From e7cd0e4375a48d32eea6776d6d26e92eed9fedbe Mon Sep 17 00:00:00 2001
From: "Justin M. Keyes" <justinkz@gmail.com>
Date: Mon, 12 Oct 2026 13:51:18 -0400
Subject: fix(ui): ext_messages/ui2: stale 'rulerformat' "[+]" after :write
 #42315

Problem:
With 'ruler' in the cmdline ('laststatus=0') and ext_messages (ui2), a
'rulerformat' "%m" does not update the "[+]" indicator after ":write",
until a cursor-move.

Analysis:
`redraw_buf_status_later()` only marks windows with a statusline or
winbar. The symptom is hidden by the legacy message grid because the
write message overwrites the cmdline, which redraws the ruler.

Solution:
Also mark the cmdline 'ruler', like `status_redraw_buf()`.
---
 src/nvim/drawscreen.c                 |  8 ++++++--
 test/functional/ui/messages2_spec.lua | 19 ++++++++++++++++++-
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/src/nvim/drawscreen.c b/src/nvim/drawscreen.c
index e376a4d135..eb4a1a3fd8 100644
--- a/src/nvim/drawscreen.c
+++ b/src/nvim/drawscreen.c
@@ -2741,7 +2741,7 @@ void redraw_buf_range_later(buf_T *buf, linenr_T first, linenr_T last)
   }
 }
 
-/// called when the status bars for the buffer 'buf' need to be updated
+/// Marks the statuslines, 'winbar' and cmdline ruler of `buf` for redraw.
 void redraw_buf_status_later(buf_T *buf)
 {
   FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
@@ -2753,6 +2753,10 @@ void redraw_buf_status_later(buf_T *buf)
       set_must_redraw(UPD_VALID);
     }
   }
+  // Redraw 'ruler' if it is in cmdline (e.g. 'laststatus=0') and was not marked for redraw above.
+  if (p_ru && curwin->w_buffer == buf && !curwin->w_status_height && !curwin->w_redr_status) {
+    redraw_cmdline = true;
+  }
 }
 
 /// Mark all status lines and window bars for redraw; used after first :cd
@@ -2787,7 +2791,7 @@ void status_redraw_buf(buf_T *buf)
       redraw_later(wp, UPD_VALID);
     }
   }
-  // Redraw the ruler if it is in the command line and was not marked for redraw above
+  // Redraw 'ruler' if it is in cmdline (e.g. 'laststatus=0') and was not marked for redraw above.
   if (p_ru && !curwin->w_status_height && !curwin->w_redr_status) {
     redraw_cmdline = true;
     redraw_later(curwin, UPD_VALID);
diff --git a/test/functional/ui/messages2_spec.lua b/test/functional/ui/messages2_spec.lua
index b79db68af8..3f8168ca95 100644
--- a/test/functional/ui/messages2_spec.lua
+++ b/test/functional/ui/messages2_spec.lua
@@ -1306,7 +1306,7 @@ describe('messages2', function()
     ]])
   end)
 
-  it('crops long messages to make place for ruler', function()
+  it("'ruler' placement truncates long messages", function()
     command('set noruler | echo "-"->repeat(&columns)')
     screen:expect([[
       ^                                                     |
@@ -1405,6 +1405,23 @@ describe('messages2', function()
     ]])
   end)
 
+  it("'ruler' updates on 'modified' change #42255", function()
+    command('set laststatus=0 ruler rulerformat=%m noautoread')
+    command(('edit %s'):format(t.tmpname(false)))
+    feed('ihello<Esc>')
+    screen:expect([[
+      hell^o                                                |
+      {1:~                                                    }|*12
+                                                        [+]|
+    ]])
+    command('silent write')
+    screen:expect([[
+      hell^o                                                |
+      {1:~                                                    }|*12
+                                                           |
+    ]])
+  end)
+
   it('pager statusline is not clobbered by DiagnosticChanged redraw #41130', function()
     exec_lua(function()
       vim.o.laststatus = 3
-- 
cgit