How to drag the midArrow to change link curviness?

How to drag the midArrow to change curviness of link ?

We created an instance of GoLabeledLink and drawed a midArrow on it. We want to change curviness of link by dragging midArrow not by default selection handle.
The below is screenshot. The link style is bezier.

Well, I’m not entirely sure that’s possible. Curviness has some (undocumented) impact on the the 2 middle control points in the bezier. But if you want to grab that arrowhead and drag it up 10 pixels and over 4… I can’t tell you how to change Curviness to get the bezier to match that spot.

Now, I’ve sent you email on how to compute the location of the arrowhead based on the control points… but you can’t compute the location of both control points given the (desired) location of the arrowhead.

You can look at DrawDemo.BlockArrow (for example) to see how to add an extra resize handle and then handle DoResize on that handle. That’s the easiest way for you to handle a dragging action to see if you can get the “feel” of grabbing the arrowhead right. (I’m suggesting you put an extra resize handle in the middle of the arrowhead.)