Start with centered window

src/framework/WindowManager.cpp

@@ -138,8 +138,8 @@ bool WindowManager::initialize(const int width, const int height, const int fram
 	// finally, get window
 	m_Window = SDL_CreateWindow(
 							"Einstein@Home",
-							SDL_WINDOWPOS_UNDEFINED,
-							SDL_WINDOWPOS_UNDEFINED,
+							SDL_WINDOWPOS_CENTERED,
+							SDL_WINDOWPOS_CENTERED,
 							m_CurrentWidth,
 							m_CurrentHeight,
 							m_VideoModeFlags);
@@ -168,8 +168,8 @@ bool WindowManager::initialize(const int width, const int height, const int fram
 		// reset window
 		m_Window = SDL_CreateWindow(
 								"Einstein@Home",
-								SDL_WINDOWPOS_UNDEFINED,
-								SDL_WINDOWPOS_UNDEFINED,
+								SDL_WINDOWPOS_CENTERED,
+								SDL_WINDOWPOS_CENTERED,
 								m_CurrentWidth,
 								m_CurrentHeight,
 								m_VideoModeFlags);