vim-patch:9.1.1170: wildmenu highlighting in popup can be improved (#32728)

Problem:  wildmenu highlighting in popup can be improved
Solution: Check if the completion items contain submatches of the
          entered text (Girish Palya).

This update enables highlighting in the popup menu even when the matched
fragment or pattern appears within an item (string) rather than only at the
beginning. This is especially useful for custom completion, where menu items
may not always start with the typed pattern.

For specific use cases, refer to the two examples in
https://github.com/vim/vim/pull/16759

A sliding window approach is used with direct string comparison. Performance
is not a concern, as highlighting is applied only to displayed lines, even if
the menu list is arbitrarily long.

closes: vim/vim#16785

https://github.com/vim/vim/commit/4ec46f32102e5569b247840e05a99221747a9381

Co-authored-by: Girish Palya <girishji@gmail.com>

3 files changed, 56 insertions, 7 deletions

diff --git a/src/nvim/popupmenu.c b/src/nvim/popupmenu.c
index 2e533bea23..3860ba8f6a 100644
--- a/src/nvim/popupmenu.c
+++ b/src/nvim/popupmenu.c
@@ -430,12 +430,10 @@ static int *pum_compute_text_attrs(char *text, hlf_T hlf, int user_hlattr)
   size_t leader_len = strlen(leader);
 
   garray_T *ga = NULL;
-  bool matched_start = false;
+  int matched_len = -1;
 
   if (in_fuzzy) {
     ga = fuzzy_match_str_with_pos(text, leader);
-  } else {
-    matched_start = mb_strnicmp(text, leader, leader_len) == 0;
   }
 
   const char *ptr = text;
@@ -456,10 +454,16 @@ static int *pum_compute_text_attrs(char *text, hlf_T hlf, int user_hlattr)
           break;
         }
       }
-    } else if (matched_start && ptr < text + leader_len) {
-      new_attr = win_hl_attr(curwin, is_select ? HLF_PMSI : HLF_PMNI);
-      new_attr = hl_combine_attr(win_hl_attr(curwin, HLF_PMNI), new_attr);
-      new_attr = hl_combine_attr(win_hl_attr(curwin, (int)hlf), new_attr);
+    } else {
+      if (matched_len < 0 && mb_strnicmp(ptr, leader, leader_len) == 0) {
+        matched_len = (int)leader_len;
+      }
+      if (matched_len > 0) {
+        new_attr = win_hl_attr(curwin, is_select ? HLF_PMSI : HLF_PMNI);
+        new_attr = hl_combine_attr(win_hl_attr(curwin, HLF_PMNI), new_attr);
+        new_attr = hl_combine_attr(win_hl_attr(curwin, (int)hlf), new_attr);
+        matched_len--;
+      }
     }
 
     new_attr = hl_combine_attr(win_hl_attr(curwin, HLF_PNI), new_attr);
diff --git a/test/functional/ui/popupmenu_spec.lua b/test/functional/ui/popupmenu_spec.lua
index f6c9236037..0206900c06 100644
--- a/test/functional/ui/popupmenu_spec.lua
+++ b/test/functional/ui/popupmenu_spec.lua
@@ -5145,6 +5145,29 @@ describe('builtin popupmenu', function()
         ]])
       end)
 
+      -- oldtest: Test_wildmenu_pum_hl_nonfirst()
+      it('highlight matched text in the middle in cmdline pum', function()
+        exec([[
+          set wildoptions=pum wildchar=<tab> wildmode=noselect,full
+          hi PmenuMatchSel  guifg=Blue guibg=Grey
+          hi PmenuMatch     guifg=Blue guibg=Plum1
+          func T(a, c, p)
+            return ["oneA", "o neBneB", "aoneC"]
+          endfunc
+          command -nargs=1 -complete=customlist,T MyCmd
+        ]])
+
+        feed(':MyCmd ne<tab>')
+        screen:expect([[
+                                          |
+          {1:~                               }|*15
+          {1:~     }{n: o}{mn:ne}{n:A           }{1:          }|
+          {1:~     }{n: o }{mn:ne}{n:BneB       }{1:          }|
+          {1:~     }{n: ao}{mn:ne}{n:C          }{1:          }|
+          :MyCmd ne^                       |
+        ]])
+      end)
+
       it(
         'cascading highlights for matched text (PmenuMatch, PmenuMatchSel) in cmdline pum',
         function()
diff --git a/test/old/testdir/test_cmdline.vim b/test/old/testdir/test_cmdline.vim
index d9496ba2a6..639a4c1d32 100644
--- a/test/old/testdir/test_cmdline.vim
+++ b/test/old/testdir/test_cmdline.vim
@@ -3025,6 +3025,28 @@ func Test_wildmenu_pum_rightleft()
   call StopVimInTerminal(buf)
 endfunc
 
+" Test highlighting when pattern matches non-first character of item
+func Test_wildmenu_pum_hl_nonfirst()
+  CheckScreendump
+  let lines =<< trim END
+    set wildoptions=pum wildchar=<tab> wildmode=noselect,full
+    hi PmenuMatchSel  ctermfg=6 ctermbg=7
+    hi PmenuMatch     ctermfg=4 ctermbg=225
+    func T(a, c, p)
+      return ["oneA", "o neBneB", "aoneC"]
+    endfunc
+    command -nargs=1 -complete=customlist,T MyCmd
+  END
+
+  call writefile(lines, 'Xwildmenu_pum_hl_nonf', 'D')
+  let buf = RunVimInTerminal('-S Xwildmenu_pum_hl_nonf', #{rows: 10, cols: 50})
+
+  call term_sendkeys(buf, ":MyCmd ne\<tab>")
+  call VerifyScreenDump(buf, 'Test_wildmenu_pum_hl_match_nonf', {})
+  call term_sendkeys(buf, "\<Esc>")
+  call StopVimInTerminal(buf)
+endfunc
+
 " Test highlighting matched text in cmdline completion popup menu.
 func Test_wildmenu_pum_hl_match()
   CheckScreendump