fix(ruler): show ruler of curwin with no statusline in cmdline

Problem: After neovim/neovim@846a056, only the ruler for current floating or
last window without a statusline is drawn in the cmdline. This means that if the
current window is not one of these, but has no statusline, its ruler will not be
drawn anymore.

Solution: Make `showmode()` draw the ruler of the current window or the last
window in the cmdline if it has no statusline. This also maintains the
previously restored floating window case (`float->w_status_height` should be 0).

This behaviour should again match Vim, but without the overdraw it seems to do
to achieve the same effect; it calls `showmode()` to draw the ruler for the last
window without a statusline, then may draw over it in `showruler()` (which is
now `show_cursor_info_later()` in Nvim) to show the ruler for the current
window..? It's very confusing.

Also update the logic in `win_redr_ruler()` to mirror the check done in
`showmode()`, so that the ruler doesn't potentially draw over the long
ins-completion mode message in some cases.

src/nvim/drawscreen.c

@@ -1052,11 +1052,11 @@ int showmode(void)
     clear_showcmd();
   }
 
-  // If the last window has no status line and global statusline is disabled,
+  // If the current or last window has no status line and global statusline is disabled,
   // the ruler is after the mode message and must be redrawn
-  win_T *last = curwin->w_floating ? curwin : lastwin_nofloating();
+  win_T *ruler_win = curwin->w_status_height == 0 ? curwin : lastwin_nofloating();
-  if (redrawing() && last->w_status_height == 0 && global_stl_height() == 0) {
+  if (redrawing() && ruler_win->w_status_height == 0 && global_stl_height() == 0) {
-    win_redr_ruler(last);
+    win_redr_ruler(ruler_win);
   }
 
   redraw_cmdline = false;

src/nvim/statusline.c

@@ -497,7 +497,8 @@ void win_redr_ruler(win_T *wp)
 
   // Don't draw the ruler while doing insert-completion, it might overwrite
   // the (long) mode message.
-  if (wp == lastwin && lastwin->w_status_height == 0 && !is_stl_global) {
+  win_T *ruler_win = curwin->w_status_height == 0 ? curwin : lastwin_nofloating();
+  if (wp == ruler_win && ruler_win->w_status_height == 0 && !is_stl_global) {
     if (edit_submode != NULL) {
       return;
     }
@@ -510,7 +511,7 @@ void win_redr_ruler(win_T *wp)
 
   // Check if not in Insert mode and the line is empty (will show "0-1").
   int empty_line = (State & MODE_INSERT) == 0
-                   && *ml_get_buf(curwin->w_buffer, curwin->w_cursor.lnum, false) == NUL;
+                   && *ml_get_buf(wp->w_buffer, wp->w_cursor.lnum, false) == NUL;
 
   int width;
   int row;

test/functional/ui/float_spec.lua

@@ -2340,6 +2340,121 @@ describe('float window', function()
       end
     end)
 
+    it('does not show ruler of not-last current float during ins-completion', function()
+      screen:try_resize(50,9)
+      command 'set ruler showmode'
+      meths.open_win(0, false, {relative='editor', width=3, height=3, row=0, col=0})
+      meths.open_win(0, false, {relative='editor', width=3, height=3, row=0, col=5})
+      feed '<c-w>w'
+      neq('', meths.win_get_config(0).relative)
+      neq(funcs.winnr '$', funcs.winnr())
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [3:--------------------------------------------------]|
+        ## grid 2
+                                                            |
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+        ## grid 3
+                                          0,0-1         All |
+        ## grid 4
+          {1:   }|
+          {2:~  }|
+          {2:~  }|
+        ## grid 5
+          {1:^   }|
+          {2:~  }|
+          {2:~  }|
+        ]], float_pos={
+          [5] = {{id = 1002}, "NW", 1, 0, 5, true, 50};
+          [4] = {{id = 1001}, "NW", 1, 0, 0, true, 50};
+        }, win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1, sum_scroll_delta = 0};
+          [4] = {win = {id = 1001}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1, sum_scroll_delta = 0};
+          [5] = {win = {id = 1002}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1, sum_scroll_delta = 0};
+        }}
+      else
+        screen:expect{grid=[[
+          {1:   }  {1:^   }                                          |
+          {2:~  }{0:  }{2:~  }{0:                                          }|
+          {2:~  }{0:  }{2:~  }{0:                                          }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+                                          0,0-1         All |
+        ]]}
+      end
+      feed 'i<c-x>'
+      if multigrid then
+        screen:expect{grid=[[
+        ## grid 1
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [2:--------------------------------------------------]|
+          [3:--------------------------------------------------]|
+        ## grid 2
+                                                            |
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+        ## grid 3
+          {3:-- ^X mode (^]^D^E^F^I^K^L^N^O^Ps^U^V^Y)}          |
+        ## grid 4
+          {1:   }|
+          {2:~  }|
+          {2:~  }|
+        ## grid 5
+          {1:^   }|
+          {2:~  }|
+          {2:~  }|
+        ]], float_pos={
+          [5] = {{id = 1002}, "NW", 1, 0, 5, true, 50};
+          [4] = {{id = 1001}, "NW", 1, 0, 0, true, 50};
+        }, win_viewport={
+          [2] = {win = {id = 1000}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1, sum_scroll_delta = 0};
+          [4] = {win = {id = 1001}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1, sum_scroll_delta = 0};
+          [5] = {win = {id = 1002}, topline = 0, botline = 2, curline = 0, curcol = 0, linecount = 1, sum_scroll_delta = 0};
+        }}
+      else
+        screen:expect{grid=[[
+          {1:   }  {1:^   }                                          |
+          {2:~  }{0:  }{2:~  }{0:                                          }|
+          {2:~  }{0:  }{2:~  }{0:                                          }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {0:~                                                 }|
+          {3:-- ^X mode (^]^D^E^F^I^K^L^N^O^Ps^U^V^Y)}          |
+        ]]}
+      end
+    end)
+
     it('can have minimum size', function()
       insert("the background text")
       local buf = meths.create_buf(false, true)

test/functional/ui/statusline_spec.lua

@@ -653,3 +653,62 @@ it('ruler is redrawn in cmdline with redrawstatus #22804', function()
                           other value       |
   ]])
 end)
+
+it("shows correct ruler in cmdline with no statusline", function()
+  clear()
+  local screen = Screen.new(30, 8)
+  screen:set_default_attr_ids {
+    [1] = {bold = true, foreground = Screen.colors.Blue},  -- NonText
+    [2] = {bold = true, reverse = true},  -- StatusLine
+    [3] = {reverse = true},  -- StatusLineNC
+  }
+  screen:attach()
+  -- Use long ruler to check 'ruler' with 'rulerformat' set has correct width.
+  command [[
+    set ruler rulerformat=%{winnr()}longlonglong ls=0 winwidth=10
+    split
+    wincmd b
+    vsplit
+    wincmd t
+    wincmd |
+    mode
+  ]]
+  -- Window 1 is current. It has a statusline, so cmdline should show the
+  -- last window's ruler, which has no statusline.
+  command '1wincmd w'
+  screen:expect [[
+    ^                              |
+    {1:~                             }|
+    {1:~                             }|
+    {2:[No Name]      1longlonglong  }|
+                   │              |
+    {1:~              }│{1:~             }|
+    {1:~              }│{1:~             }|
+                   3longlonglong  |
+  ]]
+  -- Window 2 is current. It has no statusline, so cmdline should show its
+  -- ruler instead.
+  command '2wincmd w'
+  screen:expect [[
+                                  |
+    {1:~                             }|
+    {1:~                             }|
+    {3:[No Name]      1longlonglong  }|
+    ^               │              |
+    {1:~              }│{1:~             }|
+    {1:~              }│{1:~             }|
+                   2longlonglong  |
+  ]]
+  -- Window 3 is current. Cmdline should again show its ruler.
+  command '3wincmd w'
+  screen:expect [[
+                                  |
+    {1:~                             }|
+    {1:~                             }|
+    {3:[No Name]      1longlonglong  }|
+                   │^              |
+    {1:~              }│{1:~             }|
+    {1:~              }│{1:~             }|
+                   3longlonglong  |
+  ]]
+end)