vim-patch:9.0.1000: with 'smoothscroll' skipcol may be reset unnecessarily

Problem:    With 'smoothscroll' skipcol may be reset unnecessarily.
Solution:   Check the line does actually fit in the window.

b21b8e9ed0

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

src/nvim/move.c

@@ -1465,7 +1465,10 @@ void adjust_skipcol(void)
   bool scrolled = false;
 
   validate_cheight();
-  if (curwin->w_cline_height == curwin->w_height) {
+  if (curwin->w_cline_height == curwin->w_height
+      // w_cline_height may be capped at w_height, check there aren't
+      // actually more lines.
+      && plines_win(curwin, curwin->w_cursor.lnum, false) <= curwin->w_height) {
     // the line just fits in the window, don't scroll
     reset_skipcol(curwin);
     return;

test/functional/legacy/scroll_opt_spec.lua

@@ -494,14 +494,7 @@ describe('smoothscroll', function()
     ]])
     -- 'scrolloff' set to 2, scrolling down, cursor moves screen line up
     feed('<C-E>gj<C-Y>')
-    screen:expect([[
-      <<<ots of text with lots of text with lo|
-      ts of text with lots of text with lots o|
-      f text wi^th lots of text with lots of te|
-      xt with lots of text with lots of text w|
-      ith lots of text with lots of text with |
-                                              |
-    ]])
+    screen:expect_unchanged()
     -- 'scrolloff' set to 0, move cursor down one line. Cursor should move properly,
     -- and since this is a really long line, it will be put on top of the screen.
     exec('set scrolloff=0')

test/old/testdir/test_scroll_opt.vim

@@ -498,6 +498,13 @@ func Test_smoothscroll_cursor_scrolloff()
   exe "normal 20h"
   call s:check_col_calc(1, 4, 61)
 
+  " cursor on last line, "gk" should not cause a scroll
+  set scrolloff=0
+  normal G0
+  call s:check_col_calc(1, 7, 1)
+  normal gk
+  call s:check_col_calc(1, 6, 101)
+
   bwipe!
 endfunc