fix(events): triggered WinScrolled when only skipcol changed (#19972)

fix(events): trigger WinScrolled when only skipcol changed

vim-patch:9.0.0304: WinScrolled is not triggered when only skipcol changes

Problem:    WinScrolled is not triggered when only skipcol changes.
Solution:   Add w_last_skipcol and use it. (closes vim/vim#10998)
670ab0334b

src/nvim/autocmd.c

@@ -1119,6 +1119,7 @@ int autocmd_register(int64_t id, event_T event, char *pat, int patlen, int group
     if (event == EVENT_WINSCROLLED && !has_event(EVENT_WINSCROLLED)) {
       curwin->w_last_topline = curwin->w_topline;
       curwin->w_last_leftcol = curwin->w_leftcol;
+      curwin->w_last_skipcol = curwin->w_skipcol;
       curwin->w_last_width = curwin->w_width;
       curwin->w_last_height = curwin->w_height;
     }

src/nvim/buffer_defs.h

@@ -1240,9 +1240,10 @@ struct window_S {
   colnr_T w_skipcol;                // starting column when a single line
                                     // doesn't fit in the window
 
-  // four fields that are only used when there is a WinScrolled autocommand
+  // five fields that are only used when there is a WinScrolled autocommand
   linenr_T w_last_topline;          ///< last known value for w_topline
   colnr_T w_last_leftcol;           ///< last known value for w_leftcol
+  colnr_T w_last_skipcol;           ///< last known value for w_skipcol
   int w_last_width;                 ///< last known value for w_width
   int w_last_height;                ///< last known value for w_height
 

src/nvim/testdir/test_autocmd.vim

@@ -341,6 +341,39 @@ func Test_WinScrolled_close_curwin()
   call delete('Xtestout')
 endfunc
 
+func Test_WinScrolled_long_wrapped()
+  CheckRunVimInTerminal
+
+  let lines =<< trim END
+    set scrolloff=0
+    let height = winheight(0)
+    let width = winwidth(0)
+    let g:scrolled = 0
+    au WinScrolled * let g:scrolled += 1
+    call setline(1, repeat('foo', height * width))
+    call cursor(1, height * width)
+  END
+  call writefile(lines, 'Xtest_winscrolled_long_wrapped')
+  let buf = RunVimInTerminal('-S Xtest_winscrolled_long_wrapped', {'rows': 6})
+
+  call term_sendkeys(buf, ":echo g:scrolled\<CR>")
+  call WaitForAssert({-> assert_match('^0 ', term_getline(buf, 6))}, 1000)
+
+  call term_sendkeys(buf, 'gj')
+  call term_sendkeys(buf, ":echo g:scrolled\<CR>")
+  call WaitForAssert({-> assert_match('^1 ', term_getline(buf, 6))}, 1000)
+
+  call term_sendkeys(buf, '0')
+  call term_sendkeys(buf, ":echo g:scrolled\<CR>")
+  call WaitForAssert({-> assert_match('^2 ', term_getline(buf, 6))}, 1000)
+
+  call term_sendkeys(buf, '$')
+  call term_sendkeys(buf, ":echo g:scrolled\<CR>")
+  call WaitForAssert({-> assert_match('^3 ', term_getline(buf, 6))}, 1000)
+
+  call delete('Xtest_winscrolled_long_wrapped')
+endfunc
+
 func Test_WinClosed()
   " Test that the pattern is matched against the closed window's ID, and both
   " <amatch> and <afile> are set to it.

src/nvim/window.c

@@ -5362,6 +5362,7 @@ void may_trigger_winscrolled(void)
   win_T *wp = curwin;
   if (wp->w_last_topline != wp->w_topline
       || wp->w_last_leftcol != wp->w_leftcol
+      || wp->w_last_skipcol != wp->w_skipcol
       || wp->w_last_width != wp->w_width
       || wp->w_last_height != wp->w_height) {
     char winid[NUMBUFLEN];
@@ -5375,6 +5376,7 @@ void may_trigger_winscrolled(void)
     if (win_valid_any_tab(wp)) {
       wp->w_last_topline = wp->w_topline;
       wp->w_last_leftcol = wp->w_leftcol;
+      wp->w_last_skipcol = wp->w_skipcol;
       wp->w_last_width = wp->w_width;
       wp->w_last_height = wp->w_height;
     }

test/functional/autocmd/winscrolled_spec.lua

@@ -61,6 +61,20 @@ describe('WinScrolled', function()
     eq(3, eval('g:scrolled'))
   end)
 
+  it('is triggered by scrolling on a long wrapped line #19968', function()
+    local height = meths.win_get_height(0)
+    local width = meths.win_get_width(0)
+    meths.buf_set_lines(0, 0, -1, true, {('foo'):rep(height * width)})
+    meths.win_set_cursor(0, {1, height * width - 1})
+    eq(0, eval('g:scrolled'))
+    feed('gj')
+    eq(1, eval('g:scrolled'))
+    feed('0')
+    eq(2, eval('g:scrolled'))
+    feed('$')
+    eq(3, eval('g:scrolled'))
+  end)
+
   it('is triggered when the window scrolls in Insert mode', function()
     local height = meths.win_get_height(0)
     local lines = {}