So to reveiew

- Visio guy constrained a control handle for a circle

- I extended to an ellipsis

- Here for an elliptical arc

Using the nice tutorial from visio guy, here is how to constrain and elliptical arc

Just need to change the controls.pntperimenter.y

From setatref(user.chy,setatrefexpr(),true)+pnt(x,y)

To setatref(user.chy,setatrefeval(bound(setatrefexpr(),0, false, height*0.5, height*1),true) + pnt(x,y)

The bound function essentially locks the controls to upper half of the ellipse.

In all cases - circle, ellipsis, elliptical arc - the rest of visio guys tutorial applies

I suspect you can do the same on controls.pntperimeter to constrain the x dimension

(maybe constrain a "slice of pie" in both X and Y axis).)

I would proffer that one can now constrain any simple curve.