implement header subtitle widget

src/app/browser/header/main/subtitle.cpp

@@ -0,0 +1,36 @@
+#include "subtitle.hpp"
+
+using namespace app::browser::header::main;
+
+Subtitle::Subtitle()
+{
+    add_css_class(
+        "subtitle"
+    );
+
+    set_single_line_mode(
+        true
+    );
+
+    set_ellipsize(
+        Pango::EllipsizeMode::END
+    );
+
+    set_valign(
+        Gtk::Align::CENTER
+    );
+
+    set_width_chars(
+        WIDTH_CHARS
+    );
+}
+
+Subtitle::~Subtitle() = default;
+
+void Subtitle::set(
+    const Glib::ustring & TEXT
+) {
+    set_text(
+        TEXT
+    );
+}

src/app/browser/header/main/subtitle.hpp

@@ -0,0 +1,27 @@
+#ifndef APP_BROWSER_HEADER_MAIN_SUBTITLE_HPP
+#define APP_BROWSER_HEADER_MAIN_SUBTITLE_HPP
+
+#include <glibmm/ustring.h>
+#include <gtkmm/enums.h>
+#include <gtkmm/label.h>
+#include <pangomm/layout.h>
+
+namespace app::browser::header::main
+{
+    class Subtitle : public Gtk::Label
+    {
+        const int WIDTH_CHARS = 5;
+
+        public:
+
+            Subtitle();
+
+            ~Subtitle();
+
+            void set(
+                const Glib::ustring & TEXT
+            );
+    };
+}
+
+#endif // APP_BROWSER_HEADER_MAIN_SUBTITLE_HPP