updated for version 7.0001v7.0001

1 files changed, 2796 insertions, 0 deletions

diff --git a/src/move.c b/src/move.c
new file mode 100644
index 000000000..daa0fb7c1
--- /dev/null
+++ b/src/move.c
@@ -0,0 +1,2796 @@
+/* vi:set ts=8 sts=4 sw=4:
+ *
+ * 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 void comp_botline __ARGS((win_T *wp));
+static int check_top_offset __ARGS((void));
+static void curs_rows __ARGS((win_T *wp, int do_botline));
+static void validate_botline_win __ARGS((win_T *wp));
+static void validate_cheight __ARGS((void));
+
+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 __ARGS((lineoff_T *lp));
+static void botline_forw __ARGS((lineoff_T *lp));
+#ifdef FEAT_DIFF
+static void botline_topline __ARGS((lineoff_T *lp));
+static void topline_botline __ARGS((lineoff_T *lp));
+static void max_topfill __ARGS((void));
+#endif
+
+/*
+ * Compute wp->w_botline for the current wp->w_topline.  Can be called after
+ * wp->w_topline changed.
+ */
+    static void
+comp_botline(wp)
+    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
+#ifdef FEAT_DIFF
+	    if (lnum == wp->w_topline)
+		n = plines_win_nofill(wp, lnum, TRUE) + wp->w_topfill;
+	    else
+#endif
+		n = plines_win(wp, lnum, TRUE);
+	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
+	    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);
+}
+
+/*
+ * Update curwin->w_topline and redraw if necessary.
+ * Used to update the screen before printing a message.
+ */
+    void
+update_topline_redraw()
+{
+    update_topline();
+    if (must_redraw)
+	update_screen(0);
+}
+
+/*
+ * Update curwin->w_topline to move the cursor onto the screen.
+ */
+    void
+update_topline()
+{
+    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;
+#ifdef FEAT_MOUSE
+    int		save_so = p_so;
+#endif
+
+    if (!screen_valid(TRUE))
+	return;
+
+    check_cursor_moved(curwin);
+    if (curwin->w_valid & VALID_TOPLINE)
+	return;
+
+#ifdef FEAT_MOUSE
+    /* When dragging with the mouse, don't scroll that quickly */
+    if (mouse_dragging)
+	p_so = mouse_dragging - 1;
+#endif
+
+    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(NOT_VALID);
+	curwin->w_topline = 1;
+#ifdef FEAT_DIFF
+	curwin->w_topfill = 0;
+#endif
+	curwin->w_botline = 2;
+	curwin->w_valid |= VALID_BOTLINE|VALID_BOTLINE_AP;
+#ifdef FEAT_SCROLLBIND
+	curwin->w_scbind_pos = 1;
+#endif
+    }
+
+    /*
+     * 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)
+	{
+	    /* 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;
+	}
+#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 + p_so (approximation of how much will be
+		 * scrolled). */
+		n = 0;
+		for (lnum = curwin->w_cursor.lnum;
+				      lnum < curwin->w_topline + p_so; ++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 + p_so - 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);
+	    else
+	    {
+		scroll_cursor_top((int)p_sj, 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
+		    && ((long)curwin->w_cursor.lnum
+					     >= (long)curwin->w_botline - p_so
+#ifdef FEAT_FOLDING
+			|| hasAnyFolding(curwin)
+#endif
+			))
+	    {
+		lineoff_T	loff;
+
+		/* Cursor is 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 >= p_so)
+			break;
+		    botline_forw(&loff);
+		}
+		if (n >= p_so)
+		    /* 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 - p_so (approximation of how much will be
+		     * scrolled). */
+		    line_count = 0;
+		    for (lnum = curwin->w_cursor.lnum;
+				     lnum >= curwin->w_botline - p_so; --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 + p_so;
+		if (line_count <= curwin->w_height + 1)
+		    scroll_cursor_bot((int)p_sj, FALSE);
+		else
+		    scroll_cursor_halfway(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 = 0;
+	if (curwin->w_skipcol)
+	{
+	    curwin->w_skipcol = 0;
+	    redraw_later(NOT_VALID);
+	}
+	else
+	    redraw_later(VALID);
+	/* May need to set w_skipcol when cursor in w_topline. */
+	if (curwin->w_cursor.lnum == curwin->w_topline)
+	    validate_cursor();
+    }
+
+#ifdef FEAT_MOUSE
+    p_so = save_so;
+#endif
+}
+
+/*
+ * Return TRUE when there are not 'scrolloff' lines above the cursor for the
+ * current window.
+ */
+    static int
+check_top_offset()
+{
+    lineoff_T	loff;
+    int		n;
+
+    if (curwin->w_cursor.lnum < curwin->w_topline + p_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 < p_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 < p_so)
+	    return TRUE;
+    }
+    return FALSE;
+}
+
+    void
+update_curswant()
+{
+    if (curwin->w_set_curswant)
+    {
+	validate_virtcol();
+	curwin->w_curswant = curwin->w_virtcol;
+	curwin->w_set_curswant = FALSE;
+    }
+}
+
+/*
+ * Check if the cursor has moved.  Set the w_valid flag accordingly.
+ */
+    void
+check_cursor_moved(wp)
+    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);
+	wp->w_valid_cursor = wp->w_cursor;
+	wp->w_valid_leftcol = wp->w_leftcol;
+    }
+    else if (wp->w_cursor.col != wp->w_valid_cursor.col
+	     || wp->w_leftcol != wp->w_valid_leftcol
+#ifdef FEAT_VIRTUALEDIT
+	     || wp->w_cursor.coladd != wp->w_valid_cursor.coladd
+#endif
+	     )
+    {
+	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;
+#ifdef FEAT_VIRTUALEDIT
+	wp->w_valid_cursor.coladd = wp->w_cursor.coladd;
+#endif
+    }
+}
+
+/*
+ * 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()
+{
+    changed_window_setting_win(curwin);
+}
+
+    void
+changed_window_setting_win(wp)
+    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, NOT_VALID);
+}
+
+/*
+ * Set wp->w_topline to a certain number.
+ */
+    void
+set_topline(wp, lnum)
+    win_T	*wp;
+    linenr_T	lnum;
+{
+#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;
+    wp->w_topline = lnum;
+#ifdef FEAT_DIFF
+    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(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()
+{
+    curwin->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL
+						|VALID_CHEIGHT|VALID_TOPLINE);
+}
+
+    void
+changed_cline_bef_curs_win(wp)
+    win_T	*wp;
+{
+    wp->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL
+						|VALID_CHEIGHT|VALID_TOPLINE);
+}
+
+#if 0 /* not used */
+/*
+ * Call this function when the length of the cursor line (in screen
+ * characters) has changed, and the position of the cursor doesn't change.
+ * Need to take care of w_botline separately!
+ */
+    void
+changed_cline_aft_curs()
+{
+    curwin->w_valid &= ~VALID_CHEIGHT;
+}
+#endif
+
+/*
+ * 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()
+{
+    curwin->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL|VALID_CROW
+						|VALID_CHEIGHT|VALID_TOPLINE);
+}
+
+    void
+changed_line_abv_curs_win(wp)
+    win_T	*wp;
+{
+    wp->w_valid &= ~(VALID_WROW|VALID_WCOL|VALID_VIRTCOL|VALID_CROW
+						|VALID_CHEIGHT|VALID_TOPLINE);
+}
+
+/*
+ * Make sure the value of curwin->w_botline is valid.
+ */
+    void
+validate_botline()
+{
+    if (!(curwin->w_valid & VALID_BOTLINE))
+	comp_botline(curwin);
+}
+
+/*
+ * Make sure the value of wp->w_botline is valid.
+ */
+    static void
+validate_botline_win(wp)
+    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()
+{
+    curwin->w_valid &= ~(VALID_BOTLINE|VALID_BOTLINE_AP);
+}
+
+    void
+invalidate_botline_win(wp)
+    win_T	*wp;
+{
+    wp->w_valid &= ~(VALID_BOTLINE|VALID_BOTLINE_AP);
+}
+
+#if 0 /* never used */
+/*
+ * Mark curwin->w_botline as approximated (because of some small change in the
+ * buffer).
+ */
+    void
+approximate_botline()
+{
+    curwin->w_valid &= ~VALID_BOTLINE;
+}
+#endif
+
+    void
+approximate_botline_win(wp)
+    win_T	*wp;
+{
+    wp->w_valid &= ~VALID_BOTLINE;
+}
+
+#if 0 /* not used */
+/*
+ * Return TRUE if curwin->w_botline is valid.
+ */
+    int
+botline_valid()
+{
+    return (curwin->w_valid & VALID_BOTLINE);
+}
+#endif
+
+#if 0 /* not used */
+/*
+ * Return TRUE if curwin->w_botline is valid or approximated.
+ */
+    int
+botline_approximated()
+{
+    return (curwin->w_valid & VALID_BOTLINE_AP);
+}
+#endif
+
+/*
+ * Return TRUE if curwin->w_wrow and curwin->w_wcol are valid.
+ */
+    int
+cursor_valid()
+{
+    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()
+{
+    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()
+{
+    /*
+     * 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, FALSE);
+}
+#endif
+
+/*
+ * Compute wp->w_cline_row and wp->w_cline_height, based on the current value
+ * of wp->w_topine.
+ *
+ * Returns OK when cursor is in the window, FAIL when it isn't.
+ */
+    static void
+curs_rows(wp, do_botline)
+    win_T	*wp;
+    int		do_botline;		/* also compute w_botline */
+{
+    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
+#ifdef FEAT_DIFF
+		if (lnum == wp->w_topline)
+		    wp->w_cline_row += plines_win_nofill(wp, lnum++, TRUE)
+							      + wp->w_topfill;
+		else
+#endif
+		    wp->w_cline_row += plines_win(wp, lnum++, TRUE);
+	}
+    }
+
+    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
+	}
+    }
+
+    wp->w_valid |= VALID_CROW|VALID_CHEIGHT;
+
+    /* validate botline too, if update_screen doesn't do it */
+    if (do_botline && all_invalid)
+	validate_botline_win(wp);
+}
+
+/*
+ * Validate curwin->w_virtcol only.
+ */
+    void
+validate_virtcol()
+{
+    validate_virtcol_win(curwin);
+}
+
+/*
+ * Validate wp->w_virtcol only.
+ */
+    void
+validate_virtcol_win(wp)
+    win_T	*wp;
+{
+    check_cursor_moved(wp);
+    if (!(wp->w_valid & VALID_VIRTCOL))
+    {
+	getvvcol(wp, &wp->w_cursor, NULL, &(wp->w_virtcol), NULL);
+	wp->w_valid |= VALID_VIRTCOL;
+    }
+}
+
+/*
+ * Validate curwin->w_cline_height only.
+ */
+    static void
+validate_cheight()
+{
+    check_cursor_moved(curwin);
+    if (!(curwin->w_valid & VALID_CHEIGHT))
+    {
+#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.	Only correct when 'wrap' on!
+ */
+    void
+validate_cursor_col()
+{
+    colnr_T off;
+    colnr_T col;
+
+    validate_virtcol();
+    if (!(curwin->w_valid & VALID_WCOL))
+    {
+	col = curwin->w_virtcol;
+	off = curwin_col_off();
+	col += off;
+
+	/* long line wrapping, adjust curwin->w_wrow */
+	if (curwin->w_p_wrap && col >= (colnr_T)W_WIDTH(curwin)
+#ifdef FEAT_VERTSPLIT
+		&& curwin->w_width != 0
+#endif
+		)
+	{
+	    col -= W_WIDTH(curwin);
+	    col = col % (W_WIDTH(curwin) - off + curwin_col_off2());
+	}
+	curwin->w_wcol = col;
+	curwin->w_valid |= VALID_WCOL;
+    }
+}
+
+/*
+ * Compute offset of a window, occupied by line number, fold column and sign
+ * column (these don't move when scrolling horizontally).
+ */
+    int
+win_col_off(wp)
+    win_T	*wp;
+{
+    return ((wp->w_p_nu ? 8 : 0)
+#ifdef FEAT_CMDWIN
+	    + (cmdwin_type == 0 || wp != curwin ? 0 : 1)
+#endif
+#ifdef FEAT_FOLDING
+	    + wp->w_p_fdc
+#endif
+#ifdef FEAT_SIGNS
+	    + (
+# ifdef FEAT_NETBEANS_INTG
+		/* always show glyph gutter in netbeans */
+		usingNetbeans ||
+# endif
+		wp->w_buffer->b_signlist != NULL ? 2 : 0)
+#endif
+	   );
+}
+
+    int
+curwin_col_off()
+{
+    return win_col_off(curwin);
+}
+
+/*
+ * Return the difference in column offset for the second screen line of a
+ * wrapped line.  It's 8 if 'number' is on and 'n' is in 'cpoptions'.
+ */
+    int
+win_col_off2(wp)
+    win_T	*wp;
+{
+    if (wp->w_p_nu && vim_strchr(p_cpo, CPO_NUMCOL) != NULL)
+	return 8;
+    return 0;
+}
+
+    int
+curwin_col_off2()
+{
+    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(scroll)
+    int		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		width = 0;
+    int		textwidth;
+    int		new_leftcol;
+    colnr_T	startcol;
+    colnr_T	endcol;
+    colnr_T	prev_skipcol;
+
+    /*
+     * 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, FALSE);
+
+    /*
+     * 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 = 0;
+
+    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;
+
+    textwidth = W_WIDTH(curwin) - extra;
+    if (textwidth <= 0)
+    {
+	/* No room for text, put cursor in last char of window. */
+	curwin->w_wcol = W_WIDTH(curwin) - 1;
+	curwin->w_wrow = curwin->w_height - 1;
+    }
+    else if (curwin->w_p_wrap
+#ifdef FEAT_VERTSPLIT
+	    && curwin->w_width != 0
+#endif
+	    )
+    {
+	width = textwidth + curwin_col_off2();
+
+	/* long line wrapping, adjust curwin->w_wrow */
+	if (curwin->w_wcol >= W_WIDTH(curwin))
+	{
+	    n = (curwin->w_wcol - W_WIDTH(curwin)) / width + 1;
+	    curwin->w_wcol -= n * width;
+	    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 */
+	    if (*p_sbr && *ml_get_cursor() == NUL
+		    && curwin->w_wcol == (int)vim_strsize(p_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 (scroll
+#ifdef FEAT_FOLDING
+	    && !curwin->w_cline_folded
+#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 - p_siso;
+	off_right = (int)endcol - (int)(curwin->w_leftcol + W_WIDTH(curwin)
+								- p_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 >= textwidth / 2 || off_right >= off_left)
+		new_leftcol = curwin->w_wcol - extra - textwidth / 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(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 + p_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
+	    && width > 0
+#ifdef FEAT_VERTSPLIT
+	    && curwin->w_width != 0
+#endif
+	    )
+    {
+	/* 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 "p_so" lines above
+	 * 2: Less than "p_so" lines below
+	 * 3: both of them */
+	extra = 0;
+	if (curwin->w_skipcol + p_so * width > 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 + p_so)
+	    n = curwin->w_wrow + p_so;
+	else
+	    n = p_lines;
+	if ((colnr_T)n >= curwin->w_height + curwin->w_skipcol / width)
+	    extra += 2;
+
+	if (extra == 3 || p_lines < p_so * 2)
+	{
+	    /* not enough room for 'scrolloff', put cursor in the middle */
+	    n = curwin->w_virtcol / width;
+	    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 * width;
+	}
+	else if (extra == 1)
+	{
+	    /* less then 'scrolloff' lines above, decrease skipcol */
+	    extra = (curwin->w_skipcol + p_so * width - curwin->w_virtcol
+				     + width - 1) / width;
+	    if (extra > 0)
+	    {
+		if ((colnr_T)(extra * width) > curwin->w_skipcol)
+		    extra = curwin->w_skipcol / width;
+		curwin->w_skipcol -= extra * width;
+	    }
+	}
+	else if (extra == 2)
+	{
+	    /* less then 'scrolloff' lines below, increase skipcol */
+	    endcol = (n - curwin->w_height + 1) * width;
+	    while (endcol > curwin->w_virtcol)
+		endcol -= width;
+	    if (endcol > curwin->w_skipcol)
+		curwin->w_skipcol = endcol;
+	}
+
+	curwin->w_wrow -= curwin->w_skipcol / width;
+	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 * width;
+	    curwin->w_wrow -= extra;
+	}
+
+	extra = ((int)prev_skipcol - (int)curwin->w_skipcol) / width;
+	if (extra > 0)
+	    win_ins_lines(curwin, 0, extra, FALSE, FALSE);
+	else if (extra < 0)
+	    win_del_lines(curwin, 0, -extra, FALSE, FALSE);
+    }
+    else
+	curwin->w_skipcol = 0;
+    if (prev_skipcol != curwin->w_skipcol)
+	redraw_later(NOT_VALID);
+
+    curwin->w_valid |= VALID_WCOL|VALID_WROW|VALID_VIRTCOL;
+}
+
+/*
+ * Scroll the current window down by "line_count" logical lines.  "CTRL-Y"
+ */
+/*ARGSUSED*/
+    void
+scrolldown(line_count, byfold)
+    long	line_count;
+    int		byfold;		/* TRUE: count a closed fold as one line */
+{
+    long	done = 0;	/* total # of physical lines done */
+    int		wrow;
+    int		moved = FALSE;
+
+#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 */
+    while (line_count-- > 0)
+    {
+#ifdef FEAT_DIFF
+	if (curwin->w_topfill < diff_check(curwin, curwin->w_topline))
+	{
+	    ++curwin->w_topfill;
+	    ++done;
+	}
+	else
+#endif
+	{
+	    if (curwin->w_topline == 1)
+		break;
+	    --curwin->w_topline;
+#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)
+		    line_count -= curwin->w_topline - first - 1;
+		curwin->w_botline -= curwin->w_topline - first;
+		curwin->w_topline = first;
+	    }
+	    else
+#endif
+#ifdef FEAT_DIFF
+		done += plines_nofill(curwin->w_topline);
+#else
+		done += plines(curwin->w_topline);
+#endif
+	}
+	--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
+#ifdef FEAT_VERTSPLIT
+		&& curwin->w_width != 0
+#endif
+	    )
+    {
+	validate_virtcol();
+	validate_cheight();
+	wrow += curwin->w_cline_height - 1 -
+	    curwin->w_virtcol / W_WIDTH(curwin);
+    }
+    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);
+    }
+}
+
+/*
+ * Scroll the current window up by "line_count" logical lines.  "CTRL-E"
+ */
+/*ARGSUSED*/
+    void
+scrollup(line_count, byfold)
+    long	line_count;
+    int		byfold;		/* TRUE: count a closed fold as one line */
+{
+#if defined(FEAT_FOLDING) || defined(FEAT_DIFF)
+    linenr_T	lnum;
+
+    if (
+# ifdef FEAT_FOLDING
+	    (byfold && hasAnyFolding(curwin))
+#  ifdef FEAT_DIFF
+	    ||
+#  endif
+# endif
+# ifdef FEAT_DIFF
+	    curwin->w_p_diff
+# endif
+	    )
+    {
+	/* count each sequence of folded lines as one logical line */
+	lnum = curwin->w_topline;
+	while (line_count--)
+	{
+# ifdef FEAT_DIFF
+	    if (curwin->w_topfill > 0)
+		--curwin->w_topfill;
+	    else
+# endif
+	    {
+# ifdef FEAT_FOLDING
+		if (byfold)
+		    (void)hasFolding(lnum, NULL, &lnum);
+# endif
+		if (lnum >= curbuf->b_ml.ml_line_count)
+		    break;
+		++lnum;
+# ifdef FEAT_DIFF
+		curwin->w_topfill = diff_check_fill(curwin, lnum);
+# endif
+	    }
+	}
+	/* approximate w_botline */
+	curwin->w_botline += lnum - curwin->w_topline;
+	curwin->w_topline = lnum;
+    }
+    else
+#endif
+    {
+	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);
+    }
+}
+
+#ifdef FEAT_DIFF
+/*
+ * Don't end up with too many filler lines in the window.
+ */
+    void
+check_topfill(wp, down)
+    win_T	*wp;
+    int		down;	/* when TRUE scroll down when not enough space */
+{
+    int		n;
+
+    if (wp->w_topfill > 0)
+    {
+	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()
+{
+    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
+
+#if defined(FEAT_INS_EXPAND) || defined(PROTO)
+/*
+ * Scroll the screen one line down, but don't do it if it would move the
+ * cursor off the screen.
+ */
+    void
+scrolldown_clamp()
+{
+    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
+#ifdef FEAT_VERTSPLIT
+		&& curwin->w_width != 0
+#endif
+	    )
+    {
+	validate_cheight();
+	validate_virtcol();
+	end_row += curwin->w_cline_height - 1 -
+	    curwin->w_virtcol / W_WIDTH(curwin);
+    }
+    if (end_row < curwin->w_height - p_so)
+    {
+#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
+	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()
+{
+    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
+#ifdef FEAT_VERTSPLIT
+		&& curwin->w_width != 0
+#endif
+	    )
+    {
+	validate_virtcol();
+	start_row -= curwin->w_virtcol / W_WIDTH(curwin);
+    }
+    if (start_row >= p_so)
+    {
+#ifdef FEAT_DIFF
+	if (curwin->w_topfill > 0)
+	    --curwin->w_topfill;
+	else
+#endif
+	    ++curwin->w_topline;
+	++curwin->w_botline;		/* approximate w_botline */
+	curwin->w_valid &= ~(VALID_WROW|VALID_CROW|VALID_BOTLINE);
+    }
+}
+#endif /* FEAT_INS_EXPAND */
+
+/*
+ * 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.
+ */
+    static void
+topline_back(lp)
+    lineoff_T	*lp;
+{
+#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
+	{
+#ifdef FEAT_DIFF
+	    lp->height = plines_nofill(lp->lnum);
+#else
+	    lp->height = plines(lp->lnum);
+#endif
+	}
+    }
+}
+
+/*
+ * 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(lp)
+    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
+	{
+#ifdef FEAT_DIFF
+	    lp->height = plines_nofill(lp->lnum);
+#else
+	    lp->height = plines(lp->lnum);
+#endif
+	}
+    }
+}
+
+#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(lp)
+    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(lp)
+    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(min_scroll, always)
+    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;
+#ifdef FEAT_DIFF
+    linenr_T	old_topfill = curwin->w_topfill;
+#endif
+    linenr_T	new_topline;
+    int		off = p_so;
+
+#ifdef FEAT_MOUSE
+    if (mouse_dragging > 0)
+	off = mouse_dragging - 1;
+#endif
+
+    /*
+     * 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;
+    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
+    /* count filler lines of the cursor window as context */
+    i = diff_check_fill(curwin, curwin->w_cursor.lnum);
+    used += i;
+    extra += i;
+#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(top);
+	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;
+	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;
+
+	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);
+    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
+	if (curwin->w_topline != old_topline
+#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(wp, used)
+    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.
+ * 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(min_scroll, set_topbot)
+    int		min_scroll;
+    int		set_topbot;
+{
+    int		used;
+    int		scrolled = 0;
+    int		extra = 0;
+    int		i;
+    linenr_T	line_count;
+    linenr_T	old_topline = curwin->w_topline;
+    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 */
+
+    cln = curwin->w_cursor.lnum;
+    if (set_topbot)
+    {
+	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(&loff);
+	    if (used + loff.height > curwin->w_height)
+		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
+		)
+	    curwin->w_valid &= ~(VALID_WROW|VALID_CROW);
+    }
+    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 below botline, we will at least scroll by the height
+     * of the cursor line.  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;
+    }
+
+    /*
+     * Stop counting lines to scroll when
+     * - hitting start of the file
+     * - scrolled nothing or at least 'sj' lines
+     * - at least 'so' 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 >= (
+#ifdef FEAT_MOUSE
+			    mouse_dragging ? mouse_dragging - 1 :
+#endif
+			    p_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);
+	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
+			    && boff.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 < (
+#ifdef FEAT_MOUSE
+			mouse_dragging > 0 ? mouse_dragging - 1 :
+#endif
+			p_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);
+    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 && 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(atend)
+    int		atend;
+{
+    int		above = 0;
+    linenr_T	topline;
+#ifdef FEAT_DIFF
+    int		topfill = 0;
+#endif
+    int		below = 0;
+    int		used;
+    lineoff_T	loff;
+    lineoff_T	boff;
+
+    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;
+    while (topline > 1)
+    {
+	if (below <= above)	    /* add a line below the cursor first */
+	{
+	    if (boff.lnum < curbuf->b_ml.ml_line_count)
+	    {
+		botline_forw(&boff);
+		used += boff.height;
+		if (used > curwin->w_height)
+		    break;
+		below += boff.height;
+	    }
+	    else
+	    {
+		++below;	    /* count a "~" line */
+		if (atend)
+		    ++used;
+	    }
+	}
+
+	if (below > above)	    /* add a line above the cursor */
+	{
+	    topline_back(&loff);
+	    used += loff.height;
+	    if (used > curwin->w_height)
+		break;
+	    above += loff.height;
+	    topline = loff.lnum;
+#ifdef FEAT_DIFF
+	    topfill = loff.fill;
+#endif
+	}
+    }
+#ifdef FEAT_FOLDING
+    if (!hasFolding(topline, &curwin->w_topline, NULL))
+#endif
+	curwin->w_topline = topline;
+#ifdef FEAT_DIFF
+    curwin->w_topfill = topfill;
+    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
+ * 'so' 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()
+{
+    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;
+
+    /*
+     * 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 = p_so;
+    below_wanted = p_so;
+#ifdef FEAT_MOUSE
+    if (mouse_dragging)
+    {
+	above_wanted = mouse_dragging - 1;
+	below_wanted = mouse_dragging - 1;
+    }
+#endif
+    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
+#ifdef FEAT_MOUSE
+	    && !mouse_dragging
+#endif
+	    )
+    {
+	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;
+
+    /*
+     * 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
+#ifndef FEAT_DIFF
+		above += plines(topline);
+#else
+		above += plines_nofill(topline);
+
+	    /* 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 __ARGS((lineoff_T *lp, int dir));
+
+/*
+ * move screen 'count' pages up or down and update screen
+ *
+ * return FAIL for failure, OK otherwise
+ */
+    int
+onepage(dir, count)
+    int		dir;
+    long	count;
+{
+    long	n;
+    int		retval = OK;
+    lineoff_T	loff;
+    linenr_T	old_topline = curwin->w_topline;
+
+    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 - p_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)
+	{
+					/* at end of file */
+	    if (curwin->w_botline > curbuf->b_ml.ml_line_count)
+	    {
+		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
+	    /* 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);
+		n += loff.height;
+	    }
+	    if (n <= curwin->w_height)		    /* 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();
+    beginline(BL_SOL | BL_FIX);
+    curwin->w_valid &= ~(VALID_WCOL|VALID_WROW|VALID_VIRTCOL);
+
+    /*
+     * 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 (retval == OK && dir == FORWARD && 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
+	}
+    }
+
+    redraw_later(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(lp, dir)
+    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 + 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 + 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 + h3 + h2 > min_height || h3 + h2 + h1 > min_height)
+	*lp = loff1;	/* 1 line overlap */
+    else
+	*lp = loff2;	/* 2 lines overlap */
+    return;
+}
+
+/* #define KEEP_SCREEN_LINE */
+/*
+ * Scroll 'scroll' lines up or down.
+ */
+    void
+halfpage(flag, Prenum)
+    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;
+
+    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;
+		if (--n < 0 && scrolled > 0)
+		    break;
+		--curwin->w_topfill;
+	    }
+	    else
+#endif
+	    {
+#ifdef FEAT_DIFF
+		i = plines_nofill(curwin->w_topline);
+#else
+		i = plines(curwin->w_topline);
+#endif
+		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
+
+#ifndef KEEP_SCREEN_LINE
+		if (curwin->w_cursor.lnum < curbuf->b_ml.ml_line_count)
+		{
+		    ++curwin->w_cursor.lnum;
+		    curwin->w_valid &=
+				    ~(VALID_VIRTCOL|VALID_CHEIGHT|VALID_WCOL);
+		}
+#endif
+	    }
+	    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);
+	    }
+	}
+
+#ifndef KEEP_SCREEN_LINE
+	/*
+	 * 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
+	/* try to put the cursor in the same screen line */
+	while ((curwin->w_cursor.lnum < curwin->w_topline || scrolled > 0)
+			     && curwin->w_cursor.lnum < curwin->w_botline - 1)
+	{
+	    scrolled -= plines(curwin->w_cursor.lnum);
+	    if (scrolled < 0 && curwin->w_cursor.lnum >= curwin->w_topline)
+		break;
+# ifdef FEAT_FOLDING
+	    (void)hasFolding(curwin->w_cursor.lnum, NULL,
+						      &curwin->w_cursor.lnum);
+# endif
+	    ++curwin->w_cursor.lnum;
+	}
+#endif
+    }
+    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;
+		if (--n < 0 && scrolled > 0)
+		    break;
+		++curwin->w_topfill;
+	    }
+	    else
+#endif
+	    {
+#ifdef FEAT_DIFF
+		i = plines_nofill(curwin->w_topline - 1);
+#else
+		i = plines(curwin->w_topline - 1);
+#endif
+		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;
+#ifndef KEEP_SCREEN_LINE
+	    if (curwin->w_cursor.lnum > 1)
+	    {
+		--curwin->w_cursor.lnum;
+		curwin->w_valid &= ~(VALID_VIRTCOL|VALID_CHEIGHT|VALID_WCOL);
+	    }
+#endif
+	}
+#ifndef KEEP_SCREEN_LINE
+	/*
+	 * 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;
+	}
+#else
+	/* try to put the cursor in the same screen line */
+	scrolled += n;	    /* move cursor when topline is 1 */
+	while (curwin->w_cursor.lnum > curwin->w_topline
+	      && (scrolled > 0 || curwin->w_cursor.lnum >= curwin->w_botline))
+	{
+	    scrolled -= plines(curwin->w_cursor.lnum - 1);
+	    if (scrolled < 0 && curwin->w_cursor.lnum < curwin->w_botline)
+		break;
+	    --curwin->w_cursor.lnum;
+# ifdef FEAT_FOLDING
+	    foldAdjustCursor();
+# endif
+	}
+#endif
+    }
+# 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(VALID);
+}