Add /clear chat command

src/chat_command_handler.cpp

@@ -135,4 +135,8 @@ void chat_command_handler::do_info() {
 	chat_handler_.send_to_server(data);
 }
 
+void chat_command_handler::do_clear_messages() {
+	chat_handler_.clear_messages();
+}
+
 }

src/chat_command_handler.hpp

@@ -40,6 +40,7 @@ protected:
 	void do_remove();
 	void do_display();
 	void do_version();
+	void do_clear_messages();
 
 	/** Request information about a user from the server. */
 	void do_info();
@@ -113,6 +114,8 @@ protected:
 			_("Display version information."));
 		register_command("info", &chat_command_handler::do_info,
 			_("Request information about a nickname."), _("<nickname>"));
+		register_command("clear", &chat_command_handler::do_clear_messages,
+			_("Clear chat history."));
 	}
 private:
 	chat_handler& chat_handler_;

src/chat_events.hpp

@@ -64,6 +64,8 @@ protected:
 
 	void change_logging(const std::string& data);
 
+	virtual void clear_messages() = 0;
+
 	friend class chat_command_handler;
 };
 

src/gui/widgets/chatbox.cpp

@@ -226,8 +226,9 @@ void chatbox::append_to_chatbox(const std::string& text, std::size_t id, const b
 	const bool chatbox_at_end = log.vertical_scrollbar_at_end();
 	const unsigned chatbox_position = log.get_vertical_scrollbar_item_position();
 
+	const std::string before_message = log.get_label().empty() ? "" : "\n";
 	const std::string new_text = formatter()
-		<< log.get_label() << "\n" << "<span color='#bcb088'>" << preferences::get_chat_timestamp(std::time(0)) << text << "</span>";
+		<< log.get_label() << before_message << "<span color='#bcb088'>" << preferences::get_chat_timestamp(std::time(0)) << text << "</span>";
 
 	log.set_use_markup(true);
 	log.set_label(new_text);
@@ -255,6 +256,14 @@ void chatbox::send_chat_message(const std::string& message, bool /*allies_only*/
 	send_to_server(c);
 }
 
+void chatbox::clear_messages()
+{
+	const auto id = active_window_;
+	grid& grid = chat_log_container_->page_grid(id);
+	scroll_label& log = find_widget<scroll_label>(&grid, "log_text", false);
+	log.set_label("");
+}
+
 void chatbox::user_relation_changed(const std::string& /*name*/)
 {
 	if(active_window_changed_callback_) {

src/gui/widgets/chatbox.hpp

@@ -205,6 +205,8 @@ public:
 	/** Inherited form @ref chat_handler */
 	virtual void send_chat_message(const std::string& message, bool allies_only) override;
 
+	virtual void clear_messages() override;
+
 	/**
 	 * Switch to the window given by a valid pointer (e.g. received from a call
 	 * to *_window_open)

src/menu_events.hpp

@@ -96,7 +96,7 @@ public:
 	void user_command();
 	void custom_command();
 	void ai_formula();
-	void clear_messages();
+	virtual void clear_messages() override;
 	std::vector<std::string> get_commands_list();
 
 	unit_map::iterator current_unit();

src/tests/gui/test_gui2.cpp

@@ -871,6 +871,7 @@ class fake_chat_handler : public events::chat_handler {
 		MESSAGE_TYPE) {}
 	void send_chat_message(const std::string&, bool) {}
 	void send_to_server(const config&) {}
+	void clear_messages() {}
 };
 
 template<>