We have recently implemented isPointInStroke(x,y) in Firefox (https://bugzilla.mozilla.org/show_bug.cgi?id=803124). This is a parallel to isPointInPath(x,y) and returns true if the point is inside the area contained by the stroking of a path. It was easily implemented on top of Direct2D, Cairo, Skia, and CoreGraphics and shouldn't be difficult for other systems.
We implemented this to help support functionality needed for shumway (flash on html) -Jeff
