User request for a simple Curved Line
I just want to specify 3 points (the start point, the end point, the mid point) and have a
line that traverse through those points in a nice smooth, even, non-inflection-point-changing arc.
Most drawing tools (except the online ones) seem to have this feature. Make a line between two points. You get a handle (i.e. a draggable square) at the mid point of that line. You can move that mid-point only perpendicular to the original straight line that was drawn thus creating a smooth even curve.