7.6 Interfaces and COM

When using interfaces on Windows which should be available to the COM subsystem, the calling convention should be stdcall – this is not the default Free Pascal calling convention, so it should be specified explicitly.

COM does not know properties. It only knows methods. So when specifying property definitions as part of an interface definition, be aware that the properties will only be known in the Free Pascal compiled program: other Windows programs will not be aware of the property definitions.