SdlCompareCallbackRDart typedef
        SdlCompareCallbackRDart =
     int Function(Pointer<NativeType>  userdata, Pointer<NativeType>  a, Pointer<NativeType>  b)
    
    
    
Implementation
typedef SdlCompareCallbackRDart =
    int Function(
      Pointer<NativeType> userdata,
      Pointer<NativeType> a,
      Pointer<NativeType> b,
    );