while (SDL_PollEvent(&event)) // goes through until done with each event{   switch (event.type) // differ the types of events   {      case SDL_MOUSEBUTTONUP:          // mouse button is up      break;      case SDL_MOUSEBUTTONDOWN: // see which mouse buttons were hit         if(SDL_GetMouseState(null, null)&SDL_BUTTON_LMASK)            // left mouse down         if(SDL_GetMouseState(null, null)&SDL_BUTTON_MMASK)            // middle mouse down         if(SDL_GetMouseState(null, null)&SDL_BUTTON_RMASK)            // right button down                  break;       case SDL_MOUSEMOTION:         mouseX = event.button.x;         mouseY = event.button.y;      break;    } // switch} // while