I got sick of having to switch to Widget mode, lock the contraption, and switch back to see what the curve “really” looked like, then do the dance again to resume editing. Now there’s a little “pin” button in the top left to hide and disable the handles in Interact mode. Locking the contraption now hides the handles and the pin.
I also updated the rendering code to try rounding coordinates to the nearest pixel, which might make lines a bit smoother.