From ab48a57a406f0db467986a1f0752e0e4f9d4971a Mon Sep 17 00:00:00 2001
From: Vraiment <jemc44@gmail.com>
Date: Sat, 5 Aug 2017 16:39:02 -0700
Subject: [PATCH] Added enable_if for the EventHandler templates

---
 SDL2pp/Private/EventHandler.hh        | 16 +++++++++-------
 SDL2pp/Private/EventHandlerFunctor.hh |  4 +++-
 SDL2pp/Private/EventHandlerObject.hh  | 16 ++++++++++++----
 3 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/SDL2pp/Private/EventHandler.hh b/SDL2pp/Private/EventHandler.hh
index e8a825e..9ca240d 100644
--- a/SDL2pp/Private/EventHandler.hh
+++ b/SDL2pp/Private/EventHandler.hh
@@ -91,13 +91,15 @@ namespace Private {
 	struct IsEventHandler<
 		EventHandlerType,
 		EventType,
-		And<
-			Or<
-				IsEventHandlerObject<EventHandlerType, EventType>,
-				IsEventHandlerFunctor<EventHandlerType, EventType>
-			>,
-			TupleHasType<EventType, ValidEventTypes>
-		>
+		typename std::enable_if<
+			And<
+				Or<
+					IsEventHandlerObject<EventHandlerType, EventType>,
+					IsEventHandlerFunctor<EventHandlerType, EventType>
+				>,
+				TupleHasType<EventType, ValidEventTypes>
+			>::value
+		>::type
 	> : std::true_type { };
 }
 }
diff --git a/SDL2pp/Private/EventHandlerFunctor.hh b/SDL2pp/Private/EventHandlerFunctor.hh
index 17ca78b..1b2f41e 100644
--- a/SDL2pp/Private/EventHandlerFunctor.hh
+++ b/SDL2pp/Private/EventHandlerFunctor.hh
@@ -52,7 +52,9 @@ namespace Private {
 	struct IsEventHandlerFunctor<
 		EventHandlerType,
 		EventType,
-		std::is_convertible<EventHandlerType, EventHandlerFunctorSignature<EventType>>
+		typename std::enable_if<
+			std::is_convertible<EventHandlerType, EventHandlerFunctorSignature<EventType>>::value
+		>::type
 	> : std::true_type { };
 }
 }
diff --git a/SDL2pp/Private/EventHandlerObject.hh b/SDL2pp/Private/EventHandlerObject.hh
index 45a486c..df3d9ee 100644
--- a/SDL2pp/Private/EventHandlerObject.hh
+++ b/SDL2pp/Private/EventHandlerObject.hh
@@ -29,6 +29,15 @@ namespace SDL2pp {
  * This is code not to be used directly by users of SDL2pp.
  */
 namespace Private {
+	/*
+	 * Templated class to detect if a given type can handle a given event.
+	 */
+	template <typename EventHandlerType, typename EventType>
+	struct HasEventHandlerMethod : std::is_same<
+		decltype(std::declval<EventHandlerType>().HandleEvent(std::declval<const EventType &>())),
+		void
+	> { };
+	
 	/*
 	 * Templated class to identify a class that is not an event handler object.
 	 */
@@ -45,10 +54,9 @@ namespace Private {
 	struct IsEventHandlerObject<
 		EventHandlerType,
 		EventType,
-		std::is_same<
-			decltype(std::declval<EventHandlerType>().HandleEvent(std::declval<const EventType &>())),
-			void
-		>
+		typename std::enable_if<
+			HasEventHandlerMethod<EventHandlerType, EventType>::value
+		>::type
 	> : std::true_type { };
 }
 }