4 files changed, 21 insertions, 5 deletions
diff --git a/src/nvim/api/keysets.lua b/src/nvim/api/keysets.lua
index bd709b7b25..30dcef6127 100644
--- a/src/nvim/api/keysets.lua
+++ b/src/nvim/api/keysets.lua
@@ -114,6 +114,7 @@ return {
     "underdashed";
     "italic";
     "reverse";
+    "altfont";
     "nocombine";
     "default";
     "cterm";
@@ -140,6 +141,7 @@ return {
     "underdashed";
     "italic";
     "reverse";
+    "altfont";
     "nocombine";
   }};
   -- Autocmds
diff --git a/src/nvim/highlight.c b/src/nvim/highlight.c
index e3fb409f34..9dab91cc2b 100644
--- a/src/nvim/highlight.c
+++ b/src/nvim/highlight.c
@@ -867,6 +867,10 @@ void hlattrs2dict(Dictionary *dict, HlAttrs ae, bool use_rgb)
     PUT_C(hl, "strikethrough", BOOLEAN_OBJ(true));
   }
 
+  if (mask & HL_ALTFONT) {
+    PUT_C(hl, "altfont", BOOLEAN_OBJ(true));
+  }
+
   if (mask & HL_NOCOMBINE) {
     PUT_C(hl, "nocombine", BOOLEAN_OBJ(true));
   }
@@ -932,6 +936,7 @@ HlAttrs dict2hlattrs(Dict(highlight) *dict, bool use_rgb, int *link_id, Error *e
   CHECK_FLAG(dict, mask, underdashed, , HL_UNDERDASHED);
   CHECK_FLAG(dict, mask, standout, , HL_STANDOUT);
   CHECK_FLAG(dict, mask, strikethrough, , HL_STRIKETHROUGH);
+  CHECK_FLAG(dict, mask, altfont, , HL_ALTFONT);
   if (use_rgb) {
     CHECK_FLAG(dict, mask, fg_indexed, , HL_FG_INDEXED);
     CHECK_FLAG(dict, mask, bg_indexed, , HL_BG_INDEXED);
@@ -1014,6 +1019,7 @@ HlAttrs dict2hlattrs(Dict(highlight) *dict, bool use_rgb, int *link_id, Error *e
     CHECK_FLAG(cterm, cterm_mask, undercurl, , HL_UNDERCURL);
     CHECK_FLAG(cterm, cterm_mask, standout, , HL_STANDOUT);
     CHECK_FLAG(cterm, cterm_mask, strikethrough, , HL_STRIKETHROUGH);
+    CHECK_FLAG(cterm, cterm_mask, altfont, , HL_ALTFONT);
     CHECK_FLAG(cterm, cterm_mask, nocombine, , HL_NOCOMBINE);
   } else if (dict->cterm.type == kObjectTypeArray && dict->cterm.data.array.size == 0) {
     // empty list from Lua API should clear all cterm attributes
diff --git a/src/nvim/highlight_defs.h b/src/nvim/highlight_defs.h
index 1e109a0316..a4dcf6eb60 100644
--- a/src/nvim/highlight_defs.h
+++ b/src/nvim/highlight_defs.h
@@ -22,10 +22,11 @@ typedef enum {
   HL_UNDERCURL       = 0x18,
   HL_UNDERDOTTED     = 0x20,
   HL_UNDERDASHED     = 0x28,
-                       // 0x30 and 0x38 spare for underline styles
+  // 0x30 and 0x38 spare for underline styles
   HL_STANDOUT      = 0x0040,
   HL_STRIKETHROUGH = 0x0080,
-  // 0x0100-0x0200 spare
+  HL_ALTFONT       = 0x0100,
+  // 0x0200 spare
   HL_NOCOMBINE     = 0x0400,
   HL_BG_INDEXED    = 0x0800,
   HL_FG_INDEXED    = 0x1000,
diff --git a/src/nvim/highlight_group.c b/src/nvim/highlight_group.c
index 373ce32e05..5b1ea9967d 100644
--- a/src/nvim/highlight_group.c
+++ b/src/nvim/highlight_group.c
@@ -67,11 +67,13 @@ Map(cstr_t, int) highlight_unames = MAP_INIT;
 static char *(hl_name_table[]) =
 { "bold", "standout", "underline",
   "undercurl", "underdouble", "underdotted", "underdashed",
-  "italic", "reverse", "inverse", "strikethrough", "nocombine", "NONE" };
+  "italic", "reverse", "inverse", "strikethrough", "altfont",
+  "nocombine", "NONE" };
 static int hl_attr_table[] =
 { HL_BOLD, HL_STANDOUT, HL_UNDERLINE,
   HL_UNDERCURL, HL_UNDERDOUBLE, HL_UNDERDOTTED, HL_UNDERDASHED,
-  HL_ITALIC, HL_INVERSE, HL_INVERSE, HL_STRIKETHROUGH, HL_NOCOMBINE, 0 };
+  HL_ITALIC, HL_INVERSE, HL_INVERSE, HL_STRIKETHROUGH, HL_ALTFONT,
+  HL_NOCOMBINE, 0 };
 
 /// Structure that stores information about a highlight group.
 /// The ID of a highlight group is also called group ID.  It is the index in
@@ -1595,7 +1597,12 @@ const char *highlight_has_attr(const int id, const int flag, const int modec)
     attr = hl_table[id - 1].sg_cterm;
   }
 
-  return (attr & flag) ? "1" : NULL;
+  if (flag & HL_UNDERLINE_MASK) {
+    int ul = attr & HL_UNDERLINE_MASK;
+    return ul == flag ? "1" : NULL;
+  } else {
+    return (attr & flag) ? "1" : NULL;
+  }
 }
 
 /// Return color name of the given highlight group