我有一段鼠标随手绘图的程序（屏幕绘图），现在想实现内存绘图，但是不知道程序应该怎么写，写在哪里，请大家帮忙

void CNotepadView::OnLButtonDown(UINT nFlags, CPoint point)
{
// TODO: Add your message handler code here and/or call default
m_bDraw=TRUE;
xTemp = point.x;
yTemp = point.y;

CEditView::OnLButtonDown(nFlags, point);
}

void CNotepadView::OnLButtonUp(UINT nFlags, CPoint point)
{
// TODO: Add your message handler code here and/or call default
m_bDraw=FALSE;
CEditView::OnLButtonUp(nFlags, point);
}

void CNotepadView::OnMouseMove(UINT nFlags, CPoint point)
{
// TODO: Add your message handler code here and/or call default
CPoint *pt;
CDC *pDC=GetDC();
HCURSOR m_HCross;
m_HCross=AfxGetApp()->LoadStandardCursor(IDC_CROSS);
SetCursor(m_HCross);
//鼠标画线
if(m_bDraw==TRUE)
{
CClientDC dc(this);
dc.MoveTo (xTemp,yTemp);
dc.LineTo (point.x,point.y);
xTemp = point.x;
yTemp = point.y;
pt = new CPoint(point.x,point.y);
m_ptrArray.Add(pt);
}
ReleaseDC(pDC);
CEditView::OnMouseMove(nFlags, point);
}