Messages and Commands: Overview
In traditional programs for Windows, Windows messages are handled in a large switch statement in a window procedure. MFC instead uses message maps to map direct messages to distinct class member functions. Message maps are more efficient than virtual functions for this purpose, and they allow messages to be handled by the most appropriate C++ object?application, document, view, and so on. You can map a single message or a range of messages, command IDs, or control IDs.
WM_COMMAND messages — usually generated by menus, toolbar buttons, or accelerators — also use the message-map mechanism. MFC defines a standard routing of command messages among the application, frame window, view, and Active documents in your program. You can override this routing if you need to.
Message maps also supply a way to update user-interface objects (such as menus and toolbar buttons), enabling or disabling them to suit the current context.
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General Message-Mapping Topics
Advanced Message-Mapping Topics