arrowHead in visualization is not working

[nivedkrishnans]

The arrowHead seems to appear in CanvasGrid for (heading_x, heading_y) in (-1,0), (1,0), (0,-1) and (0,1), but it doesn't appear at all for any other combination I tried. I have tried options like (1,1), (sqrt(0.5),sqrt(0.5)), etc.
Are only those 4 values valid, or am I doing something wrong?

[envilk]

Maybe too late, but now starting to use mesa, and realized that also you have to put "x" and "y" position, and for that reason an error is probably appearing on js console from client side.