Commit: patch 9.1.1388: Scrolling one line too far with 'nosmoothscroll' page scrolling

[Christian Brabandt]

patch 9.1.1388: Scrolling one line too far with 'nosmoothscroll' page scrolling

Commit: https://github.com/vim/vim/commit/c6c72d165c90e94eee1d9107d82fb180ed138190
Author: Luuk van Baal <luuk...@gmail.com>
Date: Wed May 14 20:21:55 2025 +0200

patch 9.1.1388: Scrolling one line too far with 'nosmoothscroll' page scrolling

Problem: One-off error in "count" to make "w_skipcol" zero with
'nosmoothscroll' page scrolling when last virtual line
in a buffer line is exactly the entire window width.
(Hirohito Higashi)
Solution: Properly compute the smallest integer value necessary
to make "w_skipcol" zero (Luuk van Baal)

fixes: #17317
closes: #17318

Signed-off-by: Luuk van Baal <luuk...@gmail.com>
Signed-off-by: Christian Brabandt <c...@256bit.org>

diff --git a/src/move.c b/src/move.c
index 1c1eddeef..e3771a5e2 100644
--- a/src/move.c
+++ b/src/move.c
@@ -3215,10 +3215,10 @@ static int scroll_with_sms(int dir, long count, long *curscount)

int width1 = curwin->w_width - curwin_col_off();
int width2 = width1 + curwin_col_off2();
- count = 1 + (curwin->w_skipcol - width1) / width2;
+ count = 1 + (curwin->w_skipcol - width1 - 1) / width2;
if (fixdir == FORWARD)
- count = 2 + (linetabsize_eol(curwin, curwin->w_topline)
- - curwin->w_skipcol - width1) / width2;
+ count = 1 + (linetabsize_eol(curwin, curwin->w_topline)
+ - curwin->w_skipcol - width1 + width2 - 1) / width2;
scroll_redraw(fixdir == FORWARD, count);
*curscount += count * (fixdir == dir ? 1 : -1);
}
diff --git a/src/testdir/test_normal.vim b/src/testdir/test_normal.vim
index 7f4f90964..069651f6b 100644
--- a/src/testdir/test_normal.vim
+++ b/src/testdir/test_normal.vim
@@ -4354,4 +4354,21 @@ func Test_scroll_longline_benchmark()
bwipe!
endfunc

+" Test Ctrl-B with 'nosmoothscroll' not stuck with line exactly window width.
+func Test_scroll_longline_winwidth()
+ 10new
+ call setline(1, ['']->repeat(20) + ['A'->repeat(20 * winwidth(0))] + ['']->repeat(20))
+ exe "normal! G3\<C-B>"
+ call assert_equal(22, line('w0'))
+ exe "normal! \<C-B>"
+ call assert_equal(21, line('w0'))
+ exe "normal! \<C-B>"
+ call assert_equal(11, line('w0'))
+ exe "normal! \<C-B>"
+ call assert_equal(3, line('w0'))
+ exe "normal! \<C-B>"
+ call assert_equal(1, line('w0'))
+ bwipe!
+endfunc
+
" vim: shiftwidth=2 sts=2 expandtab nofoldenable
diff --git a/src/version.c b/src/version.c
index 7e6e862de..89c9fb0f3 100644
--- 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 */
+/**/
+ 1388,
/**/
1387,
/**/