fix(float): missing default highlight for title

Problem: there is missing default title highlight when highlight not defined in title text chunk.

Solution: when attr is not set use default title highlight group.

runtime/doc/api.txt

@@ -3270,13 +3270,15 @@ nvim_open_win({buffer}, {enter}, {config})                   *nvim_open_win()*
 <
                   • title: Title (optional) in window border, string or list.
                     List should consist of `[text, highlight]` tuples. If
-                    string, the default highlight group is `FloatTitle`.
+                    string, or a tuple lacks a highlight, the default
+                    highlight group is `FloatTitle`.
                   • title_pos: Title position. Must be set with `title`
                     option. Value can be one of "left", "center", or "right".
                     Default is `"left"`.
                   • footer: Footer (optional) in window border, string or
                     list. List should consist of `[text, highlight]` tuples.
-                    If string, the default highlight group is `FloatFooter`.
+                    If string, or a tuple lacks a highlight, the default
+                    highlight group is `FloatFooter`.
                   • footer_pos: Footer position. Must be set with `footer`
                     option. Value can be one of "left", "center", or "right".
                     Default is `"left"`.

runtime/lua/vim/_meta/api.lua

@@ -1731,13 +1731,15 @@ function vim.api.nvim_open_term(buffer, opts) end
 ---
 ---               • title: Title (optional) in window border, string or list.
 ---                 List should consist of `[text, highlight]` tuples. If
----                 string, the default highlight group is `FloatTitle`.
+---                 string, or a tuple lacks a highlight, the default
+---                 highlight group is `FloatTitle`.
 ---               • title_pos: Title position. Must be set with `title`
 ---                 option. Value can be one of "left", "center", or "right".
 ---                 Default is `"left"`.
 ---               • footer: Footer (optional) in window border, string or
 ---                 list. List should consist of `[text, highlight]` tuples.
----                 If string, the default highlight group is `FloatFooter`.
+---                 If string, or a tuple lacks a highlight, the default
+---                 highlight group is `FloatFooter`.
 ---               • footer_pos: Footer position. Must be set with `footer`
 ---                 option. Value can be one of "left", "center", or "right".
 ---                 Default is `"left"`.

src/nvim/api/win_config.c

@@ -189,13 +189,13 @@
 ///     ```
 ///   - title: Title (optional) in window border, string or list.
 ///     List should consist of `[text, highlight]` tuples.
-///     If string, the default highlight group is `FloatTitle`.
+///     If string, or a tuple lacks a highlight, the default highlight group is `FloatTitle`.
 ///   - title_pos: Title position. Must be set with `title` option.
 ///     Value can be one of "left", "center", or "right".
 ///     Default is `"left"`.
 ///   - footer: Footer (optional) in window border, string or list.
 ///     List should consist of `[text, highlight]` tuples.
-///     If string, the default highlight group is `FloatFooter`.
+///     If string, or a tuple lacks a highlight, the default highlight group is `FloatFooter`.
 ///   - footer_pos: Footer position. Must be set with `footer` option.
 ///     Value can be one of "left", "center", or "right".
 ///     Default is `"left"`.
@@ -851,7 +851,6 @@ static void parse_bordertext(Object bordertext, BorderTextType bordertext_type,
   bool *is_present;
   VirtText *chunks;
   int *width;
-  int default_hl_id;
   switch (bordertext_type) {
   case kBorderTextTitle:
     if (fconfig->title) {
@@ -861,7 +860,6 @@ static void parse_bordertext(Object bordertext, BorderTextType bordertext_type,
     is_present = &fconfig->title;
     chunks = &fconfig->title_chunks;
     width = &fconfig->title_width;
-    default_hl_id = syn_check_group(S_LEN("FloatTitle"));
     break;
   case kBorderTextFooter:
     if (fconfig->footer) {
@@ -871,7 +869,6 @@ static void parse_bordertext(Object bordertext, BorderTextType bordertext_type,
     is_present = &fconfig->footer;
     chunks = &fconfig->footer_chunks;
     width = &fconfig->footer_width;
-    default_hl_id = syn_check_group(S_LEN("FloatFooter"));
     break;
   }
 
@@ -881,7 +878,7 @@ static void parse_bordertext(Object bordertext, BorderTextType bordertext_type,
       return;
     }
     kv_push(*chunks, ((VirtTextChunk){ .text = xstrdup(bordertext.data.string.data),
-                                       .hl_id = default_hl_id }));
+                                       .hl_id = -1 }));
     *width = (int)mb_string2cells(bordertext.data.string.data);
     *is_present = true;
     return;

src/nvim/drawscreen.c

@@ -65,6 +65,7 @@
 #include "nvim/autocmd.h"
 #include "nvim/autocmd_defs.h"
 #include "nvim/buffer.h"
+#include "nvim/buffer_defs.h"
 #include "nvim/charset.h"
 #include "nvim/cmdexpand.h"
 #include "nvim/cursor.h"
@@ -715,14 +716,17 @@ void end_search_hl(void)
   screen_search_hl.rm.regprog = NULL;
 }
 
-static void win_redr_bordertext(win_T *wp, VirtText vt, int col)
+static void win_redr_bordertext(win_T *wp, VirtText vt, int col, BorderTextType bt)
 {
   for (size_t i = 0; i < kv_size(vt);) {
-    int attr = 0;
+    int attr = -1;
     char *text = next_virt_text_chunk(vt, &i, &attr);
     if (text == NULL) {
       break;
     }
+    if (attr == -1) {  // No highlight specified.
+      attr = wp->w_ns_hl_attr[bt == kBorderTextTitle ? HLF_BTITLE : HLF_BFOOTER];
+    }
     attr = hl_apply_winblend(wp, attr);
     col += grid_line_puts(col, text, -1, attr);
   }
@@ -773,7 +777,7 @@ static void win_redr_border(win_T *wp)
     if (wp->w_config.title) {
       int title_col = win_get_bordertext_col(icol, wp->w_config.title_width,
                                              wp->w_config.title_pos);
-      win_redr_bordertext(wp, wp->w_config.title_chunks, title_col);
+      win_redr_bordertext(wp, wp->w_config.title_chunks, title_col, kBorderTextTitle);
     }
     if (adj[1]) {
       grid_line_put_schar(icol + adj[3], chars[2], attrs[2]);
@@ -809,7 +813,7 @@ static void win_redr_border(win_T *wp)
     if (wp->w_config.footer) {
       int footer_col = win_get_bordertext_col(icol, wp->w_config.footer_width,
                                               wp->w_config.footer_pos);
-      win_redr_bordertext(wp, wp->w_config.footer_chunks, footer_col);
+      win_redr_bordertext(wp, wp->w_config.footer_chunks, footer_col, kBorderTextFooter);
     }
     if (adj[1]) {
       grid_line_put_schar(icol + adj[3], chars[4], attrs[4]);

test/functional/ui/float_spec.lua

@@ -2127,7 +2127,7 @@ describe('float window', function()
         ## grid 3
                                                   |
         ## grid 4
-          {5:╔═════}🦄BB{5:╗}|
+          {5:╔═════}{11:🦄BB}{5:╗}|
           {5:║}{1: halloj! }{5:║}|
           {5:║}{1: BORDAA  }{5:║}|
           {5:╚═════════╝}|
@@ -2141,7 +2141,7 @@ describe('float window', function()
         screen:expect{grid=[[
           ^                                        |
           {0:~                                       }|
-          {0:~    }{5:╔═════}🦄BB{5:╗}{0:                        }|
+          {0:~    }{5:╔═════}{11:🦄BB}{5:╗}{0:                        }|
           {0:~    }{5:║}{1: halloj! }{5:║}{0:                        }|
           {0:~    }{5:║}{1: BORDAA  }{5:║}{0:                        }|
           {0:~    }{5:╚═════════╝}{0:                        }|
@@ -2275,7 +2275,7 @@ describe('float window', function()
           {5:╔═════════╗}|
           {5:║}{1: halloj! }{5:║}|
           {5:║}{1: BORDAA  }{5:║}|
-          {5:╚═════}🦄BB{5:╝}|
+          {5:╚═════}{11:🦄BB}{5:╝}|
         ]], float_pos={
           [4] = { 1001, "NW", 1, 2, 5, true }
         }, win_viewport={
@@ -2289,7 +2289,7 @@ describe('float window', function()
           {0:~    }{5:╔═════════╗}{0:                        }|
           {0:~    }{5:║}{1: halloj! }{5:║}{0:                        }|
           {0:~    }{5:║}{1: BORDAA  }{5:║}{0:                        }|
-          {0:~    }{5:╚═════}🦄BB{5:╝}{0:                        }|
+          {0:~    }{5:╚═════}{11:🦄BB}{5:╝}{0:                        }|
                                                   |
         ]]}
       end
@@ -2423,10 +2423,10 @@ describe('float window', function()
         ## grid 3
                                                   |
         ## grid 4
-          {5:╔═════}🦄{7:BB}{5:╗}|
+          {5:╔═════}{11:🦄}{7:BB}{5:╗}|
           {5:║}{1: halloj! }{5:║}|
           {5:║}{1: BORDAA  }{5:║}|
-          {5:╚═════}🦄{7:BB}{5:╝}|
+          {5:╚═════}{11:🦄}{7:BB}{5:╝}|
         ]], float_pos={
           [4] = { 1001, "NW", 1, 2, 5, true }
         }, win_viewport={
@@ -2437,10 +2437,10 @@ describe('float window', function()
         screen:expect{grid=[[
           ^                                        |
           {0:~                                       }|
-          {0:~    }{5:╔═════}🦄{7:BB}{5:╗}{0:                        }|
+          {0:~    }{5:╔═════}{11:🦄}{7:BB}{5:╗}{0:                        }|
           {0:~    }{5:║}{1: halloj! }{5:║}{0:                        }|
           {0:~    }{5:║}{1: BORDAA  }{5:║}{0:                        }|
-          {0:~    }{5:╚═════}🦄{7:BB}{5:╝}{0:                        }|
+          {0:~    }{5:╚═════}{11:🦄}{7:BB}{5:╝}{0:                        }|
                                                   |
         ]]}
       end