support loading gui2 themes from add-ons

Requires a `gui-theme.cfg` file in Add-on root with a `[gui]` tag.
(Add-ons without all buttons in title_screen may get flagged as defunct.)

changelog_entries/gui2-theme-support-in-addons.md

@@ -0,0 +1,5 @@
+ ### User interface
+    GUI2 themes can be loaded from add-ons. Requires a `gui-theme.cfg` file in add-on root with a `[gui]` tag that acts as the entry point for the theme.
+
+ ### Lua API
+    Added new function gui.switch_theme() to allow switching to another gui2 theme from inside a scenario.

data/schema/gui/widget_definitions.cfg

@@ -867,6 +867,8 @@
     min="0"
     max="infinite"
     super="$generic/widget_definition"
+    {REQUIRED_KEY "id" string}
+    {REQUIRED_KEY "description" string}
     [tag]
         name="resolution"
         min="0"

src/game_initialization/playcampaign.cpp

@@ -28,6 +28,7 @@
 #include "game_initialization/multiplayer.hpp"
 #include "generators/map_generator.hpp"
 #include "gettext.hpp"
+#include "gui/gui.hpp"
 #include "gui/dialogs/message.hpp"
 #include "gui/dialogs/outro.hpp"
 #include "gui/widgets/retval.hpp"
@@ -204,7 +205,6 @@ level_result::type campaign_controller::play_game()
 					gui2::dialogs::outro::display(state_.classification());
 				}
 			}
-
 			return res;
 		} else if(res == level_result::type::observer_end && mp_info_ && !mp_info_->is_host) {
 			const int dlg_res = gui2::show_message(_("Game Over"),
@@ -291,3 +291,10 @@ level_result::type campaign_controller::play_game()
 
 	return level_result::type::victory;
 }
+
+campaign_controller::~campaign_controller()
+{
+	// If the scenario changed the current gui2 theme,
+	// change it back to the value stored in preferences
+	gui2::switch_theme(prefs::get().gui2_theme());
+}

src/game_initialization/playcampaign.hpp

@@ -56,6 +56,8 @@ public:
 	{
 	}
 
+	~campaign_controller();
+
 	level_result::type play_game();
 	level_result::type play_replay()
 	{

src/gui/dialogs/title_screen.cpp

@@ -86,18 +86,19 @@ title_screen::~title_screen()
 {
 }
 
-using btn_callback = std::function<void()>;
-
-static void register_button(window& win, const std::string& id, hotkey::HOTKEY_COMMAND hk, btn_callback callback)
+void title_screen::register_button(const std::string& id, hotkey::HOTKEY_COMMAND hk, std::function<void()> callback)
 {
 	if(hk != hotkey::HOTKEY_NULL) {
-		win.register_hotkey(hk, std::bind(callback));
+		register_hotkey(hk, std::bind(callback));
 	}
 
-	auto b = find_widget<button>(&win, id, false, false);
-	if(b != nullptr)
-	{
-		connect_signal_mouse_left_click(*b, std::bind(callback));
+	try {
+		button& btn = find_widget<button>(this, id, false);
+		connect_signal_mouse_left_click(btn, std::bind(callback));
+	} catch(const wml_exception& e) {
+		ERR_GUI_P << e.user_message;
+		prefs::get().set_gui2_theme("default");
+		set_retval(RELOAD_UI);
 	}
 }
 
@@ -235,16 +236,16 @@ void title_screen::init_callbacks()
 		update_tip(true);
 	}
 
-	register_button(*this, "next_tip", hotkey::TITLE_SCREEN__NEXT_TIP,
+	register_button("next_tip", hotkey::TITLE_SCREEN__NEXT_TIP,
 		std::bind(&title_screen::update_tip, this, true));
 
-	register_button(*this, "previous_tip", hotkey::TITLE_SCREEN__PREVIOUS_TIP,
+	register_button("previous_tip", hotkey::TITLE_SCREEN__PREVIOUS_TIP,
 		std::bind(&title_screen::update_tip, this, false));
 
 	//
 	// Help
 	//
-	register_button(*this, "help", hotkey::HOTKEY_HELP, []() {
+	register_button("help", hotkey::HOTKEY_HELP, []() {
 		if(gui2::new_widgets) {
 			gui2::dialogs::help_browser::display();
 		}
@@ -255,12 +256,12 @@ void title_screen::init_callbacks()
 	//
 	// About
 	//
-	register_button(*this, "about", hotkey::HOTKEY_NULL, std::bind(&game_version::display<>));
+	register_button("about", hotkey::HOTKEY_NULL, std::bind(&game_version::display<>));
 
 	//
 	// Campaign
 	//
-	register_button(*this, "campaign", hotkey::TITLE_SCREEN__CAMPAIGN, [this]() {
+	register_button("campaign", hotkey::TITLE_SCREEN__CAMPAIGN, [this]() {
 		try{
 			if(game_.new_campaign()) {
 				// Suspend drawing of the title screen,
@@ -276,13 +277,13 @@ void title_screen::init_callbacks()
 	//
 	// Multiplayer
 	//
-	register_button(*this, "multiplayer", hotkey::TITLE_SCREEN__MULTIPLAYER,
+	register_button("multiplayer", hotkey::TITLE_SCREEN__MULTIPLAYER,
 		std::bind(&title_screen::button_callback_multiplayer, this));
 
 	//
 	// Load game
 	//
-	register_button(*this, "load", hotkey::HOTKEY_LOAD_GAME, [this]() {
+	register_button("load", hotkey::HOTKEY_LOAD_GAME, [this]() {
 		if(game_.load_game()) {
 			// Suspend drawing of the title screen,
 			// so it doesn't flicker in between loading screens.
@@ -294,7 +295,7 @@ void title_screen::init_callbacks()
 	//
 	// Addons
 	//
-	register_button(*this, "addons", hotkey::TITLE_SCREEN__ADDONS, [this]() {
+	register_button("addons", hotkey::TITLE_SCREEN__ADDONS, [this]() {
 		if(manage_addons()) {
 			set_retval(RELOAD_GAME_DATA);
 		}
@@ -303,7 +304,7 @@ void title_screen::init_callbacks()
 	//
 	// Editor
 	//
-	register_button(*this, "editor", hotkey::TITLE_SCREEN__EDITOR, [this]() { set_retval(MAP_EDITOR); });
+	register_button("editor", hotkey::TITLE_SCREEN__EDITOR, [this]() { set_retval(MAP_EDITOR); });
 
 	//
 	// Cores
@@ -314,7 +315,7 @@ void title_screen::init_callbacks()
 	//
 	// Language
 	//
-	register_button(*this, "language", hotkey::HOTKEY_LANGUAGE, [this]() {
+	register_button("language", hotkey::HOTKEY_LANGUAGE, [this]() {
 		try {
 			if(game_.change_language()) {
 				on_resize();
@@ -328,53 +329,32 @@ void title_screen::init_callbacks()
 	//
 	// Preferences
 	//
-	register_button(*this, "preferences", hotkey::HOTKEY_PREFERENCES, [this]() {
-		gui2::dialogs::preferences_dialog pref_dlg;
-		pref_dlg.show();
-		if (pref_dlg.get_retval() == RELOAD_UI) {
-			set_retval(RELOAD_UI);
-		}
-
-		// Currently blurred windows don't capture well if there is something
-		// on top of them at the time of blur. Resizing the game window in
-		// preferences will cause the title screen tip and menu panels to
-		// capture the prefs dialog in their blur. This workaround simply
-		// forces them to re-capture the blur after the dialog closes.
-		panel* tip_panel = find_widget<panel>(this, "tip_panel", false, false);
-		if(tip_panel != nullptr) {
-			tip_panel->get_canvas(tip_panel->get_state()).queue_reblur();
-			tip_panel->queue_redraw();
-		}
-		panel* menu_panel = find_widget<panel>(this, "menu_panel", false, false);
-		if(menu_panel != nullptr) {
-			menu_panel->get_canvas(menu_panel->get_state()).queue_reblur();
-			menu_panel->queue_redraw();
-		}
-	});
+	register_button("preferences", hotkey::HOTKEY_PREFERENCES,
+		std::bind(&title_screen::show_preferences, this));
 
 	//
 	// Achievements
 	//
-	register_button(*this, "achievements", hotkey::HOTKEY_ACHIEVEMENTS,
+	register_button("achievements", hotkey::HOTKEY_ACHIEVEMENTS,
 		std::bind(&title_screen::show_achievements, this));
 
 	//
 	// Community
 	//
-	register_button(*this, "community", hotkey::HOTKEY_NULL,
+	register_button("community", hotkey::HOTKEY_NULL,
 		std::bind(&title_screen::show_community, this));
 
 	//
 	// Quit
 	//
-	register_button(*this, "quit", hotkey::HOTKEY_QUIT_TO_DESKTOP, [this]() { set_retval(QUIT_GAME); });
+	register_button("quit", hotkey::HOTKEY_QUIT_TO_DESKTOP, [this]() { set_retval(QUIT_GAME); });
 	// A sanity check, exit immediately if the .cfg file didn't have a "quit" button.
 	find_widget<button>(this, "quit", false, true);
 
 	//
 	// Debug clock
 	//
-	register_button(*this, "clock", hotkey::HOTKEY_NULL,
+	register_button("clock", hotkey::HOTKEY_NULL,
 		std::bind(&title_screen::show_debug_clock_window, this));
 
 	auto clock = find_widget<button>(this, "clock", false, false);
@@ -385,7 +365,7 @@ void title_screen::init_callbacks()
 	//
 	// GUI Test and Debug Window
 	//
-	register_button(*this, "test_dialog", hotkey::HOTKEY_NULL,
+	register_button("test_dialog", hotkey::HOTKEY_NULL,
 		std::bind(&title_screen::show_gui_test_dialog, this));
 
 	auto test_dialog = find_widget<button>(this, "test_dialog", false, false);
@@ -484,11 +464,6 @@ void title_screen::show_debug_clock_window()
 	}
 }
 
-void title_screen::show_gui_test_dialog()
-{
-	gui2::dialogs::gui_test_dialog::execute();
-}
-
 void title_screen::hotkey_callback_select_tests()
 {
 	game_config_manager::get()->load_game_config_for_create(false, true);
@@ -525,6 +500,36 @@ void title_screen::show_community()
 	dlg.display(4);
 }
 
+void title_screen::show_gui_test_dialog()
+{
+	gui2::dialogs::gui_test_dialog::execute();
+}
+
+void title_screen::show_preferences()
+{
+	gui2::dialogs::preferences_dialog pref_dlg;
+	pref_dlg.show();
+	if (pref_dlg.get_retval() == RELOAD_UI) {
+		set_retval(RELOAD_UI);
+	}
+
+	// Currently blurred windows don't capture well if there is something
+	// on top of them at the time of blur. Resizing the game window in
+	// preferences will cause the title screen tip and menu panels to
+	// capture the prefs dialog in their blur. This workaround simply
+	// forces them to re-capture the blur after the dialog closes.
+	panel* tip_panel = find_widget<panel>(this, "tip_panel", false, false);
+	if(tip_panel != nullptr) {
+		tip_panel->get_canvas(tip_panel->get_state()).queue_reblur();
+		tip_panel->queue_redraw();
+	}
+	panel* menu_panel = find_widget<panel>(this, "menu_panel", false, false);
+	if(menu_panel != nullptr) {
+		menu_panel->get_canvas(menu_panel->get_state()).queue_reblur();
+		menu_panel->queue_redraw();
+	}
+}
+
 void title_screen::button_callback_multiplayer()
 {
 	while(true) {

src/gui/dialogs/title_screen.hpp

@@ -71,6 +71,8 @@ private:
 
 	void init_callbacks();
 
+	void register_button(const std::string& id, hotkey::HOTKEY_COMMAND hk, std::function<void()> callback);
+
 	/***** ***** ***** ***** Callbacks ***** ***** ****** *****/
 
 	void on_resize();
@@ -91,6 +93,9 @@ private:
 	/** Shows the gui test window. */
 	void show_gui_test_dialog();
 
+	/** Shows the preferences dialog. */
+	void show_preferences();
+
 	void hotkey_callback_select_tests();
 
 	void show_achievements();

src/gui/gui.cpp

@@ -38,34 +38,94 @@ void init()
 	// Save current screen size.
 	settings::update_screen_size_variables();
 
-	//
-	// Read and validate the WML files.
-	//
-	config guis_cfg;
-	try {
-		schema_validation::schema_validator validator(filesystem::get_wml_location("schema/gui.cfg").value());
+	config guis_cfg, addons_cfg;
+	preproc_map preproc(game_config::config_cache::instance().get_preproc_map());
 
-		preproc_map preproc(game_config::config_cache::instance().get_preproc_map());
-		filesystem::scoped_istream stream = preprocess_file(filesystem::get_wml_location("gui/_main.cfg").value(), &preproc);
+	//
+	// Read and validate theme WML files from mainline
+	//
+	std::string current_file;
+	const std::string schema_file = "schema/gui.cfg";
+	try {
+		schema_validation::schema_validator validator(filesystem::get_wml_location(schema_file).value());
+
+		// Core theme files
+		current_file = "gui/_main.cfg";
+		filesystem::scoped_istream stream = preprocess_file(filesystem::get_wml_location(current_file).value(), &preproc);
 		read(guis_cfg, *stream, &validator);
+
 	} catch(const config::error& e) {
 		ERR_GUI_P << e.what();
-		ERR_GUI_P << "Setting: could not read file 'data/gui/_main.cfg'.";
+		ERR_GUI_P << "Setting: could not read gui file: " << current_file;
 	} catch(const abstract_validator::error& e) {
-		ERR_GUI_P << "Setting: could not read file 'data/schema/gui.cfg'.";
+		ERR_GUI_P << "Setting: could not read schema file: " << schema_file;
 		ERR_GUI_P << e.message;
 	}
 
 	//
-	// Parse GUI definitions.
+	// Read and validate theme WML files from addons
+	//
+
+	// Add the $user_campaign_dir/*/gui.cfg files to the addon gui config.
+	std::vector<std::string> user_dirs;
+	{
+		const std::string user_campaign_dir = filesystem::get_addons_dir();
+		std::vector<std::string> user_files;
+		filesystem::get_files_in_dir(
+			user_campaign_dir, &user_files, &user_dirs, filesystem::name_mode::ENTIRE_FILE_PATH);
+	}
+
+	for(const std::string& umc : user_dirs) {
+		try {
+			const std::string gui_file = umc + "/gui-theme.cfg";
+			current_file = filesystem::get_short_wml_path(gui_file);
+			if(filesystem::file_exists(gui_file)) {
+				config addon_cfg;
+				schema_validation::schema_validator validator(filesystem::get_wml_location(schema_file).value());
+				read(addon_cfg, *preprocess_file(gui_file, &preproc), &validator);
+				addons_cfg.append(addon_cfg);
+			}
+		} catch(const config::error& e) {
+			ERR_GUI_P << e.what();
+			ERR_GUI_P << "Setting: could not read gui file: " << current_file;
+		} catch(const abstract_validator::error& e) {
+			ERR_GUI_P << "Setting: could not read schema file: " << schema_file;
+			ERR_GUI_P << e.message;
+		}
+	}
+
+	//
+	// Parse GUI definitions from mainline
 	//
 	for(const config& g : guis_cfg.child_range("gui")) {
 		const std::string id = g["id"];
 
-		auto iter = guis.emplace(id, gui_definition(g)).first;
+		auto [iter, is_unique] = guis.try_emplace(id, g);
 
-		if(id == "default") {
-			default_gui = iter;
+		if (!is_unique) {
+			ERR_GUI_P << "GUI Theme ID '" << id << "' already exists.";
+		} else {
+			if(id == "default") {
+				default_gui = iter;
+			}
+		}
+	}
+
+	//
+	// Parse GUI definitions from addons
+	//
+	for(const config& g : addons_cfg.child_range("gui")) {
+		const std::string id = g["id"];
+
+		try {
+			auto [iter, is_unique] = guis.try_emplace(id, g);
+
+			if (!is_unique) {
+				ERR_GUI_P << "GUI Theme ID '" << id << "' already exists.";
+			}
+		} catch (const wml_exception& e) {
+			ERR_GUI_P << "Non-functional theme: " << id;
+			ERR_GUI_P << e.user_message;
 		}
 	}
 

src/hotkey/command_executor.cpp

@@ -16,6 +16,7 @@
 #include "hotkey/command_executor.hpp"
 #include "hotkey/hotkey_item.hpp"
 
+#include "gui/gui.hpp"
 #include "gui/dialogs/achievements_dialog.hpp"
 #include "gui/dialogs/lua_interpreter.hpp"
 #include "gui/dialogs/message.hpp"
@@ -361,6 +362,7 @@ bool command_executor::do_execute_command(const hotkey::ui_command& cmd, bool pr
 			quit_confirmation::quit_to_desktop();
 			break;
 		case HOTKEY_QUIT_GAME:
+			gui2::switch_theme(prefs::get().gui2_theme());
 			quit_confirmation::quit_to_title();
 			break;
 		case HOTKEY_SURRENDER:

src/serialization/schema_validator.cpp

@@ -418,6 +418,10 @@ void schema_validator::close_tag()
 
 void schema_validator::print_cache()
 {
+	if (cache_.empty()) {
+		return;
+	}
+
 	for(auto& m : cache_.top()) {
 		for(auto& list : m.second) {
 			print(list);
@@ -432,10 +436,12 @@ void schema_validator::validate(const config& cfg, const std::string& name, int
 	// close previous errors and print them to output.
 	print_cache();
 
-	// clear cache
-	auto cache_it = cache_.top().find(&cfg);
-	if(cache_it != cache_.top().end()) {
-		cache_it->second.clear();
+	if (!cache_.empty()) {
+		// clear cache
+		auto cache_it = cache_.top().find(&cfg);
+		if(cache_it != cache_.top().end()) {
+			cache_it->second.clear();
+		}
 	}
 
 	// Please note that validating unknown tag keys the result will be false

src/wesnoth.cpp

@@ -882,6 +882,8 @@ static int do_gameloop(commandline_options& cmdline_opts)
 		case gui2::dialogs::title_screen::RELOAD_GAME_DATA:
 			gui2::dialogs::loading_screen::display([&config_manager]() {
 				config_manager.reload_changed_game_config();
+				gui2::init();
+				gui2::switch_theme(prefs::get().gui2_theme());
 			});
 			break;
 		case gui2::dialogs::title_screen::MAP_EDITOR: