Enable the preferences hotkey in the lobby.

Also add a helper wrapper so a void member function can be used as
hotkey callback.

src/gui/dialogs/lobby_main.cpp

@@ -302,7 +302,9 @@ tlobby_main::tlobby_main(const config& game_config
 	, filter_text_(NULL)
 	, selected_game_id_()
 	, player_list_()
-	, player_list_dirty_(false), disp_(disp)
+	, player_list_dirty_(false)
+	, disp_(disp)
+	, preferences_wrapper_()
 {
 }
 
@@ -375,11 +377,25 @@ twindow* tlobby_main::build_window(CVideo& video)
 	window->register_hotkey(hotkey::HOTKEY_FULLSCREEN
 			, boost::bind(fullscreen, boost::ref(video)));
 
+
 	/** @todo Remove this code once the resizing in twindow is finished. */
 	window->connect_signal<event::SDL_VIDEO_RESIZE>(
 			  boost::bind(&signal_handler_sdl_video_resize
 				  , _2, _3, _4, _5, boost::ref(video))
 			, event::tdispatcher::front_child);
+
+	/*** Local hotkeys. ***/
+	preferences_wrapper_ = boost::bind(
+			  &tlobby_main::show_preferences_button_callback
+			, this
+			, boost::ref(*window));
+
+	window->register_hotkey(
+			  hotkey::HOTKEY_PREFERENCES
+			, boost::bind(function_wrapper<bool, boost::function<void()> >
+				, true
+				, boost::cref(preferences_wrapper_)));
+
 	return window;
 }
 

src/gui/dialogs/lobby_main.hpp

@@ -359,6 +359,9 @@ private:
 	bool player_list_dirty_;
 
 	display& disp_;
+
+	/** Wrapper for the preferences hotkey. */
+	boost::function<void()> preferences_wrapper_;
 };
 
 } // namespace gui2

src/gui/widgets/helper.hpp

@@ -203,6 +203,28 @@ tpoint get_mouse_position();
  */
 std::string debug_truncate(const std::string& text);
 
+/**
+ * Helper for function wrappers.
+ *
+ * For boost bind the a function sometimes needs to return a value althought
+ * the function called doesn't return one. This wrapper function can return a
+ * fixed result for a certain functor.
+ *
+ * @tparam R                      The return type.
+ * @tparam F                      The type of the functor.
+ *
+ * @param result                  The result value.
+ * @param function                The functor to call.
+ *
+ * @returns                       result.
+ */
+template<class R, class F>
+R function_wrapper(const R result, const F& function)
+{
+	function();
+	return result;
+}
+
 } // namespace gui2
 
 #endif