OpenGL error output in debug window + highdpi mode test

src/DesktopLauncher.h

@@ -5,8 +5,16 @@
 
 namespace Game {
 
-#define WINDOW_WIDTH = 800;
-#define WINDOW_HEIGHT = 600;
+const int SCREEN_WIDTH = 800;
+const int SCREEN_HEIGHT = 600;
+
+//Diagonal DPI of the display used while starting
+extern float DDPI;
+//horizontal DPI of the display used while starting
+extern float HDPI;
+//vertical DPI of the display used while starting
+extern float VDPI;
+
 
 void exit();