Overview

The focus of this chapter is on the processing of events. Most events are caused by a user interacting with the interface, and the rest are caused by the driving application. Events, and their processing, are the methods of communication between an MWAPI interface and application code; they can occur for windows, menu choices, timers, and most gadgets. This chapter presents a solid foundation upon which to build an MWAPI application through a detailed discussion of the event object.

The MWAPI uses a high-level callback method for notifying entities of events in the windowing environment's event queue, while more mainstream windowing APIs use a low-level polling approach. Callback processing simplifies event handling and does not require the developer to possess an in-depth knowledge of any particular windowing system or event queue. The callback processing technique standardizes the process of event handling across windowing platforms to give portability to a conforming application.

An understanding of the fundamentals for "hand shaking" between an interface and the applications code is crucial to the functioning of a windowing application. An MWAPI entity can process several types of events, which are discussed below in the Event Types section. The Event Processing section takes an in-depth look into the mechanics of event processing. The Event Information Attributes section focuses on the characteristics that make up event objects and the Implementation section discusses various schemes for processing events that are demonstrated in the remaining chapters. This chapter ends with Highlights and Exercises.

Event Types

Event type...