Load GUI from XML

Singleton.hh

@@ -0,0 +1,24 @@
+#ifndef __OPENGLPLAYGROUND_SINGLETON_HH__
+#define __OPENGLPLAYGROUND_SINGLETON_HH__
+
+#include <memory>
+#include <mutex>
+
+template<typename T>
+class Singleton {
+public:
+  static T& getInstance() {
+    call_once(instance_flag, init);
+    return *instance;
+  }
+
+private:
+  static std::unique_ptr<T> instance;
+  static std::once_flag instance_flag;
+  
+  static void init() {
+    instance.reset(new T{});
+  }
+};
+
+#endif