code: public void setFullscreen(boolean fullscreen) throws SlickException {
  		if (isFullscreen() == fullscreen) {
  			return;
  		}
  		
  		if (!fullscreen) {
  			try {
  				Display.setFullscreen(fullscreen);
  			} catch (LWJGLException e) {
  				throw new SlickException("Unable to set fullscreen="+fullscreen, e);
  			}
  		} else {
  			setDisplayMode(width, height, fullscreen);
  		}
  		getDelta();
  	}
docs: Indicate whether we want to be in fullscreen mode. Note that the current
  display mode must be valid as a fullscreen mode for this to work
  
  @param fullscreen True if we want to be in fullscreen mode
  @throws SlickException Indicates we failed to change the display mode