[readonly] the UI element that caused the event to be raised, or nil.
[readonly] Some events involve 2 UI elements. This will usually be nil.
[readonly] If a key event, returns the key character of the pressed key.
[readonly] If a key event, returns the keycode of the pressed key.
[readonly] If this is an op event, returns the op number (TBD: example).
[readonly] Op base string (TBD: explanation/example).
[readonly] If this is an op event, returns the subop number (TBD: example)
[readonly] for mouse events, will be the X screen coordinate of the mouse cursor.
[readonly] for mouse events, will be the Y screen coordinate of the mosue cursor.
[readonly]. Is this an event raised from a mouse action.
[readonly] TBD explanation/example (unlikely to be true for UI events).
[readonly] what caused this hook to fire
This class is a functional superset of all possible inputs into client runescript. Lua plugins are allowed to hook all the same UI events that runescript does. Runescript receives specific arguments from the HookReq depending on the type of hook it is, but the lua binding is not yet that fancy; it instead returns the whole HookReq, trusting that lua logic will be able to pull out the relevant bits for the type of subscribed event.