Inside Macintosh: Macintosh Toolbox Essentials /

Chapter 2 - Event Manager

This chapter describes how your application can use the Toolbox Event Manager to receive information about actions performed by the user, to receive notice of changes in the processing status of your application, and to communicate with other applications.

For example, you can retrieve information from the Toolbox Event Manager that gives your application details about whether the user has pressed a key or the mouse button, whether one of your application's windows needs updating, or whether some other hardware-related or software-related action requires a response from your application.

Your application also uses the Event Manager to support the cooperative, multitasking environment available on Macintosh computers. This environment allows users to switch between many open applications and allows other applications to receive background processing time. By using Event Manager routines, you allow the system software to coordinate the scheduling of processing time between your application and other applications.

The Event Manager and Process Manager maintain the cooperative, multitasking environment. The Process Manager coordinates the scheduling of applications, and the Event Manager communicates information about changes in your application's processing status to your application.

See the chapter "Process Manager" in Inside Macintosh: Processes for complete information on how the Process Manager schedules applications for execution.

You can use the Event Manager to communicate with other applications. Your application can also communicate with other applications using the services of the Apple Event Manager.

The Event Manager and Apple Event Manager routines that let your application communicate with other applications depend on the services of the Program-to-Program Communications (PPC) Toolbox. The services performed by the Event Manager and Apple Event Manager meet the needs of most applications for interapplication communication. However, to get additional control or capabilities not provided by the Event Manager or Apple Event Manager, you can choose to access the PPC Toolbox directly. The chapter "Program-to-Program Communications Toolbox" in Inside Macintosh: Interapplication Communication describes the PPC Toolbox routines that are available to your application.

For a comparison of the services provided by the Event Manager, Apple Event Manager, and PPC Toolbox, see Inside Macintosh: Interapplication Communication. For additional information about Apple events, including descriptions of how to process the required Apple events, see Inside Macintosh: Interapplication Communication.

This chapter describes both the Toolbox Event Manager and the Operating System Event Manager. The Operating System Event Manager maintains a queue in which it stores hardware-related occurrences that you may want your application to respond to. The Toolbox Event Manager communicates the information maintained by the Operating System Event Manager to your application. In most cases, your application needs to interact only with the Toolbox Event Manager. In this chapter, the name Event Manager refers to the Toolbox Event Manager.

This chapter provides a general introduction to events and then explains how you can use the Event Manager to

• receive keypresses and mouse clicks as input for your application
• receive indication that your application's windows need to be activated or updated
• allow other applications to use the available system resources when your application isn't using them
• communicate with other applications

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Chapter Contents

Introduction to Events

Low-Level Events

Operating-System Events

High-Level Events

Priority of Events

Switching Contexts

About the Event Manager

Using the Event Manager

Obtaining Information About Events

Processing Events

Using the WaitNextEvent Function

Writing an Event Loop

Setting the Event Mask

Handling Events in a Dialog Box

Creating a Size Resource

Handling Low-Level Events

Responding to Mouse Events

Responding to Keyboard Events

Scanning for a Cancel Event

Responding to Update Events

Responding to Activate Events

Responding to Disk-Inserted Events

Responding to Null Events

Handling Operating-System Events

Responding to Suspend and Resume Events

Responding to Mouse-Moved Events

Handling High-Level Events

Responding to Events From Other Applications

Searching for a Specific High-Level Event

Determining the Sender of a High-Level Event

Sending High-Level Events

Requesting Return Receipts

Handling Apple Events

Event Manager Reference

Data Structures

The Event Record

The Target ID Record

The High-Level Event Message Record

The Event Queue

Event Manager Routines

Receiving Events

Sending Events

Converting Process Serial Numbers and Port Names

Reading the Mouse

Reading the Keyboard

Getting Timing Information

Application-Defined Routine

Filter Function for Searching the High-Level Event Queue

Resource

The Size Resource

Summary of the Event Manager

Pascal Summary

Constants

Data Types

Event Manager Routines

Application-Defined Routine

C Summary

Constants

Data Types

Event Manager Routines

Application-Defined Routine

Assembly-Language Summary

Data Structures

Trap Macros

Global Variables

Result Codes