Added single instance lock and release error system

NothinFancy/src/Application.cpp

@@ -103,14 +103,19 @@ namespace nf {
 	}
 
 	void Application::registerWindowClass() {
-		m_wclassName = L"NFClass";
-		WNDCLASS wclass = { };
-		wclass.lpszClassName = m_wclassName;
-		wclass.hCursor = LoadCursor(NULL, IDC_ARROW);
-		wclass.hIcon = NULL;
-		wclass.hInstance = m_hInst;
-		wclass.lpfnWndProc = Application::WindowProc;
-		RegisterClass(&wclass);
+		if (!FindWindow(L"NFClass", NULL)) {
+			m_wclassName = L"NFClass";
+			WNDCLASS wclass = { };
+			wclass.lpszClassName = m_wclassName;
+			wclass.hCursor = LoadCursor(NULL, IDC_ARROW);
+			wclass.hIcon = NULL;
+			wclass.hInstance = m_hInst;
+			wclass.lpfnWndProc = Application::WindowProc;
+			RegisterClass(&wclass);
+		}
+		else {
+			Error("Cannot run two NF applications at once.");
+		}
 	}
 
 	void Application::toggleFullscreen() {

NothinFancy/src/include/Utility.h

@@ -28,7 +28,8 @@ DebugBreak();
 #else
 #define DEBUGINIT
 #define Log(x)
-#define Error(x)
+#define Error(x) MessageBox(FindWindow(L"NFClass", NULL), toWide(x), L"NF Engine Error", MB_OK | MB_ICONERROR);\
+std::exit(-1)
 #endif
 
 	const wchar_t* toWide(const char* in);