In reply to @devlop_gaming "Bru we are two": No drama, its up to you. But whatever tool you use I think its worth understanding the concept, that you need a FFI definition for every C function or struct you call from Nim (ie a wrapper), and your issue stems from using SDL and Imgui wrappers that appear to be incompatible. You can try to cast to the correct pointer type, but your error above suggests Nim has internally cast two forward definitions of `SDL_Window` to different pointer types, so you can either cast one to the other, or both to `pointer` and change the FFI definition. However its hard to do that when using a random wrapper from the internet.