Advanced MFC Programming

Chapter 8. DC, Pen, Brush and Palette
If m_nCurrentPt is 0, this means it is the first control point. In this case, we do not need to draw or
erase anything. However, we need to set the window capture.
If m_nCurrentPt is not 0, we need to erase the previous curve, record the new point, assign its value to
the rest points (This is for the convenience of drawing curve outline, because when we draw a curve, we
always need four control points), and draw the curve outline.
Then the implementation of CGDIView::OnMouseMove(…) becomes easy. We just need to check if there
is an existing curve outline. If so, we need to erase it before drawing a new curve outline. Otherwise we just
draw the curve outline directly and set m_bNeedErase flag:
void CGDIView::OnMouseMove(UINT nFlags, CPoint point)
{
CClientDC dc(this);
CPen pen;
CPen *ptrPenOld;
int nMode;
int i;
}
pen.CreatePen(PS_DOT, 1, RGB(0, 0, 0));
ptrPenOld=dc.SelectObject(&pen);
nMode=dc.SetROP2(R2_XORPEN);
if(m_bNeedErase == TRUE)
{
dc.PolyBezier(m_ptCurve, 4);
m_ptCurve[m_nCurrentPt]=point;
for(i=m_nCurrentPt+1; i