feat(api): add ev.win to autocmd callback args #39826

Problem: Autocmd callbacks currently have to rely on curwin, which may
already have changed by the time they run. This is especially noticeable
for WinNew, WinClosed, WinResized and WinScrolled.

Solution: Track the window in the autocmd context and expose it as ev.win.
Pass it explicitly for the window events that need it.

runtime/doc/api.txt

@@ -2204,15 +2204,17 @@ nvim_create_autocmd({event}, {opts})                   *nvim_create_autocmd()*
                    triggered. Lua callback can return |lua-truthy| to delete
                    the autocommand. Callback receives one argument, a table
                    with keys:                                     *event-args*
-                   • buf: (`number`) <abuf>
+                   • buf: (`integer`) <abuf>
                    • data: (`any`) Arbitrary data passed from
                      |nvim_exec_autocmds()|                       *event-data*
                    • event: (`vim.api.keyset.events`) Name of the triggered
                      event |autocmd-events|
                    • file: (`string`) <afile> (not expanded to a full path)
-                   • group: (`number?`) Group id, if any
-                   • id: (`number`) Autocommand id
+                   • group: (`integer?`) Group id, if any
+                   • id: (`integer`) Autocommand id
                    • match: (`string`) <amatch> (expanded to a full path)
+                   • win: (`integer`) id of the window for the event, see
+                     |window-ID|
                  • command (string?) Vim command executed on event. Not
                    allowed with {callback}.
                  • desc (`string?`) Description (for documentation and

runtime/doc/news.txt

@@ -238,6 +238,7 @@ API
 • |nvim_set_option_value()| returns the new option value.
 • |nvim_create_autocmd()| is now |api-fast|, so it can be called from a fast
   event context (e.g. |vim.uv| callbacks).
+• |nvim_create_autocmd()| callback |event-args| provide `win`.
 
 BUILD
 

runtime/lua/vim/_meta/api.gen.lua

@@ -969,13 +969,14 @@ function vim.api.nvim_create_augroup(name, opts) end
 --- - callback (`function|string?`) Lua function (or Vimscript function name, if string)
 ---   called when the event(s) is triggered. Lua callback can return `lua-truthy` to delete
 ---   the autocommand. Callback receives one argument, a table with keys: [event-args]()
----     - buf: (`number`) [<abuf>]
+---     - buf: (`integer`) [<abuf>]
 ---     - data: (`any`) Arbitrary data passed from [nvim_exec_autocmds()] [event-data]()
 ---     - event: (`vim.api.keyset.events`) Name of the triggered event `autocmd-events`
 ---     - file: (`string`) [<afile>] (not expanded to a full path)
----     - group: (`number?`) Group id, if any
----     - id: (`number`) Autocommand id
+---     - group: (`integer?`) Group id, if any
+---     - id: (`integer`) Autocommand id
 ---     - match: (`string`) [<amatch>] (expanded to a full path)
+---     - win: (`integer`) id of the window for the event, see `window-ID`
 --- - command (string?) Vim command executed on event. Not allowed with {callback}.
 --- - desc (`string?`) Description (for documentation and troubleshooting).
 --- - group (`string|integer?`) Group name or id to match against.

runtime/lua/vim/_meta/api_keysets_extra.lua

@@ -76,6 +76,7 @@ error('Cannot require a meta file')
 --- @field match string expanded value of <amatch>
 --- @field buf integer expanded value of <abuf>
 --- @field file string expanded value of <afile>
+--- @field win integer id of the window for the event, see |window-ID|
 --- @field data? any arbitrary data passed from |nvim_exec_autocmds()|
 
 --- @class vim.api.keyset.create_user_command.command_args

src/nvim/api/autocmd.c

@@ -373,13 +373,14 @@ cleanup:
 ///        - callback (`function|string?`) Lua function (or Vimscript function name, if string)
 ///          called when the event(s) is triggered. Lua callback can return |lua-truthy| to delete
 ///          the autocommand. Callback receives one argument, a table with keys: [event-args]()
-///            - buf: (`number`) [<abuf>]
+///            - buf: (`integer`) [<abuf>]
 ///            - data: (`any`) Arbitrary data passed from [nvim_exec_autocmds()] [event-data]()
 ///            - event: (`vim.api.keyset.events`) Name of the triggered event |autocmd-events|
 ///            - file: (`string`) [<afile>] (not expanded to a full path)
-///            - group: (`number?`) Group id, if any
-///            - id: (`number`) Autocommand id
+///            - group: (`integer?`) Group id, if any
+///            - id: (`integer`) Autocommand id
 ///            - match: (`string`) [<amatch>] (expanded to a full path)
+///            - win: (`integer`) id of the window for the event, see |window-ID|
 ///        - command (string?) Vim command executed on event. Not allowed with {callback}.
 ///        - desc (`string?`) Description (for documentation and troubleshooting).
 ///        - group (`string|integer?`) Group name or id to match against.
@@ -764,8 +765,8 @@ void nvim_exec_autocmds(Object event, Dict(exec_autocmds) *opts, Arena *arena, E
 
     FOREACH_ITEM(patterns, pat, {
       char *fname = !has_buf ? pat.data.string.data : NULL;
-      did_aucmd |= apply_autocmds_group(event_nr, fname, NULL, true, au_group, b, NULL, data,
-                                        has_buf);
+      did_aucmd |= apply_autocmds_group(event_nr, fname, NULL, true, au_group, b, curwin, NULL,
+                                        data, has_buf);
     })
   })
 

src/nvim/api/win_config.c

@@ -299,7 +299,7 @@ Window nvim_open_win(Buffer buf, Boolean enter, Dict(win_config) *config, Error
     const bool result = ctx_switch(&switchwin, wp, tp, NULL, kCtxNoDisplay);
     assert(result);
     (void)result;
-    if (apply_autocmds(EVENT_WINNEW, NULL, NULL, false, curbuf)) {
+    if (apply_autocmds_win(EVENT_WINNEW, NULL, NULL, false, curbuf, wp)) {
       tp = win_find_tabpage(wp);
     }
     ctx_restore(&switchwin);

src/nvim/autocmd.c

@@ -88,6 +88,10 @@ static const char e_autocommand_nesting_too_deep[]
 // Code for automatic commands.
 static AutoPatCmd *active_apc_list = NULL;  // stack of active autocommands
 
+/// Window handle for `ev.win`.  Unlike autocmd_bufnr/_match this needn't be a
+/// global: only au_callback() reads it.
+static handle_T autocmd_winid = 0;
+
 // ID for associating autocmds created via nvim_create_autocmd
 // Used to delete autocmds from nvim_del_autocmd
 static int next_augroup_id = 1;
@@ -1165,7 +1169,7 @@ int do_doautocmd(char *arg_start, bool do_msg, bool *did_something)
   // Loop over the events.
   while (*arg && !ends_excmd(*arg) && !ascii_iswhite(*arg)) {
     if (apply_autocmds_group(event_name2nr(arg, &arg), fname, NULL, true, group,
-                             curbuf, NULL, NULL, false)) {
+                             curbuf, curwin, NULL, NULL, false)) {
       nothing_done = false;
     }
   }
@@ -1311,9 +1315,11 @@ static void deferred_event(void **argv)
     }
     tv_dict_set_keys_readonly(v_event);
 
+    win_T *win = curwin;  // before ctx_switch() may make the context window current
+
     CtxSwitch aco = { 0 };
     ctx_switch(&aco, NULL, NULL, buf, 0);
-    apply_autocmds_group(event, fname, fname_io, false, group, buf, eap, data, false);
+    apply_autocmds_group(event, fname, fname_io, false, group, buf, win, eap, data, false);
     ctx_restore(&aco);
 
     restore_v_event(v_event, &save_v_event);
@@ -1359,6 +1365,8 @@ void aucmd_defer_modified(buf_T *buf, bool new_val)
 
 /// Execute autocommands for "event" and file name "fname".
 ///
+/// `ev.win` is curwin; use apply_autocmds_win() for window-specific events.
+///
 /// @param event event that occurred
 /// @param fname filename, NULL or empty means use actual file name
 /// @param fname_io filename to use for <afile> on cmdline
@@ -1368,7 +1376,20 @@ void aucmd_defer_modified(buf_T *buf, bool new_val)
 /// @return true if some commands were executed.
 bool apply_autocmds(event_T event, char *fname, char *fname_io, bool force, buf_T *buf)
 {
-  return apply_autocmds_group(event, fname, fname_io, force, AUGROUP_ALL, buf, NULL, NULL, false);
+  return apply_autocmds_group(event, fname, fname_io, force, AUGROUP_ALL, buf, curwin, NULL, NULL,
+                              false);
+}
+
+/// Like apply_autocmds(), but with an explicit window for `ev.win`.
+///
+/// @param win Window for `ev.win`, NULL for the current window.
+///
+/// @return true if some commands were executed.
+bool apply_autocmds_win(event_T event, char *fname, char *fname_io, bool force, buf_T *buf,
+                        win_T *win)
+{
+  return apply_autocmds_group(event, fname, fname_io, force, AUGROUP_ALL, buf, win, NULL, NULL,
+                              false);
 }
 
 /// Like apply_autocmds(), but with extra "eap" argument.  This takes care of
@@ -1385,7 +1406,8 @@ bool apply_autocmds(event_T event, char *fname, char *fname_io, bool force, buf_
 bool apply_autocmds_exarg(event_T event, char *fname, char *fname_io, bool force, buf_T *buf,
                           exarg_T *eap)
 {
-  return apply_autocmds_group(event, fname, fname_io, force, AUGROUP_ALL, buf, eap, NULL, false);
+  return apply_autocmds_group(event, fname, fname_io, force, AUGROUP_ALL, buf, curwin, eap, NULL,
+                              false);
 }
 
 /// Like apply_autocmds(), but handles the caller's retval.  If the script
@@ -1408,8 +1430,8 @@ bool apply_autocmds_retval(event_T event, char *fname, char *fname_io, bool forc
     return false;
   }
 
-  bool did_cmd = apply_autocmds_group(event, fname, fname_io, force, AUGROUP_ALL, buf, NULL, NULL,
-                                      false);
+  bool did_cmd = apply_autocmds_group(event, fname, fname_io, force, AUGROUP_ALL, buf, curwin, NULL,
+                                      NULL, false);
   if (did_cmd && aborting()) {
     *retval = FAIL;
   }
@@ -1453,12 +1475,13 @@ bool trigger_cursorhold(void) FUNC_ATTR_PURE FUNC_ATTR_WARN_UNUSED_RESULT
 /// @param force Ignore autocmd_busy (force "++nested" behavior)
 /// @param group autocmd group ID or AUGROUP_ALL
 /// @param buf Buffer for <abuf>
+/// @param win Window for `ev.win`, NULL for the current window.
 /// @param eap Ex command arguments
 /// @param with_buf Run callbacks with "buf" as the current buffer
 ///
 /// @return true if some commands were executed.
 bool apply_autocmds_group(event_T event, char *fname, char *fname_io, bool force, int group,
-                          buf_T *buf, exarg_T *eap, Object *data, bool with_buf)
+                          buf_T *buf, win_T *win, exarg_T *eap, Object *data, bool with_buf)
 {
   char *sfname = NULL;  // short file name
   bool retval = false;
@@ -1539,6 +1562,7 @@ bool apply_autocmds_group(event_T event, char *fname, char *fname_io, bool force
   char *save_autocmd_fname = autocmd_fname;
   bool save_autocmd_fname_full = autocmd_fname_full;
   int save_autocmd_bufnr = autocmd_bufnr;
+  handle_T save_autocmd_winid = autocmd_winid;
   char *save_autocmd_match = autocmd_match;
   int save_autocmd_busy = autocmd_busy;
   int save_autocmd_nested = autocmd_nested;
@@ -1640,6 +1664,10 @@ bool apply_autocmds_group(event_T event, char *fname, char *fname_io, bool force
     goto BYPASS_AU;
   }
 
+  // Set the window handle for `ev.win`.  After the last "goto BYPASS_AU", which
+  // skips the restore below, and before ctx_switch().
+  autocmd_winid = win != NULL ? win->handle : (curwin != NULL ? curwin->handle : 0);
+
   if (with_buf && buf != NULL && buf != curbuf) {
     ctx_switch(&aco, NULL, NULL, buf, 0);
   }
@@ -1770,6 +1798,7 @@ bool apply_autocmds_group(event_T event, char *fname, char *fname_io, bool force
   autocmd_fname = save_autocmd_fname;
   autocmd_fname_full = save_autocmd_fname_full;
   autocmd_bufnr = save_autocmd_bufnr;
+  autocmd_winid = save_autocmd_winid;
   autocmd_match = save_autocmd_match;
   current_sctx = save_current_sctx;
   restore_funccal();
@@ -1839,7 +1868,7 @@ void do_termresponse_autocmd(const String sequence, uint64_t channel_id)
   MAXSIZE_TEMP_DICT(data, 2);
   PUT_C(data, "sequence", STRING_OBJ(sequence));
   PUT_C(data, "chan", INTEGER_OBJ((Integer)channel_id));
-  apply_autocmds_group(EVENT_TERMRESPONSE, NULL, NULL, true, AUGROUP_ALL, NULL, NULL,
+  apply_autocmds_group(EVENT_TERMRESPONSE, NULL, NULL, true, AUGROUP_ALL, NULL, curwin, NULL,
                        &DICT_OBJ(data), false);
   termresponse_changed = true;
   termresponse_chan_id = channel_id;
@@ -1945,12 +1974,13 @@ static bool au_callback(const AutoCmd *ac, const AutoPatCmd *apc)
 {
   Callback callback = ac->handler_fn;
   if (callback.type == kCallbackLua) {
-    MAXSIZE_TEMP_DICT(data, 7);
+    MAXSIZE_TEMP_DICT(data, 8);
     PUT_C(data, "id", INTEGER_OBJ(ac->id));
     PUT_C(data, "event", CSTR_AS_OBJ(event_nr2name(apc->event)));
     PUT_C(data, "file", CSTR_AS_OBJ(apc->afile_orig));
     PUT_C(data, "match", CSTR_AS_OBJ(autocmd_match));
     PUT_C(data, "buf", INTEGER_OBJ(autocmd_bufnr));
+    PUT_C(data, "win", INTEGER_OBJ(autocmd_winid));
 
     if (apc->data) {
       PUT_C(data, "data", *apc->data);

src/nvim/buffer.c

@@ -636,8 +636,8 @@ bool close_buffer(win_T *win, buf_T *buf, int action, bool abort_if_last, bool i
   if (win_valid && win->w_buffer == buf && buf->b_nwindows == 1) {
     buf->b_locked++;
     buf->b_locked_split++;
-    if (apply_autocmds(EVENT_BUFWINLEAVE, buf->b_fname, buf->b_fname, false,
-                       buf) && !bufref_valid(&bufref)) {
+    if (apply_autocmds_win(EVENT_BUFWINLEAVE, buf->b_fname, buf->b_fname, false,
+                           buf, win) && !bufref_valid(&bufref)) {
       // Autocommands deleted the buffer.
       emsg(_(e_auabort));
       return false;

src/nvim/ex_docmd.c

@@ -4725,7 +4725,7 @@ bool before_quit_autocmds(win_T *wp, bool quit_all, bool forceit)
   if (*get_vim_var_str(VV_EXITREASON) == NUL) {
     set_vim_var_string(VV_EXITREASON, S_LEN("quit"));
   }
-  apply_autocmds(EVENT_QUITPRE, NULL, NULL, false, wp->w_buffer);
+  apply_autocmds_win(EVENT_QUITPRE, NULL, NULL, false, wp->w_buffer, wp);
 
   // Bail out when autocommands closed the window.
   // Refuse to quit when the buffer in the last window is being closed (can

src/nvim/main.c

@@ -795,7 +795,7 @@ void getout(int exitval)
           bufref_T bufref;
 
           set_bufref(&bufref, buf);
-          apply_autocmds(EVENT_BUFWINLEAVE, buf->b_fname, buf->b_fname, false, buf);
+          apply_autocmds_win(EVENT_BUFWINLEAVE, buf->b_fname, buf->b_fname, false, buf, wp);
           if (bufref_valid(&bufref)) {
             buf_set_changedtick(buf, -1);  // note that we did it already
           }

src/nvim/message.c

@@ -1184,7 +1184,7 @@ void do_autocmd_progress(MsgID msg_id, HlMessage msg, MessageData *msg_data)
   apply_autocmds_group(EVENT_PROGRESS,
                        (msg_data && msg_data->source.size > 0) ? msg_data->source.data : "", NULL,
                        true,
-                       AUGROUP_ALL, NULL, NULL, &DICT_OBJ(data), false);
+                       AUGROUP_ALL, NULL, curwin, NULL, &DICT_OBJ(data), false);
   kv_destroy(messages);
 }
 

src/nvim/terminal.c

@@ -280,7 +280,7 @@ static void emit_termrequest(void **argv)
         VTERM_TERMINATOR_BEL ? STATIC_CSTR_AS_OBJ("\x07") : STATIC_CSTR_AS_OBJ("\x1b\\"));
 
   term->refcount++;
-  apply_autocmds_group(EVENT_TERMREQUEST, NULL, NULL, true, AUGROUP_ALL, buf, NULL,
+  apply_autocmds_group(EVENT_TERMREQUEST, NULL, NULL, true, AUGROUP_ALL, buf, curwin, NULL,
                        &DICT_OBJ(data), false);
   term->refcount--;
   xfree(sequence);
@@ -744,7 +744,7 @@ void terminal_close(Terminal **termpp, int status)
     PUT_C(data, "pos", INTEGER_OBJ(pos));
 
     apply_autocmds_group(EVENT_TERMCLOSE, NULL, NULL, status >= 0, AUGROUP_ALL,
-                         buf, NULL, &DICT_OBJ(data), false);
+                         buf, curwin, NULL, &DICT_OBJ(data), false);
 
     restore_v_event(dict, &save_v_event);
   }

src/nvim/window.c

@@ -3119,7 +3119,7 @@ static void do_autocmd_winclosed(win_T *win)
   recursive = true;
   char winid[NUMBUFLEN];
   vim_snprintf(winid, sizeof(winid), "%d", win->handle);
-  apply_autocmds(EVENT_WINCLOSED, winid, winid, false, win->w_buffer);
+  apply_autocmds_win(EVENT_WINCLOSED, winid, winid, false, win->w_buffer, win);
   recursive = false;
 }
 
@@ -6084,17 +6084,21 @@ void may_trigger_win_scrolled_resized(void)
 
   // Save window info before autocmds since they can free windows
   char resize_winid[NUMBUFLEN];
+  win_T *resize_win = NULL;
   bufref_T resize_bufref;
   if (trigger_resize) {
-    vim_snprintf(resize_winid, sizeof(resize_winid), "%d", first_size_win->handle);
-    set_bufref(&resize_bufref, first_size_win->w_buffer);
+    resize_win = first_size_win;
+    vim_snprintf(resize_winid, sizeof(resize_winid), "%d", resize_win->handle);
+    set_bufref(&resize_bufref, resize_win->w_buffer);
   }
 
   char scroll_winid[NUMBUFLEN];
+  win_T *scroll_win = NULL;
   bufref_T scroll_bufref;
   if (trigger_scroll) {
-    vim_snprintf(scroll_winid, sizeof(scroll_winid), "%d", first_scroll_win->handle);
-    set_bufref(&scroll_bufref, first_scroll_win->w_buffer);
+    scroll_win = first_scroll_win;
+    vim_snprintf(scroll_winid, sizeof(scroll_winid), "%d", scroll_win->handle);
+    set_bufref(&scroll_bufref, scroll_win->w_buffer);
   }
 
   // If both are to be triggered do WinResized first.
@@ -6105,7 +6109,9 @@ void may_trigger_win_scrolled_resized(void)
     if (tv_dict_add_list(v_event, S_LEN("windows"), windows_list) == OK) {
       tv_dict_set_keys_readonly(v_event);
       buf_T *buf = bufref_valid(&resize_bufref) ? resize_bufref.br_buf : curbuf;
-      apply_autocmds(EVENT_WINRESIZED, resize_winid, resize_winid, false, buf);
+      // May have been freed by an earlier autocmd.
+      win_T *win = win_valid_any_tab(resize_win) ? resize_win : curwin;
+      apply_autocmds_win(EVENT_WINRESIZED, resize_winid, resize_winid, false, buf, win);
     }
     restore_v_event(v_event, &save_v_event);
   }
@@ -6120,7 +6126,9 @@ void may_trigger_win_scrolled_resized(void)
     tv_dict_unref(scroll_dict);
 
     buf_T *buf = bufref_valid(&scroll_bufref) ? scroll_bufref.br_buf : curbuf;
-    apply_autocmds(EVENT_WINSCROLLED, scroll_winid, scroll_winid, false, buf);
+    // May have been freed by the WinResized autocmds above.
+    win_T *win = win_valid_any_tab(scroll_win) ? scroll_win : curwin;
+    apply_autocmds_win(EVENT_WINSCROLLED, scroll_winid, scroll_winid, false, buf, win);
 
     restore_v_event(v_event, &save_v_event);
   }

test/functional/api/autocmd_spec.lua

@@ -370,6 +370,7 @@ describe('autocmd api', function()
         event = event,
         match = amatch,
         file = exec_pat,
+        win = api.nvim_get_current_win(),
         buf = 1,
       }, api.nvim_get_var('autocmd_args'))
 
@@ -392,6 +393,7 @@ describe('autocmd api', function()
         event = event,
         match = amatch,
         file = exec_pat,
+        win = api.nvim_get_current_win(),
         buf = 1,
       }, api.nvim_get_var('autocmd_args'))
     end
@@ -406,6 +408,134 @@ describe('autocmd api', function()
       end)
     end)
 
+    describe('ev.win #25844', function()
+      it('is the current window for events that are not about a window', function()
+        local win = api.nvim_get_current_win()
+        exec_lua(function()
+          vim.api.nvim_create_autocmd('BufAdd', {
+            callback = function(ev)
+              vim.g.ev_win = ev.win
+            end,
+          })
+        end)
+        command('badd some_file')
+        eq(win, api.nvim_get_var('ev_win'))
+      end)
+
+      it('WinClosed reports the closed window', function()
+        command('split')
+        local closed_win = api.nvim_get_current_win()
+        exec_lua(function()
+          vim.api.nvim_create_autocmd('WinClosed', {
+            callback = function(ev)
+              vim.g.ev_win = ev.win
+              vim.g.ev_match = ev.match
+            end,
+          })
+        end)
+        command('quit')
+        eq(closed_win, api.nvim_get_var('ev_win'))
+        eq(tostring(closed_win), api.nvim_get_var('ev_match'))
+      end)
+
+      it('WinNew reports the new window, not the focused one', function()
+        local origin_win = api.nvim_get_current_win()
+        local buf = api.nvim_create_buf(false, true)
+        exec_lua(function()
+          vim.api.nvim_create_autocmd('WinNew', {
+            callback = function(ev)
+              vim.g.ev_win = ev.win
+            end,
+          })
+        end)
+        local new_win = api.nvim_open_win(buf, false, {
+          relative = 'editor',
+          row = 0,
+          col = 0,
+          width = 10,
+          height = 5,
+        })
+        eq(origin_win, api.nvim_get_current_win())
+        eq(new_win, api.nvim_get_var('ev_win'))
+      end)
+
+      it('WinResized reports the resized window, not curwin', function()
+        local top_win = api.nvim_get_current_win()
+        command('botright split')
+        local bot_win = api.nvim_get_current_win()
+        neq(top_win, bot_win)
+        command('redraw') -- flush the WinResized caused by the split itself
+        exec_lua(function()
+          vim.api.nvim_create_autocmd('WinResized', {
+            callback = function(ev)
+              vim.g.ev_win = ev.win
+              vim.g.ev_match = ev.match
+              vim.g.ev_curwin = vim.api.nvim_get_current_win()
+            end,
+          })
+        end)
+        command('resize 3')
+        command('redraw')
+        -- ev.win is the first window whose size changed, matching <amatch>.
+        eq(top_win, api.nvim_get_var('ev_win'))
+        eq(tostring(top_win), api.nvim_get_var('ev_match'))
+        eq(bot_win, api.nvim_get_var('ev_curwin'))
+      end)
+
+      it('WinScrolled reports the scrolled window, not curwin', function()
+        command('split')
+        local scrolled = api.nvim_get_current_win()
+        exec_lua(function()
+          local lines = {}
+          for i = 1, 30 do
+            lines[i] = 'line ' .. i
+          end
+          vim.api.nvim_buf_set_lines(0, 0, -1, false, lines)
+        end)
+        command('wincmd w')
+        neq(scrolled, api.nvim_get_current_win())
+        command('redraw')
+        exec_lua(function(scroll_win)
+          vim.api.nvim_create_autocmd('WinScrolled', {
+            callback = function(ev)
+              vim.g.ev_win = ev.win
+              vim.g.ev_match = ev.match
+              vim.g.ev_curwin = vim.api.nvim_get_current_win()
+            end,
+          })
+          vim.api.nvim_win_call(scroll_win, function()
+            vim.cmd('normal! G')
+          end)
+        end, scrolled)
+        command('redraw')
+        eq(scrolled, api.nvim_get_var('ev_win'))
+        eq(tostring(scrolled), api.nvim_get_var('ev_match'))
+        neq(scrolled, api.nvim_get_var('ev_curwin'))
+      end)
+
+      it('is restored after a nested autocmd', function()
+        command('edit a')
+        command('rightbelow vsplit b')
+        command('wincmd w')
+        local trigger_win = api.nvim_get_current_win()
+        exec_lua(function()
+          -- Fires BufLeave/WinLeave/WinEnter/BufEnter, each with its own ev.win.
+          vim.api.nvim_create_autocmd('ColorScheme', {
+            callback = function()
+              vim.cmd('wincmd w')
+            end,
+          })
+          vim.api.nvim_create_autocmd('ColorScheme', {
+            callback = function(ev)
+              vim.g.ev_win = ev.win
+            end,
+          })
+        end)
+        command('colorscheme blue')
+        eq(trigger_win, api.nvim_get_var('ev_win'))
+      end)
+    end)
+
     it('can receive arbitrary data', function()
       local function test(data)
         eq(