Advanced MFC Programming

Chapter 8. DC, Pen, Brush and Palette
}
nMode=dc.SetROP2(R2_XORPEN);
if(m_bNeedErase == TRUE)
{
dc.Rectangle(m_rectDraw);
}
else m_bNeedErase=TRUE;
m_rectDraw.right=point.x;
m_rectDraw.bottom=point.y;
dc.Rectangle(m_rectDraw);
dc.SetROP2(nMode);
dc.SelectObject(ptrBrushOld);
brush.Detach();
dc.SelectObject(ptrPenOld);
}
CView::OnMouseMove(nFlags, point);
Also, function CGDIView::OnDraw(…) is modified as follows:
void CGDIView::OnDraw(CDC* pDC)
{
CPen pen;
CPen *ptrPenOld;
CBrush brush;
CBrush *ptrBrushOld;
int nMode;
int nNumOfRects;
int i;
CGDIDoc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
}
pen.CreatePen(PS_SOLID, 1, RGB(0, 255, 0));
ptrPenOld=pDC->SelectObject(&pen);
brush.CreateSolidBrush(RGB(255, 0, 255));
ptrBrushOld=pDC->SelectObject(&brush);
nMode=pDC->SetROP2(R2_COPYPEN);
nNumOfRects=pDoc->GetNumOfRects();
for(i=0; iRectangle(pDoc->GetRect(i));
}
pDC->SetROP2(nMode);
pDC->SelectObject(ptrBrushOld);
pDC->SelectObject(ptrPenOld);
With the above implementation, the application will be able to let the user draw rectangles.
With only minor modifications we can let the application draw ellipses. Sample 8.2-2\GDI
demonstrates how to implement interactive ellipse drawing. It is based on sample 8.2-1\GDI.
To draw an ellipse, we need to call function CDC::Ellipse(…)and pass a CRect type value to it. This is
exactly the same with calling function CDC::Rectangle(…). So in the previous sample, if we change all the
“Rectangle” keywords to “Ellipse”, the application will be implemented to draw ellipses instead of
rectangles.
In sample 8.2-2\GDI, function CDC::Ellipse(…) is called within CGDIView::OnMouseMove(…) and
CGDIView::OnDraw(…). The following shows the modified portion of two functions:
……
void CGDIView::OnMouseMove(UINT nFlags, CPoint point)
{
if(m_bNeedErase == TRUE)
{
dc.Ellipse(m_rectDraw);
}
else m_bNeedErase=TRUE;
m_rectDraw.right=point.x;
m_rectDraw.bottom=point.y;
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