A link annotation as a HitTestIndex holds it: the annotation, what activating it does, and its region.
public sealed class HitTestLink
ISO 32000-2 §12.5.6.5, Table 176: the region is QuadPoints when present and inside Rect, else Rect
(ActivationRegion), in default user space. A point hits the link when it is inside one of the
region's quadrilaterals (their convex hull, so writers' corner orders all work). Links that are hidden (Hidden or
NoView, §12.5.3) or whose optional content is off (§8.11.3.3) are not in the index.
kind:method, kind:property, kind:ctor. Press Esc to clear.ActionGets the action performed when the link is activated, read from the annotation (A), or null.AnnotationGets the link annotation, a live view over its dictionary.DestinationGets the destination displayed when the link is activated, read from the annotation (Dest), or null.RegionGets the quadrilaterals that activate the link, as when the index was built.