2D scene graph node. An actor has a position, rectangular size, origin, scale, rotation, Z index, and color. The position corresponds to the unrotated, unscaled bottom left corner of the actor. The position is relative to the actor's parent. The origin is relative to the position and is used for scale and rotation.
An actor has a list of in progress {@link Action actions} that are applied to the actor (often over time). These are generallyused to change the presentation of the actor (moving it, resizing it, etc). See {@link #act(float)}, {@link Action} and itsmany subclasses.
An actor has two kinds of listeners associated with it: "capture" and regular. The listeners are notified of events the actor or its children receive. The regular listeners are designed to allow an actor to respond to events that have been delivered. The capture listeners are designed to allow a parent or container actor to handle events before child actors. See {@link #fire}for more details.
An {@link InputListener} can receive all the basic input events. More complex listeners (like {@link ClickListener} and{@link ActorGestureListener}) can listen for and combine primitive events and recognize complex interactions like multi-touch or pinch.
@author mzechner
@author Nathan Sweet