feat(highlight): implement CurSearch highlight

Adds a `CurSearch` highlight group to highlight the current search result under the cursor.

runtime/doc/options.txt

@@ -3176,8 +3176,12 @@ A jump table for the options with a short description can be found at |Q_op|.
 'hlsearch' 'hls'	boolean	(default on)
 			global
 	When there is a previous search pattern, highlight all its matches.
-	The |hl-Search| highlight group determines the highlighting. Note that
-	only the matching text is highlighted, any offsets are not applied.
+	The |hl-Search| highlight group determines the highlighting for all
+	matches not under the cursor while the |hl-CurSearch| highlight group
+	(if defined) determines the highlighting for the match under the
+	cursor. If |hl-CurSearch| is not defined, then |hl-Search| is used for
+	both. Note that only the matching text is highlighted, any offsets
+	are not applied.
 	See also: 'incsearch' and |:match|.
 	When you get bored looking at the highlighted matches, you can turn it
 	off with |:nohlsearch|.  This does not change the option value, as

runtime/doc/syntax.txt

@@ -5090,6 +5090,9 @@ ColorColumn	used for the columns set with 'colorcolumn'
 							*hl-Conceal*
 Conceal		placeholder characters substituted for concealed
 		text (see 'conceallevel')
+							*hl-CurSearch*
+CurSearch	used for highlighting a search pattern under the cursor
+		(see 'hlsearch')
 							*hl-Cursor*
 Cursor		character under the cursor
 lCursor		the character under the cursor when |language-mapping|

runtime/doc/vim_diff.txt

@@ -351,6 +351,8 @@ Functions:
 Highlight groups:
   |hl-ColorColumn|, |hl-CursorColumn| are lower priority than most other
   groups
+  |hl-CurSearch| highlights match under cursor instead of last match found
+  using |n| or |N|
   |hl-CursorLine| is low-priority unless foreground color is set
   *hl-VertSplit* superseded by |hl-WinSeparator|
 

src/nvim/highlight_defs.h

@@ -63,6 +63,7 @@ typedef enum {
   HLF_E,          // error messages
   HLF_I,          // incremental search
   HLF_L,          // last search string
+  HLF_LC,         // current search match
   HLF_M,          // "--More--" message
   HLF_CM,         // Mode (e.g., "-- INSERT --")
   HLF_N,          // line number for ":number" and ":#" commands
@@ -123,6 +124,7 @@ EXTERN const char *hlf_names[] INIT(= {
   [HLF_E] = "ErrorMsg",
   [HLF_I] = "IncSearch",
   [HLF_L] = "Search",
+  [HLF_LC] = "CurSearch",
   [HLF_M] = "MoreMsg",
   [HLF_CM] = "ModeMsg",
   [HLF_N] = "LineNr",

src/nvim/highlight_group.c

@@ -1927,7 +1927,7 @@ void highlight_changed(void)
     }
 
     highlight_attr[hlf] = hl_get_ui_attr(hlf, final_id,
-                                         hlf == HLF_INACTIVE);
+                                         (hlf == HLF_INACTIVE || hlf == HLF_LC));
 
     if (highlight_attr[hlf] != highlight_attr_last[hlf]) {
       if (hlf == HLF_MSG) {

src/nvim/match.c

@@ -4,6 +4,7 @@
 // match.c: functions for highlighting matches
 
 #include <stdbool.h>
+#include "nvim/buffer_defs.h"
 #include "nvim/charset.h"
 #include "nvim/fold.h"
 #include "nvim/highlight_group.h"
@@ -667,7 +668,16 @@ int update_search_hl(win_T *wp, linenr_T lnum, colnr_T col, char_u **line, match
         if (shl->endcol < next_col) {
           shl->endcol = next_col;
         }
+        // Use "CurSearch" highlight for current search match
+        if (shl == search_hl
+            && (HL_ATTR(HLF_LC) || wp->w_hl_ids[HLF_LC])
+            && wp->w_cursor.lnum == lnum
+            && wp->w_cursor.col >= shl->startcol
+            && wp->w_cursor.col < shl->endcol) {
+          shl->attr_cur = win_hl_attr(wp, HLF_LC) ? win_hl_attr(wp, HLF_LC) : HL_ATTR(HLF_LC);
+        } else {
           shl->attr_cur = shl->attr;
+        }
         // Match with the "Conceal" group results in hiding
         // the match.
         if (cur != NULL

src/nvim/move.c

@@ -95,27 +95,31 @@ static void comp_botline(win_T *wp)
   win_check_anchored_floats(wp);
 }
 
-/// Redraw when w_cline_row changes and 'relativenumber' or 'cursorline' is set.
+/// Redraw when w_cline_row changes and 'relativenumber' or 'cursorline' is set
+/// or if the 'CurSearch' highlight is defined.
 /// Also when concealing is on and 'concealcursor' is not active.
 void redraw_for_cursorline(win_T *wp)
   FUNC_ATTR_NONNULL_ALL
 {
   if ((wp->w_valid & VALID_CROW) == 0 && !pum_visible()
-      && (wp->w_p_rnu || win_cursorline_standout(wp))) {
-    // win_line() will redraw the number column and cursorline only.
+      && (wp->w_p_rnu || win_cursorline_standout(wp)
+          || HL_ATTR(HLF_LC) || wp->w_hl_ids[HLF_LC])) {
+    // win_line() will redraw the number column and cursorline only
+    // and also update the CurSearch highlight (if needed).
     redraw_later(wp, VALID);
   }
 }
 
 /// Redraw when w_virtcol changes and 'cursorcolumn' is set or 'cursorlineopt'
-/// contains "screenline".
+/// contains "screenline" or when the 'CurSearch' highlight is defined.
 /// Also when concealing is on and 'concealcursor' is active.
 static void redraw_for_cursorcolumn(win_T *wp)
   FUNC_ATTR_NONNULL_ALL
 {
   if ((wp->w_valid & VALID_VIRTCOL) == 0 && !pum_visible()) {
-    if (wp->w_p_cuc) {
-      // When 'cursorcolumn' is set need to redraw with SOME_VALID.
+    if (wp->w_p_cuc || HL_ATTR(HLF_LC) || wp->w_hl_ids[HLF_LC]) {
+      // When 'cursorcolumn' is set or 'CurSearch' is defined
+      // need to redraw with SOME_VALID.
       redraw_later(wp, SOME_VALID);
     } else if (wp->w_p_cul && (wp->w_p_culopt_flags & CULOPT_SCRLINE)) {
       // When 'cursorlineopt' contains "screenline" need to redraw with VALID.

test/functional/ui/cursor_spec.lua

@@ -212,10 +212,10 @@ describe('ui/cursor', function()
         if m.blinkwait then m.blinkwait = 700 end
       end
       if m.hl_id then
-          m.hl_id = 61
+          m.hl_id = 62
           m.attr = {background = Screen.colors.DarkGray}
       end
-      if m.id_lm then m.id_lm = 62 end
+      if m.id_lm then m.id_lm = 63 end
     end
 
     -- Assert the new expectation.

test/functional/ui/searchhl_spec.lua

@@ -109,6 +109,56 @@ describe('search highlighting', function()
     ]])
   end)
 
+  it('works for match under cursor', function()
+    screen:set_default_attr_ids({
+        [1] = {background = Screen.colors.Yellow},
+        [2] = {foreground = Screen.colors.Gray100, background = Screen.colors.Gray0},
+        [3] = {foreground = Screen.colors.Red},
+    })
+
+    command('highlight CurSearch guibg=Black guifg=White')
+    insert([[
+      There is no way that a bee should be
+      able to fly. Its wings are too small
+      to get its fat little body off the
+      ground. The bee, of course, flies
+      anyway because bees don't care what
+      humans think is impossible.]])
+
+    feed('/bee<CR>')
+    screen:expect{grid=[[
+      There is no way that a {2:^bee} should be    |
+      able to fly. Its wings are too small    |
+      to get its fat little body off the      |
+      ground. The {1:bee}, of course, flies       |
+      anyway because {1:bee}s don't care what     |
+      humans think is impossible.             |
+      {3:search hit BOTTOM, continuing at TOP}    |
+    ]]}
+
+    feed('nn')
+    screen:expect{grid=[[
+      There is no way that a {1:bee} should be    |
+      able to fly. Its wings are too small    |
+      to get its fat little body off the      |
+      ground. The {1:bee}, of course, flies       |
+      anyway because {2:^bee}s don't care what     |
+      humans think is impossible.             |
+      /bee                                    |
+    ]]}
+
+    feed('N')
+    screen:expect{grid=[[
+      There is no way that a {1:bee} should be    |
+      able to fly. Its wings are too small    |
+      to get its fat little body off the      |
+      ground. The {2:^bee}, of course, flies       |
+      anyway because {1:bee}s don't care what     |
+      humans think is impossible.             |
+      ?bee                                    |
+    ]]}
+  end)
+
   it('highlights after EOL', function()
     insert("\n\n\n\n\n\n")