"Headless" is useless in its current state because it can't be changed, and it's only read from a single line of code in TiledMap: here
How it should
work is by preventing image data from being loaded, which, for example, means a server wouldn't have to initialize any Slick-specific stuff just to load collision data from a Tiled
Based on what I've seen/read, making the static function that changes "headless" public should be perfect as a fix. Even the word "headless" only
appears in this single java file, so it should be isolated.