Internal data structures

• double lastTime - the clock time when the last position was determined. This is used to determine if the animation should proceed to a new frame, to control the speed.
• int frameChanged - whether the animation has changed to a new frame recently.
• int needSetFrameChanged - when this flag is set, then the frameChanged flag should be changed the next time it is possible to do so.
• ResizeArray<Timestep *> tsList - the frames themselves.
• int currFrame - the current frame, an index into tsList.
• int frameSkip - if we are jumping to a new frame, this indicates the frame to jump to.
• float Speed - the animation speed, from 0 (slowest) to 1 (fastest).
• AnimPos appendPos - the method to use the next time a frame is to be appended.
• int appendFrame - if we are inserting frames, the frame which we are to append before or after.
• AnimDir animDir - the current animation direction.
• AnimStyle animStyle - the method for doing animation.
• int moveTo - if this is not negative, this indicates a frame to which we are to jump the next time the animation position is updated.
• float currTime - the time which has elapsed since the beginning of the animation.