Chapter Summary

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This chapter rounded out your understanding of COM by introducing you to the fine art of building an ActiveX control with ATL. As you have seen, ActiveX controls are used as graphical building blocks in larger applications. To supply the additional services above and beyond a simple coclass, controls implement a number of standard COM interfaces to allow support rendering, persistence, and property page objects. Building a full control in ATL begins with the ATL Object Wizard. The framework provides stock implementations for each of the necessary COM interfaces, as well as all the previous templates and maps examined throughout this book.

We examined the use of COM persistence, and how ATL provides support for each of the client-specified persistence techniques using a handful of templates and the property map. This map serves double duty, in that it also associates a given property to the correct property page. A property page is yet another COM class supporting the standard IPropertyPage interface. The container discovers the set of pages that works with your coclass by querying for ISpecifyPropertyPages.

We discovered a number of minor (but important) details which make for a polished control: component categories, About boxes, and custom enumerations used with bound properties. Finally, we have seen how to make use of our object from a web page, as well as Microsoft Visual Basic, and how to create a licensed class factory.

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