Re: Overrides-Messages concept in MFC

From:
"Nobody" <Nobody@yahoo.com>
Newsgroups:
microsoft.public.vc.mfc
Date:
Thu, 16 Aug 2007 18:57:34 -0700
Message-ID:
<uYzv7HH4HHA.5360@TK2MSFTNGP03.phx.gbl>
Hi,

An Over-ride is within the same class
CBase
{
    DoSomething()
}

CMyGreatClass : public CBase
{
   //This overrides DoSomething in Base
    DoSomething()
   {
        //Calls base class functionality if needed
       CBase::DoSomething()
    }
}

Now, on to messages...
There is this concept called a "Window".
A window is something that can send and receive messages.

In order for a class to be a "Window", it must inherit from CWnd and be =
registered.

So, instead of having pointers to every class, I can just send or post a =
message
to a window class.

So, in some child control it does something like this.

CSomeChildControl::OnDrawItem()
{
     GetParent()->PostMessage(DRAW_ITEM, 1, 2);
}

ON_MESSAGE(DRAW_ITEM, OnDrawItem)
CView::OnDrawItem(SomeParam, OtherParam)
{
        int a = SomeParam; /* = 1 */
         int b = OtherParam; /* = 2 */
        "Yay, we got a message to draw something"
}
/* The Child window is whatever control and the Parent window is the =
View window. */

This will really explain alot.
http://www.codeproject.com/miscctrl/customcontrol.asp

HTH
"sawer" <sawer@discussions.microsoft.com> wrote in message =
news:194C49D5-EAAF-47B9-A140-485C64FED41E@microsoft.com...

Hi
I have a basic question about MFC.
There are methods in MFC which are in overrides section or Message =

Section.

What is the difference?
For example: For CView class
OnDraw is in overrides section. But OnDrawItem is in messages section.
Why is it so?
What is the concept/logic behind this?
I hope i could explain my question.
 
Thanks

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