The implementation will show that a combination of callbacks are needed to create an effective solution to the problem. The pointer can be used to activate windows, navigate the display, move objects and text, and produce graphical results. A familiar use of the pointer in drawing programs is that of an artist tool such as scissors, pencil, even an eraser. An event is created when some action has just been performed and is usually caused by a user interacting with an application. Context sensitive information contained in the event data packet describe specifics on its origin and usefulness.
Applications are able to respond to events via modules called event handlers.
These routines are written by developers to inspect certain events or groups of events and subsequently provide appropriate visual feedback. Repetition can be implemented using a construct called time out. A time out merely invokes a user identified callback function after a specified time has elapsed. For each event processed by a server there usually exists one and only one action that can be associated with it. One specific type of event is called a pointer event and is used to describe the precise movement and location of the pointer on the display at a given time.