MFC: flickering issue with GDI+ - mfc

Question

I create a sample dialog application which has a circle drawn. Also on mouse move the circle will be re-drawn. I am providing my code below. Its also compilable.
I tried using double buffering and erasebackground, i was not getting the flickering issue, but i observed that the drawining is not erased properly. So to erase, in OnPaint i wrote the erasing code. Again i am facing the flickering issue.
void CPOCDlg::OnPaint()
{
CPaintDC dc(this);
GetClientRect(&clientRect);
circle = clientRect;
circle.DeflateRect(100,100);
dc.SelectStockObject(NULL_BRUSH);
dc.SelectStockObject(NULL_PEN);
dc.FillSolidRect(circle, ::GetSysColor(COLOR_BTNFACE));
Bitmap buffer(circle.right, circle.bottom);
Graphics graphicsbuf(&buffer);
Graphics graphics(dc.m_hDC);
graphicsbuf.SetSmoothingMode(SmoothingModeHighQuality);
SolidBrush brush(Color(255,71,71,71));
Pen bluePen(Color(255, 0, 0, 255),1);
graphicsbuf.DrawEllipse(&bluePen,Rect(circle.left,circle.top,circle.Width(),circle.Height()));
graphicsbuf.SetSmoothingMode(SmoothingModeHighQuality);
graphics.DrawImage(&buffer, 0, 0);
}
void CPOCDlg::OnMouseMove(UINT nFlags, CPoint point)
{
m_point = point;
InvalidateRect(circle,FALSE);
CDialogEx::OnMouseMove(nFlags, point);
}
BOOL CPOCDlg::OnEraseBkgnd(CDC* pDC)
{
return TRUE;
}
Please let me know if i am doing any mistake.

Answer 1

You need to use so called double buffer technique to prevent flickering:
// create Mem DC
dcMemory = new CDC;
dcMemory->CreateCompatibleDC(pDC);
pDC->SetMapMode(MM_TEXT);
dcMemory->SetMapMode(MM_TEXT);
// TODO: draw to memDC here
//switch back to paint dc
pDC->BitBlt(rectDirty.left, rectDirty.top,
rectDirty.Width(), rectDirty.Height(),
dcMemory,
rectDirty.left,rectDirty.top,SRCCOPY);
dcMemory->DeleteDC();
delete dcMemory;
dcMemory = NULL;