basic about AIS_Drawer

Hello everyone,
I'm confused using the AIS_Drawer, I'm trying to change an ais aspect: I want to draw an arrow at the end of each line, so this is the code of my sample:

...
Handle(Geom_Point) pnt1 = new Geom_CartesianPoint(p1);
Handle(Geom_Point) pnt2 = new Geom_CartesianPoint(p2);
Handle(AIS_Line) ais = new AIS_Line(pnt1, pnt2);
ais->Attributes()->SetLineArrowDraw(true); // TODO: is not working
ais->Attributes()->Link()->SetLineArrowDraw(true);
context->Display(ais);
...

and the line is displayed but with no arrows.
How should I properly use the AIS_Drawer ?
Any help would be appreciated.
Thanks in advance!