I'm sorry for the long delay on my side.
Daniel, the only remaining point of our discussion that I feel deserves
I realize that it is possible to describe touch sensitive concave
shapes, but I am not sure they matter for this. If developers are
going to go to the trouble of defining a concave shape that they want
to be touch sensitive within its area but not in all of its bounding
box, are they really then going to want that area to be extended? I’d
consider a concave touch shape with extended capture zone to be
sufficiently unlikely that we could treat it as concave. Which, I
realize is not quite what my proposed algorithm does.
We could reasonably limit the algorithm to dealing with convex shapes.
Can we? What about paths, polygons etc?
I can imagine, for instance, an application showing a graph - a set of
vertices connected by edges. The edges are not straight lines, but are
e.g. QuadCurves. I can touch an edge and drag it to change its shape
(the control point). Now to be able to touch the curve, I certainly want
it to have the extended capture zone (it's thin). But if an edge circles
around the graph, I don't want it to be picked everywhere in between.
I'm not sure if this is compelling enough, but to me it sounds like a
reasonable use-case that needs concave extended capture zones..