How should I use the QueryInterface() and GetInterfaceByName() methods?

Renga API adheres to the COM convention regarding the QueryInterface() method: it is intended for obtaining supported interfaces of the same object, but not for obtaining any other object instances. E.g. you can obtain the ILevelObject interface from a wall but not the ILevel interface: a wall is a level object, not a level. COM clients that use late binding can't access these alternative interfaces the same way because the QueryInterface() method is inaccessible from IDispatch. To circumvent this limitation in a uniform way Renga API provides the GetInterfaceByName() method, which preserves the semantics of QueryInterface(), but accepts a string parameter instead of an IID.

Does Renga API support multi-threading access?

No, it does not. Renga does not guarantee safe access from any thread except main (UI) thread and we do not recommend to call the API methods from parallel threads.