An object that can be registered on VisualElements to react to any event type.
The same callback instance can be registered on multiple different elements, resulting in effective memory
sharing. If the element instance is needed by the callback code, an optional argument can be used to provide it.
Additional resources: EventCallback, EventCallbackDefinition<T0>, EventCallbackGroup
| Method | Description |
|---|---|
| Register | Adds this callback's event handler to the given element. |
| Unregister | Removes this callback from the given element. |