Building Cocoa Applications: A Step by Step Guide

Controls

Mac OS X controls are on-screen graphical objects that perform like physical control devices we use every day. Consider a car stereo system that has an on-off switch with an indicator light, a row of buttons to select a radio station, a sliding knob to set volume, and a push button for ejecting an audio CD. Each of these devices is a control device with a different function. The on-off switch is a toggle, the radio buttons allow a choice of one out of many options, the slider sets a level or value, and the push button causes an action. All of these physical control devices have analogous on-screen controls that can be manipulated by the mouse in Mac OS X.

There are several common control types in the Mac OS X user interface, which we will discuss in the following sections:

• Push buttons

• Radio buttons and checkboxes

• Pop-up menus, command pop-down menus, and combination boxes

• Text fields and scrolling lists

• Sliders and scrollers

• Color wells and image wells

• Disclosure triangles

Buttons

There are several types of on-screen buttons. They fall into two main groups: action buttons and two-state buttons. An action button performs a single task, such as opening a dialog, saving a file, copying text, or closing a window. A two-state button sets a single feature or attribute on or off, such as whether text should be in bold font or a drawer should be displayed. In the car stereo analogy, the eject button is an action button, while the on-off switch is a two-state button. The set of car radio ...