The issue is MKTYPLIB doesn't support optional and most people use that for VB6 typelibs, because midl is a colossal pain in the ass and forbids you from redefining anything in the IDL files it force-includes with no way to disable, and trying to get around that eventually dead-ends with it telling you it can't create the typelib, but can't tell you what the error is or where it's occurring. So you can't use it for typelibs that include anything low level from oaidl.idl.

Re: call semantics... I tend to not like rewriting things to be different from the documentation and how it's called in every other language... plus it's much more involved going through and doing it. It does make more sense in some ways, but matching other references is more important to me.

oleexp uses The trick's definitions for what was in D2DVB.tlb (minus optionals because of the need to compile with mktypelib), but for the rest of Direct 2D I recently added I don't rewrite things to out,retval.