Finds the topmost annotation at a point: links by their activation region (QuadPoints, else Rect), others by
Rect, edges included.
public AnnotationTarget? HitTest(in PagePoint point)
The point, from TryGetPageAt(in Viewport, Double, Double, out PagePoint).
null (also when the page is not loaded).ISO 32000-2 §12.5.2 and §12.5.6.5 (Table 176, QuadPoints). Allocates nothing.