"OS X v10.6 and later automatically optimize the performance of screen-sized windows, allowing your application to take complete advantage of the window server

"OS X v10.6 and later automatically optimize the performance of screen-sized windows, allowing your application to take complete advantage of the window server environment on OS X. For example, critical operating system dialogs may be displayed over your content when necessary." https://developer.apple.com/library/content/documentation/GraphicsImaging/Conceptual/OpenGL-MacProgGuide/opengl_fullscreen/opengl_cgl.html#//apple_ref/doc/uid/TP40001987-CH210-SW4 https://developer.apple.com/library/content/documentation/Gr...