diff/highlight: Show underline for low-priority CursorLine

2 files changed, 25 insertions, 3 deletions

diff --git a/src/nvim/highlight.c b/src/nvim/highlight.c
index ae2b90d8a1..89a41e73de 100644
--- a/src/nvim/highlight.c
+++ b/src/nvim/highlight.c
@@ -177,6 +177,24 @@ void update_window_hl(win_T *wp, bool invalid)
   }
 }
 
+/// Gets HL_UNDERLINE highlight.
+int hl_get_underline(void)
+{
+  return get_attr_entry((HlEntry){
+      .attr = (HlAttrs){
+          .cterm_ae_attr = (int16_t)HL_UNDERLINE,
+          .cterm_fg_color = 0,
+          .cterm_bg_color = 0,
+          .rgb_ae_attr = (int16_t)HL_UNDERLINE,
+          .rgb_fg_color = 0,
+          .rgb_bg_color = 0,
+      },
+      .kind = kHlUI,
+      .id1 = 0,
+      .id2 = 0,
+  });
+}
+
 /// Get attribute code for forwarded :terminal highlights.
 int hl_get_term_attr(HlAttrs *aep)
 {
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index 2a1dae1767..eb24e2af1c 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -3052,9 +3052,13 @@ win_line (
           diff_hlf = HLF_CHD;                   // changed line
         }
         line_attr = win_hl_attr(wp, diff_hlf);
-        // Overlay CursorLine onto diff highlight, unless it's low-priority.
-        if (!line_attr_lowprio && wp->w_p_cul && lnum == wp->w_cursor.lnum) {
-          line_attr = hl_combine_attr(line_attr, win_hl_attr(wp, HLF_CUL));
+        // Overlay CursorLine onto diff-mode highlight.
+        if (wp->w_p_cul && lnum == wp->w_cursor.lnum) {
+          line_attr = 0 != line_attr_lowprio  // Low-priority CursorLine
+            ? hl_combine_attr(hl_combine_attr(win_hl_attr(wp, HLF_CUL),
+                                              line_attr),
+                              hl_get_underline())
+            : hl_combine_attr(line_attr, win_hl_attr(wp, HLF_CUL));
         }
       }