Visual C++ and MFC Programming 2nd Edition

Visual C++ and MFC Fundamentals Chapter 9: Strings

As seen already, the SetViewportOrg() member function can be used to change the origin

of the device context. It also uses an orientation of axes so that the horizontal axis moves

positively from (0, 0) to the right. The vertical axis moves positively from (0, 0) down:

To illustrate this, we will draw a green line at 45° from the origin:

void CExoView::OnDraw(CDC* pDC)

{

CExoDoc* pDoc = GetDocument();

ASSERT_VALID(pDoc);

pDC->SetViewportOrg(220, 150);

// Use a red pen

CPen PenRed(PS_SOLID, 1, RGB(255, 0, 0));

CPen *pOld = pDC->SelectObject(&PenRed);

// A circle whose center is at the origin (0, 0)

pDC->Ellipse(-100, -100, 100, 100);

// Use a blue pen

CPen PenBlue(PS_SOLID, 1, RGB(0, 0, 255));

pOld = pDC->SelectObject(&PenBlue);