A big part of the Wine code doesn't follow the COM guideline. Most notably, there are many uses of the ICOM_MULTI_THIS or DEFINE_THIS technique. The plan is to get rid of them in favor of the standard implementation. To fix an existing interface implementation, we need to:

• Change vtbl pointer in object to interface instance. This change usually look like:

  • - IMyInterfaceVtbl *lpIMyInterfaceVtbl;
    + IMyInterface IMyInterface_iface;
    

    and fix its vtbl initialization to follow the change

    - obj->lpIMyInterfaceVtbl = &MyInterfaceVtbl;
    + obj->IMyInterface_iface.lpVtbl = &MyInterfaceVtbl;
    

• Add impl_from_* functions.
• Replace all ICOM_MULTI_THIS and *_THIS occurrences to impl_from_* calls.
• Replace all object to interface casts to address of instance expressions, for example:

  • - *ppv = (IMyInterface*) &This->lpIMyInterfaceVtbl;
    + *ppv = &This->IMyInterface_iface;
      

    as well as:

    - *ppv = (IMyInterface*)This;
    + *ppv = &This->IMyInterface_iface;
    

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