Is it possible to create a message map for a class not directly derived from CWnd or CFrameWnd ?

Question

Hi All,

Is it possible to create a message map for a class not directly derived from CWnd or CFrameWnd ?
(It's parent is derived from CWnd though)..

When I tried to Create the message map in usual manner for a registered message using the following code, I get a type casting error:

// pseudo code
public class Parent : public CWnd
{
DECLARE_MESSAGE_MAP()
};

public class Child: public parent
{
DECLARE_MESSAGE_MAP()
afx_msg long MyHandler(LPARAM lp,WPARAM wp);
};

// inside the implementation file for Child

BEGIN_MESSAGE_MAP(Child,Parent)
    ON_REGISTERED_MESSAGE(MyRegMsg,MyHandler)
END_MESSAGE_MAP()

// MyHandler implementation....

On compiling the project, I get the following compiler error:
error C2440: 'type cast' : cannot convert from 'long (__thiscall Child::*)(long,unsigned int)' to 'long (__thiscall CWnd::*)(unsigned int,long)'

Where have I gone wrong in the above implementation ?
Does Child class need to be direct derivative of CWnd class to declare a message map ?

I'm using VC++ 6.0 with SP4.

Thanks,
Pavan

Answer 1

You accidentally reversed the LPARAM and WPARAM arguments.

---

Hans Passant.

Answer 2

Thanks a lot nobugz.
That's the thing I have got wrong.