This allows GUI elements to use a texture as their "mouse event mask", making it possible to have arbitrarily-shaped GUI elements.
The current use case if a very-secret-project™ of mine, but this could be used for:
- the minimap
- the buttons around the minimap.
- ... ?
- check if inline TODOs shouldn't be done first.
- add tests?
- Check if we don't have an obscure ticket about this.