Fixed NSApplication not retaining its delegate

src/SFML/Window/OSX/SFApplicationDelegate.h

@@ -50,4 +50,10 @@
 ////////////////////////////////////////////////////////////
 -(BOOL)applicationShouldTerminateAfterLastWindowClosed:(NSApplication*)theApplication;
 
+////////////////////////////////////////////////////////////
+/// \brief Return a singleton instance of this class
+///
+////////////////////////////////////////////////////////////
++(id)instance;
+
 @end

src/SFML/Window/OSX/SFApplicationDelegate.m

@@ -49,6 +49,14 @@
     return YES;
 }
 
+////////////////////////////////////////////////////////////
++(id)instance
+{
+    static SFApplicationDelegate* singleton = nil;
+    if (singleton == nil)
+        singleton = [[SFApplicationDelegate alloc] init];
+    return singleton;
+}
 
 @end
 

src/SFML/Window/OSX/WindowImplCocoa.mm

@@ -139,7 +139,7 @@ void WindowImplCocoa::setUpProcess(void)
 
         // Register an application delegate if there is none
         if (![[SFApplication sharedApplication] delegate])
-            [NSApp setDelegate:[[SFApplicationDelegate alloc] init]];
+            [NSApp setDelegate:[SFApplicationDelegate instance]];
 
         // Create menus for the application (before finishing launching!)
         [SFApplication setUpMenuBar];