MFC application is crashing when I declare cpen variable in class scope and using it in ondraw(...)

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Hi All, I'm trying to declare a CPen object in class scope and using it in OnDraw(...).But my application is crashing when I run it.If I declare the object in OnDraw(...) it is working fine. Can anyone please let me know do I need to any extra thing if declare CPen object in class scope? Thanks in advance.

What I have tried:

C++

xxxxx.h
private:
  CPen cPen;


xxxxx.cpp

void CMFCApplication2View::OnDraw(CDC* pDC)
{
        //CPen cPen;  If I do it here its working fine.
	CPen* pOldPen = NULL;

	BOOL bCPen = cPen.CreatePen(PS_SOLID, 10, RGB(255, 0, 0));

	
	if (bCPen)
	{
		pOldPen = pDC->SelectObject(&cPen);

		pDC->MoveTo(95, 125);
		pDC->LineTo(230, 125);

		pDC->SelectObject(pOldPen);
		//cPen.DeleteObject();
	}
}

Posted 26-Jul-16 3:40am

cppcoder1

Updated 26-Jul-16 18:28pm

v4

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Richard MacCutchan 27-Jul-16 3:52am

Run the code through the debugger to see exactly where it crashes and which variable is causing the problem.

2 solutions

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Jochen Arndt · Answer 1 · 2016-07-26T04:03:00

Solution 1

You are calling CreatePen again and again with each drawing.

The simplest solution would be calling CreatePen in the constructor of your class and remove it from the draw function:

C++

CMFCApplication2View::CMFCApplication2View()
{
    // Other initialisation goes here

    cPen.CreatePen(PS_SOLID, 10, RGB(255, 0, 0));
}

void CMFCApplication2View::OnDraw(CDC* pDC)
{
    CPen* pOldPen = pDC->SelectObject(&cPen);

    // Perform drawing here

    pDC->SelectObject(pOldPen);
}

Posted 26-Jul-16 4:03am

Jochen Arndt

Comments

cppcoder1 27-Jul-16 0:25am

Thanks Jochen Arndt, But it's not solving my problem.Its crashing when I create Cpen object in class scope

Jochen Arndt 27-Jul-16 2:59am

Are you sure that the crash occurs when calling CreatePen() in the constructor? That is rather unlikely.

What kind of crash is it? Are you using a debug build and start the application within the debugger?

Richard MacCutchan · Answer 2 · 2016-07-26T04:44:00

Solution 2

C++

BOOL CPen = cPen.CreatePen(PS_SOLID, 10, RGB(255, 0, 0));

What on earth is that statement supposed to be? You are redeclaring a class name (CPen) as a BOOLean variable.

Posted 26-Jul-16 4:44am

Richard MacCutchan

Updated 26-Jul-16 4:45am

v2