vim-patch:9.0.0893: 'smoothscroll' cursor calculations wrong when 'number' is set

Problem:    'smoothscroll' cursor calculations wrong when 'number' is set.
Solution:   Correct the code that computes the width. (closes vim/vim#11492)

01ee52bab6

Co-authored-by: Yee Cheng Chin <ychin.git@gmail.com>

src/nvim/move.c

@@ -815,13 +815,14 @@ void curs_columns(win_T *wp, int may_scroll)
     if (wp->w_cursor.lnum == wp->w_topline
         && wp->w_skipcol > 0
         && wp->w_wcol >= wp->w_skipcol) {
-      // w_skipcol excludes win_col_off().  Include it here, since w_wcol
+      // Deduct by multiples of width2.  This allows the long line wrapping
-      // counts actual screen columns.
+      // formula below to correctly calculate the w_wcol value when wrapping.
       if (wp->w_skipcol <= width1) {
-        wp->w_wcol -= wp->w_width;
+        wp->w_wcol -= width2;
       } else {
-        wp->w_wcol -= wp->w_width * (((wp->w_skipcol - width1) / width2) + 1);
+        wp->w_wcol -= width2 * (((wp->w_skipcol - width1) / width2) + 1);
       }
+
       did_sub_skipcol = true;
     }
 

test/functional/legacy/scroll_opt_spec.lua

@@ -279,8 +279,8 @@ describe('smoothscroll', function()
     ]])
     exec('call DoRel()')
     screen:expect([[
-      2<<<ong text very long text very lon^g te|
+      2<<<ong text very long text very long te|
-          xt very long text very long text ver|
+          ^xt very long text very long text ver|
           y long text very long text very long|
            text very long text very long text |
         1 three                               |

test/old/testdir/test_scroll_opt.vim

@@ -325,5 +325,71 @@ func Test_smoothscroll_one_long_line()
   call StopVimInTerminal(buf)
 endfunc
 
+" Test that if the current cursor is on a smooth scrolled line, we correctly
+" reposition it. Also check that we don't miscalculate the values by checking
+" the consistency between wincol() and col('.') as they are calculated
+" separately in code.
+func Test_smoothscroll_cursor_position()
+  call NewWindow(10, 20)
+  setl smoothscroll wrap
+  call setline(1, "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
+
+  func s:check_col_calc(win_col, win_line, buf_col)
+    call assert_equal(a:win_col, wincol())
+    call assert_equal(a:win_line, winline())
+    call assert_equal(a:buf_col, col('.'))
+  endfunc
+
+  call s:check_col_calc(1, 1, 1)
+  exe "normal \<C-E>"
+
+  " Move down another line to avoid blocking the <<< display
+  call s:check_col_calc(1, 2, 41)
+  exe "normal \<C-Y>"
+  call s:check_col_calc(1, 3, 41)
+  normal ggg$
+  exe "normal \<C-E>"
+
+  " Move down only 1 line when we are out of the range of the <<< display
+  call s:check_col_calc(20, 1, 40)
+  exe "normal \<C-Y>"
+  call s:check_col_calc(20, 2, 40)
+  normal gg
+
+  " Test number, where we have indented lines
+  setl number
+  call s:check_col_calc(5, 1, 1)
+  exe "normal \<C-E>"
+  call s:check_col_calc(5, 2, 33)
+  exe "normal \<C-Y>"
+  call s:check_col_calc(5, 3, 33)
+  normal ggg$
+  exe "normal \<C-E>"
+  call s:check_col_calc(20, 1, 32)
+  exe "normal \<C-Y>"
+  call s:check_col_calc(20, 2, 32)
+  normal gg
+
+  " Test number + showbreak, so test that the additional indentation works
+  setl number showbreak=+++
+  call s:check_col_calc(5, 1, 1)
+  exe "normal \<C-E>"
+  call s:check_col_calc(8, 2, 30)
+  exe "normal \<C-Y>"
+  call s:check_col_calc(8, 3, 30)
+  normal gg
+
+  " Test number + cpo+=n mode, where wrapped lines aren't indented
+  setl number cpo+=n showbreak=
+  call s:check_col_calc(5, 1, 1)
+  exe "normal \<C-E>"
+  call s:check_col_calc(1, 2, 37)
+  exe "normal \<C-Y>"
+  call s:check_col_calc(1, 3, 37)
+  normal gg
+
+  bwipeout!
+endfunc
+
 
 " vim: shiftwidth=2 sts=2 expandtab