上次写了《VC＋＋开发地理信息系统的源码ＨｆＧＩＳ（１）》，GIS不可避免地要涉及绘图，在MFC是如何绘图呢。
请看例程：
void CDrawRect::Draw(CDC* pDC)
{
ASSERT_VALID(this);
CBrush brush;
if (!brush.CreateBrushIndirect(&m_logbrush))
return;
CPen pen;
if (!pen.CreatePenIndirect(&m_logpen))
return;
CBrush* pOldBrush;
CPen* pOldPen;
if (m_bBrush)
pOldBrush = pDC->SelectObject(&brush);
else
pOldBrush = (CBrush*)pDC->SelectStockObject(NULL_BRUSH);
if (m_bPen)
pOldPen = pDC->SelectObject(&pen);
else
pOldPen = (CPen*)pDC->SelectStockObject(NULL_PEN);
CRect rect = m_position;
switch (m_nShape)
{
case rectangle:
pDC->Rectangle(rect);
break;
case roundRectangle:
pDC->RoundRect(rect, m_roundness);
break;
case ellipse:
pDC->Ellipse(rect);
break;
case circle:
DrawCircle(pDC,rect);
//pDC->Circle(rect);
break;
case line:
if (rect.top > rect.bottom)
{
rect.top -= m_logpen.lopnWidth.y / 2;
rect.bottom += (m_logpen.lopnWidth.y + 1) / 2;
}
else
{
rect.top += (m_logpen.lopnWidth.y + 1) / 2;
rect.bottom -= m_logpen.lopnWidth.y / 2;
}
if (rect.left > rect.right)
{
rect.left -= m_logpen.lopnWidth.x / 2;
rect.right += (m_logpen.lopnWidth.x + 1) / 2;
}
else
{
rect.left += (m_logpen.lopnWidth.x + 1) / 2;
rect.right -= m_logpen.lopnWidth.x / 2;
}
pDC->MoveTo(rect.TopLeft());
pDC->LineTo(rect.BottomRight());
break;
}
pDC->SelectObject(pOldBrush);
pDC->SelectObject(pOldPen);
}