3 files changed, 43 insertions, 18 deletions

diff --git a/src/nvim/drawscreen.c b/src/nvim/drawscreen.c
index 1626e46cf6..402f7fa428 100644
--- a/src/nvim/drawscreen.c
+++ b/src/nvim/drawscreen.c
@@ -1513,7 +1513,7 @@ static void win_update(win_T *wp)
 
   // Make sure skipcol is valid, it depends on various options and the window
   // width.
-  if (wp->w_skipcol > 0) {
+  if (wp->w_skipcol > 0 && wp->w_width_inner > win_col_off(wp)) {
     int w = 0;
     int width1 = wp->w_width_inner - win_col_off(wp);
     int width2 = width1 + win_col_off2(wp);
diff --git a/test/old/testdir/test_scroll_opt.vim b/test/old/testdir/test_scroll_opt.vim
index a1987ed3c9..8130f7a1ac 100644
--- a/test/old/testdir/test_scroll_opt.vim
+++ b/test/old/testdir/test_scroll_opt.vim
@@ -963,4 +963,42 @@ func Test_smoothscroll_insert_bottom()
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_smoothscroll_in_zero_width_window()
+  set cpo+=n number smoothscroll
+  set winwidth=99999 winminwidth=0
+
+  vsplit
+  call assert_equal(0, winwidth(winnr('#')))
+  call win_execute(win_getid(winnr('#')), "norm! \<C-Y>")
+
+  only!
+  set winwidth& winminwidth&
+  set cpo-=n nonumber nosmoothscroll
+endfunc
+
+func Test_smoothscroll_textoff_small_winwidth()
+  set smoothscroll number
+  call setline(1, 'llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch')
+  vsplit
+
+  let textoff = getwininfo(win_getid())[0].textoff
+  execute 'vertical resize' textoff + 1
+  redraw
+  call assert_equal(0, winsaveview().skipcol)
+  execute "normal! 0\<C-E>"
+  redraw
+  call assert_equal(1, winsaveview().skipcol)
+  execute 'vertical resize' textoff - 1
+  " This caused a signed integer overflow.
+  redraw
+  call assert_equal(1, winsaveview().skipcol)
+  execute 'vertical resize' textoff
+  " This caused an infinite loop.
+  redraw
+  call assert_equal(1, winsaveview().skipcol)
+
+  %bw!
+  set smoothscroll& number&
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/test/old/testdir/test_window_cmd.vim b/test/old/testdir/test_window_cmd.vim
index 1f2eb2b624..02fa3ac407 100644
--- a/test/old/testdir/test_window_cmd.vim
+++ b/test/old/testdir/test_window_cmd.vim
@@ -2105,19 +2105,6 @@ func Test_new_help_window_on_error()
   call assert_equal(expand("<cword>"), "'mod'")
 endfunc
 
-func Test_smoothscroll_in_zero_width_window()
-  set cpo+=n number smoothscroll
-  set winwidth=99999 winminwidth=0
-
-  vsplit
-  call assert_equal(0, winwidth(winnr('#')))
-  call win_execute(win_getid(winnr('#')), "norm! \<C-Y>")
-
-  only!
-  set winwidth& winminwidth&
-  set cpo-=n nonumber nosmoothscroll
-endfunc
-
 func Test_splitmove_flatten_frame()
   split
   vsplit
@@ -2131,7 +2118,7 @@ func Test_splitmove_flatten_frame()
   only!
 endfunc
 
-func Test_splitmove_autocmd_window_no_room()
+func Test_autocmd_window_force_room()
   " Open as many windows as possible
   while v:true
     try
@@ -2158,7 +2145,7 @@ func Test_splitmove_autocmd_window_no_room()
   edit unload me
   enew
   bunload! unload\ me
-  augroup SplitMoveAucmdWin
+  augroup AucmdWinForceRoom
     au!
     au BufEnter * ++once let s:triggered = v:true
                       \| call assert_equal('autocmd', win_gettype())
@@ -2172,8 +2159,8 @@ func Test_splitmove_autocmd_window_no_room()
   call assert_equal(winrestcmd(), restcmd)
 
   unlet! s:triggered
-  au! SplitMoveAucmdWin
-  augroup! SplitMoveAucmdWin
+  au! AucmdWinForceRoom
+  augroup! AucmdWinForceRoom
   %bw!
 endfunc