vim-patch:9.0.0915: WinScrolled may trigger immediately when defined

Problem:    WinScrolled may trigger immediately when defined.
Solution:   Initialize the fields in all windows. (closes vim/vim#11582)

2996773276

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

src/nvim/autocmd.c

@@ -1142,13 +1142,17 @@ int autocmd_register(int64_t id, event_T event, char *pat, int patlen, int group
     }
 
     // Initialize the fields checked by the WinScrolled trigger to
-    // stop it from firing right after the first autocmd is defined.
+    // prevent it from firing right after the first autocmd is
+    // defined.
     if (event == EVENT_WINSCROLLED && !has_event(EVENT_WINSCROLLED)) {
-      curwin->w_last_topline = curwin->w_topline;
+      tabpage_T *save_curtab = curtab;
-      curwin->w_last_leftcol = curwin->w_leftcol;
+      FOR_ALL_TABS(tp) {
-      curwin->w_last_skipcol = curwin->w_skipcol;
+        unuse_tabpage(curtab);
-      curwin->w_last_width = curwin->w_width;
+        use_tabpage(tp);
-      curwin->w_last_height = curwin->w_height;
+        snapshot_windows_scroll_size();
+      }
+      unuse_tabpage(curtab);
+      use_tabpage(save_curtab);
     }
 
     ap->cmds = NULL;

src/nvim/testdir/test_autocmd.vim

@@ -428,6 +428,32 @@ func Test_WinScrolled_once_only()
   call StopVimInTerminal(buf)
 endfunc
 
+" Check that WinScrolled is not triggered immediately when defined and there
+" are split windows.
+func Test_WinScrolled_not_when_defined()
+  CheckRunVimInTerminal
+
+  let lines =<< trim END
+      call setline(1, ['aaa', 'bbb'])
+      echo 'nothing happened'
+      func ShowTriggered(id)
+        echo 'triggered'
+      endfunc
+  END
+  call writefile(lines, 'Xtest_winscrolled_not', 'D')
+  let buf = RunVimInTerminal('-S Xtest_winscrolled_not', #{rows: 10, cols: 60, statusoff: 2})
+  call term_sendkeys(buf, ":split\<CR>")
+  call TermWait(buf)
+  " use a timer to show the message after redrawing
+  call term_sendkeys(buf, ":au WinScrolled * call timer_start(100, 'ShowTriggered')\<CR>")
+  call VerifyScreenDump(buf, 'Test_winscrolled_not_when_defined_1', {})
+
+  call term_sendkeys(buf, "\<C-E>")
+  call VerifyScreenDump(buf, 'Test_winscrolled_not_when_defined_2', {})
+
+  call StopVimInTerminal(buf)
+endfunc
+
 func Test_WinScrolled_long_wrapped()
   CheckRunVimInTerminal
 

src/nvim/window.c

@@ -3868,6 +3868,27 @@ void close_others(int message, int forceit)
   }
 }
 
+/// Store the relevant window pointers for tab page "tp".  To be used before
+/// use_tabpage().
+void unuse_tabpage(tabpage_T *tp)
+{
+  tp->tp_topframe = topframe;
+  tp->tp_firstwin = firstwin;
+  tp->tp_lastwin = lastwin;
+  tp->tp_curwin = curwin;
+}
+
+/// Set the relevant pointers to use tab page "tp".  May want to call
+/// unuse_tabpage() first.
+void use_tabpage(tabpage_T *tp)
+{
+  curtab = tp;
+  topframe = curtab->tp_topframe;
+  firstwin = curtab->tp_firstwin;
+  lastwin = curtab->tp_lastwin;
+  curwin = curtab->tp_curwin;
+}
+
 // Allocate the first window and put an empty buffer in it.
 // Only called from main().
 void win_alloc_first(void)
@@ -3878,11 +3899,8 @@ void win_alloc_first(void)
   }
 
   first_tabpage = alloc_tabpage();
-  first_tabpage->tp_topframe = topframe;
   curtab = first_tabpage;
-  curtab->tp_firstwin = firstwin;
+  unuse_tabpage(first_tabpage);
-  curtab->tp_lastwin = lastwin;
-  curtab->tp_curwin = curwin;
 }
 
 // Init `aucmd_win`. This can only be done after the first window
@@ -4253,10 +4271,7 @@ static void enter_tabpage(tabpage_T *tp, buf_T *old_curbuf, bool trigger_enter_a
   win_T *next_prevwin = tp->tp_prevwin;
   tabpage_T *old_curtab = curtab;
 
-  curtab = tp;
+  use_tabpage(tp);
-  firstwin = tp->tp_firstwin;
-  lastwin = tp->tp_lastwin;
-  topframe = tp->tp_topframe;
 
   if (old_curtab != curtab) {
     tabpage_check_windows(old_curtab);
@@ -5265,7 +5280,7 @@ void win_new_screen_cols(void)
 
 /// Make a snapshot of all the window scroll positions and sizes of the current
 /// tab page.
-static void snapshot_windows_scroll_size(void)
+void snapshot_windows_scroll_size(void)
 {
   FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
     wp->w_last_topline = wp->w_topline;

test/functional/autocmd/winscrolled_spec.lua

@@ -104,6 +104,7 @@ describe('WinScrolled', function()
       let g:scrolled = 0
       au WinScrolled * let g:scrolled += 1
     ]])
+    eq(0, eval('g:scrolled'))
 
     -- With the upper split focused, send a scroll-down event to the unfocused one.
     meths.input_mouse('wheel', 'down', '', 0, 6, 0)