Add support for double underline

8 files changed, 26 insertions, 17 deletions

diff --git a/doc/json_ui.asciidoc b/doc/json_ui.asciidoc
index 0fc0378b..63c5f325 100644
--- a/doc/json_ui.asciidoc
+++ b/doc/json_ui.asciidoc
@@ -15,7 +15,7 @@ Kakoune won't be able to parse named parameters in requests.
 Here are the data structures used:
 
 * Color: a string, either a named color, or #rrggbb, or 'default'
-* Attribute: one of {underline, reverse, blink, bold, dim, italic, final_fg, final_bg, final_attr}
+* Attribute: one of {underline, curly_underline, double_underline, reverse, blink, bold, dim, italic, final_fg, final_bg, final_attr}
 * Face { Color fg; Color bg; Array<Attribute> attributes; }
 * Atom { Face face; String contents; }
 * Line : Array of Atom
diff --git a/doc/pages/changelog.asciidoc b/doc/pages/changelog.asciidoc
index a553433a..3a6804e5 100644
--- a/doc/pages/changelog.asciidoc
+++ b/doc/pages/changelog.asciidoc
@@ -6,6 +6,7 @@ released versions.
 == Development version
 
 * Expose env vars that are mentionned in the arguments passed to shell expansions
+* Support for colored double underlines
 
 == Kakoune 2024.05.18
 
diff --git a/doc/pages/faces.asciidoc b/doc/pages/faces.asciidoc
index b7c6ad44..1b9ef468 100644
--- a/doc/pages/faces.asciidoc
+++ b/doc/pages/faces.asciidoc
@@ -33,6 +33,9 @@ attributes::
         *c*:::
             curly underline
             Note: This takes precedence over underline if both are specified.
+        *U*:::
+            double underline
+            Note: This takes precedence over underline and curly underline if also specified.
         *r*:::
             reverse
         *b*:::
diff --git a/src/commands.cc b/src/commands.cc
index d22c0647..e4a41ead 100644
--- a/src/commands.cc
+++ b/src/commands.cc
@@ -2482,8 +2482,9 @@ const CommandDesc set_face_cmd = {
     "    <fg color>[,<bg color>[,<underline color>]][+<attributes>][@<base>]\n"
     "colors are either a color name, rgb:######, or rgba:######## values.\n"
     "attributes is a combination of:\n"
-    "    u: underline, c: curly underline, i: italic, b: bold,\n"
-    "    r: reverse,   s: strikethrough,   B: blink,  d: dim,\n"
+    "    u: underline, c: curly underline, U: double underline,\n"
+    "    i: italic,            b: bold,            r: reverse,\n"
+    "    s: strikethrough,     B: blink,           d: dim,\n"
     "    f: final foreground,              g: final background,\n"
     "    a: final attributes,              F: same as +fga\n"
     "facespec can as well just be the name of another face.\n"
diff --git a/src/face.hh b/src/face.hh
index 1ed986ef..7e887705 100644
--- a/src/face.hh
+++ b/src/face.hh
@@ -9,19 +9,20 @@ namespace Kakoune
 
 enum class Attribute : int
 {
-    Normal         = 0,
-    Underline      = 1 << 1,
-    CurlyUnderline = 1 << 2,
-    Reverse        = 1 << 3,
-    Blink          = 1 << 4,
-    Bold           = 1 << 5,
-    Dim            = 1 << 6,
-    Italic         = 1 << 7,
-    Strikethrough  = 1 << 8,
-    FinalFg        = 1 << 9,
-    FinalBg        = 1 << 10,
-    FinalAttr      = 1 << 11,
-    Final          = FinalFg | FinalBg | FinalAttr
+    Normal          = 0,
+    Underline       = 1 << 1,
+    CurlyUnderline  = 1 << 2,
+    DoubleUnderline = 1 << 3,
+    Reverse         = 1 << 4,
+    Blink           = 1 << 5,
+    Bold            = 1 << 6,
+    Dim             = 1 << 7,
+    Italic          = 1 << 8,
+    Strikethrough   = 1 << 9,
+    FinalFg         = 1 << 10,
+    FinalBg         = 1 << 11,
+    FinalAttr       = 1 << 12,
+    Final           = FinalFg | FinalBg | FinalAttr
 };
 
 constexpr bool with_bit_ops(Meta::Type<Attribute>) { return true; }
diff --git a/src/face_registry.cc b/src/face_registry.cc
index d6c5cd53..ebb71986 100644
--- a/src/face_registry.cc
+++ b/src/face_registry.cc
@@ -50,6 +50,7 @@ FaceSpec parse_face(StringView facedesc)
             {
                 case 'u': face.attributes |= Attribute::Underline; break;
                 case 'c': face.attributes |= Attribute::CurlyUnderline; break;
+                case 'U': face.attributes |= Attribute::DoubleUnderline; break;
                 case 'r': face.attributes |= Attribute::Reverse; break;
                 case 'b': face.attributes |= Attribute::Bold; break;
                 case 'B': face.attributes |= Attribute::Blink; break;
@@ -78,6 +79,7 @@ String to_string(Attribute attributes)
     attrs[] {
         { Attribute::Underline, "u" },
         { Attribute::CurlyUnderline, "c" },
+        { Attribute::DoubleUnderline, "U" },
         { Attribute::Reverse, "r" },
         { Attribute::Blink, "B" },
         { Attribute::Bold, "b" },
diff --git a/src/json_ui.cc b/src/json_ui.cc
index 01768897..66674cf7 100644
--- a/src/json_ui.cc
+++ b/src/json_ui.cc
@@ -39,6 +39,7 @@ String to_json(Attribute attributes)
     attrs[] {
         { Attribute::Underline, "underline" },
         { Attribute::CurlyUnderline, "curly_underline" },
+        { Attribute::DoubleUnderline, "double_underline" },
         { Attribute::Reverse, "reverse" },
         { Attribute::Blink, "blink" },
         { Attribute::Bold, "bold" },
diff --git a/src/terminal_ui.cc b/src/terminal_ui.cc
index 33574e90..912dfb57 100644
--- a/src/terminal_ui.cc
+++ b/src/terminal_ui.cc
@@ -224,7 +224,7 @@ void TerminalUI::Screen::set_face(const Face& face, Writer& writer)
     static constexpr int fg_table[]{ 39, 30, 31, 32, 33, 34, 35, 36, 37, 90, 91, 92, 93, 94, 95, 96, 97 };
     static constexpr int bg_table[]{ 49, 40, 41, 42, 43, 44, 45, 46, 47, 100, 101, 102, 103, 104, 105, 106, 107 };
     static constexpr int ul_table[]{ 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
-    static constexpr const char* attr_table[]{ "0", "4", "4:3", "7", "5", "1", "2", "3", "9" };
+    static constexpr const char* attr_table[]{ "0", "4", "4:3", "21", "7", "5", "1", "2", "3", "9" };
 
     auto set_color = [&](bool fg, const Color& color, bool join) {
         if (join)