1. The Basics of Microsoft Foundation Classes

1. Mfc general information

MFC - Microsoft Foundation Classes is a set of C++ classes that encapsulates the functionality of applications written for the Microsoft Windows operating systems.

That library contains more then 200 members. MFC was designed to simplify the programming process, mainly oriented to multiple usage of the same code. MFC make simpler the process of user interaction with Application Programming Interface (API) of Windows operational system. The classes of MFC aren’t included to Windows immediately, but they really make programs shorter.

Talking about MFC we should resemble some special data types, used in MFC. These are:

HANDLE - Handle of an object.

HWND - Handle of a window

BYTE - Byte (8 bits).

WORD - Unsigned word (16 bits).

DWORD - Doubleword (32 bits).

UINT - Unsigned integer.

BOOL - Boolean variable (should be TRUE or FALSE).

LONG - 32-bit signed value.

LPSTR - Pointer to a null-terminated Windows character string.

LPCSTR - Pointer to a constant null-terminated Windows character string.

MFC includes many classes you can use to write your applications more quickly and easily. These classes represent objects from which a Windows application is created objects such as windows, dialog boxes, menu bars, window controls, and many more, including some special objects such as status bars and control bars. In addition, MFC provides many general purpose classes for handling things like strings, arrays, and linked lists.

Specifically, MFC provides the following main categories of classes:

• Applications

• Windows

• Menus

• Dialog boxes

• Documents and views

• Controls

• Graphics

• Archival and file

• Database

• Various support classes.

If you examine the MFC class hierarchy, you'll see that almost every class in the library is derived from the CObject class. You might think that a class that is the granddaddy to almost the entire MFC class library would be huge and complex. Ironically, though, CObject is one of the smallest classes in MFC. Although CObject acts as the base class for the majority of MFC classes, you can derive your own custom classes from CObject and, thus, automatically acquire built-in support for the functionality built into CObject most notably the capability to serialize your custom object. Any custom class you want to develop that needs to save and load data should be derived, directly or indirectly, from CObject.

CObject is the principal base class for the Microsoft Foundation Class Library. It serves as the root not only for library classes such as CFile and CObList, but also for the classes that you write. CObject provides basic services, including

• Serialization support

• Run-time class information

• Object diagnostic output

• Compatibility with collection classes

Note that CObject does not support multiple inheritances. Your derived classes can have only one CObject base class, and that CObject must be leftmost in the hierarchy. It is permissible, however, to have structures and non-CObject-derived classes in right-hand multiple-inheritance branches.

CObject class contains basic properties, which are inherited by several child (of CObject) classes. Among them are CCmdTarget, CException, CFile, CMenu, CDC, CGdiObject.

CCmdTarget is the base class for the Microsoft Foundation Class Library message-map architecture. A message map routes commands or messages to the member functions you write to handle them. (A command is a message from a menu item, command button, or accelerator key.)

CException is the base class for all exceptions in the MFC Library.

CFile is the base class for Microsoft Foundation file classes. It directly provides unbuffered, binary disk input/output services, and it indirectly supports text files and memory files through its derived classes. CFile works in conjunction with the CArchive class to support serialization of Microsoft Foundation Class objects.

The CMenu class is an encapsulation of the Windows HMENU. It provides member functions for creating, tracking, updating, and destroying a menu.

The CDC class defines a class of device-context objects. The CDC object provides member functions for working with a device context, such as a display or printer, as well as members for working with a display context associated with the client area of a window.

The CGdiObject class provides a base class for various kinds of Windows graphics device interface (GDI) objects such as bitmaps, regions, brushes, pens, palettes, and fonts. You never create a CGdiObject directly. Rather, you create an object from one of its derived classes, such as CPen or CBrush.

From CCmdTarget there is originated a very important MFC class – CWnd. The CWnd class provides the base functionality of all window classes in the Microsoft Foundation Class Library.

A CWnd object is distinct from a Windows window, but the two are tightly linked. A CWnd object is created or destroyed by the CWnd constructor and destructor. The Windows window, on the other hand, is a data structure internal to Windows that is created by a Create member function and destroyed by the CWnd virtual destructor. The DestroyWindow function destroys the Windows window without destroying the object.

In it’s turn, the CFrameWnd class provides the functionality of a Windows single document interface (SDI) overlapped or pop-up frame window, along with members for managing the window. It is a child of CWnd class.

A CWinThread object represents a thread of execution within an application. It inherits the property of CCmdTarget. The main thread of execution is usually provided by an object derived from CWinApp; CWinApp is derived from CWinThread. Additional CWinThread objects allow multiple threads within a given application.

The CWinApp class is the base class from which you derive a Windows application object. An application object provides member functions for initializing your application (and each instance of it) and for running the application.