OnEraseBackground

[Orf]

Hi gurus.
I have some problems overriding OnEraseBackground in my MFC dialog-based applications (the framework doesn't call my override).
Can anyone suggest how to handle this matter?
(before you ask: yes, I added the OnEraseBackground declaration in the message map... well, at leas I think I didi it properly )
Thanks!

[shosha]

can u plz come up with some amount of code??

[VictorN]

The best way to "override OnEraseBackground" would be to let ClassWizard add Windows message handler WM_ERASEBKGND into your class.
After doing this you'd have to get
a) in your header:

	afx_msg BOOL OnEraseBkgnd(CDC* pDC);

b) in your cpp:

BEGIN_MESSAGE_MAP(<your_class> ,<Base_class>)
	//{{AFX_MSG_MAP(<your_class>)
	ON_WM_ERASEBKGND()
	.............
	//}}AFX_MSG_MAP
............
BOOL <your_class>::OnEraseBkgnd(CDC* pDC) 
{
	return <Base_class>::OnEraseBkgnd(pDC);
}

[Amit Sebiz]

Hey,

Once i also had the same problem. But it figured out that i was returning from the function before actual code.

some thing like

BOOL <your_class>::OnEraseBkgnd(CDC* pDC)
{
return <Base_class>::OnEraseBkgnd(pDC);

//your own code

}

In case this is the problem.

Amit

[Orf]

Ok... VictorN helped me understand... I forgot to put "ON_WM_ERASEBKGND()" in the message map...
Sorry for the silly question... crunch time is almost killing me!

P.S. VictorN, you wrote
BOOL <your_class>::OnEraseBkgnd(CDC* pDC)
{
return <Base_class>::OnEraseBkgnd(pDC);
}

...I think the function should return TRUE if it handles the background erasing task, right?

[VictorN]

...I think the function should return TRUE if it handles the background erasing task, right?

Yes!
Sorry, i forgot to paste the rest of my code in OnEraseBkgnd() body.

BOOL <myClass>::OnEraseBkgnd(CDC* pDC) 
{
	if(<I do smth. myself>)
	{	
		//  do it	
		return TRUE;
	}
	else
		return <aseClass>::OnEraseBkgnd(pDC);
}

[VladimirF]

Originally posted by Amit Sebiz
Once i also had the same problem. But it figured out that i was returning from the function before actual code.

some thing like

BOOL <your_class>::OnEraseBkgnd(CDC* pDC)
{
return <Base_class>::OnEraseBkgnd(pDC);

//your own code

}

The compiler would produce a warning (level 4) about unreachable code in such case.
You should really read your compiler output. Oh, and set your Warning Level to 4 (if it isn't yet).