Use and Understanding Of MESSAGE_MAP along with Message

Handlers

Presented By : Sheth Shraddha(50)

Tamhane Vaidehi(54)

Use of MESSAGE_MAP

Windows Operating Systems – A Message Driven System

Example : Mouse click, Printer signal MESSAGE_MAP supports Message Driven

Programming in MFC. Class Member Functions are used.

Role Of Class Member Functions

To execute commands Messages are directed to class member

functions by the use of macros in MFC. Convenience

Components Of MESSAGE_MAP

Declaration Beginning Termination

Declaration

DECLARE_MESSAGE_MAP– Declared in the class which allows to respond to messages.– A class is eligible to execute a message map if it is derived

from CCmdTarget or a class which is derived from CCmdTarget.

– A class can have only one message map.– It should be the last member declared within a class.– If not then next member should be preceded by an access

specifier.

BEGINNING

BEGIN_MESSAGE_MAP– Parameters

Class name which implements the message map. Base class

– Succeeded by macros which represent messages.

Termination

END_MESSAGE_MAP– Messages macros are succeeded by

END_MESSAGE_MAP

Message Handlers

To respond to a message one must add a message handler.

Members of CWnd class. Can be overridden.

Naming Pattern Of Message Handlers

Start with “On”. Succeeded by message name. Should be in camel case. Ex:

– Macro: WM_SIZE– Handler: OnSize()

ExampleExample

References

Thank You!!