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Why not virtual functions to handle messages?
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Answer / chandrasekharreddy siddamreddy
In MFC we have lot of base classes those are having so many
virtual functions. For each class one virtual table will be
created. This will consume lot of memory and our application
performance will go down. This is the only reason MFC is not
using virtual function for message mapping.
| Is This Answer Correct ? | 13 Yes | 4 No |
Answer / abhijit
Implementing virtual mechanism to handle messages would
have made the message dispatch process very expensive as
* every class of any window type would have a huge virtual
function dispatch table associated with it.
Instead having static array of function pointers ensures
only one copy for a given class
| Is This Answer Correct ? | 5 Yes | 2 No |
Answer / spiker
Only classes derived from the CCmdTarget class can get the benefits of message map.For that we need to use DECLARE_MESSAGEMAP, BEGIN_MESSAGEMAP, END_MESSAGEMAP macros.
when we declare a message map it will create an array to keep all the information about the messages to be handled.
Overall the messages are handled by the base class CCmdTarget.
Virtual function is one of the best concept of oops,its for managing objects and functions.
No need of vtables to handle messages.
| Is This Answer Correct ? | 1 Yes | 0 No |
Virtual functions are not space-efficient because they require vtables, and vtables consume memory even if the functions in them are not overridden.
The amount of memory used by a message map, in contrast, is proportional to the number of message entries it contains.
Since it's extremely rare for a developer to implement a window class that includes handlers for all of the different types of messages, message mapping conserves a few hundred bytes of memory just about every time a CWnd is wrapped around an HWnd.
| Is This Answer Correct ? | 1 Yes | 0 No |
Answer / malli
we have to prefix "afx_msg" before every function to create
message map.
| Is This Answer Correct ? | 0 Yes | 12 No |
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