Add support for italic text attribute

README.asciidoc

@@ -781,6 +781,9 @@ attributes is a string of letters each defining an attributes:
  * `u`: Underline
  * `r`: Reverse
  * `b`: Bold
+ * `B`: Blink
+ * `d`: Dim
+ * `i`: Italic
 
 Using named faces instead of facespec permits to change the effective faces
 afterwards.

src/face.hh

@@ -14,7 +14,8 @@ enum class Attribute : int
     Reverse   = 1 << 2,
     Blink     = 1 << 3,
     Bold      = 1 << 4,
-    Dim       = 1 << 5
+    Dim       = 1 << 5,
+    Italic    = 1 << 6,
 };
 
 template<> struct WithBitOps<Attribute> : std::true_type {};

src/face_registry.cc

@@ -28,6 +28,7 @@ static Face parse_face(StringView facedesc)
                 case 'b': res.attributes |= Attribute::Bold; break;
                 case 'B': res.attributes |= Attribute::Blink; break;
                 case 'd': res.attributes |= Attribute::Dim; break;
+                case 'i': res.attributes |= Attribute::Italic; break;
                 default: throw runtime_error(format("unknown face attribute '{}'", StringView{*attr_it}));
             }
         }

src/ncurses_ui.cc

@@ -241,6 +241,9 @@ void set_face(WINDOW* window, Face face, const Face& default_face)
     set_attribute(window, A_BLINK, face.attributes & Attribute::Blink);
     set_attribute(window, A_BOLD, face.attributes & Attribute::Bold);
     set_attribute(window, A_DIM, face.attributes & Attribute::Dim);
+    #if defined(A_ITALIC)
+    set_attribute(window, A_ITALIC, face.attributes & Attribute::Italic);
+    #endif
 }
 
 static sig_atomic_t resize_pending = 0;