vim-patch:9.0.1513: text scrolls unnecessarily when splitting

Problem:    Text scrolls unnecessarily when splitting and 'splitkeep' is not
            "cursor".
Solution:   Avoid resetting w_skipcol. (Luuk van Baal, closes vim/vim#12334)

https://github.com/vim/vim/commit/b926bf47d61360a4ec5e4867714a08d70fd49965

3 files changed, 46 insertions, 1 deletions

diff --git a/src/nvim/window.c b/src/nvim/window.c
index a15be27f74..fd6755a382 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -1616,6 +1616,9 @@ static void win_init(win_T *newp, win_T *oldp, int flags)
                     ? NULL : xstrdup(oldp->w_prevdir);
 
   if (*p_spk != 'c') {
+    if (*p_spk == 't') {
+      newp->w_skipcol = oldp->w_skipcol;
+    }
     newp->w_botline = oldp->w_botline;
     newp->w_prev_height = oldp->w_height;
     newp->w_prev_winrow = oldp->w_winrow;
@@ -6605,13 +6608,13 @@ void win_set_inner_size(win_T *wp, bool valid_cursor)
         set_fraction(wp);
       }
     }
-    wp->w_skipcol = 0;
     wp->w_height_inner = height;
     win_comp_scroll(wp);
 
     // There is no point in adjusting the scroll position when exiting.  Some
     // values might be invalid.
     if (valid_cursor && !exiting && *p_spk == 'c') {
+      wp->w_skipcol = 0;
       scroll_to_fraction(wp, prev_height);
     }
     redraw_later(wp, UPD_SOME_VALID);
diff --git a/test/functional/legacy/window_cmd_spec.lua b/test/functional/legacy/window_cmd_spec.lua
index 3a51f7a23f..373a9c7163 100644
--- a/test/functional/legacy/window_cmd_spec.lua
+++ b/test/functional/legacy/window_cmd_spec.lua
@@ -254,4 +254,29 @@ describe('splitkeep', function()
                                                            |
     ]])
   end)
+
+  -- oldtest: Test_splitkeep_skipcol()
+  it('skipcol is not reset unnecessarily and is copied to new window', function()
+    screen:try_resize(40, 12)
+    exec([[
+      set splitkeep=topline smoothscroll splitbelow scrolloff=0
+      call setline(1, 'with lots of text in one line '->repeat(6))
+      norm 2
+      wincmd s
+    ]])
+    screen:expect([[
+      <<<e line with lots of text in one line |
+      with lots of text in one line with lots |
+      of text in one line                     |
+      ~                                       |
+      [No Name] [+]                           |
+      <<<e line with lots of text in one line |
+      ^with lots of text in one line with lots |
+      of text in one line                     |
+      ~                                       |
+      ~                                       |
+      [No Name] [+]                           |
+                                              |
+    ]])
+  end)
 end)
diff --git a/test/old/testdir/test_window_cmd.vim b/test/old/testdir/test_window_cmd.vim
index f18d1719c0..d4ff241366 100644
--- a/test/old/testdir/test_window_cmd.vim
+++ b/test/old/testdir/test_window_cmd.vim
@@ -1879,6 +1879,23 @@ func Test_splitkeep_status()
   call StopVimInTerminal(buf)
 endfunc
 
+" skipcol is not reset unnecessarily and is copied to new window
+func Test_splitkeep_skipcol()
+  CheckScreendump
+
+  let lines =<< trim END
+    set splitkeep=topline smoothscroll splitbelow scrolloff=0
+    call setline(1, 'with lots of text in one line '->repeat(6))
+    norm 2
+    wincmd s
+  END
+
+  call writefile(lines, 'XTestSplitkeepSkipcol', 'D')
+  let buf = RunVimInTerminal('-S XTestSplitkeepSkipcol', #{rows: 12, cols: 40})
+
+  call VerifyScreenDump(buf, 'Test_splitkeep_skipcol_1', {})
+endfunc
+
 func Test_new_help_window_on_error()
   help change.txt
   execute "normal! /CTRL-@\<CR>"