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.

2 files changed, 7 insertions, 6 deletions

diff --git a/src/nvim/drawscreen.c b/src/nvim/drawscreen.c
index 5ced55b2c7..810175aeba 100644
--- a/src/nvim/drawscreen.c
+++ b/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();
-  if (redrawing() && last->w_status_height == 0 && global_stl_height() == 0) {
-    win_redr_ruler(last);
+  win_T *ruler_win = curwin->w_status_height == 0 ? curwin : lastwin_nofloating();
+  if (redrawing() && ruler_win->w_status_height == 0 && global_stl_height() == 0) {
+    win_redr_ruler(ruler_win);
   }
 
   redraw_cmdline = false;
diff --git a/src/nvim/statusline.c b/src/nvim/statusline.c
index 5a1f7e3a7f..e809922be3 100644
--- a/src/nvim/statusline.c
+++ b/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;