void CworkflowDlg::DrawLine(CPoint p1, CPoint p2)
{
        CClientDC dc(this);//获取客户窗口DC
    CPen pen,pen1,*oldpen;
    int PenLineWidth=2;//为了根据线条宽度设置箭头的大小
    pen.CreatePen(PS_SOLID, PenLineWidth, RGB(0, 0, 0));
    pen1.CreatePen(PS_SOLID, PenLineWidth, RGB(0, 0, 0));
    oldpen=dc.SelectObject(&pen);
    
    double theta=3.1415926/15*PenLineWidth;//转换为弧度
    double Px,Py,P1x,P1y,P2x,P2y;
    //以P2为原点得到向量P2P1（P）
    Px=p1.x-p2.x;
    Py=p1.y-p2.y;
    //向量P旋转theta角得到向量P1
    P1x=Px*cos(theta)-Py*sin(theta);
    P1y=Px*sin(theta)+Py*cos(theta);
    //向量P旋转-theta角得到向量P2
    P2x=Px*cos(-theta)-Py*sin(-theta);
    P2y=Px*sin(-theta)+Py*cos(-theta);
    //伸缩向量至制定长度
    double x1,x2;
    int length=10;
    x1=sqrt(P1x*P1x+P1y*P1y);
    P1x=P1x*length/x1;
    P1y=P1y*length/x1;
    x2=sqrt(P2x*P2x+P2y*P2y);
    P2x=P2x*length/x2;
    P2y=P2y*length/x2;
    //平移变量到直线的末端
    P1x=P1x+p2.x;
    P1y=P1y+p2.y;
    P2x=P2x+p2.x;
    P2y=P2y+p2.y;

    

    dc.MoveTo(p1.x,p1.y);
    dc.LineTo(p2.x,p2.y);
    dc.SelectObject(&pen1);
    dc.MoveTo(p2.x,p2.y);
    dc.LineTo(P1x,P1y);
    dc.MoveTo(p2.x,p2.y);
    dc.LineTo(P2x,P2y);

    dc.MoveTo(P1x,P1y);
    dc.LineTo(P2x,P2y);

    CPoint ptVertex[3];

    ptVertex[0].x = p2.x;
    ptVertex[0].y = p2.y;
    ptVertex[1].x = P1x;
    ptVertex[1].y = P1y;
    ptVertex[2].x = P2x;
    ptVertex[2].y = P2y;
        //填充三角形区域
    CBrush br(RGB(40,130,170));  
    CRgn rgn; 
    rgn.CreatePolygonRgn(ptVertex,3,ALTERNATE);
    dc.FillRgn(&rgn, &br);  

    dc.SelectObject(oldpen);

    br.DeleteObject();  
    rgn.DeleteObject();
}