Contents  Design Principles  The Window Class  The Window Class  and the Application  Message Pump  Printable version  Discuss this article

Anyone familiar with the Win32 API knows that the process for creating windows is rather lengthy: you create a WNDCLASSEX structure, initialize its members and register it (per window class); create the window, check for the validity of the returned handle, and finally display the window. Of course, I neglected to mention that initializing the WNDCLASSEX structures members requires that you define a window procedure first...

So it's logical that the enterprising C++ developer would like to wrap all of the above in a nice class that would allow her write something like:

Window *wnd = new Window(...);
wnd->Create(...);
wnd->Show(...);
// use window
// window's destructor is automatically called, and
// performs necessary cleanup

Doesn't look to hard... Ha! It took me a good 2 hours to perfect the object association and proper message pump termination. I'll share my design principles, implementation, revisions and discoveries in the process of creating this wrapper class. I will not be covering the fundamentals of creating windows with Win32, or any other technology I consider to be elementary. There are several good references available on the web for these topics; please take advantage of them.

Without further ado, let's dive in!

Design Principles

In writing a Win32 window wrapper class, I wanted a method that would allow for as little coupling into the main application as possible, that would require the minimum user intervention necessary yet be extremely flexible. I also wanted the user to be able to extend the class without having to inherit or reimplement any methods. Most methods of wrapping windows in Win32 that I have seen on the web require the user to implement a full window procedure and handle all messages she is interested in (you may notice my habitual use of the singular feminine pronoun; deal with it). Microsoft's MFC and Borland's VCL use preprocessor "message maps", restricting the flexibility of the window class in terms of dynamic runtime modification since they are evaluated at compile time. Given the advent of the Standard Template Library and its integral part in the C++ language, I was sure I could find a container that would be as fast and flexible as the image in my mind.

As much as possible, I wanted defaults such that the wrappers could be used with minimal code. I also wanted the class to be sufficiently generic that it could be used for general-purpose applications as well as for high-performance applications like videogames. Over the course of the class development various features to accomplish this were added, and it was constantly interesting to find a way to integrate such features in a consistent way. Wherever possible and reasonable, I also tried to use names consistent with the Win32 API as a form of assitance to the developer.

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