如何在delphi 中画带箭头的直线（改自网上一位论坛版主的vb代码）[1]

procedure tlineitem.draw(acanvas: tcanvas);

var

  xa, ya, xb, yb: real;

  d: real;

  x1, y1, x0, y0: integer;

begin

  acanvas.pen.style := pssolid;

  acanvas.pen.color := clwhite;

//画直线

  acanvas.moveto(ptstart.x, ptstart.y);

  acanvas.lineto(ptend.x, ptend.y);

  //画箭头

  x0 := ptstart.x;//ptstart是箭头的起点，ptend是终点，都是tpoint型

  y0 := ptstart.y;

  x1 := ptend.x;

  y1 := ptend.y;

  d := sqrt((y1 - y0) * (y1 - y0) + (x1 - x0) * (x1 - x0));

  if d > 0 then begin

    xa := x1 + arrowlen * ((x0 - x1) + (y0 - y1) / 2) / d;

    ya := y1 + arrowlen * ((y0 - y1) - (x0 - x1) / 2) / d;

    xb := x1 + arrowlen * ((x0 - x1) - (y0 - y1) / 2) / d;

    yb := y1 + arrowlen * ((y0 - y1) + (x0 - x1) / 2) / d;

    acanvas.moveto(ptend.x, ptend.y);

    acanvas.lineto(trunc(xa), trunc(ya));

    acanvas.moveto(ptend.x, ptend.y);

    acanvas.lineto(trunc(xb), trunc(yb));

  end;

//如果选中画出焦点矩形，可以不要