cancel faction_select when the game starts

or when the hosts assigned  control of  that side to another player.

(cherry-picked from commit 2dd6557449)

src/gui/dialogs/multiplayer/faction_select.cpp

@@ -52,11 +52,19 @@ faction_select::faction_select(ng::flg_manager& flg_manager, const std::string&
 	, last_faction_(flg_manager.current_faction_index())
 	, last_leader_(flg_manager.current_leader_index())
 	, last_gender_(flg_manager.current_gender_index())
+	, w_(nullptr)
 {
 }
 
+void faction_select::cancel()
+{
+	if(w_) {
+		w_->set_retval(retval::CANCEL);
+	}
+}
 void faction_select::pre_show(window& window)
 {
+	w_ = &window;
 	find_widget<label>(&window, "starting_pos", false).set_label(std::to_string(side_));
 
 	//

src/gui/dialogs/multiplayer/faction_select.hpp

@@ -32,6 +32,9 @@ public:
 
 	DEFINE_SIMPLE_EXECUTE_WRAPPER(faction_select)
 
+	void cancel();
+	
+	int get_side_num() const { return side_; }
 private:
 	ng::flg_manager& flg_manager_;
 
@@ -43,6 +46,7 @@ private:
 
 	const int last_faction_, last_leader_, last_gender_;
 
+	gui2::window* w_;
 	/** Inherited from modal_dialog, implemented by REGISTER_DIALOG. */
 	virtual const std::string& window_id() const override;
 

src/gui/dialogs/multiplayer/mp_join_game.cpp

@@ -45,6 +45,7 @@
 #include "mp_ui_alerts.hpp"
 #include "statistics.hpp"
 #include "units/types.hpp"
+#include "utils/scope_exit.hpp"
 #include "wesnothd_connection.hpp"
 
 
@@ -72,6 +73,7 @@ mp_join_game::mp_join_game(saved_game& state, mp::lobby_info& lobby_info, wesnot
 	, observe_game_(observe_game)
 	, stop_updates_(false)
 	, player_list_(nullptr)
+	, open_flg_dialog_(nullptr)
 {
 	set_show_even_without_video(true);
 }
@@ -350,9 +352,15 @@ void mp_join_game::show_flg_select(int side_num)
 
 		ng::flg_manager flg(era_factions, side_choice, lock_settings, use_map_settings, saved_game);
 
-		gui2::dialogs::faction_select dlg(flg, color, side_num);
-		dlg.show();
 
+		gui2::dialogs::faction_select dlg(flg, color, side_num);
+
+
+		{
+			open_flg_dialog_ = &dlg;
+			utils::scope_exit se([this](){ open_flg_dialog_ = nullptr; });
+			dlg.show();
+		}
 		if(dlg.get_retval() != gui2::retval::OK) {
 			return;
 		}
@@ -518,11 +526,20 @@ void mp_join_game::network_handler(window& window)
 	}
 
 	if(data["failed"].to_bool()) {
+		if(open_flg_dialog_) {
+			open_flg_dialog_->cancel();
+		}
 		window.set_retval(retval::CANCEL);
 	} else if(data.child("start_game")) {
+		if(open_flg_dialog_) {
+			open_flg_dialog_->cancel();
+		}
 		level_["started"] = true;
 		window.set_retval(retval::OK);
 	} else if(data.child("leave_game")) {
+		if(open_flg_dialog_) {
+			open_flg_dialog_->cancel();
+		}
 		window.set_retval(retval::CANCEL);
 	}
 
@@ -537,6 +554,10 @@ void mp_join_game::network_handler(window& window)
 		if(config& side_to_change = get_scenario().find_child("side", "side", change["side"])) {
 			side_to_change.merge_with(change);
 		}
+		if(open_flg_dialog_ && open_flg_dialog_->get_side_num() == change["side"].to_int()) {
+			open_flg_dialog_->cancel();
+		}
+
 	} else if(data.has_child("scenario") || data.has_child("snapshot") || data.child("next_scenario")) {
 		level_ = first_scenario_ ? data : data.child("next_scenario");
 

src/gui/dialogs/multiplayer/mp_join_game.hpp

@@ -31,6 +31,7 @@ class tree_view_node;
 
 namespace dialogs
 {
+class faction_select;
 
 class mp_join_game : public modal_dialog, private plugin_executor
 {
@@ -78,6 +79,8 @@ private:
 	std::map<std::string, tree_view_node*> team_tree_map_;
 
 	std::unique_ptr<player_list_helper> player_list_;
+
+	gui2::dialogs::faction_select* open_flg_dialog_;
 };
 
 } // namespace dialogs

src/utils/scope_exit.hpp

@@ -0,0 +1,30 @@
+/*
+   Copyright (C) 2003 - 2018 the Battle for Wesnoth Project http://www.wesnoth.org/
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY.
+
+   See the COPYING file for more details.
+*/
+
+#pragma once
+
+#include "global.hpp"
+
+#include <functional>
+
+namespace utils {
+
+class scope_exit {
+	//TODO: with c++17 we could make this a template class with 'F f_' instead of 'std::function<void ()> f_';
+	std::function<void ()> f_;
+public:
+	template<typename F>
+	explicit scope_exit(F&& f) : f_(f) {}
+	~scope_exit() { if(f_) { f_(); }}
+};
+} // namespace utils