leftcol;
+	wp->w_valid_skipcol = wp->w_skipcol;
+    }
+    else if (wp->w_cursor.col != wp->w_valid_cursor.col
+	     || wp->w_leftcol != wp->w_valid_leftcol
+	     || wp->w_cursor.coladd != wp->w_valid_cursor.coladd)
+    {
+	wp->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL);
+	wp->w_valid_cursor.col = wp->w_cursor.col;
+	wp->w_valid_leftcol = wp->w_leftcol;
+	wp->w_valid_cursor.coladd = wp->w_cursor.coladd;
+    }
+}
+
+/*
+ * Call this function when some window settings have changed, which require
+ * the cursor position, botline and topline to be recomputed and the window to
+ * be redrawn.  E.g, when changing the 'wrap' option or folding.
+ */
+    void
+changed_window_setting(void)
+{
+    changed_window_setting_win(curwin);
+}
+
+    void
+changed_window_setting_win(win_T *wp)
+{
+    wp->w_lines_valid = 0;
+    changed_line_abv_curs_win(wp);
+    wp->w_valid &= ~(VALID_BOTLINE|VALID_BOTLINE_AP|VALID_TOPLINE);
+    redraw_win_later(wp, UPD_NOT_VALID);
+}
+
+/*
+ * Call changed_window_setting_win() for every window containing "buf".
+ */
+    void
+changed_window_setting_buf(buf_T *buf)
+{
+    tabpage_T	*tp;
+    win_T	*wp;
+
+    FOR_ALL_TAB_WINDOWS(tp, wp)
+	if (wp->w_buffer == buf)
+	    changed_window_setting_win(wp);
+}
+
+/*
+ * Set wp->w_topline to a certain number.
+ */
+    void
+set_topline(win_T *wp, linenr_T lnum)
+{
+#ifdef FEAT_DIFF
+    linenr_T prev_topline = wp->w_topline;
+#endif
+
+#ifdef FEAT_FOLDING
+    // go to first of folded lines
+    (void)hasFoldingWin(wp, lnum, &lnum, NULL, TRUE, NULL);
+#endif
+    // Approximate the value of w_botline
+    wp->w_botline += lnum - wp->w_topline;
+    if (wp->w_botline > wp->w_buffer->b_ml.ml_line_count + 1)
+	wp->w_botline = wp->w_buffer->b_ml.ml_line_count + 1;
+    wp->w_topline = lnum;
+    wp->w_topline_was_set = TRUE;
+#ifdef FEAT_DIFF
+    if (lnum != prev_topline)
+	// Keep the filler lines when the topline didn't change.
+	wp->w_topfill = 0;
+#endif
+    wp->w_valid &= ~(VALID_WROW|VALID_CROW|VALID_BOTLINE|VALID_TOPLINE);
+    // Don't set VALID_TOPLINE here, 'scrolloff' needs to be checked.
+    redraw_later(UPD_VALID);
+}
+
+/*
+ * Call this function when the length of the cursor line (in screen
+ * characters) has changed, and the change is before the cursor.
+ * Need to take care of w_botline separately!
+ */
+    void
+changed_cline_bef_curs(void)
+{
+    curwin->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL
+						|VALID_CHEIGHT|VALID_TOPLINE);
+}
+
+    void
+changed_cline_bef_curs_win(win_T *wp)
+{
+    wp->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL
+						|VALID_CHEIGHT|VALID_TOPLINE);
+}
+
+/*
+ * Call this function when the length of a line (in screen characters) above
+ * the cursor have changed.
+ * Need to take care of w_botline separately!
+ */
+    void
+changed_line_abv_curs(void)
+{
+    curwin->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL|VALID_CROW
+						|VALID_CHEIGHT|VALID_TOPLINE);
+}
+
+    void
+changed_line_abv_curs_win(win_T *wp)
+{
+    wp->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL|VALID_CROW
+						|VALID_CHEIGHT|VALID_TOPLINE);
+}
+
+/*
+ * Display of line has changed for "buf", invalidate cursor position and
+ * w_botline.
+ */
+    void
+changed_line_display_buf(buf_T *buf)
+{
+    win_T *wp;
+
+    FOR_ALL_WINDOWS(wp)
+	if (wp->w_buffer == buf)
+	    wp->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL
+				|VALID_CROW|VALID_CHEIGHT
+				|VALID_TOPLINE|VALID_BOTLINE|VALID_BOTLINE_AP);
+}
+
+/*
+ * Make sure the value of curwin->w_botline is valid.
+ */
+    void
+validate_botline(void)
+{
+    validate_botline_win(curwin);
+}
+
+/*
+ * Make sure the value of wp->w_botline is valid.
+ */
+    void
+validate_botline_win(win_T *wp)
+{
+    if (!(wp->w_valid & VALID_BOTLINE))
+	comp_botline(wp);
+}
+
+/*
+ * Mark curwin->w_botline as invalid (because of some change in the buffer).
+ */
+    void
+invalidate_botline(void)
+{
+    curwin->w_valid &= ~(VALID_BOTLINE|VALID_BOTLINE_AP);
+}
+
+    void
+invalidate_botline_win(win_T *wp)
+{
+    wp->w_valid &= ~(VALID_BOTLINE|VALID_BOTLINE_AP);
+}
+
+    void
+approximate_botline_win(
+    win_T	*wp)
+{
+    wp->w_valid &= ~VALID_BOTLINE;
+}
+
+/*
+ * Return TRUE if curwin->w_wrow and curwin->w_wcol are valid.
+ */
+    int
+cursor_valid(void)
+{
+    check_cursor_moved(curwin);
+    return ((curwin->w_valid & (VALID_WROW|VALID_WCOL)) ==
+						      (VALID_WROW|VALID_WCOL));
+}
+
+/*
+ * Validate cursor position.  Makes sure w_wrow and w_wcol are valid.
+ * w_topline must be valid, you may need to call update_topline() first!
+ */
+    void
+validate_cursor(void)
+{
+    check_cursor_lnum();
+    check_cursor_moved(curwin);
+    if ((curwin->w_valid & (VALID_WCOL|VALID_WROW)) != (VALID_WCOL|VALID_WROW))
+	curs_columns(TRUE);
+}
+
+#if defined(FEAT_GUI) || defined(PROTO)
+/*
+ * validate w_cline_row.
+ */
+    void
+validate_cline_row(void)
+{
+    /*
+     * First make sure that w_topline is valid (after moving the cursor).
+     */
+    update_topline();
+    check_cursor_moved(curwin);
+    if (!(curwin->w_valid & VALID_CROW))
+	curs_rows(curwin);
+}
+#endif
+
+/*
+ * Compute wp->w_cline_row and wp->w_cline_height, based on the current value
+ * of wp->w_topline.
+ */
+    static void
+curs_rows(win_T *wp)
+{
+    linenr_T	lnum;
+    int		i;
+    int		all_invalid;
+    int		valid;
+#ifdef FEAT_FOLDING
+    long	fold_count;
+#endif
+
+    // Check if wp->w_lines[].wl_size is invalid
+    all_invalid = (!redrawing()
+			|| wp->w_lines_valid == 0
+			|| wp->w_lines[0].wl_lnum > wp->w_topline);
+    i = 0;
+    wp->w_cline_row = 0;
+    for (lnum = wp->w_topline; lnum < wp->w_cursor.lnum; ++i)
+    {
+	valid = FALSE;
+	if (!all_invalid && i < wp->w_lines_valid)
+	{
+	    if (wp->w_lines[i].wl_lnum < lnum || !wp->w_lines[i].wl_valid)
+		continue;		// skip changed or deleted lines
+	    if (wp->w_lines[i].wl_lnum == lnum)
+	    {
+#ifdef FEAT_FOLDING
+		// Check for newly inserted lines below this row, in which
+		// case we need to check for folded lines.
+		if (!wp->w_buffer->b_mod_set
+			|| wp->w_lines[i].wl_lastlnum < wp->w_cursor.lnum
+			|| wp->w_buffer->b_mod_top
+					     > wp->w_lines[i].wl_lastlnum + 1)
+#endif
+		valid = TRUE;
+	    }
+	    else if (wp->w_lines[i].wl_lnum > lnum)
+		--i;			// hold at inserted lines
+	}
+	if (valid
+#ifdef FEAT_DIFF
+		&& (lnum != wp->w_topline || !wp->w_p_diff)
+#endif
+		)
+	{
+#ifdef FEAT_FOLDING
+	    lnum = wp->w_lines[i].wl_lastlnum + 1;
+	    // Cursor inside folded lines, don't count this row
+	    if (lnum > wp->w_cursor.lnum)
+		break;
+#else
+	    ++lnum;
+#endif
+	    wp->w_cline_row += wp->w_lines[i].wl_size;
+	}
+	else
+	{
+#ifdef FEAT_FOLDING
+	    fold_count = foldedCount(wp, lnum, NULL);
+	    if (fold_count)
+	    {
+		lnum += fold_count;
+		if (lnum > wp->w_cursor.lnum)
+		    break;
+		++wp->w_cline_row;
+	    }
+	    else
+#endif
+	    {
+		wp->w_cline_row += plines_correct_topline(wp, lnum);
+		++lnum;
+	    }
+	}
+    }
+
+    check_cursor_moved(wp);
+    if (!(wp->w_valid & VALID_CHEIGHT))
+    {
+	if (all_invalid
+		|| i == wp->w_lines_valid
+		|| (i < wp->w_lines_valid
+		    && (!wp->w_lines[i].wl_valid
+			|| wp->w_lines[i].wl_lnum != wp->w_cursor.lnum)))
+	{
+#ifdef FEAT_DIFF
+	    if (wp->w_cursor.lnum == wp->w_topline)
+		wp->w_cline_height = plines_win_nofill(wp, wp->w_cursor.lnum,
+							TRUE) + wp->w_topfill;
+	    else
+#endif
+		wp->w_cline_height = plines_win(wp, wp->w_cursor.lnum, TRUE);
+#ifdef FEAT_FOLDING
+	    wp->w_cline_folded = hasFoldingWin(wp, wp->w_cursor.lnum,
+						      NULL, NULL, TRUE, NULL);
+#endif
+	}
+	else if (i > wp->w_lines_valid)
+	{
+	    // a line that is too long to fit on the last screen line
+	    wp->w_cline_height = 0;
+#ifdef FEAT_FOLDING
+	    wp->w_cline_folded = hasFoldingWin(wp, wp->w_cursor.lnum,
+						      NULL, NULL, TRUE, NULL);
+#endif
+	}
+	else
+	{
+	    wp->w_cline_height = wp->w_lines[i].wl_size;
+#ifdef FEAT_FOLDING
+	    wp->w_cline_folded = wp->w_lines[i].wl_folded;
+#endif
+	}
+    }
+
+    redraw_for_cursorline(curwin);
+    wp->w_valid |= VALID_CROW|VALID_CHEIGHT;
+}
+
+/*
+ * Validate curwin->w_virtcol only.
+ */
+    void
+validate_virtcol(void)
+{
+    validate_virtcol_win(curwin);
+}
+
+/*
+ * Validate wp->w_virtcol only.
+ */
+    void
+validate_virtcol_win(win_T *wp)
+{
+    check_cursor_moved(wp);
+
+    if (wp->w_valid & VALID_VIRTCOL)
+	return;
+
+#ifdef FEAT_PROP_POPUP
+    wp->w_virtcol_first_char = 0;
+#endif
+    getvvcol(wp, &wp->w_cursor, NULL, &(wp->w_virtcol), NULL);
+#ifdef FEAT_SYN_HL
+    redraw_for_cursorcolumn(wp);
+#endif
+    wp->w_valid |= VALID_VIRTCOL;
+}
+
+/*
+ * Validate curwin->w_cline_height only.
+ */
+    void
+validate_cheight(void)
+{
+    check_cursor_moved(curwin);
+
+    if (curwin->w_valid & VALID_CHEIGHT)
+	return;
+
+#ifdef FEAT_DIFF
+    if (curwin->w_cursor.lnum == curwin->w_topline)
+	curwin->w_cline_height = plines_nofill(curwin->w_cursor.lnum)
+	    + curwin->w_topfill;
+    else
+#endif
+	curwin->w_cline_height = plines(curwin->w_cursor.lnum);
+#ifdef FEAT_FOLDING
+    curwin->w_cline_folded = hasFolding(curwin->w_cursor.lnum, NULL, NULL);
+#endif
+    curwin->w_valid |= VALID_CHEIGHT;
+}
+
+/*
+ * Validate w_wcol and w_virtcol only.
+ */
+    void
+validate_cursor_col(void)
+{
+    colnr_T off;
+    colnr_T col;
+    int     width;
+
+    validate_virtcol();
+
+    if (curwin->w_valid & VALID_WCOL)
+	return;
+
+    col = curwin->w_virtcol;
+    off = curwin_col_off();
+    col += off;
+    width = curwin->w_width - off + curwin_col_off2();
+
+    // long line wrapping, adjust curwin->w_wrow
+    if (curwin->w_p_wrap
+	    && col >= (colnr_T)curwin->w_width
+	    && width > 0)
+	// use same formula as what is used in curs_columns()
+	col -= ((col - curwin->w_width) / width + 1) * width;
+    if (col > (int)curwin->w_leftcol)
+	col -= curwin->w_leftcol;
+    else
+	col = 0;
+    curwin->w_wcol = col;
+
+    curwin->w_valid |= VALID_WCOL;
+#ifdef FEAT_PROP_POPUP
+    curwin->w_flags &= ~WFLAG_WCOL_OFF_ADDED;
+#endif
+}
+
+/*
+ * Compute offset of a window, occupied by absolute or relative line number,
+ * fold column and sign column (these don't move when scrolling horizontally).
+ */
+    int
+win_col_off(win_T *wp)
+{
+    return (((wp->w_p_nu || wp->w_p_rnu) ? number_width(wp) + 1 : 0)
+	    + (cmdwin_type == 0 || wp != curwin ? 0 : 1)
+#ifdef FEAT_FOLDING
+	    + wp->w_p_fdc
+#endif
+#ifdef FEAT_SIGNS
+	    + (signcolumn_on(wp) ? 2 : 0)
+#endif
+	   );
+}
+
+    int
+curwin_col_off(void)
+{
+    return win_col_off(curwin);
+}
+
+/*
+ * Return the difference in column offset for the second screen line of a
+ * wrapped line.  It's positive if 'number' or 'relativenumber' is on and 'n'
+ * is in 'cpoptions'.
+ */
+    int
+win_col_off2(win_T *wp)
+{
+    if ((wp->w_p_nu || wp->w_p_rnu) && vim_strchr(p_cpo, CPO_NUMCOL) != NULL)
+	return number_width(wp) + 1;
+    return 0;
+}
+
+    int
+curwin_col_off2(void)
+{
+    return win_col_off2(curwin);
+}
+
+/*
+ * Compute curwin->w_wcol and curwin->w_virtcol.
+ * Also updates curwin->w_wrow and curwin->w_cline_row.
+ * Also updates curwin->w_leftcol.
+ */
+    void
+curs_columns(
+    int		may_scroll)	// when TRUE, may scroll horizontally
+{
+    int		diff;
+    int		extra;		// offset for first screen line
+    int		off_left, off_right;
+    int		n;
+    int		p_lines;
+    int		width1;		// text width for first screen line
+    int		width2 = 0;	// text width for second and later screen line
+    int		new_leftcol;
+    colnr_T	startcol;
+    colnr_T	endcol;
+    colnr_T	prev_skipcol;
+    long	so = get_scrolloff_value();
+    long	siso = get_sidescrolloff_value();
+    int		did_sub_skipcol = FALSE;
+
+    /*
+     * First make sure that w_topline is valid (after moving the cursor).
+     */
+    update_topline();
+
+    /*
+     * Next make sure that w_cline_row is valid.
+     */
+    if (!(curwin->w_valid & VALID_CROW))
+	curs_rows(curwin);
+
+#ifdef FEAT_PROP_POPUP
+    // will be set by getvvcol() but not reset
+    curwin->w_virtcol_first_char = 0;
+#endif
+
+    /*
+     * Compute the number of virtual columns.
+     */
+#ifdef FEAT_FOLDING
+    if (curwin->w_cline_folded)
+	// In a folded line the cursor is always in the first column
+	startcol = curwin->w_virtcol = endcol = curwin->w_leftcol;
+    else
+#endif
+	getvvcol(curwin, &curwin->w_cursor,
+				&startcol, &(curwin->w_virtcol), &endcol);
+
+    // remove '$' from change command when cursor moves onto it
+    if (startcol > dollar_vcol)
+	dollar_vcol = -1;
+
+    extra = curwin_col_off();
+    curwin->w_wcol = curwin->w_virtcol + extra;
+    endcol += extra;
+
+    /*
+     * Now compute w_wrow, counting screen lines from w_cline_row.
+     */
+    curwin->w_wrow = curwin->w_cline_row;
+
+    width1 = curwin->w_width - extra;
+    if (width1 <= 0)
+    {
+	// No room for text, put cursor in last char of window.
+	// If not wrapping, the last non-empty line.
+	curwin->w_wcol = curwin->w_width - 1;
+	if (curwin->w_p_wrap)
+	    curwin->w_wrow = curwin->w_height - 1;
+	else
+	    curwin->w_wrow = curwin->w_height - 1 - curwin->w_empty_rows;
+    }
+    else if (curwin->w_p_wrap && curwin->w_width != 0)
+    {
+	width2 = width1 + curwin_col_off2();
+
+	// skip columns that are not visible
+	if (curwin->w_cursor.lnum == curwin->w_topline
+		&& curwin->w_skipcol > 0
+		&& curwin->w_wcol >= curwin->w_skipcol)
+	{
+	    // Deduct by multiples of width2.  This allows the long line
+	    // wrapping formula below to correctly calculate the w_wcol value
+	    // when wrapping.
+	    if (curwin->w_skipcol <= width1)
+		curwin->w_wcol -= width2;
+	    else
+		curwin->w_wcol -= width2
+			       * (((curwin->w_skipcol - width1) / width2) + 1);
+
+	    did_sub_skipcol = TRUE;
+	}
+
+	// long line wrapping, adjust curwin->w_wrow
+	if (curwin->w_wcol >= curwin->w_width)
+	{
+	    // this same formula is used in validate_cursor_col()
+	    n = (curwin->w_wcol - curwin->w_width) / width2 + 1;
+	    curwin->w_wcol -= n * width2;
+	    curwin->w_wrow += n;
+
+#ifdef FEAT_LINEBREAK
+	    // When cursor wraps to first char of next line in Insert
+	    // mode, the 'showbreak' string isn't shown, backup to first
+	    // column
+	    char_u *sbr = get_showbreak_value(curwin);
+	    if (*sbr && *ml_get_cursor() == NUL
+				    && curwin->w_wcol == vim_strsize(sbr))
+		curwin->w_wcol = 0;
+#endif
+	}
+    }
+
+    // No line wrapping: compute curwin->w_leftcol if scrolling is on and line
+    // is not folded.
+    // If scrolling is off, curwin->w_leftcol is assumed to be 0
+    else if (may_scroll
+#ifdef FEAT_FOLDING
+	    && !curwin->w_cline_folded
+#endif
+	    )
+    {
+#ifdef FEAT_PROP_POPUP
+	if (curwin->w_virtcol_first_char > 0)
+	{
+	    int cols = (curwin->w_width - extra);
+	    int rows = cols > 0 ? curwin->w_virtcol_first_char / cols : 1;
+
+	    // each "above" text prop shifts the text one row down
+	    curwin->w_wrow += rows;
+	    curwin->w_wcol -= rows * cols;
+	    endcol -= rows * cols;
+	    curwin->w_cline_height = rows + 1;
+	}
+#endif
+	/*
+	 * If Cursor is left of the screen, scroll rightwards.
+	 * If Cursor is right of the screen, scroll leftwards
+	 * If we get closer to the edge than 'sidescrolloff', scroll a little
+	 * extra
+	 */
+	off_left = (int)startcol - (int)curwin->w_leftcol - siso;
+	off_right = (int)endcol - (int)(curwin->w_leftcol + curwin->w_width
+								- siso) + 1;
+	if (off_left < 0 || off_right > 0)
+	{
+	    if (off_left < 0)
+		diff = -off_left;
+	    else
+		diff = off_right;
+
+	    // When far off or not enough room on either side, put cursor in
+	    // middle of window.
+	    if (p_ss == 0 || diff >= width1 / 2 || off_right >= off_left)
+		new_leftcol = curwin->w_wcol - extra - width1 / 2;
+	    else
+	    {
+		if (diff < p_ss)
+		    diff = p_ss;
+		if (off_left < 0)
+		    new_leftcol = curwin->w_leftcol - diff;
+		else
+		    new_leftcol = curwin->w_leftcol + diff;
+	    }
+	    if (new_leftcol < 0)
+		new_leftcol = 0;
+	    if (new_leftcol != (int)curwin->w_leftcol)
+	    {
+		curwin->w_leftcol = new_leftcol;
+		// screen has to be redrawn with new curwin->w_leftcol
+		redraw_later(UPD_NOT_VALID);
+	    }
+	}
+	curwin->w_wcol -= curwin->w_leftcol;
+    }
+    else if (curwin->w_wcol > (int)curwin->w_leftcol)
+	curwin->w_wcol -= curwin->w_leftcol;
+    else
+	curwin->w_wcol = 0;
+
+#ifdef FEAT_DIFF
+    // Skip over filler lines.  At the top use w_topfill, there
+    // may be some filler lines above the window.
+    if (curwin->w_cursor.lnum == curwin->w_topline)
+	curwin->w_wrow += curwin->w_topfill;
+    else
+	curwin->w_wrow += diff_check_fill(curwin, curwin->w_cursor.lnum);
+#endif
+
+    prev_skipcol = curwin->w_skipcol;
+
+    p_lines = 0;
+
+    if ((curwin->w_wrow >= curwin->w_height
+		|| ((prev_skipcol > 0
+			|| curwin->w_wrow + so >= curwin->w_height)
+		    && (p_lines =
+#ifdef FEAT_DIFF
+			plines_win_nofill
+#else
+			plines_win
+#endif
+			(curwin, curwin->w_cursor.lnum, FALSE))
+						    - 1 >= curwin->w_height))
+	    && curwin->w_height != 0
+	    && curwin->w_cursor.lnum == curwin->w_topline
+	    && width2 > 0
+	    && curwin->w_width != 0)
+    {
+	// Cursor past end of screen.  Happens with a single line that does
+	// not fit on screen.  Find a skipcol to show the text around the
+	// cursor.  Avoid scrolling all the time. compute value of "extra":
+	// 1: Less than 'scrolloff' lines above
+	// 2: Less than 'scrolloff' lines below
+	// 3: both of them
+	extra = 0;
+	if (curwin->w_skipcol + so * width2 > curwin->w_virtcol)
+	    extra = 1;
+	// Compute last display line of the buffer line that we want at the
+	// bottom of the window.
+	if (p_lines == 0)
+	    p_lines = plines_win(curwin, curwin->w_cursor.lnum, FALSE);
+	--p_lines;
+	if (p_lines > curwin->w_wrow + so)
+	    n = curwin->w_wrow + so;
+	else
+	    n = p_lines;
+	if ((colnr_T)n >= curwin->w_height + curwin->w_skipcol / width2 - so)
+	    extra += 2;
+
+	if (extra == 3 || curwin->w_height <= so * 2)
+	{
+	    // not enough room for 'scrolloff', put cursor in the middle
+	    n = curwin->w_virtcol / width2;
+	    if (n > curwin->w_height / 2)
+		n -= curwin->w_height / 2;
+	    else
+		n = 0;
+	    // don't skip more than necessary
+	    if (n > p_lines - curwin->w_height + 1)
+		n = p_lines - curwin->w_height + 1;
+	    curwin->w_skipcol = n * width2;
+	}
+	else if (extra == 1)
+	{
+	    // less than 'scrolloff' lines above, decrease skipcol
+	    extra = (curwin->w_skipcol + so * width2 - curwin->w_virtcol
+				     + width2 - 1) / width2;
+	    if (extra > 0)
+	    {
+		if ((colnr_T)(extra * width2) > curwin->w_skipcol)
+		    extra = curwin->w_skipcol / width2;
+		curwin->w_skipcol -= extra * width2;
+	    }
+	}
+	else if (extra == 2)
+	{
+	    // less than 'scrolloff' lines below, increase skipcol
+	    endcol = (n - curwin->w_height + 1) * width2;
+	    while (endcol > curwin->w_virtcol)
+		endcol -= width2;
+	    if (endcol > curwin->w_skipcol)
+		curwin->w_skipcol = endcol;
+	}
+
+	// adjust w_wrow for the changed w_skipcol
+	if (did_sub_skipcol)
+	    curwin->w_wrow -= (curwin->w_skipcol - prev_skipcol) / width2;
+	else
+	    curwin->w_wrow -= curwin->w_skipcol / width2;
+
+	if (curwin->w_wrow >= curwin->w_height)
+	{
+	    // small window, make sure cursor is in it
+	    extra = curwin->w_wrow - curwin->w_height + 1;
+	    curwin->w_skipcol += extra * width2;
+	    curwin->w_wrow -= extra;
+	}
+
+	extra = ((int)prev_skipcol - (int)curwin->w_skipcol) / width2;
+	if (extra > 0)
+	    win_ins_lines(curwin, 0, extra, FALSE, FALSE);
+	else if (extra < 0)
+	    win_del_lines(curwin, 0, -extra, FALSE, FALSE, 0);
+    }
+    else if (!curwin->w_p_sms)
+	curwin->w_skipcol = 0;
+    if (prev_skipcol != curwin->w_skipcol)
+	redraw_later(UPD_SOME_VALID);
+
+#ifdef FEAT_SYN_HL
+    redraw_for_cursorcolumn(curwin);
+#endif
+#if defined(FEAT_PROP_POPUP) && defined(FEAT_TERMINAL)
+    if (popup_is_popup(curwin) && curbuf->b_term != NULL)
+    {
+	curwin->w_wrow += popup_top_extra(curwin);
+	curwin->w_wcol += popup_left_extra(curwin);
+	curwin->w_flags |= WFLAG_WCOL_OFF_ADDED + WFLAG_WROW_OFF_ADDED;
+    }
+    else
+	curwin->w_flags &= ~(WFLAG_WCOL_OFF_ADDED + WFLAG_WROW_OFF_ADDED);
+#endif
+
+    // now w_leftcol and w_skipcol are valid, avoid check_cursor_moved()
+    // thinking otherwise
+    curwin->w_valid_leftcol = curwin->w_leftcol;
+    curwin->w_valid_skipcol = curwin->w_skipcol;
+
+    curwin->w_valid |= VALID_WCOL|VALID_WROW|VALID_VIRTCOL;
+}
+
+#if (defined(FEAT_EVAL) || defined(FEAT_PROP_POPUP)) || defined(PROTO)
+/*
+ * Compute the screen position of text character at "pos" in window "wp"
+ * The resulting values are one-based, zero when character is not visible.
+ */
+    void
+textpos2screenpos(
+	win_T	*wp,
+	pos_T	*pos,
+	int	*rowp,	// screen row
+	int	*scolp,	// start screen column
+	int	*ccolp,	// cursor screen column
+	int	*ecolp)	// end screen column
+{
+    colnr_T	scol = 0, ccol = 0, ecol = 0;
+    int		row = 0;
+    int		rowoff = 0;
+    colnr_T	coloff = 0;
+
+    if (pos->lnum >= wp->w_topline && pos->lnum <= wp->w_botline)
+    {
+	colnr_T	    col;
+	int	    width;
+	linenr_T    lnum = pos->lnum;
+#ifdef FEAT_FOLDING
+	int	    is_folded;
+
+	is_folded = hasFoldingWin(wp, lnum, &lnum, NULL, TRUE, NULL);
+#endif
+	row = plines_m_win(wp, wp->w_topline, lnum - 1) + 1;
+
+#ifdef FEAT_DIFF
+	// Add filler lines above this buffer line.
+	row += diff_check_fill(wp, lnum);
+#endif
+
+	colnr_T	off = win_col_off(wp);
+#ifdef FEAT_FOLDING
+	if (is_folded)
+	{
+	    row += W_WINROW(wp);
+	    coloff = wp->w_wincol + 1 + off;
+	}
+	else
+#endif
+	{
+	    getvcol(wp, pos, &scol, &ccol, &ecol);
+
+	    // similar to what is done in validate_cursor_col()
+	    col = scol;
+	    col += off;
+	    width = wp->w_width - off + win_col_off2(wp);
+
+	    // long line wrapping, adjust row
+	    if (wp->w_p_wrap
+		    && col >= (colnr_T)wp->w_width
+		    && width > 0)
+	    {
+		// use same formula as what is used in curs_columns()
+		rowoff = ((col - wp->w_width) / width + 1);
+		col -= rowoff * width;
+	    }
+	    col -= wp->w_leftcol;
+	    if (col >= wp->w_width)
+		col = -1;
+	    if (col >= 0 && row + rowoff <= wp->w_height)
+	    {
+		coloff = col - scol + wp->w_wincol + 1;
+		row += W_WINROW(wp);
+	    }
+	    else
+		// character is left, right or below of the window
+		row = rowoff = scol = ccol = ecol = 0;
+	}
+    }
+    *rowp = row + rowoff;
+    *scolp = scol + coloff;
+    *ccolp = ccol + coloff;
+    *ecolp = ecol + coloff;
+}
+#endif
+
+#if defined(FEAT_EVAL) || defined(PROTO)
+/*
+ * "screenpos({winid}, {lnum}, {col})" function
+ */
+    void
+f_screenpos(typval_T *argvars UNUSED, typval_T *rettv)
+{
+    dict_T	*dict;
+    win_T	*wp;
+    pos_T	pos;
+    int		row = 0;
+    int		scol = 0, ccol = 0, ecol = 0;
+
+    if (rettv_dict_alloc(rettv) == FAIL)
+	return;
+    dict = rettv->vval.v_dict;
+
+    if (in_vim9script()
+	    && (check_for_number_arg(argvars, 0) == FAIL
+		|| check_for_number_arg(argvars, 1) == FAIL
+		|| check_for_number_arg(argvars, 2) == FAIL))
+	return;
+
+    wp = find_win_by_nr_or_id(&argvars[0]);
+    if (wp == NULL)
+	return;
+
+    pos.lnum = tv_get_number(&argvars[1]);
+    if (pos.lnum > wp->w_buffer->b_ml.ml_line_count)
+    {
+	semsg(_(e_invalid_line_number_nr), pos.lnum);
+	return;
+    }
+    pos.col = tv_get_number(&argvars[2]) - 1;
+    pos.coladd = 0;
+    textpos2screenpos(wp, &pos, &row, &scol, &ccol, &ecol);
+
+    dict_add_number(dict, "row", row);
+    dict_add_number(dict, "col", scol);
+    dict_add_number(dict, "curscol", ccol);
+    dict_add_number(dict, "endcol", ecol);
+}
+
+/*
+ * "virtcol2col({winid}, {lnum}, {col})" function
+ */
+    void
+f_virtcol2col(typval_T *argvars UNUSED, typval_T *rettv)
+{
+    win_T	*wp;
+    linenr_T	lnum;
+    int		screencol;
+    int		error = FALSE;
+
+    rettv->vval.v_number = -1;
+
+    if (check_for_number_arg(argvars, 0) == FAIL
+	    || check_for_number_arg(argvars, 1) == FAIL
+	    || check_for_number_arg(argvars, 2) == FAIL)
+	return;
+
+    wp = find_win_by_nr_or_id(&argvars[0]);
+    if (wp == NULL)
+	return;
+
+    lnum = tv_get_number_chk(&argvars[1], &error);
+    if (error || lnum < 0 || lnum > wp->w_buffer->b_ml.ml_line_count)
+	return;
+
+    screencol = tv_get_number_chk(&argvars[2], &error);
+    if (error || screencol < 0)
+	return;
+
+    rettv->vval.v_number = vcol2col(wp, lnum, screencol);
+}
+#endif
+
+/*
+ * Scroll the current window down by "line_count" logical lines.  "CTRL-Y"
+ */
+    void
+scrolldown(
+    long	line_count,
+    int		byfold UNUSED)	// TRUE: count a closed fold as one line
+{
+    long	done = 0;	// total # of physical lines done
+    int		wrow;
+    int		moved = FALSE;
+    int		do_sms = curwin->w_p_wrap && curwin->w_p_sms;
+    int		width1 = 0;
+    int		width2 = 0;
+
+    if (do_sms)
+    {
+	width1 = curwin->w_width - curwin_col_off();
+	width2 = width1 + curwin_col_off2();
+    }
+
+#ifdef FEAT_FOLDING
+    linenr_T	first;
+
+    // Make sure w_topline is at the first of a sequence of folded lines.
+    (void)hasFolding(curwin->w_topline, &curwin->w_topline, NULL);
+#endif
+    validate_cursor();		// w_wrow needs to be valid
+    for (int todo = line_count; todo > 0; --todo)
+    {
+#ifdef FEAT_DIFF
+	if (curwin->w_topfill < diff_check(curwin, curwin->w_topline)
+		&& curwin->w_topfill < curwin->w_height - 1)
+	{
+	    ++curwin->w_topfill;
+	    ++done;
+	}
+	else
+#endif
+	{
+	    // break when at the very top
+	    if (curwin->w_topline == 1
+				   && (!do_sms || curwin->w_skipcol < width1))
+		break;
+	    if (do_sms && curwin->w_skipcol >= width1)
+	    {
+		// scroll a screen line down
+		if (curwin->w_skipcol >= width1 + width2)
+		    curwin->w_skipcol -= width2;
+		else
+		    curwin->w_skipcol -= width1;
+		redraw_later(UPD_NOT_VALID);
+		++done;
+	    }
+	    else
+	    {
+		// scroll a text line down
+		--curwin->w_topline;
+		curwin->w_skipcol = 0;
+#ifdef FEAT_DIFF
+		curwin->w_topfill = 0;
+#endif
+#ifdef FEAT_FOLDING
+		// A sequence of folded lines only counts for one logical line
+		if (hasFolding(curwin->w_topline, &first, NULL))
+		{
+		    ++done;
+		    if (!byfold)
+			todo -= curwin->w_topline - first - 1;
+		    curwin->w_botline -= curwin->w_topline - first;
+		    curwin->w_topline = first;
+		}
+		else
+#endif
+		if (do_sms)
+		{
+		    int size = win_linetabsize(curwin, curwin->w_topline,
+				   ml_get(curwin->w_topline), (colnr_T)MAXCOL);
+		    if (size > width1)
+		    {
+			curwin->w_skipcol = width1;
+			size -= width1;
+			redraw_later(UPD_NOT_VALID);
+		    }
+		    while (size > width2)
+		    {
+			curwin->w_skipcol += width2;
+			size -= width2;
+		    }
+		    ++done;
+		}
+		else
+		    done += PLINES_NOFILL(curwin->w_topline);
+	    }
+	}
+	--curwin->w_botline;		// approximate w_botline
+	invalidate_botline();
+    }
+    curwin->w_wrow += done;		// keep w_wrow updated
+    curwin->w_cline_row += done;	// keep w_cline_row updated
+
+#ifdef FEAT_DIFF
+    if (curwin->w_cursor.lnum == curwin->w_topline)
+	curwin->w_cline_row = 0;
+    check_topfill(curwin, TRUE);
+#endif
+
+    /*
+     * Compute the row number of the last row of the cursor line
+     * and move the cursor onto the displayed part of the window.
+     */
+    wrow = curwin->w_wrow;
+    if (curwin->w_p_wrap && curwin->w_width != 0)
+    {
+	validate_virtcol();
+	validate_cheight();
+	wrow += curwin->w_cline_height - 1 -
+	    curwin->w_virtcol / curwin->w_width;
+    }
+    while (wrow >= curwin->w_height && curwin->w_cursor.lnum > 1)
+    {
+#ifdef FEAT_FOLDING
+	if (hasFolding(curwin->w_cursor.lnum, &first, NULL))
+	{
+	    --wrow;
+	    if (first == 1)
+		curwin->w_cursor.lnum = 1;
+	    else
+		curwin->w_cursor.lnum = first - 1;
+	}
+	else
+#endif
+	    wrow -= plines(curwin->w_cursor.lnum--);
+	curwin->w_valid &=
+	      ~(VALID_WROW|VALID_WCOL|VALID_CHEIGHT|VALID_CROW|VALID_VIRTCOL);
+	moved = TRUE;
+    }
+    if (moved)
+    {
+#ifdef FEAT_FOLDING
+	// Move cursor to first line of closed fold.
+	foldAdjustCursor();
+#endif
+	coladvance(curwin->w_curswant);
+    }
+
+    if (curwin->w_cursor.lnum == curwin->w_topline && do_sms)
+    {
+	long	so = get_scrolloff_value();
+	int	scrolloff_cols = so == 0 ? 0 : width1 + (so - 1) * width2;
+
+	// make sure the cursor is in the visible text
+	validate_virtcol();
+	int col = curwin->w_virtcol - curwin->w_skipcol + scrolloff_cols;
+	int row = 0;
+	if (col >= width1)
+	{
+	    col -= width1;
+	    ++row;
+	}
+	if (col > width2 && width2 > 0)
+	{
+	    row += col / width2;
+	    col = col % width2;
+	}
+	if (row >= curwin->w_height)
+	{
+	    curwin->w_curswant = curwin->w_virtcol
+				       - (row - curwin->w_height + 1) * width2;
+	    coladvance(curwin->w_curswant);
+	}
+    }
+}
+
+/*
+ * Return TRUE if scrollup() will scroll by screen line rather than text line.
+ */
+    static int
+scrolling_screenlines(int byfold UNUSED)
+{
+    return (curwin->w_p_wrap && curwin->w_p_sms)
+# ifdef FEAT_FOLDING
+	|| (byfold && hasAnyFolding(curwin))
+# endif
+# ifdef FEAT_DIFF
+	|| curwin->w_p_diff
+# endif
+	;
+}
+
+/*
+ * Scroll the current window up by "line_count" logical lines.  "CTRL-E"
+ */
+    void
+scrollup(
+    long	line_count,
+    int		byfold UNUSED)	// TRUE: count a closed fold as one line
+{
+    int		do_sms = curwin->w_p_wrap && curwin->w_p_sms;
+
+    if (scrolling_screenlines(byfold))
+    {
+	int	    width1 = curwin->w_width - curwin_col_off();
+	int	    width2 = width1 + curwin_col_off2();
+	int	    size = 0;
+	linenr_T    prev_topline = curwin->w_topline;
+
+	if (do_sms)
+	    size = linetabsize(curwin, curwin->w_topline);
+
+	// diff mode: first consume "topfill"
+	// 'smoothscroll': increase "w_skipcol" until it goes over the end of
+	// the line, then advance to the next line.
+	// folding: count each sequence of folded lines as one logical line.
+	for (int todo = line_count; todo > 0; --todo)
+	{
+# ifdef FEAT_DIFF
+	    if (curwin->w_topfill > 0)
+		--curwin->w_topfill;
+	    else
+# endif
+	    {
+		linenr_T lnum = curwin->w_topline;
+
+# ifdef FEAT_FOLDING
+		if (byfold)
+		    // for a closed fold: go to the last line in the fold
+		    (void)hasFolding(lnum, NULL, &lnum);
+# endif
+		if (lnum == curwin->w_topline && do_sms)
+		{
+		    // 'smoothscroll': increase "w_skipcol" until it goes over
+		    // the end of the line, then advance to the next line.
+		    int add = curwin->w_skipcol > 0 ? width2 : width1;
+		    curwin->w_skipcol += add;
+		    if (curwin->w_skipcol >= size)
+		    {
+			if (lnum == curbuf->b_ml.ml_line_count)
+			{
+			    // at the last screen line, can't scroll further
+			    curwin->w_skipcol -= add;
+			    break;
+			}
+			++lnum;
+		    }
+		}
+		else
+		{
+		    if (lnum >= curbuf->b_ml.ml_line_count)
+			break;
+		    ++lnum;
+		}
+
+		if (lnum > curwin->w_topline)
+		{
+		    // approximate w_botline
+		    curwin->w_botline += lnum - curwin->w_topline;
+		    curwin->w_topline = lnum;
+# ifdef FEAT_DIFF
+		    curwin->w_topfill = diff_check_fill(curwin, lnum);
+# endif
+		    curwin->w_skipcol = 0;
+		    if (todo > 1 && do_sms)
+			size = linetabsize(curwin, curwin->w_topline);
+		}
+	    }
+	}
+
+	if (curwin->w_topline == prev_topline)
+	    // need to redraw even though w_topline didn't change
+	    redraw_later(UPD_NOT_VALID);
+    }
+    else
+    {
+	curwin->w_topline += line_count;
+	curwin->w_botline += line_count;	// approximate w_botline
+    }
+
+    if (curwin->w_topline > curbuf->b_ml.ml_line_count)
+	curwin->w_topline = curbuf->b_ml.ml_line_count;
+    if (curwin->w_botline > curbuf->b_ml.ml_line_count + 1)
+	curwin->w_botline = curbuf->b_ml.ml_line_count + 1;
+
+#ifdef FEAT_DIFF
+    check_topfill(curwin, FALSE);
+#endif
+
+#ifdef FEAT_FOLDING
+    if (hasAnyFolding(curwin))
+	// Make sure w_topline is at the first of a sequence of folded lines.
+	(void)hasFolding(curwin->w_topline, &curwin->w_topline, NULL);
+#endif
+
+    curwin->w_valid &= ~(VALID_WROW|VALID_CROW|VALID_BOTLINE);
+    if (curwin->w_cursor.lnum < curwin->w_topline)
+    {
+	curwin->w_cursor.lnum = curwin->w_topline;
+	curwin->w_valid &=
+	      ~(VALID_WROW|VALID_WCOL|VALID_CHEIGHT|VALID_CROW|VALID_VIRTCOL);
+	coladvance(curwin->w_curswant);
+    }
+    if (curwin->w_cursor.lnum == curwin->w_topline
+					    && do_sms && curwin->w_skipcol > 0)
+    {
+	int	col_off = curwin_col_off();
+	int	col_off2 = curwin_col_off2();
+
+	int	width1 = curwin->w_width - col_off;
+	int	width2 = width1 + col_off2;
+	int	extra2 = col_off - col_off2;
+	long	so = get_scrolloff_value();
+	int	scrolloff_cols = so == 0 ? 0 : width1 + (so - 1) * width2;
+	int	space_cols = (curwin->w_height - 1) * width2;
+
+	// If we have non-zero scrolloff, just ignore the <<< marker as we are
+	// going past it anyway.
+	int smoothscroll_overlap = scrolloff_cols != 0 ? 0 :
+					   smoothscroll_marker_overlap(extra2);
+
+	// Make sure the cursor is in a visible part of the line, taking
+	// 'scrolloff' into account, but using screen lines.
+	// If there are not enough screen lines put the cursor in the middle.
+	if (scrolloff_cols > space_cols / 2)
+	    scrolloff_cols = space_cols / 2;
+	validate_virtcol();
+	if (curwin->w_virtcol < curwin->w_skipcol
+				       + smoothscroll_overlap + scrolloff_cols)
+	{
+	    colnr_T col = curwin->w_virtcol;
+
+	    if (col < width1)
+		col += width1;
+	    while (col < curwin->w_skipcol
+				       + smoothscroll_overlap + scrolloff_cols)
+		col += width2;
+	    curwin->w_curswant = col;
+	    coladvance(curwin->w_curswant);
+
+	    // validate_virtcol() marked various things as valid, but after
+	    // moving the cursor they need to be recomputed
+	    curwin->w_valid &=
+	       ~(VALID_WROW|VALID_WCOL|VALID_CHEIGHT|VALID_CROW|VALID_VIRTCOL);
+	}
+    }
+}
+
+/*
+ * Called after changing the cursor column: make sure that curwin->w_skipcol is
+ * valid for 'smoothscroll'.
+ */
+    void
+adjust_skipcol(void)
+{
+    if (!curwin->w_p_wrap
+	    || !curwin->w_p_sms
+	    || curwin->w_cursor.lnum != curwin->w_topline)
+	return;
+
+    int	    width1 = curwin->w_width - curwin_col_off();
+    if (width1 <= 0)
+	return;  // no text will be displayed
+
+    int	    width2 = width1 + curwin_col_off2();
+    long    so = get_scrolloff_value();
+    int	    scrolloff_cols = so == 0 ? 0 : width1 + (so - 1) * width2;
+    int	    scrolled = FALSE;
+
+    validate_cheight();
+    if (curwin->w_cline_height == curwin->w_height
+	    // w_cline_height may be capped at w_height, check there aren't
+	    // actually more lines.
+	    && plines_win(curwin, curwin->w_cursor.lnum, FALSE)
+							   <= curwin->w_height)
+    {
+	// the line just fits in the window, don't scroll
+	reset_skipcol();
+	return;
+    }
+
+    validate_virtcol();
+    while (curwin->w_skipcol > 0
+		 && curwin->w_virtcol < curwin->w_skipcol + 3 + scrolloff_cols)
+    {
+	// scroll a screen line down
+	if (curwin->w_skipcol >= width1 + width2)
+	    curwin->w_skipcol -= width2;
+	else
+	    curwin->w_skipcol -= width1;
+	redraw_later(UPD_NOT_VALID);
+	scrolled = TRUE;
+	validate_virtcol();
+    }
+    if (scrolled)
+	return;  // don't scroll in the other direction now
+
+    int col = curwin->w_virtcol - curwin->w_skipcol + scrolloff_cols;
+    int row = 0;
+    if (col >= width1)
+    {
+	col -= width1;
+	++row;
+    }
+    if (col > width2)
+    {
+	row += col / width2;
+	col = col % width2;
+    }
+    if (row >= curwin->w_height)
+    {
+	if (curwin->w_skipcol == 0)
+	{
+	    curwin->w_skipcol += width1;
+	    --row;
+	}
+	if (row >= curwin->w_height)
+	    curwin->w_skipcol += (row - curwin->w_height) * width2;
+	redraw_later(UPD_NOT_VALID);
+    }
+}
+
+#ifdef FEAT_DIFF
+/*
+ * Don't end up with too many filler lines in the window.
+ */
+    void
+check_topfill(
+    win_T	*wp,
+    int		down)	// when TRUE scroll down when not enough space
+{
+    int		n;
+
+    if (wp->w_topfill <= 0)
+	return;
+
+    n = plines_win_nofill(wp, wp->w_topline, TRUE);
+    if (wp->w_topfill + n > wp->w_height)
+    {
+	if (down && wp->w_topline > 1)
+	{
+	    --wp->w_topline;
+	    wp->w_topfill = 0;
+	}
+	else
+	{
+	    wp->w_topfill = wp->w_height - n;
+	    if (wp->w_topfill < 0)
+		wp->w_topfill = 0;
+	}
+    }
+}
+
+/*
+ * Use as many filler lines as possible for w_topline.  Make sure w_topline
+ * is still visible.
+ */
+    static void
+max_topfill(void)
+{
+    int		n;
+
+    n = plines_nofill(curwin->w_topline);
+    if (n >= curwin->w_height)
+	curwin->w_topfill = 0;
+    else
+    {
+	curwin->w_topfill = diff_check_fill(curwin, curwin->w_topline);
+	if (curwin->w_topfill + n > curwin->w_height)
+	    curwin->w_topfill = curwin->w_height - n;
+    }
+}
+#endif
+
+/*
+ * Scroll the screen one line down, but don't do it if it would move the
+ * cursor off the screen.
+ */
+    void
+scrolldown_clamp(void)
+{
+    int		end_row;
+#ifdef FEAT_DIFF
+    int		can_fill = (curwin->w_topfill
+				< diff_check_fill(curwin, curwin->w_topline));
+#endif
+
+    if (curwin->w_topline <= 1
+#ifdef FEAT_DIFF
+	    && !can_fill
+#endif
+	    )
+	return;
+
+    validate_cursor();	    // w_wrow needs to be valid
+
+    /*
+     * Compute the row number of the last row of the cursor line
+     * and make sure it doesn't go off the screen. Make sure the cursor
+     * doesn't go past 'scrolloff' lines from the screen end.
+     */
+    end_row = curwin->w_wrow;
+#ifdef FEAT_DIFF
+    if (can_fill)
+	++end_row;
+    else
+	end_row += plines_nofill(curwin->w_topline - 1);
+#else
+    end_row += plines(curwin->w_topline - 1);
+#endif
+    if (curwin->w_p_wrap && curwin->w_width != 0)
+    {
+	validate_cheight();
+	validate_virtcol();
+	end_row += curwin->w_cline_height - 1 -
+	    curwin->w_virtcol / curwin->w_width;
+    }
+    if (end_row < curwin->w_height - get_scrolloff_value())
+    {
+#ifdef FEAT_DIFF
+	if (can_fill)
+	{
+	    ++curwin->w_topfill;
+	    check_topfill(curwin, TRUE);
+	}
+	else
+	{
+	    --curwin->w_topline;
+	    curwin->w_topfill = 0;
+	}
+#else
+	--curwin->w_topline;
+#endif
+#ifdef FEAT_FOLDING
+	(void)hasFolding(curwin->w_topline, &curwin->w_topline, NULL);
+#endif
+	--curwin->w_botline;	    // approximate w_botline
+	curwin->w_valid &= ~(VALID_WROW|VALID_CROW|VALID_BOTLINE);
+    }
+}
+
+/*
+ * Scroll the screen one line up, but don't do it if it would move the cursor
+ * off the screen.
+ */
+    void
+scrollup_clamp(void)
+{
+    int	    start_row;
+
+    if (curwin->w_topline == curbuf->b_ml.ml_line_count
+#ifdef FEAT_DIFF
+	    && curwin->w_topfill == 0
+#endif
+	    )
+	return;
+
+    validate_cursor();	    // w_wrow needs to be valid
+
+    /*
+     * Compute the row number of the first row of the cursor line
+     * and make sure it doesn't go off the screen. Make sure the cursor
+     * doesn't go before 'scrolloff' lines from the screen start.
+     */
+#ifdef FEAT_DIFF
+    start_row = curwin->w_wrow - plines_nofill(curwin->w_topline)
+							  - curwin->w_topfill;
+#else
+    start_row = curwin->w_wrow - plines(curwin->w_topline);
+#endif
+    if (curwin->w_p_wrap && curwin->w_width != 0)
+    {
+	validate_virtcol();
+	start_row -= curwin->w_virtcol / curwin->w_width;
+    }
+    if (start_row >= get_scrolloff_value())
+    {
+#ifdef FEAT_DIFF
+	if (curwin->w_topfill > 0)
+	    --curwin->w_topfill;
+	else
+#endif
+	{
+#ifdef FEAT_FOLDING
+	    (void)hasFolding(curwin->w_topline, NULL, &curwin->w_topline);
+#endif
+	    ++curwin->w_topline;
+	}
+	++curwin->w_botline;		// approximate w_botline
+	curwin->w_valid &= ~(VALID_WROW|VALID_CROW|VALID_BOTLINE);
+    }
+}
+
+/*
+ * Add one line above "lp->lnum".  This can be a filler line, a closed fold or
+ * a (wrapped) text line.  Uses and sets "lp->fill".
+ * Returns the height of the added line in "lp->height".
+ * Lines above the first one are incredibly high: MAXCOL.
+ */
+    static void
+topline_back_winheight(
+    lineoff_T	*lp,
+    int		winheight)	// when TRUE limit to window height
+{
+#ifdef FEAT_DIFF
+    if (lp->fill < diff_check_fill(curwin, lp->lnum))
+    {
+	// Add a filler line.
+	++lp->fill;
+	lp->height = 1;
+    }
+    else
+#endif
+    {
+	--lp->lnum;
+#ifdef FEAT_DIFF
+	lp->fill = 0;
+#endif
+	if (lp->lnum < 1)
+	    lp->height = MAXCOL;
+	else
+#ifdef FEAT_FOLDING
+	    if (hasFolding(lp->lnum, &lp->lnum, NULL))
+	    // Add a closed fold
+	    lp->height = 1;
+	else
+#endif
+	    lp->height = PLINES_WIN_NOFILL(curwin, lp->lnum, winheight);
+    }
+}
+
+    static void
+topline_back(lineoff_T *lp)
+{
+    topline_back_winheight(lp, TRUE);
+}
+
+
+/*
+ * Add one line below "lp->lnum".  This can be a filler line, a closed fold or
+ * a (wrapped) text line.  Uses and sets "lp->fill".
+ * Returns the height of the added line in "lp->height".
+ * Lines below the last one are incredibly high.
+ */
+    static void
+botline_forw(lineoff_T *lp)
+{
+#ifdef FEAT_DIFF
+    if (lp->fill < diff_check_fill(curwin, lp->lnum + 1))
+    {
+	// Add a filler line.
+	++lp->fill;
+	lp->height = 1;
+    }
+    else
+#endif
+    {
+	++lp->lnum;
+#ifdef FEAT_DIFF
+	lp->fill = 0;
+#endif
+	if (lp->lnum > curbuf->b_ml.ml_line_count)
+	    lp->height = MAXCOL;
+	else
+#ifdef FEAT_FOLDING
+	    if (hasFolding(lp->lnum, NULL, &lp->lnum))
+	    // Add a closed fold
+	    lp->height = 1;
+	else
+#endif
+	    lp->height = PLINES_NOFILL(lp->lnum);
+    }
+}
+
+#ifdef FEAT_DIFF
+/*
+ * Switch from including filler lines below lp->lnum to including filler
+ * lines above loff.lnum + 1.  This keeps pointing to the same line.
+ * When there are no filler lines nothing changes.
+ */
+    static void
+botline_topline(lineoff_T *lp)
+{
+    if (lp->fill > 0)
+    {
+	++lp->lnum;
+	lp->fill = diff_check_fill(curwin, lp->lnum) - lp->fill + 1;
+    }
+}
+
+/*
+ * Switch from including filler lines above lp->lnum to including filler
+ * lines below loff.lnum - 1.  This keeps pointing to the same line.
+ * When there are no filler lines nothing changes.
+ */
+    static void
+topline_botline(lineoff_T *lp)
+{
+    if (lp->fill > 0)
+    {
+	lp->fill = diff_check_fill(curwin, lp->lnum) - lp->fill + 1;
+	--lp->lnum;
+    }
+}
+#endif
+
+/*
+ * Recompute topline to put the cursor at the top of the window.
+ * Scroll at least "min_scroll" lines.
+ * If "always" is TRUE, always set topline (for "zt").
+ */
+    void
+scroll_cursor_top(int min_scroll, int always)
+{
+    int		scrolled = 0;
+    int		extra = 0;
+    int		used;
+    int		i;
+    linenr_T	top;		// just above displayed lines
+    linenr_T	bot;		// just below displayed lines
+    linenr_T	old_topline = curwin->w_topline;
+    int		old_skipcol = curwin->w_skipcol;
+#ifdef FEAT_DIFF
+    linenr_T	old_topfill = curwin->w_topfill;
+#endif
+    linenr_T	new_topline;
+    int		off = get_scrolloff_value();
+
+    if (mouse_dragging > 0)
+	off = mouse_dragging - 1;
+
+    /*
+     * Decrease topline until:
+     * - it has become 1
+     * - (part of) the cursor line is moved off the screen or
+     * - moved at least 'scrolljump' lines and
+     * - at least 'scrolloff' lines above and below the cursor
+     */
+    validate_cheight();
+    used = curwin->w_cline_height; // includes filler lines above
+    if (curwin->w_cursor.lnum < curwin->w_topline)
+	scrolled = used;
+
+#ifdef FEAT_FOLDING
+    if (hasFolding(curwin->w_cursor.lnum, &top, &bot))
+    {
+	--top;
+	++bot;
+    }
+    else
+#endif
+    {
+	top = curwin->w_cursor.lnum - 1;
+	bot = curwin->w_cursor.lnum + 1;
+    }
+    new_topline = top + 1;
+
+#ifdef FEAT_DIFF
+    // "used" already contains the number of filler lines above, don't add it
+    // again.
+    // Hide filler lines above cursor line by adding them to "extra".
+    extra += diff_check_fill(curwin, curwin->w_cursor.lnum);
+#endif
+
+    /*
+     * Check if the lines from "top" to "bot" fit in the window.  If they do,
+     * set new_topline and advance "top" and "bot" to include more lines.
+     */
+    while (top > 0)
+    {
+#ifdef FEAT_FOLDING
+	if (hasFolding(top, &top, NULL))
+	    // count one logical line for a sequence of folded lines
+	    i = 1;
+	else
+#endif
+	    i = PLINES_NOFILL(top);
+	if (top < curwin->w_topline)
+	    scrolled += i;
+
+	// If scrolling is needed, scroll at least 'sj' lines.
+	if ((new_topline >= curwin->w_topline || scrolled > min_scroll)
+		&& extra >= off)
+	    break;
+
+	used += i;
+	if (extra + i <= off && bot < curbuf->b_ml.ml_line_count)
+	{
+#ifdef FEAT_FOLDING
+	    if (hasFolding(bot, NULL, &bot))
+		// count one logical line for a sequence of folded lines
+		++used;
+	    else
+#endif
+		used += plines(bot);
+	}
+	if (used > curwin->w_height)
+	    break;
+
+	extra += i;
+	new_topline = top;
+	--top;
+	++bot;
+    }
+
+    /*
+     * If we don't have enough space, put cursor in the middle.
+     * This makes sure we get the same position when using "k" and "j"
+     * in a small window.
+     */
+    if (used > curwin->w_height)
+	scroll_cursor_halfway(FALSE, FALSE);
+    else
+    {
+	/*
+	 * If "always" is FALSE, only adjust topline to a lower value, higher
+	 * value may happen with wrapping lines.
+	 */
+	if (new_topline < curwin->w_topline || always)
+	    curwin->w_topline = new_topline;
+	if (curwin->w_topline > curwin->w_cursor.lnum)
+	    curwin->w_topline = curwin->w_cursor.lnum;
+#ifdef FEAT_DIFF
+	curwin->w_topfill = diff_check_fill(curwin, curwin->w_topline);
+	if (curwin->w_topfill > 0 && extra > off)
+	{
+	    curwin->w_topfill -= extra - off;
+	    if (curwin->w_topfill < 0)
+		curwin->w_topfill = 0;
+	}
+	check_topfill(curwin, FALSE);
+#endif
+	// TODO: if the line doesn't fit may optimize w_skipcol
+	if (curwin->w_topline == curwin->w_cursor.lnum
+		&& curwin->w_skipcol >= curwin->w_cursor.col)
+	    reset_skipcol();
+	if (curwin->w_topline != old_topline
+		|| curwin->w_skipcol != old_skipcol
+#ifdef FEAT_DIFF
+		|| curwin->w_topfill != old_topfill
+#endif
+		)
+	    curwin->w_valid &=
+		      ~(VALID_WROW|VALID_CROW|VALID_BOTLINE|VALID_BOTLINE_AP);
+	curwin->w_valid |= VALID_TOPLINE;
+    }
+}
+
+/*
+ * Set w_empty_rows and w_filler_rows for window "wp", having used up "used"
+ * screen lines for text lines.
+ */
+    void
+set_empty_rows(win_T *wp, int used)
+{
+#ifdef FEAT_DIFF
+    wp->w_filler_rows = 0;
+#endif
+    if (used == 0)
+	wp->w_empty_rows = 0;	// single line that doesn't fit
+    else
+    {
+	wp->w_empty_rows = wp->w_height - used;
+#ifdef FEAT_DIFF
+	if (wp->w_botline <= wp->w_buffer->b_ml.ml_line_count)
+	{
+	    wp->w_filler_rows = diff_check_fill(wp, wp->w_botline);
+	    if (wp->w_empty_rows > wp->w_filler_rows)
+		wp->w_empty_rows -= wp->w_filler_rows;
+	    else
+	    {
+		wp->w_filler_rows = wp->w_empty_rows;
+		wp->w_empty_rows = 0;
+	    }
+	}
+#endif
+    }
+}
+
+/*
+ * Recompute topline to put the cursor at the bottom of the window.
+ * When scrolling scroll at least "min_scroll" lines.
+ * If "set_topbot" is TRUE, set topline and botline first (for "zb").
+ * This is messy stuff!!!
+ */
+    void
+scroll_cursor_bot(int min_scroll, int set_topbot)
+{
+    int		used;
+    int		scrolled = 0;
+    int		min_scrolled = 1;
+    int		extra = 0;
+    int		i;
+    linenr_T	line_count;
+    linenr_T	old_topline = curwin->w_topline;
+    int		old_skipcol = curwin->w_skipcol;
+    lineoff_T	loff;
+    lineoff_T	boff;
+#ifdef FEAT_DIFF
+    int		old_topfill = curwin->w_topfill;
+    int		fill_below_window;
+#endif
+    linenr_T	old_botline = curwin->w_botline;
+    linenr_T	old_valid = curwin->w_valid;
+    int		old_empty_rows = curwin->w_empty_rows;
+    linenr_T	cln;		    // Cursor Line Number
+    long	so = get_scrolloff_value();
+
+    cln = curwin->w_cursor.lnum;
+    if (set_topbot)
+    {
+	int set_skipcol = FALSE;
+
+	used = 0;
+	curwin->w_botline = cln + 1;
+#ifdef FEAT_DIFF
+	loff.fill = 0;
+#endif
+	for (curwin->w_topline = curwin->w_botline;
+		curwin->w_topline > 1;
+		curwin->w_topline = loff.lnum)
+	{
+	    loff.lnum = curwin->w_topline;
+	    topline_back_winheight(&loff, FALSE);
+	    if (loff.height == MAXCOL)
+		break;
+	    if (used + loff.height > curwin->w_height)
+	    {
+		if (curwin->w_p_sms && curwin->w_p_wrap)
+		{
+		    // 'smoothscroll' and 'wrap' are set.  The above line is
+		    // too long to show in its entirety, so we show just a part
+		    // of it.
+		    if (used < curwin->w_height)
+		    {
+			int plines_offset = used + loff.height
+							    - curwin->w_height;
+			used = curwin->w_height;
+#ifdef FEAT_DIFF
+			curwin->w_topfill = loff.fill;
+#endif
+			curwin->w_topline = loff.lnum;
+			curwin->w_skipcol = skipcol_from_plines(
+							curwin, plines_offset);
+			set_skipcol = TRUE;
+		    }
+		}
+		break;
+	    }
+	    used += loff.height;
+#ifdef FEAT_DIFF
+	    curwin->w_topfill = loff.fill;
+#endif
+	}
+	set_empty_rows(curwin, used);
+	curwin->w_valid |= VALID_BOTLINE|VALID_BOTLINE_AP;
+	if (curwin->w_topline != old_topline
+#ifdef FEAT_DIFF
+		|| curwin->w_topfill != old_topfill
+#endif
+		|| set_skipcol
+		|| curwin->w_skipcol != 0)
+	{
+	    curwin->w_valid &= ~(VALID_WROW|VALID_CROW);
+	    if (set_skipcol)
+		redraw_later(UPD_NOT_VALID);
+	    else
+		reset_skipcol();
+	}
+    }
+    else
+	validate_botline();
+
+    // The lines of the cursor line itself are always used.
+#ifdef FEAT_DIFF
+    used = plines_nofill(cln);
+#else
+    validate_cheight();
+    used = curwin->w_cline_height;
+#endif
+
+    // If the cursor is on or below botline, we will at least scroll by the
+    // height of the cursor line, which is "used".  Correct for empty lines,
+    // which are really part of botline.
+    if (cln >= curwin->w_botline)
+    {
+	scrolled = used;
+	if (cln == curwin->w_botline)
+	    scrolled -= curwin->w_empty_rows;
+	min_scrolled = scrolled;
+	if (curwin->w_p_sms && curwin->w_p_wrap)
+	{
+	    // 'smoothscroll' and 'wrap' are set
+	    if (cln > curwin->w_botline)
+		// add screen lines below w_botline
+		for (linenr_T lnum = curwin->w_botline + 1; lnum <= cln; ++lnum)
+		    min_scrolled += PLINES_NOFILL(lnum);
+
+	    // Calculate how many screen lines the current top line of window
+	    // occupies. If it is occupying more than the entire window, we
+	    // need to scroll the additional clipped lines to scroll past the
+	    // top line before we can move on to the other lines.
+	    int top_plines =
+#ifdef FEAT_DIFF
+			    plines_win_nofill
+#else
+			    plines_win
+#endif
+					(curwin, curwin->w_topline, FALSE);
+	    int skip_lines = 0;
+	    int width1 = curwin->w_width - curwin_col_off();
+	    int width2 = width1 + curwin_col_off2();
+	    // similar formula is used in curs_columns()
+	    if (curwin->w_skipcol > width1)
+		skip_lines += (curwin->w_skipcol - width1) / width2 + 1;
+	    else if (curwin->w_skipcol > 0)
+		skip_lines = 1;
+
+	    top_plines -= skip_lines;
+	    if (top_plines > curwin->w_height)
+	    {
+		scrolled += (top_plines - curwin->w_height);
+		min_scrolled += (top_plines - curwin->w_height);
+	    }
+	}
+    }
+
+    /*
+     * Stop counting lines to scroll when
+     * - hitting start of the file
+     * - scrolled nothing or at least 'sj' lines
+     * - at least 'scrolloff' lines below the cursor
+     * - lines between botline and cursor have been counted
+     */
+#ifdef FEAT_FOLDING
+    if (!hasFolding(curwin->w_cursor.lnum, &loff.lnum, &boff.lnum))
+#endif
+    {
+	loff.lnum = cln;
+	boff.lnum = cln;
+    }
+#ifdef FEAT_DIFF
+    loff.fill = 0;
+    boff.fill = 0;
+    fill_below_window = diff_check_fill(curwin, curwin->w_botline)
+						      - curwin->w_filler_rows;
+#endif
+
+    while (loff.lnum > 1)
+    {
+	// Stop when scrolled nothing or at least "min_scroll", found "extra"
+	// context for 'scrolloff' and counted all lines below the window.
+	if ((((scrolled <= 0 || scrolled >= min_scroll)
+		    && extra >= (mouse_dragging > 0 ? mouse_dragging - 1 : so))
+		    || boff.lnum + 1 > curbuf->b_ml.ml_line_count)
+		&& loff.lnum <= curwin->w_botline
+#ifdef FEAT_DIFF
+		&& (loff.lnum < curwin->w_botline
+		    || loff.fill >= fill_below_window)
+#endif
+		)
+	    break;
+
+	// Add one line above
+	topline_back(&loff);
+	if (loff.height == MAXCOL)
+	    used = MAXCOL;
+	else
+	    used += loff.height;
+	if (used > curwin->w_height)
+	    break;
+	if (loff.lnum >= curwin->w_botline
+#ifdef FEAT_DIFF
+		&& (loff.lnum > curwin->w_botline
+		    || loff.fill <= fill_below_window)
+#endif
+		)
+	{
+	    // Count screen lines that are below the window.
+	    scrolled += loff.height;
+	    if (loff.lnum == curwin->w_botline
+#ifdef FEAT_DIFF
+			    && loff.fill == 0
+#endif
+		    )
+		scrolled -= curwin->w_empty_rows;
+	}
+
+	if (boff.lnum < curbuf->b_ml.ml_line_count)
+	{
+	    // Add one line below
+	    botline_forw(&boff);
+	    used += boff.height;
+	    if (used > curwin->w_height)
+		break;
+	    if (extra < ( mouse_dragging > 0 ? mouse_dragging - 1 : so)
+		    || scrolled < min_scroll)
+	    {
+		extra += boff.height;
+		if (boff.lnum >= curwin->w_botline
+#ifdef FEAT_DIFF
+			|| (boff.lnum + 1 == curwin->w_botline
+			    && boff.fill > curwin->w_filler_rows)
+#endif
+		   )
+		{
+		    // Count screen lines that are below the window.
+		    scrolled += boff.height;
+		    if (boff.lnum == curwin->w_botline
+#ifdef FEAT_DIFF
+			    && boff.fill == 0
+#endif
+			    )
+			scrolled -= curwin->w_empty_rows;
+		}
+	    }
+	}
+    }
+
+    // curwin->w_empty_rows is larger, no need to scroll
+    if (scrolled <= 0)
+	line_count = 0;
+    // more than a screenfull, don't scroll but redraw
+    else if (used > curwin->w_height)
+	line_count = used;
+    // scroll minimal number of lines
+    else
+    {
+	line_count = 0;
+#ifdef FEAT_DIFF
+	boff.fill = curwin->w_topfill;
+#endif
+	boff.lnum = curwin->w_topline - 1;
+	for (i = 0; i < scrolled && boff.lnum < curwin->w_botline; )
+	{
+	    botline_forw(&boff);
+	    i += boff.height;
+	    ++line_count;
+	}
+	if (i < scrolled)	// below curwin->w_botline, don't scroll
+	    line_count = 9999;
+    }
+
+    /*
+     * Scroll up if the cursor is off the bottom of the screen a bit.
+     * Otherwise put it at 1/2 of the screen.
+     */
+    if (line_count >= curwin->w_height && line_count > min_scroll)
+	scroll_cursor_halfway(FALSE, TRUE);
+    else
+    {
+	// With 'smoothscroll' scroll at least the height of the cursor line,
+	// unless it would move the cursor.
+	if (curwin->w_p_wrap && curwin->w_p_sms && line_count < min_scrolled
+		&& (curwin->w_cursor.lnum < curwin->w_topline
+		    || (curwin->w_virtcol - curwin->w_skipcol >=
+					  curwin->w_width - curwin_col_off())))
+	    line_count = min_scrolled;
+	if (line_count > 0)
+	{
+	    if (scrolling_screenlines(TRUE))
+		scrollup(scrolled, TRUE);  // TODO
+	    else
+		scrollup(line_count, TRUE);
+	}
+    }
+
+    /*
+     * If topline didn't change we need to restore w_botline and w_empty_rows
+     * (we changed them).
+     * If topline did change, update_screen() will set botline.
+     */
+    if (curwin->w_topline == old_topline
+	    && curwin->w_skipcol == old_skipcol
+	    && set_topbot)
+    {
+	curwin->w_botline = old_botline;
+	curwin->w_empty_rows = old_empty_rows;
+	curwin->w_valid = old_valid;
+    }
+    curwin->w_valid |= VALID_TOPLINE;
+}
+
+/*
+ * Recompute topline to put the cursor halfway the window
+ * If "atend" is TRUE, also put it halfway at the end of the file.
+ */
+    void
+scroll_cursor_halfway(int atend, int prefer_above)
+{
+    int		above = 0;
+    linenr_T	topline;
+    colnr_T	skipcol = 0;
+    int		set_skipcol = FALSE;
+#ifdef FEAT_DIFF
+    int		topfill = 0;
+#endif
+    int		below = 0;
+    int		used;
+    lineoff_T	loff;
+    lineoff_T	boff;
+#ifdef FEAT_DIFF
+    linenr_T	old_topline = curwin->w_topline;
+#endif
+
+#ifdef FEAT_PROP_POPUP
+    // if the width changed this needs to be updated first
+    may_update_popup_position();
+#endif
+    loff.lnum = boff.lnum = curwin->w_cursor.lnum;
+#ifdef FEAT_FOLDING
+    (void)hasFolding(loff.lnum, &loff.lnum, &boff.lnum);
+#endif
+#ifdef FEAT_DIFF
+    used = plines_nofill(loff.lnum);
+    loff.fill = 0;
+    boff.fill = 0;
+#else
+    used = plines(loff.lnum);
+#endif
+    topline = loff.lnum;
+
+    int half_height = 0;
+    int smooth_scroll = FALSE;
+    if (curwin->w_p_sms && curwin->w_p_wrap)
+    {
+	// 'smoothscroll' and 'wrap' are set
+	smooth_scroll = TRUE;
+	half_height = (curwin->w_height - used) / 2;
+	used = 0;
+    }
+
+    while (topline > 1)
+    {
+	// If using smoothscroll, we can precisely scroll to the
+	// exact point where the cursor is halfway down the screen.
+	if (smooth_scroll)
+	{
+	    topline_back_winheight(&loff, FALSE);
+	    if (loff.height == MAXCOL)
+		break;
+	    else
+		used += loff.height;
+	    if (used > half_height)
+	    {
+		if (used - loff.height < half_height)
+		{
+		    int plines_offset = used - half_height;
+		    loff.height -= plines_offset;
+		    used = half_height;
+
+		    topline = loff.lnum;
+#ifdef FEAT_DIFF
+		    topfill = loff.fill;
+#endif
+		    skipcol = skipcol_from_plines(curwin, plines_offset);
+		    set_skipcol = TRUE;
+		}
+		break;
+	    }
+	    topline = loff.lnum;
+#ifdef FEAT_DIFF
+	    topfill = loff.fill;
+#endif
+	    continue;
+	}
+
+	// If not using smoothscroll, we have to iteratively find how many
+	// lines to scroll down to roughly fit the cursor.
+	// This may not be right in the middle if the lines'
+	// physical height > 1 (e.g. 'wrap' is on).
+
+	// Depending on "prefer_above" we add a line above or below first.
+	// Loop twice to avoid duplicating code.
+	int done = FALSE;
+	for (int round = 1; round <= 2; ++round)
+	{
+	    if (prefer_above ? (round == 2 && below < above)
+			     : (round == 1 && below <= above))
+	    {
+		// add a line below the cursor
+		if (boff.lnum < curbuf->b_ml.ml_line_count)
+		{
+		    botline_forw(&boff);
+		    used += boff.height;
+		    if (used > curwin->w_height)
+		    {
+			done = TRUE;
+			break;
+		    }
+		    below += boff.height;
+		}
+		else
+		{
+		    ++below;	    // count a "~" line
+		    if (atend)
+			++used;
+		}
+	    }
+
+	    if (prefer_above ? (round == 1 && below >= above)
+			     : (round == 1 && below > above))
+	    {
+		// add a line above the cursor
+		topline_back(&loff);
+		if (loff.height == MAXCOL)
+		    used = MAXCOL;
+		else
+		    used += loff.height;
+		if (used > curwin->w_height)
+		{
+		    done = TRUE;
+		    break;
+		}
+		above += loff.height;
+		topline = loff.lnum;
+#ifdef FEAT_DIFF
+		topfill = loff.fill;
+#endif
+	    }
+	}
+	if (done)
+	    break;
+    }
+
+#ifdef FEAT_FOLDING
+    if (!hasFolding(topline, &curwin->w_topline, NULL))
+#endif
+    {
+	if (curwin->w_topline != topline
+		|| set_skipcol
+		|| curwin->w_skipcol != 0)
+	{
+	    curwin->w_topline = topline;
+	    if (set_skipcol)
+	    {
+		curwin->w_skipcol = skipcol;
+		redraw_later(UPD_NOT_VALID);
+	    }
+	    else
+		reset_skipcol();
+	}
+    }
+#ifdef FEAT_DIFF
+    curwin->w_topfill = topfill;
+    if (old_topline > curwin->w_topline + curwin->w_height)
+	curwin->w_botfill = FALSE;
+    check_topfill(curwin, FALSE);
+#endif
+    curwin->w_valid &= ~(VALID_WROW|VALID_CROW|VALID_BOTLINE|VALID_BOTLINE_AP);
+    curwin->w_valid |= VALID_TOPLINE;
+}
+
+/*
+ * Correct the cursor position so that it is in a part of the screen at least
+ * 'scrolloff' lines from the top and bottom, if possible.
+ * If not possible, put it at the same position as scroll_cursor_halfway().
+ * When called topline must be valid!
+ */
+    void
+cursor_correct(void)
+{
+    int		above = 0;	    // screen lines above topline
+    linenr_T	topline;
+    int		below = 0;	    // screen lines below botline
+    linenr_T	botline;
+    int		above_wanted, below_wanted;
+    linenr_T	cln;		    // Cursor Line Number
+    int		max_off;
+    long	so = get_scrolloff_value();
+
+    /*
+     * How many lines we would like to have above/below the cursor depends on
+     * whether the first/last line of the file is on screen.
+     */
+    above_wanted = so;
+    below_wanted = so;
+    if (mouse_dragging > 0)
+    {
+	above_wanted = mouse_dragging - 1;
+	below_wanted = mouse_dragging - 1;
+    }
+    if (curwin->w_topline == 1)
+    {
+	above_wanted = 0;
+	max_off = curwin->w_height / 2;
+	if (below_wanted > max_off)
+	    below_wanted = max_off;
+    }
+    validate_botline();
+    if (curwin->w_botline == curbuf->b_ml.ml_line_count + 1
+	    && mouse_dragging == 0)
+    {
+	below_wanted = 0;
+	max_off = (curwin->w_height - 1) / 2;
+	if (above_wanted > max_off)
+	    above_wanted = max_off;
+    }
+
+    /*
+     * If there are sufficient file-lines above and below the cursor, we can
+     * return now.
+     */
+    cln = curwin->w_cursor.lnum;
+    if (cln >= curwin->w_topline + above_wanted
+	    && cln < curwin->w_botline - below_wanted
+#ifdef FEAT_FOLDING
+	    && !hasAnyFolding(curwin)
+#endif
+	    )
+	return;
+
+    if (curwin->w_p_sms && !curwin->w_p_wrap)
+    {
+	// 'smoothscroll is active
+	if (curwin->w_cline_height == curwin->w_height)
+	{
+	    // The cursor line just fits in the window, don't scroll.
+	    reset_skipcol();
+	    return;
+	}
+	// TODO: If the cursor line doesn't fit in the window then only adjust
+	// w_skipcol.
+    }
+
+    /*
+     * Narrow down the area where the cursor can be put by taking lines from
+     * the top and the bottom until:
+     * - the desired context lines are found
+     * - the lines from the top is past the lines from the bottom
+     */
+    topline = curwin->w_topline;
+    botline = curwin->w_botline - 1;
+#ifdef FEAT_DIFF
+    // count filler lines as context
+    above = curwin->w_topfill;
+    below = curwin->w_filler_rows;
+#endif
+    while ((above < above_wanted || below < below_wanted) && topline < botline)
+    {
+	if (below < below_wanted && (below <= above || above >= above_wanted))
+	{
+#ifdef FEAT_FOLDING
+	    if (hasFolding(botline, &botline, NULL))
+		++below;
+	    else
+#endif
+		below += plines(botline);
+	    --botline;
+	}
+	if (above < above_wanted && (above < below || below >= below_wanted))
+	{
+#ifdef FEAT_FOLDING
+	    if (hasFolding(topline, NULL, &topline))
+		++above;
+	    else
+#endif
+		above += PLINES_NOFILL(topline);
+#ifdef FEAT_DIFF
+	    // Count filler lines below this line as context.
+	    if (topline < botline)
+		above += diff_check_fill(curwin, topline + 1);
+#endif
+	    ++topline;
+	}
+    }
+    if (topline == botline || botline == 0)
+	curwin->w_cursor.lnum = topline;
+    else if (topline > botline)
+	curwin->w_cursor.lnum = botline;
+    else
+    {
+	if (cln < topline && curwin->w_topline > 1)
+	{
+	    curwin->w_cursor.lnum = topline;
+	    curwin->w_valid &=
+			    ~(VALID_WROW|VALID_WCOL|VALID_CHEIGHT|VALID_CROW);
+	}
+	if (cln > botline && curwin->w_botline <= curbuf->b_ml.ml_line_count)
+	{
+	    curwin->w_cursor.lnum = botline;
+	    curwin->w_valid &=
+			    ~(VALID_WROW|VALID_WCOL|VALID_CHEIGHT|VALID_CROW);
+	}
+    }
+    curwin->w_valid |= VALID_TOPLINE;
+}
+
+static void get_scroll_overlap(lineoff_T *lp, int dir);
+
+/*
+ * Move screen "count" pages up ("dir" is BACKWARD) or down ("dir" is FORWARD)
+ * and update the screen.
+ *
+ * Return FAIL for failure, OK otherwise.
+ */
+    int
+onepage(int dir, long count)
+{
+    long	n;
+    int		retval = OK;
+    lineoff_T	loff;
+    linenr_T	old_topline = curwin->w_topline;
+    long	so = get_scrolloff_value();
+
+    if (curbuf->b_ml.ml_line_count == 1)    // nothing to do
+    {
+	beep_flush();
+	return FAIL;
+    }
+
+    for ( ; count > 0; --count)
+    {
+	validate_botline();
+	/*
+	 * It's an error to move a page up when the first line is already on
+	 * the screen.	It's an error to move a page down when the last line
+	 * is on the screen and the topline is 'scrolloff' lines from the
+	 * last line.
+	 */
+	if (dir == FORWARD
+		? ((curwin->w_topline >= curbuf->b_ml.ml_line_count - so)
+		    && curwin->w_botline > curbuf->b_ml.ml_line_count)
+		: (curwin->w_topline == 1
+#ifdef FEAT_DIFF
+		    && curwin->w_topfill ==
+				    diff_check_fill(curwin, curwin->w_topline)
+#endif
+		    ))
+	{
+	    beep_flush();
+	    retval = FAIL;
+	    break;
+	}
+
+#ifdef FEAT_DIFF
+	loff.fill = 0;
+#endif
+	if (dir == FORWARD)
+	{
+	    if (ONE_WINDOW && p_window > 0 && p_window < Rows - 1)
+	    {
+		// Vi compatible scrolling
+		if (p_window <= 2)
+		    ++curwin->w_topline;
+		else
+		    curwin->w_topline += p_window - 2;
+		if (curwin->w_topline > curbuf->b_ml.ml_line_count)
+		    curwin->w_topline = curbuf->b_ml.ml_line_count;
+		curwin->w_cursor.lnum = curwin->w_topline;
+	    }
+	    else if (curwin->w_botline > curbuf->b_ml.ml_line_count)
+	    {
+		// at end of file
+		curwin->w_topline = curbuf->b_ml.ml_line_count;
+#ifdef FEAT_DIFF
+		curwin->w_topfill = 0;
+#endif
+		curwin->w_valid &= ~(VALID_WROW|VALID_CROW);
+	    }
+	    else
+	    {
+		// For the overlap, start with the line just below the window
+		// and go upwards.
+		loff.lnum = curwin->w_botline;
+#ifdef FEAT_DIFF
+		loff.fill = diff_check_fill(curwin, loff.lnum)
+						      - curwin->w_filler_rows;
+#endif
+		get_scroll_overlap(&loff, -1);
+		curwin->w_topline = loff.lnum;
+#ifdef FEAT_DIFF
+		curwin->w_topfill = loff.fill;
+		check_topfill(curwin, FALSE);
+#endif
+		curwin->w_cursor.lnum = curwin->w_topline;
+		curwin->w_valid &= ~(VALID_WCOL|VALID_CHEIGHT|VALID_WROW|
+				   VALID_CROW|VALID_BOTLINE|VALID_BOTLINE_AP);
+	    }
+	}
+	else	// dir == BACKWARDS
+	{
+#ifdef FEAT_DIFF
+	    if (curwin->w_topline == 1)
+	    {
+		// Include max number of filler lines
+		max_topfill();
+		continue;
+	    }
+#endif
+	    if (ONE_WINDOW && p_window > 0 && p_window < Rows - 1)
+	    {
+		// Vi compatible scrolling (sort of)
+		if (p_window <= 2)
+		    --curwin->w_topline;
+		else
+		    curwin->w_topline -= p_window - 2;
+		if (curwin->w_topline < 1)
+		    curwin->w_topline = 1;
+		curwin->w_cursor.lnum = curwin->w_topline + p_window - 1;
+		if (curwin->w_cursor.lnum > curbuf->b_ml.ml_line_count)
+		    curwin->w_cursor.lnum = curbuf->b_ml.ml_line_count;
+		continue;
+	    }
+
+	    // Find the line at the top of the window that is going to be the
+	    // line at the bottom of the window.  Make sure this results in
+	    // the same line as before doing CTRL-F.
+	    loff.lnum = curwin->w_topline - 1;
+#ifdef FEAT_DIFF
+	    loff.fill = diff_check_fill(curwin, loff.lnum + 1)
+							  - curwin->w_topfill;
+#endif
+	    get_scroll_overlap(&loff, 1);
+
+	    if (loff.lnum >= curbuf->b_ml.ml_line_count)
+	    {
+		loff.lnum = curbuf->b_ml.ml_line_count;
+#ifdef FEAT_DIFF
+		loff.fill = 0;
+	    }
+	    else
+	    {
+		botline_topline(&loff);
+#endif
+	    }
+	    curwin->w_cursor.lnum = loff.lnum;
+
+	    // Find the line just above the new topline to get the right line
+	    // at the bottom of the window.
+	    n = 0;
+	    while (n <= curwin->w_height && loff.lnum >= 1)
+	    {
+		topline_back(&loff);
+		if (loff.height == MAXCOL)
+		    n = MAXCOL;
+		else
+		    n += loff.height;
+	    }
+	    if (loff.lnum < 1)			// at begin of file
+	    {
+		curwin->w_topline = 1;
+#ifdef FEAT_DIFF
+		max_topfill();
+#endif
+		curwin->w_valid &= ~(VALID_WROW|VALID_CROW|VALID_BOTLINE);
+	    }
+	    else
+	    {
+		// Go two lines forward again.
+#ifdef FEAT_DIFF
+		topline_botline(&loff);
+#endif
+		botline_forw(&loff);
+		botline_forw(&loff);
+#ifdef FEAT_DIFF
+		botline_topline(&loff);
+#endif
+#ifdef FEAT_FOLDING
+		// We're at the wrong end of a fold now.
+		(void)hasFolding(loff.lnum, &loff.lnum, NULL);
+#endif
+
+		// Always scroll at least one line.  Avoid getting stuck on
+		// very long lines.
+		if (loff.lnum >= curwin->w_topline
+#ifdef FEAT_DIFF
+			&& (loff.lnum > curwin->w_topline
+			    || loff.fill >= curwin->w_topfill)
+#endif
+			)
+		{
+#ifdef FEAT_DIFF
+		    // First try using the maximum number of filler lines.  If
+		    // that's not enough, backup one line.
+		    loff.fill = curwin->w_topfill;
+		    if (curwin->w_topfill < diff_check_fill(curwin,
+							   curwin->w_topline))
+			max_topfill();
+		    if (curwin->w_topfill == loff.fill)
+#endif
+		    {
+			--curwin->w_topline;
+#ifdef FEAT_DIFF
+			curwin->w_topfill = 0;
+#endif
+		    }
+		    comp_botline(curwin);
+		    curwin->w_cursor.lnum = curwin->w_botline - 1;
+		    curwin->w_valid &=
+			    ~(VALID_WCOL|VALID_CHEIGHT|VALID_WROW|VALID_CROW);
+		}
+		else
+		{
+		    curwin->w_topline = loff.lnum;
+#ifdef FEAT_DIFF
+		    curwin->w_topfill = loff.fill;
+		    check_topfill(curwin, FALSE);
+#endif
+		    curwin->w_valid &= ~(VALID_WROW|VALID_CROW|VALID_BOTLINE);
+		}
+	    }
+	}
+    }
+#ifdef FEAT_FOLDING
+    foldAdjustCursor();
+#endif
+    cursor_correct();
+    check_cursor_col();
+    if (retval == OK)
+	beginline(BL_SOL | BL_FIX);
+    curwin->w_valid &= ~(VALID_WCOL|VALID_WROW|VALID_VIRTCOL);
+
+    if (retval == OK && dir == FORWARD)
+    {
+	// Avoid the screen jumping up and down when 'scrolloff' is non-zero.
+	// But make sure we scroll at least one line (happens with mix of long
+	// wrapping lines and non-wrapping line).
+	if (check_top_offset())
+	{
+	    scroll_cursor_top(1, FALSE);
+	    if (curwin->w_topline <= old_topline
+				  && old_topline < curbuf->b_ml.ml_line_count)
+	    {
+		curwin->w_topline = old_topline + 1;
+#ifdef FEAT_FOLDING
+		(void)hasFolding(curwin->w_topline, &curwin->w_topline, NULL);
+#endif
+	    }
+	}
+#ifdef FEAT_FOLDING
+	else if (curwin->w_botline > curbuf->b_ml.ml_line_count)
+	    (void)hasFolding(curwin->w_topline, &curwin->w_topline, NULL);
+#endif
+    }
+
+    redraw_later(UPD_VALID);
+    return retval;
+}
+
+/*
+ * Decide how much overlap to use for page-up or page-down scrolling.
+ * This is symmetric, so that doing both keeps the same lines displayed.
+ * Three lines are examined:
+ *
+ *  before CTRL-F	    after CTRL-F / before CTRL-B
+ *     etc.			l1
+ *  l1 last but one line	------------
+ *  l2 last text line		l2 top text line
+ *  -------------		l3 second text line
+ *  l3				   etc.
+ */
+    static void
+get_scroll_overlap(lineoff_T *lp, int dir)
+{
+    int		h1, h2, h3, h4;
+    int		min_height = curwin->w_height - 2;
+    lineoff_T	loff0, loff1, loff2;
+
+#ifdef FEAT_DIFF
+    if (lp->fill > 0)
+	lp->height = 1;
+    else
+	lp->height = plines_nofill(lp->lnum);
+#else
+    lp->height = plines(lp->lnum);
+#endif
+    h1 = lp->height;
+    if (h1 > min_height)
+	return;		// no overlap
+
+    loff0 = *lp;
+    if (dir > 0)
+	botline_forw(lp);
+    else
+	topline_back(lp);
+    h2 = lp->height;
+    if (h2 == MAXCOL || h2 + h1 > min_height)
+    {
+	*lp = loff0;	// no overlap
+	return;
+    }
+
+    loff1 = *lp;
+    if (dir > 0)
+	botline_forw(lp);
+    else
+	topline_back(lp);
+    h3 = lp->height;
+    if (h3 == MAXCOL || h3 + h2 > min_height)
+    {
+	*lp = loff0;	// no overlap
+	return;
+    }
+
+    loff2 = *lp;
+    if (dir > 0)
+	botline_forw(lp);
+    else
+	topline_back(lp);
+    h4 = lp->height;
+    if (h4 == MAXCOL || h4 + h3 + h2 > min_height || h3 + h2 + h1 > min_height)
+	*lp = loff1;	// 1 line overlap
+    else
+	*lp = loff2;	// 2 lines overlap
+}
+
+/*
+ * Scroll 'scroll' lines up or down.
+ */
+    void
+halfpage(int flag, linenr_T Prenum)
+{
+    long	scrolled = 0;
+    int		i;
+    int		n;
+    int		room;
+
+    if (Prenum)
+	curwin->w_p_scr = (Prenum > curwin->w_height) ?
+						curwin->w_height : Prenum;
+    n = (curwin->w_p_scr <= curwin->w_height) ?
+				    curwin->w_p_scr : curwin->w_height;
+
+    update_topline();
+    validate_botline();
+    room = curwin->w_empty_rows;
+#ifdef FEAT_DIFF
+    room += curwin->w_filler_rows;
+#endif
+    if (flag)
+    {
+	/*
+	 * scroll the text up
+	 */
+	while (n > 0 && curwin->w_botline <= curbuf->b_ml.ml_line_count)
+	{
+#ifdef FEAT_DIFF
+	    if (curwin->w_topfill > 0)
+	    {
+		i = 1;
+		--n;
+		--curwin->w_topfill;
+	    }
+	    else
+#endif
+	    {
+		i = PLINES_NOFILL(curwin->w_topline);
+		n -= i;
+		if (n < 0 && scrolled > 0)
+		    break;
+#ifdef FEAT_FOLDING
+		(void)hasFolding(curwin->w_topline, NULL, &curwin->w_topline);
+#endif
+		++curwin->w_topline;
+#ifdef FEAT_DIFF
+		curwin->w_topfill = diff_check_fill(curwin, curwin->w_topline);
+#endif
+
+		if (curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count)
+		{
+		    ++curwin->w_cursor.lnum;
+		    curwin->w_valid &=
+				    ~(VALID_VIRTCOL|VALID_CHEIGHT|VALID_WCOL);
+		}
+	    }
+	    curwin->w_valid &= ~(VALID_CROW|VALID_WROW);
+	    scrolled += i;
+
+	    /*
+	     * Correct w_botline for changed w_topline.
+	     * Won't work when there are filler lines.
+	     */
+#ifdef FEAT_DIFF
+	    if (curwin->w_p_diff)
+		curwin->w_valid &= ~(VALID_BOTLINE|VALID_BOTLINE_AP);
+	    else
+#endif
+	    {
+		room += i;
+		do
+		{
+		    i = plines(curwin->w_botline);
+		    if (i > room)
+			break;
+#ifdef FEAT_FOLDING
+		    (void)hasFolding(curwin->w_botline, NULL,
+							  &curwin->w_botline);
+#endif
+		    ++curwin->w_botline;
+		    room -= i;
+		} while (curwin->w_botline <= curbuf->b_ml.ml_line_count);
+	    }
+	}
+
+	/*
+	 * When hit bottom of the file: move cursor down.
+	 */
+	if (n > 0)
+	{
+# ifdef FEAT_FOLDING
+	    if (hasAnyFolding(curwin))
+	    {
+		while (--n >= 0
+			&& curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count)
+		{
+		    (void)hasFolding(curwin->w_cursor.lnum, NULL,
+						      &curwin->w_cursor.lnum);
+		    ++curwin->w_cursor.lnum;
+		}
+	    }
+	    else
+# endif
+		curwin->w_cursor.lnum += n;
+	    check_cursor_lnum();
+	}
+    }
+    else
+    {
+	/*
+	 * scroll the text down
+	 */
+	while (n > 0 && curwin->w_topline > 1)
+	{
+#ifdef FEAT_DIFF
+	    if (curwin->w_topfill < diff_check_fill(curwin, curwin->w_topline))
+	    {
+		i = 1;
+		--n;
+		++curwin->w_topfill;
+	    }
+	    else
+#endif
+	    {
+		i = PLINES_NOFILL(curwin->w_topline - 1);
+		n -= i;
+		if (n < 0 && scrolled > 0)
+		    break;
+		--curwin->w_topline;
+#ifdef FEAT_FOLDING
+		(void)hasFolding(curwin->w_topline, &curwin->w_topline, NULL);
+#endif
+#ifdef FEAT_DIFF
+		curwin->w_topfill = 0;
+#endif
+	    }
+	    curwin->w_valid &= ~(VALID_CROW|VALID_WROW|
+					      VALID_BOTLINE|VALID_BOTLINE_AP);
+	    scrolled += i;
+	    if (curwin->w_cursor.lnum > 1)
+	    {
+		--curwin->w_cursor.lnum;
+		curwin->w_valid &= ~(VALID_VIRTCOL|VALID_CHEIGHT|VALID_WCOL);
+	    }
+	}
+
+	/*
+	 * When hit top of the file: move cursor up.
+	 */
+	if (n > 0)
+	{
+	    if (curwin->w_cursor.lnum <= (linenr_T)n)
+		curwin->w_cursor.lnum = 1;
+	    else
+# ifdef FEAT_FOLDING
+	    if (hasAnyFolding(curwin))
+	    {
+		while (--n >= 0 && curwin->w_cursor.lnum > 1)
+		{
+		    --curwin->w_cursor.lnum;
+		    (void)hasFolding(curwin->w_cursor.lnum,
+						&curwin->w_cursor.lnum, NULL);
+		}
+	    }
+	    else
+# endif
+		curwin->w_cursor.lnum -= n;
+	}
+    }
+# ifdef FEAT_FOLDING
+    // Move cursor to first line of closed fold.
+    foldAdjustCursor();
+# endif
+#ifdef FEAT_DIFF
+    check_topfill(curwin, !flag);
+#endif
+    cursor_correct();
+    beginline(BL_SOL | BL_FIX);
+    redraw_later(UPD_VALID);
+}
+
+    void
+do_check_cursorbind(void)
+{
+    linenr_T	line = curwin->w_cursor.lnum;
+    colnr_T	col = curwin->w_cursor.col;
+    colnr_T	coladd = curwin->w_cursor.coladd;
+    colnr_T	curswant = curwin->w_curswant;
+    int		set_curswant = curwin->w_set_curswant;
+    win_T	*old_curwin = curwin;
+    buf_T	*old_curbuf = curbuf;
+    int		restart_edit_save;
+    int		old_VIsual_select = VIsual_select;
+    int		old_VIsual_active = VIsual_active;
+
+    /*
+     * loop through the cursorbound windows
+     */
+    VIsual_select = VIsual_active = 0;
+    FOR_ALL_WINDOWS(curwin)
+    {
+	curbuf = curwin->w_buffer;
+	// skip original window  and windows with 'noscrollbind'
+	if (curwin != old_curwin && curwin->w_p_crb)
+	{
+# ifdef FEAT_DIFF
+	    if (curwin->w_p_diff)
+		curwin->w_cursor.lnum =
+				 diff_get_corresponding_line(old_curbuf, line);
+	    else
+# endif
+		curwin->w_cursor.lnum = line;
+	    curwin->w_cursor.col = col;
+	    curwin->w_cursor.coladd = coladd;
+	    curwin->w_curswant = curswant;
+	    curwin->w_set_curswant = set_curswant;
+
+	    // Make sure the cursor is in a valid position.  Temporarily set
+	    // "restart_edit" to allow the cursor to be beyond the EOL.
+	    restart_edit_save = restart_edit;
+	    restart_edit = TRUE;
+	    check_cursor();
+
+	    // Avoid a scroll here for the cursor position, 'scrollbind' is
+	    // more important.
+	    if (!curwin->w_p_scb)
+		validate_cursor();
+
+	    restart_edit = restart_edit_save;
+	    // Correct cursor for multi-byte character.
+	    if (has_mbyte)
+		mb_adjust_cursor();
+	    redraw_later(UPD_VALID);
+
+	    // Only scroll when 'scrollbind' hasn't done this.
+	    if (!curwin->w_p_scb)
+		update_topline();
+	    curwin->w_redr_status = TRUE;
+	}
+    }
+
+    /*
+     * reset current-window
+     */
+    VIsual_select = old_VIsual_select;
+    VIsual_active = old_VIsual_active;
+    curwin = old_curwin;
+    curbuf = old_curbuf;
+}