Set a window's fullscreen state.
int SDL_SetWindowFullscreen(SDL_Window * window, Uint32 flags);
the window to change
Returns 0 on success or a negative error code on failure; call SDL_GetError() for more information.
flags may be
SDL_WINDOW_FULLSCREEN, for "real" fullscreen with a videomode change;
SDL_WINDOW_FULLSCREEN_DESKTOP for "fake" fullscreen that takes the size of the desktop; and 0 for windowed mode.
This function is available since SDL 2.0.0.