GUI2/Menu Button: changed callbacks to NOTIFY_MODIFIED ones

menu_button doesn't even actually inherit from clickable_item. The only reason
[dis]connect_click_handler was declared in this class is the original implementation
was copied extensively from the Button widget.

Using NOTIFY_MODIFIED also means callbacks can fire if set_value/set_selected is used
on a menu_button.

The [dis]connect_click_handler functions were also removed from multimenu_button. All
callbacks for this widget type already used NOTIFY_MODIFIED signals.

src/gui/dialogs/addon/manager.cpp

@@ -336,7 +336,9 @@ void addon_manager::pre_show(window& window)
 	}
 
 	status_filter.set_values(status_filter_entries);
-	status_filter.connect_click_handler(std::bind(&addon_manager::apply_filters, this, std::ref(window)));
+
+	connect_signal_notify_modified(status_filter,
+		std::bind(&addon_manager::apply_filters, this, std::ref(window)));
 
 	multimenu_button& type_filter = find_widget<multimenu_button>(&window, "type_filter", false);
 
@@ -347,7 +349,8 @@ void addon_manager::pre_show(window& window)
 
 	type_filter.set_values(type_filter_entries);
 
-	connect_signal_notify_modified(type_filter, std::bind(&addon_manager::apply_filters, this, std::ref(window)));
+	connect_signal_notify_modified(type_filter,
+		std::bind(&addon_manager::apply_filters, this, std::ref(window)));
 
 	menu_button& order_dropdown = find_widget<menu_button>(&window, "order_dropdown", false);
 
@@ -366,7 +369,9 @@ void addon_manager::pre_show(window& window)
 	}
 
 	order_dropdown.set_values(order_dropdown_entries);
-	order_dropdown.connect_click_handler(std::bind(&addon_manager::order_addons, this, std::ref(window)));
+
+	connect_signal_notify_modified(order_dropdown,
+		std::bind(&addon_manager::order_addons, this, std::ref(window)));
 
 	button& url_go_button = find_widget<button>(&window, "url_go", false);
 	button& url_copy_button = find_widget<button>(&window, "url_copy", false);

src/gui/dialogs/multiplayer/faction_select.cpp

@@ -72,7 +72,7 @@ void faction_select::pre_show(window& window)
 	//
 	// Set up leader menu button
 	//
-	find_widget<menu_button>(&window, "leader_menu", false).connect_click_handler(
+	connect_signal_notify_modified(find_widget<menu_button>(&window, "leader_menu", false),
 		std::bind(&faction_select::on_leader_select, this, std::ref(window)));
 
 	//

src/gui/dialogs/multiplayer/lobby.cpp

@@ -769,8 +769,8 @@ void mp_lobby::pre_show(window& window)
 		replay_options.set_selected(2);
 	}
 
-	replay_options.connect_click_handler(
-			std::bind(&mp_lobby::skip_replay_changed_callback, this, std::ref(window)));
+	connect_signal_notify_modified(replay_options,
+		std::bind(&mp_lobby::skip_replay_changed_callback, this, std::ref(window)));
 
 	filter_friends_ = find_widget<toggle_button>(&window, "filter_with_friends", false, true);
 	filter_ignored_ = find_widget<toggle_button>(&window, "filter_without_ignored", false, true);

src/gui/dialogs/multiplayer/mp_create_game.cpp

@@ -205,7 +205,9 @@ void mp_create_game::pre_show(window& win)
 	};
 
 	game_menu_button.set_values(game_types, get_initial_type_index());
-	game_menu_button.connect_click_handler(std::bind(&mp_create_game::update_games_list, this, std::ref(win)));
+
+	connect_signal_notify_modified(game_menu_button,
+		std::bind(&mp_create_game::update_games_list, this, std::ref(win)));
 
 	//
 	// Set up mods list
@@ -256,7 +258,9 @@ void mp_create_game::pre_show(window& win)
 	}
 
 	eras_menu_button_->set_values(era_names);
-	eras_menu_button_->connect_click_handler(std::bind(&mp_create_game::on_era_select, this, std::ref(win)));
+
+	connect_signal_notify_modified(*eras_menu_button_,
+		std::bind(&mp_create_game::on_era_select, this, std::ref(win)));
 
 	const int era_selection = create_engine_.find_extra_by_id(ng::create_engine::ERA, preferences::era());
 	if(era_selection >= 0) {
@@ -289,7 +293,9 @@ void mp_create_game::pre_show(window& win)
 	menu_button& rfm_menu_button = find_widget<menu_button>(&win, "random_faction_mode", false);
 
 	rfm_menu_button.set_values(rfm_options, initial_index);
-	rfm_menu_button.connect_click_handler(std::bind(&mp_create_game::on_random_faction_mode_select, this, std::ref(win)));
+
+	connect_signal_notify_modified(rfm_menu_button,
+		std::bind(&mp_create_game::on_random_faction_mode_select, this, std::ref(win)));
 
 	on_random_faction_mode_select(win);
 

src/gui/dialogs/multiplayer/mp_options_helper.cpp

@@ -282,7 +282,7 @@ void mp_options_helper::display_custom_options(const std::string& type, int node
 					menu->set_selected(std::distance(combo_values.begin(), iter));
 				}
 
-				menu->connect_click_handler(
+				connect_signal_notify_modified(*menu,
 					std::bind(&mp_options_helper::update_options_data_map_menu_button, this, menu, visible_options_.back(), option_cfg));
 
 			} else if(opt.key == "slider") {

src/gui/dialogs/multiplayer/mp_staging.cpp

@@ -210,7 +210,9 @@ void mp_staging::add_side_node(window& window, ng::side_engine_ptr side)
 	menu_button& ai_selection = find_widget<menu_button>(&row_grid, "ai_controller", false);
 
 	ai_selection.set_values(ai_options, selection);
-	ai_selection.connect_click_handler(std::bind(&mp_staging::on_ai_select, this, side, std::ref(ai_selection)));
+
+	connect_signal_notify_modified(ai_selection,
+		std::bind(&mp_staging::on_ai_select, this, side, std::ref(ai_selection)));
 
 	on_ai_select(side, ai_selection);
 
@@ -226,7 +228,9 @@ void mp_staging::add_side_node(window& window, ng::side_engine_ptr side)
 
 	controller_selection.set_values(controller_names, side->current_controller_index());
 	controller_selection.set_active(controller_names.size() > 1);
-	controller_selection.connect_click_handler(std::bind(&mp_staging::on_controller_select, this, side, std::ref(row_grid)));
+
+	connect_signal_notify_modified(controller_selection,
+		std::bind(&mp_staging::on_controller_select, this, side, std::ref(row_grid)));
 
 	on_controller_select(side, row_grid);
 
@@ -275,7 +279,9 @@ void mp_staging::add_side_node(window& window, ng::side_engine_ptr side)
 
 	team_selection.set_values(team_names, initial_team_selection);
 	team_selection.set_active(!saved_game);
-	team_selection.connect_click_handler(std::bind(&mp_staging::on_team_select, this, std::ref(window), side, std::ref(team_selection), _3, _4));
+
+	connect_signal_notify_modified(team_selection,
+		std::bind(&mp_staging::on_team_select, this, std::ref(window), side, std::ref(team_selection), _3, _4));
 
 	//
 	// Colors
@@ -293,7 +299,9 @@ void mp_staging::add_side_node(window& window, ng::side_engine_ptr side)
 	color_selection.set_values(color_options, side->color());
 	color_selection.set_active(!saved_game);
 	color_selection.set_use_markup(true);
-	color_selection.connect_click_handler(std::bind(&mp_staging::on_color_select, this, side, std::ref(row_grid)));
+
+	connect_signal_notify_modified(color_selection,
+		std::bind(&mp_staging::on_color_select, this, side, std::ref(row_grid)));
 
 	//
 	// Gold and Income

src/gui/dialogs/preferences_dialog.cpp

@@ -441,9 +441,8 @@ void preferences_dialog::post_build(window& window)
 
 	set_resolution_list(res_list, window.video());
 
-	res_list.connect_click_handler(
-			std::bind(&preferences_dialog::handle_res_select,
-			this, std::ref(window)));
+	connect_signal_notify_modified(res_list,
+		std::bind(&preferences_dialog::handle_res_select, this, std::ref(window)));
 
 	/* SHOW FLOATING LABELS */
 	register_bool("show_floating_labels", true,

src/gui/dialogs/statistics_dialog.cpp

@@ -73,7 +73,9 @@ void statistics_dialog::pre_show(window& window)
 	menu_button& scenario_menu = find_widget<menu_button>(&window, "scenario_menu", false);
 
 	scenario_menu.set_values(menu_items, selection_index_);
-	scenario_menu.connect_click_handler(std::bind(&statistics_dialog::on_scenario_select, this, std::ref(window)));
+
+	connect_signal_notify_modified(scenario_menu,
+		std::bind(&statistics_dialog::on_scenario_select, this, std::ref(window)));
 
 	//
 	// Set up primary stats list

src/gui/widgets/menu_button.hpp

@@ -54,18 +54,6 @@ public:
 	/** See @ref styled_widget::get_state. */
 	virtual unsigned get_state() const override;
 
-	/** Inherited from clickable_item. */
-	void connect_click_handler(const event::signal_function& signal)
-	{
-		connect_signal_mouse_left_click(*this, signal);
-	}
-
-	/** Inherited from clickable_item. */
-	void disconnect_click_handler(const event::signal_function& signal)
-	{
-		disconnect_signal_mouse_left_click(*this, signal);
-	}
-
 	/***** ***** ***** setters / getters for members ***** ****** *****/
 
 	void set_values(const std::vector<::config>& values, int selected = 0);

src/gui/widgets/multimenu_button.hpp

@@ -54,18 +54,6 @@ public:
 	/** See @ref styled_widget::get_state. */
 	virtual unsigned get_state() const override;
 
-	/** Inherited from clickable_item. */
-	void connect_click_handler(const event::signal_function& signal)
-	{
-		connect_signal_mouse_left_click(*this, signal);
-	}
-
-	/** Inherited from clickable_item. */
-	void disconnect_click_handler(const event::signal_function& signal)
-	{
-		disconnect_signal_mouse_left_click(*this, signal);
-	}
-
 	/***** ***** ***** setters / getters for members ***** ****** *****/
 
 	/**