gui/preferences: Make Themes selection a dropdown menu

Note that this doesn't remove the themes dialog functionality, since
it is currently used by the :theme command in the game console.

data/gui/window/preferences/03_display.cfg

@@ -375,11 +375,21 @@
 			border_size = 5
 			horizontal_alignment = "left"
 
-			[button]
-				id = choose_theme
-				label = _ "Theme"
+			[label]
+				label = _ "Theme:"
+				definition = "default_small"
+			[/label]
+		[/column]
+
+		[column]
+			border = "all"
+			border_size = 5
+			horizontal_alignment = "left"
+
+			[menu_button]
+				id = "choose_theme"
 				tooltip = _ "Change the in-game theme"
-			[/button]
+			[/menu_button]
 		[/column]
 	[/row]
 #enddef

src/gui/dialogs/preferences_dialog.cpp

@@ -23,6 +23,7 @@
 #include "filesystem.hpp"
 #include "formatter.hpp"
 #include "formula/string_utils.hpp"
+#include "game_data.hpp"
 #include "gettext.hpp"
 #include "hotkey/hotkey_item.hpp"
 #include "lexical_cast.hpp"
@@ -31,6 +32,8 @@
 #include "preferences/game.hpp"
 #include "preferences/general.hpp"
 #include "preferences/lobby.hpp"
+#include "resources.hpp"
+#include "theme.hpp"
 #include "video.hpp"
 
 // Sub-dialog includes
@@ -114,6 +117,7 @@ preferences_dialog::preferences_dialog(const PREFERENCE_VIEW initial_view)
 	: modal_dialog(window_id())
 	, adv_preferences_(preferences::get_advanced_preferences())
 	, resolutions_() // should be populated by set_resolution_list before use
+	, themes_() // populated by set_theme_list
 	, last_selected_item_(0)
 	, accl_speeds_({0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75, 2, 3, 4, 8, 16})
 	, visible_hotkeys_()
@@ -150,6 +154,23 @@ void preferences_dialog::set_resolution_list(menu_button& res_list)
 	res_list.set_values(options, current_res);
 }
 
+void preferences_dialog::set_theme_list(menu_button& theme_list)
+{
+	themes_ = theme::get_basic_theme_info();
+
+	std::vector<config> options;
+	for(const auto& theme : themes_) {
+		options.emplace_back("label", theme.name, "tooltip", theme.description);
+	}
+
+	const unsigned current_theme = std::distance(themes_.begin(),
+		std::find_if(themes_.begin(), themes_.end(), [](const auto& theme) {
+			return theme.id == preferences::theme();
+		}));
+
+	theme_list.set_values(options, current_theme);
+}
+
 widget_data preferences_dialog::get_friends_list_row_data(const acquaintance& entry)
 {
 	widget_data data;
@@ -498,9 +519,13 @@ void preferences_dialog::initialize_callbacks()
 	register_bool("vsync", true, vsync, set_vsync);
 
 	/* SELECT THEME */
-	connect_signal_mouse_left_click(
-			find_widget<button>(this, "choose_theme", false),
-			std::bind(&show_theme_dialog));
+	menu_button& theme_list = find_widget<menu_button>(this, "choose_theme", false);
+	set_theme_list(theme_list);
+	connect_signal_notify_modified(theme_list,
+		std::bind(&preferences_dialog::handle_theme_select, this));
+	//connect_signal_mouse_left_click(
+	//		find_widget<button>(this, "choose_theme", false),
+	//		std::bind(&show_theme_dialog));
 
 	//
 	// SOUND PANEL
@@ -1102,6 +1127,21 @@ void preferences_dialog::handle_res_select()
 	}
 }
 
+void preferences_dialog::handle_theme_select()
+{
+	menu_button& theme_list = find_widget<menu_button>(this, "choose_theme", false);
+
+	const auto selection = theme_list.get_value();
+	const auto& theme = themes_.at(selection);
+	auto* display = display::get_singleton();
+
+	preferences::set_theme(theme.id);
+	if(display && resources::gamedata && resources::gamedata->get_theme().empty()) {
+		display->set_theme(theme.id);
+	}
+
+}
+
 void preferences_dialog::on_page_select()
 {
 	const int selected_row =

src/gui/dialogs/preferences_dialog.hpp

@@ -22,6 +22,7 @@
 #include "hotkey/hotkey_command.hpp"
 #include "preferences/advanced.hpp"
 #include "preferences/game.hpp"
+#include "theme.hpp"
 
 // This file is not named preferences.hpp in order -I conflicts with
 // src/preferences.hpp.
@@ -31,6 +32,7 @@ namespace hotkey {
 }
 
 struct point;
+//struct theme_info;
 
 namespace preferences {
 	enum PREFERENCE_VIEW {
@@ -84,6 +86,7 @@ private:
 	void initialize_callbacks();
 	void initialize_tabs(listbox& selector);
 	void set_resolution_list(menu_button& res_list);
+	void set_theme_list(menu_button& theme_list);
 	listbox& setup_hotkey_list();
 
 	template<bool(*toggle_getter)(), bool(*toggle_setter)(bool), int(*vol_getter)(), void(*vol_setter)(int)>
@@ -108,6 +111,7 @@ private:
 
 	/** Special callback functions */
 	void handle_res_select();
+	void handle_theme_select();
 	void fullscreen_toggle_callback();
 	void add_hotkey_callback(listbox& hotkeys);
 	void remove_hotkey_callback(listbox& hotkeys);
@@ -119,6 +123,7 @@ private:
 	const preferences::advanced_pref_list& adv_preferences_;
 
 	std::vector<point> resolutions_;
+	std::vector<theme_info> themes_;
 
 	int last_selected_item_;