This component internally uses a HyperTextProcessor to support <a> tags and custom styling with user-defined tags and <quad> classes. See HyperTextProcessor for information on syntax, as well as automatic detection and tagging of keywords.

Links extracted by the HyperTextProcessor are then colorized and emit callbacks for different pointer events. For example, the text "Here is a <a name="some_link">link</a>" will render as Here is a link, but with coloration and mouseover events for events for the word link. When the word link is clicked, entered, or exited, the component will emit callbacks of type HyperTextHyperlinkEvent specifying that a link with the id "some_link" was involved, along with its hit boxes.

Note the remarks for each of the events defined for this class. In particular remember that, on touch platforms, a link will be entered after it has been clicked/released, as the virtual pointer is still over the most recently clicked link (see EnteredLink).

When inheriting from this class, note that the implementation of Raycast(Vector2, Camera) only tests against link hit boxes, not the entire RectTransform. As such, event interface methods (e.g., EventSystems.IPointerExitHandler.OnPointerExit(PointerEventData) will only be called as the pointer position relates to the links. If you implement these interfaces in your own class and need them to be with respect to the entire rectangle, you can override Raycast(Vector2, Camera) in the following way:

public override bool Raycast(Vector2 p, Camera c) { return base.Raycast(p, c) || RaycastRect(p, c); }

Reference