C H A P T E R 5

The Mac OS X Environment

This chapter covers relevant features of Mac OS X that can influence the design of your software. These features are not always associated with a single technology or developer type but sometimes apply to development in general. You should be familiar with these guidelines before developing your software.

The Always-On Environment

As the center of the user’s digital hub, Mac OS X is designed to be always ready to use. Because of energy saving systems, it’s common for a user to leave a computer on most of the time. To allow for the fact that a computer may be on for hours, days, weeks, or even months at a time, you should consider the following guidelines:

■Avoid relying on a restart to get rid of cached or temporary files that may use up disk space. Be prepared to remove these files yourself when they are no longer needed.

■Avoid relying on startup or login items to initiate user-level processes. If the user quits a process initiated only at boot time, that process will be unavailable until the machine restarts.

■Avoid requiring users to reboot as a part of an installation or software update unless absolutely necessary. Your application is probably not the only one they have open, so a restart can come as a rude interruption.

Displays

Avoid making assumptions about display size. Mac OS X can run on systems with a screen size as small as 800 x 600, but a user may have multiple high-resolution displays. Unless you know that your users will be using a specific display size, it is best to optimize your applications for display at 1024 x 768 pixels.

Note: A resolution of 640 x 480 is also available for the iBook and for Classic applications, games, and other multimedia applications. This does not mean that you should assume this is the minimum system resolution, however. Design your user interface for a resolution of at least 800 x 600.

Be aware that users may have the ability to rotate their displays, so you should also avoid making assumptions about the aspect ratio. Display rotation reverses the aspect ratio of the screen. For example, if a user's display is set to a screen resolution of 800 x 600 (an aspect ratio of 1.33:1), after rotation the screen resolution is 600 x 800 (an aspect ratio of .75:1).

An application can get notified of some types of screen-update events by registering for a callback, such as CGDisplayReconfigurationCallBack. For more information on this and other callbacks, see Quartz Display Services Reference.

The Always-On Environment

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2008-06-09 | © 1992, 2001-2003, 2008 Apple Inc. All Rights Reserved.