vim-patch:9.0.0672: line partly shows with 'smoothscroll' and 'scrolloff' zero

Problem:    Cursor line only partly shows with 'smoothscroll' and 'scrolloff'
            zero.
Solution:   Do not use 'smoothscroll' when adjusting the bottom of the window.
            (closes vim/vim#11269)

https://github.com/vim/vim/commit/9bab7a024393200bb2c03b3abddfda86436990a7

Co-authored-by: Bram Moolenaar <Bram@vim.org>

3 files changed, 62 insertions, 0 deletions

diff --git a/src/nvim/move.c b/src/nvim/move.c
index 5e85768865..0a91b12255 100644
--- a/src/nvim/move.c
+++ b/src/nvim/move.c
@@ -1627,6 +1627,7 @@ void scroll_cursor_bot(int min_scroll, int set_topbot)
 {
   int used;
   int scrolled = 0;
+  int min_scrolled = 1;
   int extra = 0;
   lineoff_T loff;
   lineoff_T boff;
@@ -1676,6 +1677,12 @@ void scroll_cursor_bot(int min_scroll, int set_topbot)
     if (cln == curwin->w_botline) {
       scrolled -= curwin->w_empty_rows;
     }
+    min_scrolled = scrolled;
+    if (cln > curwin->w_botline && curwin->w_p_sms && curwin->w_p_wrap) {
+      for (linenr_T lnum = curwin->w_botline + 1; lnum <= cln; lnum++) {
+        min_scrolled += plines_win_nofill(curwin, lnum, true);
+      }
+    }
   }
 
   // Stop counting lines to scroll when
@@ -1777,6 +1784,10 @@ void scroll_cursor_bot(int min_scroll, int set_topbot)
   if (line_count >= curwin->w_height_inner && line_count > min_scroll) {
     scroll_cursor_halfway(false, true);
   } else {
+    // With 'smoothscroll' scroll at least the height of the cursor line.
+    if (curwin->w_p_wrap && curwin->w_p_sms && line_count < min_scrolled) {
+      line_count = min_scrolled;
+    }
     scrollup(line_count, true);
   }
 
diff --git a/test/functional/legacy/scroll_opt_spec.lua b/test/functional/legacy/scroll_opt_spec.lua
index 90417d93f3..c63401cb02 100644
--- a/test/functional/legacy/scroll_opt_spec.lua
+++ b/test/functional/legacy/scroll_opt_spec.lua
@@ -301,4 +301,30 @@ describe('smoothscroll', function()
     feed('<C-E>')
     screen:expect_unchanged()
   end)
+
+  -- oldtest: Test_smoothscroll_wrap_scrolloff_zero()
+  it("works with zero 'scrolloff'", function()
+    screen:try_resize(40, 8)
+    exec([[
+      call setline(1, ['Line' .. (' with some text'->repeat(7))]->repeat(7))
+      set smoothscroll scrolloff=0
+      :3
+    ]])
+    screen:expect([[
+      <<<h some text with some text           |
+      Line with some text with some text with |
+      some text with some text with some text |
+      with some text with some text           |
+      ^Line with some text with some text with |
+      some text with some text with some text |
+      with some text with some text           |
+                                              |
+    ]])
+    feed('j')
+    screen:expect_unchanged()
+    feed('<C-E>j')
+    screen:expect_unchanged()
+    feed('G')
+    screen:expect_unchanged()
+  end)
 end)
diff --git a/test/old/testdir/test_scroll_opt.vim b/test/old/testdir/test_scroll_opt.vim
index 53768de6fa..799db19298 100644
--- a/test/old/testdir/test_scroll_opt.vim
+++ b/test/old/testdir/test_scroll_opt.vim
@@ -184,6 +184,31 @@ func Test_smoothscroll_diff_mode()
   call StopVimInTerminal(buf)
 endfunc
 
+func Test_smoothscroll_wrap_scrolloff_zero()
+  CheckScreendump
+
+  let lines =<< trim END
+      vim9script
+      setline(1, ['Line' .. (' with some text'->repeat(7))]->repeat(7))
+      set smoothscroll scrolloff=0
+      :3
+  END
+  call writefile(lines, 'XSmoothWrap', 'D')
+  let buf = RunVimInTerminal('-S XSmoothWrap', #{rows: 8, cols: 40})
+
+  call VerifyScreenDump(buf, 'Test_smooth_wrap_1', {})
+
+  call term_sendkeys(buf, "j")
+  call VerifyScreenDump(buf, 'Test_smooth_wrap_2', {})
+
+  call term_sendkeys(buf, "\<C-E>j")
+  call VerifyScreenDump(buf, 'Test_smooth_wrap_3', {})
+
+  call term_sendkeys(buf, "G")
+  call VerifyScreenDump(buf, 'Test_smooth_wrap_4', {})
+
+  call StopVimInTerminal(buf)
+endfunc
 
 
 " vim: shiftwidth=2 sts=2 expandtab