patch 9.1.0258: half-page scrolling broke backward compatibility

Problem: Support for 'smoothscroll' in (half-)page scrolling broke backward compatibility and can be made to work better. (after v9.1.215) Solution: Restore the previous cursor and end-of-buffer behavior for half-page scrolling and improve 'smoothscroll' support. (Luuk van Baal) fixes: #14338 closes: #14377 Signed-off-by: Luuk van Baal <luukvbaal@gmail.com> Signed-off-by: Christian Brabandt <cb@256bit.org>
2025-09-23 03:43:49 -04:00 · 2024-04-02 20:49:45 +02:00
parent f1750ca0c2
commit cb204e688e
11 changed files with 212 additions and 96 deletions
--- a/src/change.c
+++ b/src/change.c
@@ -574,8 +574,7 @@ changed_common(
 			    && wp->w_topline < lnume
 			    && win_linetabsize(wp, wp->w_topline,
 					ml_get(wp->w_topline), (colnr_T)MAXCOL)
-				    <= wp->w_skipcol + sms_marker_overlap(wp,
-					win_col_off(wp) - win_col_off2(wp)))))
+				    <= wp->w_skipcol + sms_marker_overlap(wp, -1))))
 		wp->w_skipcol = 0;

 	    // Check if a change in the buffer has invalidated the cached
--- a/src/move.c
+++ b/src/move.c
@@ -197,13 +197,15 @@ redraw_for_cursorcolumn(win_T *wp)
 * Calculates how much the 'listchars' "precedes" or 'smoothscroll' "<<<"
 * marker overlaps with buffer text for window "wp".
 * Parameter "extra2" should be the padding on the 2nd line, not the first
- * line.
+ * line. When "extra2" is -1 calculate the padding.
 * Returns the number of columns of overlap with buffer text, excluding the
 * extra padding on the ledge.
 */
     int
 sms_marker_overlap(win_T *wp, int extra2)
 {
+    if (extra2 == -1)
+	extra2 = win_col_off(wp) - win_col_off2(wp);
 #if defined(FEAT_LINEBREAK)
    // There is no marker overlap when in showbreak mode, thus no need to
    // account for it.  See wlv_screen_line().
@@ -340,12 +342,12 @@ update_topline(void)
 				 && curwin->w_cursor.lnum == curwin->w_topline)
 	    {
 		colnr_T vcol;
+		int overlap;

 		// Check that the cursor position is visible.  Add columns for
 		// the marker displayed in the top-left if needed.
 		getvvcol(curwin, &curwin->w_cursor, &vcol, NULL, NULL);
-		int overlap = sms_marker_overlap(curwin, curwin_col_off()
-							- curwin_col_off2());
+		overlap = sms_marker_overlap(curwin, -1);
 		if (curwin->w_skipcol + overlap > vcol)
 		    check_topline = TRUE;
 	    }
@@ -1854,6 +1856,9 @@ scrollup(
 		    curwin->w_topfill = diff_check_fill(curwin, lnum);
 # endif
 		    curwin->w_skipcol = 0;
+		    // Adjusting the cursor later should not adjust skipcol:
+		    // bring it to the first screenline on this new topline.
+		    curwin->w_curswant %= width1;
 		    if (todo > 1 && do_sms)
 			size = linetabsize(curwin, curwin->w_topline);
 		}
@@ -1971,8 +1976,7 @@ adjust_skipcol(void)
    }

    validate_virtcol();
-    int overlap = sms_marker_overlap(curwin,
-					 curwin_col_off() - curwin_col_off2());
+    int overlap = sms_marker_overlap(curwin, -1);
    while (curwin->w_skipcol > 0
 	    && curwin->w_virtcol < curwin->w_skipcol + overlap + scrolloff_cols)
    {
@@ -2486,6 +2490,7 @@ scroll_cursor_bot(int min_scroll, int set_topbot)
 		    {
 			int plines_offset = used + loff.height
 							    - curwin->w_height;
+			int overlap = sms_marker_overlap(curwin, -1);
 			used = curwin->w_height;
 #ifdef FEAT_DIFF
 			curwin->w_topfill = loff.fill;
@@ -2493,6 +2498,7 @@ scroll_cursor_bot(int min_scroll, int set_topbot)
 			curwin->w_topline = loff.lnum;
 			curwin->w_skipcol = skipcol_from_plines(
 							curwin, plines_offset);
+			curwin->w_cursor.col = curwin->w_skipcol + overlap;
 			set_skipcol = TRUE;
 		    }
 		}
@@ -2503,6 +2509,8 @@ scroll_cursor_bot(int min_scroll, int set_topbot)
 	    curwin->w_topfill = loff.fill;
 #endif
 	}
+	if (curwin->w_topline > curbuf->b_ml.ml_line_count)
+	    curwin->w_topline = curbuf->b_ml.ml_line_count;
 	set_empty_rows(curwin, used);
 	curwin->w_valid |= VALID_BOTLINE|VALID_BOTLINE_AP;
 	if (curwin->w_topline != old_topline
@@ -3087,19 +3095,66 @@ static int get_scroll_overlap(int dir)
 }

 /*
- * Move screen "count" pages up ("dir" is BACKWARD) or down ("dir" is FORWARD)
- * and update the screen.
+ * Scroll "count" lines with 'smoothscroll' in direction "dir". Adjust "count"
+ * when scrolling more than "count" and return TRUE when scrolling happened.
+ */
+static int scroll_with_sms(int dir, long *count)
+{
+    int		prev_sms = curwin->w_p_sms;
+    colnr_T	prev_skipcol = curwin->w_skipcol;
+    linenr_T	prev_topline = curwin->w_topline;
+#ifdef FEAT_DIFF
+    int		prev_topfill = curwin->w_topfill;
+#endif
+
+    curwin->w_p_sms = TRUE;
+    scroll_redraw(dir == FORWARD, *count);
+
+    // Not actually smoothscrolling but ended up with partially visible line.
+    // Continue scrolling and update "count" so that cursor can be moved
+    // accordingly for half-page scrolling.
+    if (!prev_sms && curwin->w_skipcol > 0)
+    {
+	int fixdir = dir;
+	// Reverse the scroll direction when topline already changed. One line
+	// extra for scrolling backward so that consuming skipcol is symmetric.
+	if (labs(curwin->w_topline - prev_topline) > (dir == BACKWARD))
+	    fixdir = dir * -1;
+	validate_cursor();
+	while (curwin->w_skipcol > 0
+	    && curwin->w_topline < curbuf->b_ml.ml_line_count)
+	{
+	    scroll_redraw(fixdir == FORWARD, 1);
+	    *count += (fixdir == dir ? 1 : -1);
+	}
+    }
+    curwin->w_p_sms = prev_sms;
+
+    return curwin->w_topline == prev_topline
+#ifdef FEAT_DIFF
+	&& curwin->w_topfill == prev_topfill
+#endif
+	&& curwin->w_skipcol == prev_skipcol;
+}
+
+/*
+ * Move screen "count" (half) pages up ("dir" is BACKWARD) or down ("dir" is
+ * FORWARD) and update the screen. Handle moving the cursor and not scrolling
+ * to reveal end of buffer lines for half-page scrolling with CTRL-D and CTRL-U.
 *
 * Return FAIL for failure, OK otherwise.
 */
    int
 pagescroll(int dir, long count, int half)
 {
-#ifdef FEAT_DIFF
-    int		prev_topfill = curwin->w_topfill;
-#endif
-    linenr_T	prev_topline = curwin->w_topline;
-    colnr_T	prev_skipcol = curwin->w_skipcol;
+    int		nochange = TRUE;
+    int		buflen = curbuf->b_ml.ml_line_count;
+    colnr_T	prev_col = curwin->w_cursor.col;
+    colnr_T	prev_curswant = curwin->w_curswant;
+    linenr_T	prev_lnum = curwin->w_cursor.lnum;
+    oparg_T	oa = { 0 };
+    cmdarg_T	ca = { 0 };
+    ca.oap = &oa;

    if (half)
    {
@@ -3107,54 +3162,61 @@ pagescroll(int dir, long count, int half)
 	if (count)
 	    curwin->w_p_scr = MIN(curwin->w_height, count);
 	count = MIN(curwin->w_height, curwin->w_p_scr);
-    }
-    else
-	// Scroll 'window' or current window height lines.
-	count *= ((ONE_WINDOW && p_window > 0 && p_window < Rows - 1) ?
-					    p_window - 2 : get_scroll_overlap(dir));

-    if (curwin->w_p_sms)
-	scroll_redraw(dir == FORWARD, count);
-    else
-    {
-	// Scroll at least one full line without 'smoothscroll'.
-#ifdef FEAT_DIFF
-	count -= plines_nofill(curwin->w_topline);
-#else
-	count -= plines(curwin->w_topline);
-#endif
-	scroll_redraw(dir == FORWARD, 1);
+	// Don't scroll if we already know that it will reveal end of buffer lines.
+	if (dir == BACKWARD
+	    || (curwin->w_botline - 1 < buflen)
+	    || (curwin->w_p_sms && curwin->w_botline - 1 == buflen
+		&& curwin->w_skipcol < linetabsize(curwin, buflen)))
+	{
+	    nochange = scroll_with_sms(dir, &count);
+	    validate_botline();
+	    // Hide any potentially revealed end of buffer lines.
+	    if (!nochange && curwin->w_botline - 1 == buflen)
+	    {
+		curwin->w_cursor.lnum = buflen;
+		scroll_cursor_bot(0, TRUE);
+	    }
+	}

-	// Temporarily set 'smoothscroll' so that scrolling count lines
-	// does not skip over parts of the buffer with wrapped lines.
-	curwin->w_p_sms = TRUE;
-	if (count > 0)
-	    scroll_redraw(dir == FORWARD, count);
-	curwin->w_p_sms = FALSE;
-    }
+	// Move the cursor "count" screen lines.
+	curwin->w_curswant = MAXCOL;
+	curwin->w_cursor.col = prev_col;
+	curwin->w_cursor.lnum = prev_lnum;
+	if (curwin->w_p_wrap)
+	    nv_screengo(&oa, dir, count);
+	else if (dir == FORWARD)
+	    cursor_down_inner(curwin, count);
+	else
+	    cursor_up_inner(curwin, count);
+	curwin->w_curswant = prev_curswant;
+
+	if (get_scrolloff_value())
+	    cursor_correct();
 #ifdef FEAT_FOLDING
 	// Move cursor to first line of closed fold.
 	foldAdjustCursor();
 #endif

-    int nochange = curwin->w_topline == prev_topline
-#ifdef FEAT_DIFF
-	&& curwin->w_topfill == prev_topfill
-#endif
-	&& curwin->w_skipcol == prev_skipcol;
-
-    // Error if the viewport did not change and the cursor is already
-    // at the boundary.
-    if (nochange)
-    {
-	int prev_cursor = curwin->w_cursor.lnum;
-	curwin->w_cursor.lnum += (count + 1) * (dir == FORWARD ? 1 : -1);
-	check_cursor();
-	if (curwin->w_cursor.lnum == prev_cursor)
-	    beep_flush();
+	nochange = nochange
+	    && prev_col == curwin->w_cursor.col
+	    && prev_lnum == curwin->w_cursor.lnum;
    }
-    else if (!curwin->w_p_sms || curwin->w_skipcol == prev_skipcol)
+    else
+    {
+	// Scroll [count] times 'window' or current window height lines.
+	count *= ((ONE_WINDOW && p_window > 0 && p_window < Rows - 1) ?
+				MAX(1, p_window - 2) : get_scroll_overlap(dir));
+	nochange = scroll_with_sms(dir, &count);
+    }
+
+    // Error if both the viewport and cursor did not change.
+    if (nochange)
+	beep_flush();
+    else if (!curwin->w_p_sms)
 	beginline(BL_SOL | BL_FIX);
+    else if (p_sol)
+	nv_g_home_m_cmd(&ca);

    return nochange;
 }
--- a/src/normal.c
+++ b/src/normal.c
@@ -2303,7 +2303,7 @@ find_decl(
 *
 * Return OK if able to move cursor, FAIL otherwise.
 */
-    static int
+    int
 nv_screengo(oparg_T *oap, int dir, long dist)
 {

@@ -5745,7 +5745,7 @@ nv_gv_cmd(cmdarg_T *cap)
 * "g0", "g^" : Like "0" and "^" but for screen lines.
 * "gm": middle of "g0" and "g$".
 */
-    static void
+    void
 nv_g_home_m_cmd(cmdarg_T *cap)
 {
    int		i;
@@ -5771,6 +5771,15 @@ nv_g_home_m_cmd(cmdarg_T *cap)
 	i = 0;
 	if (virtcol >= (colnr_T)width1 && width2 > 0)
 	    i = (virtcol - width1) / width2 * width2 + width1;
+
+	// When ending up below 'smoothscroll' marker, move just beyond it so
+	// that skipcol is not adjusted later.
+	if (curwin->w_skipcol > 0 && curwin->w_cursor.lnum == curwin->w_topline)
+	{
+	    int overlap = sms_marker_overlap(curwin, -1);
+	    if (overlap > 0 && i == curwin->w_skipcol)
+		i += overlap;
+	}
    }
    else
 	i = curwin->w_leftcol;
@@ -7263,8 +7272,9 @@ nv_at(cmdarg_T *cap)
    static void
 nv_halfpage(cmdarg_T *cap)
 {
+    int	dir = cap->cmdchar == Ctrl_D ? FORWARD : BACKWARD;
    if (!checkclearop(cap->oap))
-	pagescroll(cap->cmdchar == Ctrl_D, cap->count0, TRUE);
+	pagescroll(dir, cap->count0, TRUE);
 }

 /*
--- a/src/proto/normal.pro
+++ b/src/proto/normal.pro
@@ -22,6 +22,8 @@ void pop_showcmd(void);
 void do_check_scrollbind(int check);
 void check_scrollbind(linenr_T topline_diff, long leftcol_diff);
 int find_decl(char_u *ptr, int len, int locally, int thisblock, int flags_arg);
+void nv_g_home_m_cmd(cmdarg_T *cap);
+int nv_screengo(oparg_T *oap, int dir, long dist);
 void nv_scroll_line(cmdarg_T *cap);
 void scroll_redraw(int up, long count);
 void handle_tabmenu(void);
--- a/src/testdir/dumps/Test_cursorline_redraw_2.dump
+++ b/src/testdir/dumps/Test_cursorline_redraw_2.dump
@@ -1,20 +1,20 @@
-|T+0&#ffffff0|h|e| |{|o|p|t|i|o|n|}| |a|r|g|u|m|e|n|t|s| |t|o| |"|:|s|e|t|"| |m|a|y| |b|e| 
+| +0&#ffffff0@39
+|T|h|e| |{|o|p|t|i|o|n|}| |a|r|g|u|m|e|n|t|s| |t|o| |"|:|s|e|t|"| |m|a|y| |b|e| 
 |r|e|p|e|a|t|e|d|.| @1|F|o|r| |e|x|a|m|p|l|e|:| |>| @14
-@8|:|s|e|t| |a|i| |n|o|s|i| |s|w|=|3| |t|s|=|3| @9
-|I|f| |y|o|u| |m|a|k|e| |a|n| |e|r@1|o|r| |i|n| |o|n|e| |o|f| |t|h|e| |a|r|g|u|m
+| +8&&@7>:|s|e|t| |a|i| |n|o|s|i| |s|w|=|3| |t|s|=|3| @9
+|I+0&&|f| |y|o|u| |m|a|k|e| |a|n| |e|r@1|o|r| |i|n| |o|n|e| |o|f| |t|h|e| |a|r|g|u|m
 |e|n|t|s|,| |a|n| |e|r@1|o|r| |m|e|s@1|a|g|e| |w|i|l@1| |b|e| |g|i|v|e|n| @3
 |a|n|d| |t|h|e| |f|o|l@1|o|w|i|n|g| |a|r|g|u|m|e|n|t|s| |w|i|l@1| |b|e| |i|g|n|o
 |r|e|d|.| @35
@40
@40
@16|*|:|s|e|t|-|v|e|r|b|o|s|e|*| @9
->W+8&&|h|e|n| |'|v|e|r|b|o|s|e|'| |i|s| |n|o|n|-|z|e|r|o|,| |d|i|s|p|l|a|y|i|n|g| |a
+|W|h|e|n| |'|v|e|r|b|o|s|e|'| |i|s| |n|o|n|-|z|e|r|o|,| |d|i|s|p|l|a|y|i|n|g| |a
 |n| |o|p|t|i|o|n| |v|a|l|u|e| |w|i|l@1| |a|l|s|o| |t|e|l@1| |w|h|e|r|e| |i|t| @1
-|w+0&&|a|s| |l|a|s|t| |s|e|t|.| @1|E|x|a|m|p|l|e|:| |>| @14
+|w|a|s| |l|a|s|t| |s|e|t|.| @1|E|x|a|m|p|l|e|:| |>| @14
@8|:|v|e|r|b|o|s|e| |s|e|t| |s|h|i|f|t|w|i|d|t|h| |c|i|n|d|e|n|t|?
 |<| @1|s|h|i|f|t|w|i|d|t|h|=|4| |~| @22
@10|L|a|s|t| |s|e|t| |f|r|o|m| |m|o|d|e|l|i|n|e| |l|i|n|e| |1| 
 |~| @38
@2|c|i|n|d|e|n|t| |~| @28
-|@+0#4040ff13&@2| @36
-| +0#0000000&@21|1|2|,|1| @9|5|0|%| 
+@22|7|,|2|-|9| @8|4@1|%| 
--- a/src/testdir/dumps/Test_display_visual_block_scroll.dump
+++ b/src/testdir/dumps/Test_display_visual_block_scroll.dump
@@ -1,7 +1,7 @@
 |{+0#0000001#a8a8a8255| | +0#0000000#ffffff0@72
->}+0&#40ffff15| +0#0000001#a8a8a8255| +0#0000000#ffffff0@72
-|{| @73
-|f| @73
-|g| @73
+|}+0#0000001#a8a8a8255| | +0#0000000#ffffff0@72
+|{+0#0000001#a8a8a8255| | +0#0000000#ffffff0@72
+|f+0#0000001#a8a8a8255| | +0#0000000#ffffff0@72
+>g| +0#0000001#a8a8a8255| +0#0000000#ffffff0@72
 |}| @73
-|-+2&&@1| |V|I|S|U|A|L| |L|I|N|E| |-@1| +0&&@29|4| @8|8|,|1| @10|B|o|t| 
+|-+2&&@1| |V|I|S|U|A|L| |L|I|N|E| |-@1| +0&&@29|7| @8|1@1|,|1| @9|B|o|t| 
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
@@ -1679,8 +1679,7 @@ func Test_diff_scroll_many_filler()
  endfor

  set smoothscroll&
-  bwipe!
-  bwipe!
+  %bwipe!
 endfunc

 " This was trying to update diffs for a buffer being closed
--- a/src/testdir/test_edit.vim
+++ b/src/testdir/test_edit.vim
@@ -1302,7 +1302,7 @@ func Test_edit_PAGEUP_PAGEDOWN()
  call feedkeys("A\<PageUp>\<esc>", 'tnix')
  call assert_equal([0, 10, 1, 0], getpos('.'))
  call feedkeys("A\<PageUp>\<esc>", 'tnix')
-  call assert_equal([0, 2, 11, 0], getpos('.'))
+  call assert_equal([0, 10, 11, 0], getpos('.'))
  " <S-Up> is the same as <PageUp>
  " <S-Down> is the same as <PageDown>
  call cursor(1, 1)
@@ -1325,7 +1325,7 @@ func Test_edit_PAGEUP_PAGEDOWN()
  call feedkeys("A\<S-Up>\<esc>", 'tnix')
  call assert_equal([0, 10, 1, 0], getpos('.'))
  call feedkeys("A\<S-Up>\<esc>", 'tnix')
-  call assert_equal([0, 2, 11, 0], getpos('.'))
+  call assert_equal([0, 10, 11, 0], getpos('.'))
  set nostartofline
  call cursor(30, 11)
  norm! zt
@@ -1338,7 +1338,7 @@ func Test_edit_PAGEUP_PAGEDOWN()
  call feedkeys("A\<PageUp>\<esc>", 'tnix')
  call assert_equal([0, 10, 11, 0], getpos('.'))
  call feedkeys("A\<PageUp>\<esc>", 'tnix')
-  call assert_equal([0, 2, 11, 0], getpos('.'))
+  call assert_equal([0, 10, 11, 0], getpos('.'))
  call cursor(1, 1)
  call feedkeys("A\<PageDown>\<esc>", 'tnix')
  call assert_equal([0, 9, 11, 0], getpos('.'))
@@ -1363,7 +1363,7 @@ func Test_edit_PAGEUP_PAGEDOWN()
  call feedkeys("A\<S-Up>\<esc>", 'tnix')
  call assert_equal([0, 10, 11, 0], getpos('.'))
  call feedkeys("A\<S-Up>\<esc>", 'tnix')
-  call assert_equal([0, 2, 11, 0], getpos('.'))
+  call assert_equal([0, 10, 11, 0], getpos('.'))
  call cursor(1, 1)
  call feedkeys("A\<S-Down>\<esc>", 'tnix')
  call assert_equal([0, 9, 11, 0], getpos('.'))
--- a/src/testdir/test_normal.vim
+++ b/src/testdir/test_normal.vim
@@ -1280,13 +1280,9 @@ func Test_vert_scroll_cmds()
  exe "normal \<C-D>"
  call assert_equal(46, line('.'))
  exe "normal \<C-U>"
-  call assert_equal(36, line('w0'))
-  call assert_equal(46, line('.'))
+  call assert_equal(36, line('.'))
  exe "normal \<C-U>"
-  call assert_equal(1,  line('w0'))
-  call assert_equal(40, line('.'))
-  exe "normal \<C-U>"
-  call assert_equal(30, line('.'))
+  call assert_equal(1, line('.'))
  exe "normal \<C-U>"
  call assert_equal(1, line('.'))
  set scroll&
@@ -1307,8 +1303,9 @@ func Test_vert_scroll_cmds()
  call assert_equal(50, line('.'))
  call assert_equal(100, line('w$'))
  normal z.
+  let lnum = winline()
  exe "normal \<C-D>"
-  call assert_equal(1, winline())
+  call assert_equal(lnum, winline())
  call assert_equal(50, line('.'))
  normal zt
  exe "normal \<C-D>"
@@ -3069,8 +3066,7 @@ func Test_normal42_halfpage()
  call assert_equal(2, &scroll)
  set scroll=5
  exe "norm! \<c-u>"
-  call assert_equal('3', getline('w0'))
-  call assert_equal('8', getline('.'))
+  call assert_equal('3', getline('.'))
  1
  set scrolloff=5
  exe "norm! \<c-d>"
@@ -3818,7 +3814,7 @@ func Test_normal_vert_scroll_longline()
  call assert_equal(1, winline())
  exe "normal \<C-B>"
  call assert_equal(10, line('.'))
-  call assert_equal(10, winline())
+  call assert_equal(4, winline())
  exe "normal \<C-B>\<C-B>"
  call assert_equal(5, line('.'))
  call assert_equal(5, winline())
--- a/src/testdir/test_scroll_opt.vim
+++ b/src/testdir/test_scroll_opt.vim
@@ -552,11 +552,11 @@ func Test_smoothscroll_cursor_position()
  " Test "g0/g<Home>"
  exe "normal gg\<C-E>"
  norm $gkg0
-  call s:check_col_calc(1, 2, 21)
+  call s:check_col_calc(4, 1, 24)

  " Test moving the cursor behind the <<< display with 'virtualedit'
  set virtualedit=all
-  exe "normal \<C-E>3lgkh"
+  exe "normal \<C-E>gkh"
  call s:check_col_calc(3, 2, 23)
  set virtualedit&

@@ -1017,26 +1017,72 @@ func Test_smoothscroll_page()
  exe "norm! \<C-B>"
  call assert_equal(0, winsaveview().skipcol)

-  exe "norm! \<C-D>"
+  " Half-page scrolling does not go beyond end of buffer and moves the cursor.
+  exe "norm! 0\<C-D>"
  call assert_equal(200, winsaveview().skipcol)
+  call assert_equal(204, col('.'))
  exe "norm! \<C-D>"
  call assert_equal(400, winsaveview().skipcol)
+  call assert_equal(404, col('.'))
  exe "norm! \<C-D>"
-  call assert_equal(600, winsaveview().skipcol)
+  call assert_equal(520, winsaveview().skipcol)
+  call assert_equal(601, col('.'))
  exe "norm! \<C-D>"
-  call assert_equal(800, winsaveview().skipcol)
-  exe "norm! \<C-D>"
-  call assert_equal(880, winsaveview().skipcol)
+  call assert_equal(520, winsaveview().skipcol)
+  call assert_equal(801, col('.'))
  exe "norm! \<C-U>"
-  call assert_equal(680, winsaveview().skipcol)
+  call assert_equal(520, winsaveview().skipcol)
+  call assert_equal(601, col('.'))
  exe "norm! \<C-U>"
-  call assert_equal(480, winsaveview().skipcol)
+  call assert_equal(400, winsaveview().skipcol)
+  call assert_equal(404, col('.'))
  exe "norm! \<C-U>"
-  call assert_equal(280, winsaveview().skipcol)
-  exe "norm! \<C-U>"
-  call assert_equal(80, winsaveview().skipcol)
+  call assert_equal(200, winsaveview().skipcol)
+  call assert_equal(204, col('.'))
  exe "norm! \<C-U>"
  call assert_equal(0, winsaveview().skipcol)
+  call assert_equal(1, col('.'))
+
+  bwipe!
+endfunc
+
+func Test_smoothscroll_next_topline()
+  call NewWindow(10, 40)
+  setlocal smoothscroll
+  call setline(1, ['abcde '->repeat(150)]->repeat(2))
+
+  " Scrolling a screenline that causes the cursor to move to the next buffer
+  " line should not skip part of that line to bring the cursor into view.
+  exe "norm! 22\<C-E>"
+  call assert_equal(880, winsaveview().skipcol)
+  exe "norm! \<C-E>"
+  redraw
+  call assert_equal(0, winsaveview().skipcol)
+
+  " Cursor in correct place when not in the first screenline of a buffer line.
+  exe "norm! gg4gj20\<C-D>\<C-D>"
+  redraw
+  call assert_equal(2, line('w0'))
+
+  bwipe!
+endfunc
+
+func Test_smoothscroll_long_line_zb()
+  call NewWindow(10, 40)
+  call setline(1, 'abcde '->repeat(150))
+
+  " Also works without 'smoothscroll' when last line of buffer doesn't fit.
+  " Used to set topline to buffer line count plus one, causing an empty screen.
+  norm zb
+  redraw
+  call assert_equal(1, winsaveview().topline)
+
+  " Moving cursor to bottom works on line that doesn't fit with 'smoothscroll'.
+  " Skipcol was adjusted later for cursor being on not visible part of line.
+  setlocal smoothscroll
+  norm zb
+  redraw
+  call assert_equal(520, winsaveview().skipcol)

  bwipe!
 endfunc
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@ static char *(features[]) =

 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    258,
 /**/
    257,
 /**/