新手学习MFC遇到的一个小疑问

Question

void CLi3_1View::OnDraw(CDC* pDC)
{
CLi3_1Doc* pDoc = GetDocument();
ASSERT_VALID(pDoc);
// TODO: add draw code for native data here
CPen *PenOld,PenNew;
CBrush *BrushOld,BrushNew; PenOld=(CPen *)pDC->SelectStockObject(BLACK_PEN);
BrushOld=(CBrush *)pDC->SelectStockObject(LTGRAY_BRUSH); pDC->Rectangle(100,100,300,300);
PenNew.CreateStockObject(WHITE_PEN);
pDC->SelectObject(&PenNew);
pDC->MoveTo(100,100);
pDC->LineTo(300,300);
pDC->MoveTo(100,300);
pDC->LineTo(300,100); pDC->SelectObject(PenOld);
pDC->SelectObject(BrushOld);
}
WHITE_PEN 不是库存的对象吗》》？？？？还需要create????

Answer 1

CreateStockObject函数的功能就是创建windows预定义的stock的，MSDN有详细说明

Answer 2

This method retrieves a handle to one of the predefined stock pens, brushes or fonts, and attaches the GDI object to the CGdiObject object.