feat(highlight): implement CurSearch highlight

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

4 files changed, 24 insertions, 8 deletions

diff --git a/src/nvim/highlight_defs.h b/src/nvim/highlight_defs.h
index e0ee649013..0515842b61 100644
--- a/src/nvim/highlight_defs.h
+++ b/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",
diff --git a/src/nvim/highlight_group.c b/src/nvim/highlight_group.c
index 3092aaefab..a9ced84280 100644
--- a/src/nvim/highlight_group.c
+++ b/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) {
diff --git a/src/nvim/match.c b/src/nvim/match.c
index af89319a09..4129e84fc2 100644
--- a/src/nvim/match.c
+++ b/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;
         }
-        shl->attr_cur = shl->attr;
+        // 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
diff --git a/src/nvim/move.c b/src/nvim/move.c
index eda3298101..c55a9a296b 100644
--- a/src/nvim/move.c
+++ b/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.