vim-patch:9.0.0656: cannot specify another character to use instead of '@'

Problem:    Cannot specify another character to use instead of '@' at the end
            of the window.
Solution:   Add "lastline" to 'fillchars'. (Martin Tournoij, closes vim/vim#11264,
            closes vim/vim#10963)
https://github.com/vim/vim/commit/4ba5f1dab656103e8f4a4505452d1816b9e83c1e

Use latest code in drawscreen.c instead.

4 files changed, 36 insertions, 16 deletions

diff --git a/src/nvim/buffer_defs.h b/src/nvim/buffer_defs.h
index 1212dffcec..5850763bcb 100644
--- a/src/nvim/buffer_defs.h
+++ b/src/nvim/buffer_defs.h
@@ -1168,6 +1168,7 @@ struct window_S {
     int diff;
     int msgsep;
     int eob;
+    int lastline;
   } w_p_fcs_chars;
 
   // "w_topline", "w_leftcol" and "w_skipcol" specify the offsets for
diff --git a/src/nvim/drawscreen.c b/src/nvim/drawscreen.c
index e2bf3ed60d..8c18bf75e5 100644
--- a/src/nvim/drawscreen.c
+++ b/src/nvim/drawscreen.c
@@ -1921,24 +1921,27 @@ win_update_start:
       wp->w_filler_rows = wp->w_grid.rows - srow;
     } else if (dy_flags & DY_TRUNCATE) {      // 'display' has "truncate"
       int scr_row = wp->w_grid.rows - 1;
+      int symbol = wp->w_p_fcs_chars.lastline;
+      char fillbuf[12];  // 2 characters of 6 bytes
+      int charlen = utf_char2bytes(symbol, &fillbuf[0]);
+      utf_char2bytes(symbol, &fillbuf[charlen]);
 
       // Last line isn't finished: Display "@@@" in the last screen line.
-      grid_puts_len(&wp->w_grid, "@@", MIN(wp->w_grid.cols, 2), scr_row, 0, at_attr);
-
-      grid_fill(&wp->w_grid, scr_row, scr_row + 1, 2, wp->w_grid.cols,
-                '@', ' ', at_attr);
+      grid_puts_len(&wp->w_grid, fillbuf, MIN(wp->w_grid.cols, 2) * charlen, scr_row, 0, at_attr);
+      grid_fill(&wp->w_grid, scr_row, scr_row + 1, 2, wp->w_grid.cols, symbol, ' ', at_attr);
       set_empty_rows(wp, srow);
       wp->w_botline = lnum;
     } else if (dy_flags & DY_LASTLINE) {      // 'display' has "lastline"
       int start_col = wp->w_grid.cols - 3;
+      int symbol = wp->w_p_fcs_chars.lastline;
 
       // Last line isn't finished: Display "@@@" at the end.
       grid_fill(&wp->w_grid, wp->w_grid.rows - 1, wp->w_grid.rows,
-                MAX(start_col, 0), wp->w_grid.cols, '@', '@', at_attr);
+                MAX(start_col, 0), wp->w_grid.cols, symbol, symbol, at_attr);
       set_empty_rows(wp, srow);
       wp->w_botline = lnum;
     } else {
-      win_draw_end(wp, '@', ' ', true, srow, wp->w_grid.rows, HLF_AT);
+      win_draw_end(wp, wp->w_p_fcs_chars.lastline, ' ', true, srow, wp->w_grid.rows, HLF_AT);
       set_empty_rows(wp, srow);
       wp->w_botline = lnum;
     }
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index 1af93f061c..bc440441e1 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -1328,6 +1328,7 @@ char *set_chars_option(win_T *wp, char **varp, bool apply)
     { &wp->w_p_fcs_chars.diff,       "diff",      '-' },
     { &wp->w_p_fcs_chars.msgsep,     "msgsep",    ' ' },
     { &wp->w_p_fcs_chars.eob,        "eob",       '~' },
+    { &wp->w_p_fcs_chars.lastline,   "lastline",  '@' },
   };
 
   struct chars_tab lcs_tab[] = {
diff --git a/src/nvim/testdir/test_display.vim b/src/nvim/testdir/test_display.vim
index 217bb5d781..0962429f71 100644
--- a/src/nvim/testdir/test_display.vim
+++ b/src/nvim/testdir/test_display.vim
@@ -407,30 +407,45 @@ func Test_display_linebreak_breakat()
   let &breakat=_breakat
 endfunc
 
-func Test_display_lastline()
-  CheckScreendump
-
+func Run_Test_display_lastline(euro)
   let lines =<< trim END
-      call setline(1, ['aaa', 'b'->repeat(100)])
+      call setline(1, ['aaa', 'b'->repeat(200)])
       set display=truncate
+
       vsplit
       100wincmd <
   END
-  call writefile(lines, 'XdispLastline')
+  if a:euro != ''
+    let lines[2] = 'set fillchars=vert:\|,lastline:€'
+  endif
+  call writefile(lines, 'XdispLastline', 'D')
   let buf = RunVimInTerminal('-S XdispLastline', #{rows: 10})
-  call VerifyScreenDump(buf, 'Test_display_lastline_1', {})
+  call VerifyScreenDump(buf, $'Test_display_lastline_{a:euro}1', {})
 
   call term_sendkeys(buf, ":set display=lastline\<CR>")
-  call VerifyScreenDump(buf, 'Test_display_lastline_2', {})
+  call VerifyScreenDump(buf, $'Test_display_lastline_{a:euro}2', {})
 
   call term_sendkeys(buf, ":100wincmd >\<CR>")
-  call VerifyScreenDump(buf, 'Test_display_lastline_3', {})
+  call VerifyScreenDump(buf, $'Test_display_lastline_{a:euro}3', {})
 
   call term_sendkeys(buf, ":set display=truncate\<CR>")
-  call VerifyScreenDump(buf, 'Test_display_lastline_4', {})
+  call VerifyScreenDump(buf, $'Test_display_lastline_{a:euro}4', {})
+
+  call term_sendkeys(buf, ":close\<CR>")
+  call term_sendkeys(buf, ":3split\<CR>")
+  call VerifyScreenDump(buf, $'Test_display_lastline_{a:euro}5', {})
 
   call StopVimInTerminal(buf)
-  call delete('XdispLastline')
+endfunc
+
+func Test_display_lastline()
+  CheckScreendump
+
+  call Run_Test_display_lastline('')
+  call Run_Test_display_lastline('euro_')
+
+  call assert_fails(':set fillchars=lastline:', 'E474:')
+  call assert_fails(':set fillchars=lastline:〇', 'E474:')
 endfunc