Is it possible to create a steam like overlay using LWJGL (or even java?)
I'm trying to render puppets over TableTop simulator using Java, but I'm starting to think that this would be a lot easier in a language that I don't know.
I am pretty sure, that games distributed over Steam and displaying that Steam overlay, have been designed to interoperate with the Steam application.
This is because your local Steam application or some Steam-provided library built into the game must get a hold of the game's render surface and also must be able to intercept the keyboard events.
So adding a custom interface to this game (in any language) is likely close to impossible, unless of course that game provides some kind of SDK with an API you can program against, for building plugins. But that would most likely require a native language then (such as C/C++) and using Direct3D, since that particular game seems to be a DirectX game.