commit c6c72d165c90e94eee1d9107d82fb180ed138190
author Luuk van Baal <luukvbaal@gmail.com> Wed May 14 20:21:55 2025 +0200
committer Christian Brabandt <cb@256bit.org> Wed May 14 20:21:55 2025 +0200
tree 22128adc93e8d411a6bfe3a4228cf4012b774f01
parent 0077282c8209e5a3893d74a0176ab21895c5de4e

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 <luukvbaal@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/move.c

diff --git a/src/move.c b/src/move.c
index 1c1edde..e3771a5 100644
--- a/src/move.c
+++ b/src/move.c
@@ -3215,10 +3215,10 @@
 
 	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);
     }

src/testdir/test_normal.vim

diff --git a/src/testdir/test_normal.vim b/src/testdir/test_normal.vim
index 7f4f909..069651f 100644
--- a/src/testdir/test_normal.vim
+++ b/src/testdir/test_normal.vim
@@ -4354,4 +4354,21 @@
   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

src/version.c

diff --git a/src/version.c b/src/version.c
index 7e6e862..89c9fb0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1388,
+/**/
     1387,
 /**/
     1386,