OK, I tested it on Linux and also reproduced the error.

Interestingly, if you swap the order of SDL and Classes in the uses section of the testunit.pas unit file, then it compiles properly and uses the SDL.TPoint definition. Perhaps this is by design, I don't know. I can post this on the Free Pascal forum if you like, and see what they have to say about the matter. But we need someone with FPC v1.9.8 (or less) to test it using my source code above to verify that things have changed from v1.9.8 (or less) to v2.0.0.