Developers Workshop to COM and ATL 3.0

Objectives:

• Review the atoms of a Win32 Windows application.

• Understand the core set of ATL templates used to build a Windows application.

• Respond to system messages using the ATL message map.

• Build dialog boxes à la ATL to capture user input.

• Create an ATL main window manipulated by COM interfaces.

What would a developer's life be without the need to build a graphical user interface (GUI) once in a while? Most C++ developers who are in the business of building user interfaces tend to do so with the help of application frameworks such as MFC. Others opt for the RAD environment offered by Visual Basic. Yet another option is to use ATL as a windowing toolkit, which is the subject of this chapter.

Developing Windows applications with ATL places you somewhere in between the complexity of raw Win32 API programming and the safe and comfortable world of MFC (and very far removed from VB). We will begin this chapter with a quick review of the core parts of every Windows window: WinMain(), the WNDCLASSEX structure, and the almighty WndProc. We will then see how ATL can be used to wrap up much of this logic using a small handful of templates and a corresponding MSG_MAP.