Added class IsEventHandler to help identify valid event handlers with template metaprogramming

CMakeLists.txt

@@ -158,6 +158,7 @@ SET(LIBRARY_HEADERS
 	SDL2pp/Texture.hh
 	SDL2pp/Wav.hh
 	SDL2pp/Window.hh
+	SDL2pp/Private/EventHandler.hh
 	SDL2pp/Private/EventHandlerFunctor.hh
 	SDL2pp/Private/EventHandlerObject.hh
 	SDL2pp/Private/Utility.hh

SDL2pp/Private/EventHandler.hh

@@ -0,0 +1,105 @@
+/*
+  libSDL2pp - C++11 bindings/wrapper for SDL2
+  Copyright (C) 2017 Vraiment <jemc44@gmail.com>
+
+  This software is provided 'as-is', without any express or implied
+  warranty.  In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications, and to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef SDL2PP_PRIVATE_EVENTHANDLER_HH
+#define SDL2PP_PRIVATE_EVENTHANDLER_HH
+
+#include <SDL2pp/Private/EventHandlerFunctor.hh>
+#include <SDL2pp/Private/EventHandlerObject.hh>
+#include <SDL2pp/Private/Utility.hh>
+
+#include <tuple>
+#include <type_traits>
+
+#include <SDL_events.h>
+
+namespace SDL2pp {
+/*
+ * This is code not to be used directly by users of SDL2pp.
+ */
+namespace Private {
+	/*
+	 * Tuple containing all the valid events that can be handled.
+	 */
+	using ValidEventTypes = std::tuple<
+		SDL_Event,
+		SDL_AudioDeviceEvent,
+		SDL_ControllerAxisEvent,
+		SDL_ControllerButtonEvent,
+		SDL_ControllerDeviceEvent,
+		SDL_DollarGestureEvent,
+		SDL_DropEvent,
+		SDL_JoyAxisEvent,
+		SDL_JoyBallEvent,
+		SDL_JoyButtonEvent,
+		SDL_JoyDeviceEvent,
+		SDL_JoyHatEvent,
+		SDL_KeyboardEvent,
+		SDL_MouseButtonEvent,
+		SDL_MouseMotionEvent,
+		SDL_MouseWheelEvent,
+		SDL_MultiGestureEvent,
+		SDL_QuitEvent,
+		SDL_SysWMEvent,
+		SDL_TextEditingEvent,
+		SDL_TextInputEvent,
+		SDL_TouchFingerEvent,
+		SDL_UserEvent,
+		SDL_WindowEvent
+	>;
+	
+	/*
+	 * Templated class to identify a class that is not an event handler.
+	 */
+	template <typename, typename, typename = void>
+	struct IsEventHandler : std::false_type { };
+
+	/*
+	 * Templated class to identify a type that is an event handler, the type
+	 * EventHandlerType is considered to be an event handler if is either an
+	 * event handler object or an event handler functor for the given event
+	 * type. Also the event type must be a valid SDL event type.
+	 *
+	 * In other words, any of the following code can be executed:
+	 * {
+	 *     EventType event;
+	 *     EventHandlerType eventHandler;
+	 *     eventHandler(event);
+	 *     // or
+	 *     eventHandler.HandleEvent(event);
+	 * }
+	 */
+	template <typename EventHandlerType, typename EventType>
+	struct IsEventHandler<
+		EventHandlerType,
+		EventType,
+		And<
+			Or<
+				IsEventHandlerObject<EventHandlerType, EventType>,
+				IsEventHandlerFunctor<EventHandlerType, EventType>
+			>,
+			TupleHasType<EventType, ValidEventTypes>
+		>
+	> : std::true_type { };
+}
+}
+
+#endif