Delphi 画箭头

procedure TForm1.Line(x, y, x2, y2: integer);
begin
  canvas.MoveTo(x, y);
  canvas.LineTo(x2, y2);
end;

procedure TForm1.Button1Click(Sender: TObject);

var
  x, y, len: integer;
  r: TRect;

begin
  r := self.ClientRect;
  len := r.Right - r.Left;
  if len <  then
    len := ;
  if len >  then
    len := ;
  canvas.Pen.Color := canvas.Font.Color;
  canvas.Pen.Width := ;
  canvas.Pen.Style := psSolid;
  x := (r.Right + r.Left + len) div ;
  y := (r.Top + r.Bottom) div ;

  //Left Arrow
  Line(x, y, x - len - , y);
  begin
    x := x - len + ;
    Line(x, y - , x, y + );
    inc(x);
    Line(x, y - , x, y + );
    inc(x);
    Line(x, y - , x, y + );
  end;

  //Right Arrow
  x := x + ;
  Line(x, y, x - len - , y);
  begin
    dec(x);
    Line(x, y - , x, y + );
    dec(x);
    Line(x, y - , x, y + );
    dec(x);
    Line(x, y - , x, y + );
  end;
end;