Advanced MFC Programming

Chapter 13. Adding Special Features to Application
Chapter 13
Adding Special Features to Application
Normal applications created by Application Wizard cannot satisfy us all the time. For certain types
of applications, we need to add special features to our programs. Since Application Wizard or
Class Wizard does not directly support these features, we need to have in-depth knowledge on
Windows programming in order to customize standard applications. In this chapter, we will
discuss how to create applications with special features such as multiple documents, multiple views,
irregular-shaped window, customized non-client area. Also, we will discuss how to implement hook in the
applications.
13.1 One Instance Application
By default, a Windows application is allowed to have multiple instances working simultaneously.
Most of the time this is the desired feature of an application. For example, a word processing program may
have several instances working together, each editing a different file. But sometimes we may want an
application to have only one instance working at any time, this is especially true for some communication
programs. For example, for a file server application, if we allow two servers to work together at the same
time, it may cause inconsistency on the data contained in the files.
Window Creation
To implement one instance application, we must understand how the applications are created under
Windows. This can be easily understood if we have the experience of writing Win32 Windows
applications. However, if we started everything from MFC, it is not very obvious how a window is created.
This is because MFC hides everything from the programmer. Although it is relatively easy to create an
application by deriving classes from MFC without thinking about the actual procedure of creating
windows, if we rely too much on MFC, we will lose the power of customizing it.
Every visual object that is created under Windows is a window. This includes the frame window,
tool bar, menu, view, button and other controls. Actually, MFC is not the only tool that can be used to
create windows. A window can be created by using any computer language such as C, Basic, Pascal so long
as it abides by the rules of creating windows.
Under Windows, a window can be described by structure WNDCLASS:
typedef struct _WNDCLASS {
UINT style;
WNDPROC lpfnWndProc;
int cbClsExtra;
int cbWndExtra;
HANDLE hInstance;
HICON hIcon;
HCURSOR hCursor;
HBRUSH hbrBackground;
LPCTSTR lpszMenuName;
LPCTSTR lpszClassName;
} WNDCLASS;
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